To shape or not to shape...Simulated bougie-assisted difficult intubation in a manikin*

FORUM

A national survey of the provision for patients

with latex allergy

G. M. Yuill,1 D. Saroya2 and S. L. Yuill3

1 Specialist Registrar in Anaesthesia, North-west (E) Deanery, 2 Consultant Anaesthetist and 3 Staff Nurse in

Anaesthetics and Recovery, Stepping Hill Hospital, Stockport, Cheshire. SK2 7JE, UK

Summary

The prevalence of latex allergy has increased since the 1980s. As latex is found throughout hospitals

and operating theatres, careful planning is required for latex-allergic patients who present

pre-operatively. We conducted a postal survey of 269 departments of anaesthesia in England and

Wales; responses were received from 208 (77%). Of these, 198 (95%) had a latex allergy protocol

and 181 (87%) had a store of latex-free equipment. Only 113 (54%) had a named nurse and 58

(28%) had a named consultant responsible for the update of latex allergy provisions. Access to

allergy clinics and further investigations were available to 189 (91%). Many respondents called for

national guidelines. We are reassured that the majority of trusts have an up-to-date latex allergy

protocol and latex-free equipment store. However, relatively few have nominated members of staff

responsible for these and peri-operative care of susceptible patients.

Keywords Latex hypersensitivity. Risk management. Guidelines.

........................................................................................................

Correspondence to: Dr D. Saroya

E-mail: [email protected]

Accepted: 11 April 2003

The increase in the use of universal precautions against

infectious diseases in the early 1980s, especially the use of

gloves containing latex, has led to an increase in the

number of latex-sensitive and -allergic patients presenting

to hospitals [1,2]. The prevalence of latex allergy in the

general population is believed to be less than 1% [1,3].

When dealing with high-risk groups, however, the

prevalence increases dramatically. It has been reported

in as many as 17% of health care workers, rising to 65%

among patients with spina bifida [1,3]. Although the

incidence of anaphylaxis during anaesthesia is low,

between 1 : 10 000 and 1 : 20 000, it may be fatal [4].

In a recent study in France, latex was incriminated in

12.1% of anaphylactic reactions [4]. Indeed, latex is now

probably the second most important cause of intra-

operative anaphylaxis after neuromuscular blocking drugs

[5]. Thus the removal of all latex-containing equipment

would lower the incidence of intra-operative anaphylaxis

still further. Until this happens, it is imperative that

latex-sensitive patients are identified and managed in

latex-free environments.

The increase in prevalence of latex allergy has raised

awareness. Numerous protocols for the management of

susceptible patients and lists of latex-free equipment can

be found searching the medical literature via the Internet.

With this in mind, we endeavoured to find out how

many anaesthetic departments throughout England and

Wales had adopted such protocols, nominated responsible

personnel and installed equipment to deal with the

identification, diagnosis and peri-operative management

of the latex-allergic patient.

Methods

A one-sided, A4-sized questionnaire was developed,

which asked whether anaesthetic departments had per-

sonnel responsible for the identification and manage-

ment of latex-sensitive patients, a latex allergy protocol,

a latex-free trolley or box and access to an allergy clinic

and further investigations. An area for individuals’

comments was also provided. This questionnaire was

sent to 269 clinical directors of anaesthetic departments

Anaesthesia, 2003, 58, pages 775–803.....................................................................................................................................................................................................................

� 2003 Blackwell Publishing Ltd 775

throughout England and Wales (from the Directory of

Operating Theatres & Departments of Surgery 1999,

CMA Medical Data, Cambridge, UK) with a covering

letter and a stamped addressed envelope to aid return. In

order to improve the overall response rate, a second

questionnaire was sent to those clinical directors who did

not respond initially. Data were entered onto an EXCEL

(Microsoft, Seattle, WA) spreadsheet for analysis.

Results

Of the 269 anaesthetic departments contacted, 208

returned a completed form, a response rate of 77%.

Provisions for latex-allergic patients are shown in Table 1.

Availability of further investigations is shown in Fig. 1.

When asked to comment on the current peri-operative

care of latex-allergic patients and their future impact on

the NHS, the most common responses were split into

those who already had latex-free or nearly latex-free

theatres (21; 10%) and those who would appreciate more

advice in the form of national guidelines for latex allergy

and a national database of latex-free equipment (26; 13%).

Discussion

In 1998 Dakin & Yentis claimed, ‘It is now essential that

all hospitals develop strategies to identify and manage

patients and healthcare workers who are sensitised to

latex. Failure to do so will lead to avoidable morbidity,

mortality and litigation’ [2]. From our survey it is

encouraging to see that 95% of responding departments

had a latex allergy protocol and that 87% had a latex-free

trolley or box. We have to bear in mind, though, that

almost one quarter of clinical directors did not respond,

with the possibility that these figures are actually lower. It

is quite possible that those who did respond are from

departments that have instigated latex allergy protocols

and latex-free equipment stores. The majority of depart-

ments did not have named medical and nursing staff

responsible for the maintenance and update of protocols

and equipment, and for the identification and peri-

operative management of susceptible patients. These facts

alone suggest suboptimal management of patients at risk

and difficult management decisions for staff presented

with a latex-sensitive patient, especially out of hours.

It appears that the resources are mostly in place for

diagnosing latex allergy at allergy clinics, either on a local

or a regional basis, to which high-risk patients could be

referred pre-operatively. Thus if patients were flagged up

pre-operatively, responsible staff at the base hospital

would be suitably placed to facilitate referral and peri-

operative management.

In an ideal world, hospitals would be latex-free

environments and much work has been done towards

this goal. The majority of equipment now used in

operating theatres is latex-free and individual items can be

easily checked for their contents by contacting the

manufacturer. However, we do agree with those

respondents who suggested the need for national guide-

lines, perhaps issued by the Association of Anaesthetists of

Great Britain & Ireland. In the meantime, we suggest that

all trusts ensure that they have an up-to-date latex allergy

protocol and latex-free equipment store, and that they

have nominated members of both medical and para-

medical staff responsible for these and the safe peri-

operative passage of latex-sensitive patients.

Acknowledgements

We would like to thank all the clinical directors who took

the time to fill out the questionnaire.

References

1 Farley CA, Jones HM. Latex allergy. British Journal of

Anaesthesia CEPD Reviews 2002; 2: 20–3.

2 Dakin MJ, Yentis SM. Latex allergy: a strategy for manage-

ment. Anaesthesia 1998; 53: 774–81.

3 Agarwal S, Gawkrodger DJ. Latex allergy: a health care

problem of epidemic proportions. European Journal of

Dermatology 2002; 12: 311–15.

Table 1 Provision for latex-allergic patients in 208 anaestheticdepartments. Values are number (proportion) of departments.

Latex allergy protocol 198 (95%)Latex-free equipment store 181 (87%)Named nurse ⁄ ODA 113 (54%)Named consultant 58 (28%)

Figure 1 Access to allergy clinics and further investigationsavailable to patients in 208 anaesthetic departments.Solid ¼ available locally; clear ¼ available regionally; striped ¼unavailable. RAST ¼ radioallergosorbent testing.

Forum Anaesthesia, 2003, 58, pages 775–803......................................................................................................................................................................................................................

776 � 2003 Blackwell Publishing Ltd

4 Laxenaire MC, Mertes PM. Anaphylaxis during anaesthesia.

Results of a two-year survey in France. British Journal of

Anaesthesia 2001; 87: 549–58.

5 Lieberman P. Anaphylactic reactions during surgical and

medical procedures. Journal of Allergy and Clinical Immunology

2002; 110 (Suppl.): S64–9.

FORUM

Pain during awake nasal intubation after topical cocaine

or phenylephrine ⁄ lidocaine spray*

D. M. Cara,1 A. M. Norris2 and L. J. Neale2

1 Consultant Anaesthetist, Northampton General Hospital, Cliftonville, Northampton NN1 5BD, UK,

2 Consultant Anaesthetist, Anaesthetic Directorate, University Hospital Nottingham NHS Trust, C Floor, East Block,

Queen’s Medical Centre, Nottingham, NG7 2UH, UK

Summary

Although several local anaesthetic techniques are described for nasal analgesia during awake int-

ubation, there has been little attempt to evaluate their effectiveness. We examined pain scores

associated with nasal intubation in a randomised cross-over study of 25 volunteers. Local anaest-

hesia consisted of topical aerosol spray using either cocaine 5% or Co-phenylcaine Forte (a pro-

prietary mixture of phenylephrine hydrochloride 0.5% and lidocaine hydrochloride 5%), followed

by lidocaine gel. Topical anaesthesia using an atomiser resulted in incomplete analgesia for insertion

of nasopharyngeal airways. Larger diameter tubes resulted in higher pain scores. There was no

difference in pain scores between the two drugs.

Keywords Intubation, tracheal. Fibre optics; methods. Local anaesthetics; lidocaine. Sympathomimetics;

phenylephrine.

........................................................................................................

Correspondence to: Dr Andrew M. Norris


*Presented in part at the American Society of Anaesthesiologists Annual

Meeting, San Francisco, October 2000.


Awake tracheal intubation is an essential part of difficult

airway management [1–4]. The nasal route is often used,

and adequate analgesia is essential if the patient is to tolerate

the procedure without distress. Several local anaesthetic

techniques have been described [3–8], but there have been

few attempts to assess their effectiveness. We aimed to assess

the analgesic effectiveness of one technique of anaesthesia

using two different local anaesthetics, recording pain scores

associated with the passage of nasopharyngeal airways and a

tracheal tube through the nose.

Methods

Following Local Research Ethics Committee approval

and written informed consent, we recruited 25 healthy

volunteer subjects to the study. Exclusion criteria were

coagulopathy, a history of epistaxis, gross nasal deformity,

recent coryzal symptoms and sensitivity to local anaes-

thetic agents. Subjects were randomly allocated using

tables, and in blocks of four, to receive either cocaine 5%

or Co-phenylcaine Forte (phenylephrine hydrochloride

0.5% and lidocaine hydrochloride 5%, Paedpharm Pty

Ltd, East Perth, WA, Australia) on their first visit. The

alternative agent was used on the second visit 2 weeks

later. We kept the randomisation result for each subject in

a sealed envelope opened on the first visit. Both drugs

were prepared in batches at our pharmacy in identical

bottles marked A or B. The code was kept in the

pharmacy department until the results had been analysed.

A new bottle of the trial drug was decanted into the clean

chamber of a metered dose aerosol that delivered 100 ll

per spray for each visit.

Anaesthesia, 2003, 58, pages 775–803 Forum......................................................................................................................................................................................................................


At their first session, subjects were instructed in the use

of 100-mm visual analogue pain scales (VAS) anchored at

‘no pain’ and ‘worst pain imaginable’. Patency of the

subjects’ nasal passages was assessed as follows. The nostril

was occluded on one side without deviating the nasal

septum and the subject was asked to inspire maximally

through the other nostril. This was repeated following

occlusion of the opposite nasal passage. The subjects’

impression of which side allowed easiest inspiration was

recorded. We started ECG and non-invasive automated

blood pressure monitoring, recorded baseline values, and

sited an i.v. cannula. Five sprays (500 ll) of the trial drug

were initially applied to each nasal cavity. After approxi-

mately 5 min, patency of the nasal passages was re-assessed

using the methods described. Nasendoscopy using an

Olympus LF2 fibreoptic laryngoscope was then per-

formed. The inferior and middle meatus were identified

and an assessment of the most favourable side was made

considering the relative sises of the meatus and the

presence of anatomical obstructions such as spurs, polyps

or septal deviation. A 6-mm nasopharyngeal airway

(Portex Ltd, Hythe, Kent, UK) was coated in 2% lidocaine

gel and gently inserted into the nose as far as the flange,

first on one side and then the other. Visual analogue scores

and a verbal pain rating (none, mild, moderate, severe)

were recorded for each side. The side with the lowest VAS

was used for subsequent measurements. A 7-mm airway

and 6.5-mm nasotracheal tube (Polar Ivory Soft-Seal�Portex Ltd), also precoated in 2% lidocaine, were then

passed in the same way. We repeated pain assessments after

each manoeuvre. The nasotracheal tube was passed to

14 cm or whenever loss of resistance was felt as it entered

the nasopharynx. We recorded maximal heart rate and

blood pressure at 5-min intervals after inserting each tube.

Epistaxis was recorded on a four-point scale: none, mild

(blood-stained tube only), moderate (bleeding apparent),

severe (ongoing bleeding for 2 min or more). On the

second visit, the procedure was repeated in all respects

except that the same nostril, identified as the least painful

on the first visit, was used for airway and tube insertion

and subsequent pain measurements.

On designing the study, we aimed for a power of 80%

at the 5% significance level to identify a mean difference

in pain scores of 10 mm or more between the two drugs.

When the study was planned, the standard deviation of

the pain scores was unknown but estimated at 15 mm.

Using these figures in a paired design gave a sample size of

20 subjects [9]. Subjects’ characteristics, physiological

measurements, pain, and haemodynamic data were

recorded onto data sheets and subsequently entered into

a database (Access and Excel�, Microsoft Corp., Red-

mond, WA, USA). Data from VAS were inspected for

normality and compared using the two-tailed paired t-test.

Data from the verbal descriptive pain scale were analysed

using Fisher’s exact test. Statistical analysis was performed

using Minitab� 12 (Minitab Inc., State College, PA,

USA). A significance level of 5% was used throughout.

Results

Twenty-five subjects, 15 male, were recruited over a

9-month period. Their mean (SD) age was 29 (4.5) years,

their mean height 174 (10.6) cm and their mean weight

71 (13.7) kg. Volunteers included medical students,

surgeons, anaesthetists, nurses and theatre technicians.

Twenty-four subjects completed both parts. One subject

did not return for the second phase and her data were

excluded from the analysis. Two other subjects did not

tolerate the placement of one or more tubes. Data from

these subjects relating to the tubes that were tolerated

have been included. Pain scores were significantly greater

for the larger tube sizes than for 6-mm tubes but there

were no significant differences between the 7-mm and

the 6.5-mm tubes or between the two drugs (Table 1).

Table 1 Pain during insertion of 6-mm and 7-mm nasopharyngeal airways and 6.5-mm nasotracheal tubes after topicalisation of thenose with either cocaine 5% or Co-phenylcaine Forte. Values are number of subjects (proportion) or mean (SD). No significantdifferences between groups unless otherwise stated.

6-mm nasopharyngealairway; (n = 24)

7-mm nasopharyngealairway; (n = 23)

6.5-mm nasotrachealtube; (n = 22)

Co-phenylcaine Forte Cocaine Co-phenylcaine Forte Cocaine Co-phenylcaine Cocaine Forte

Verbal pain ratingNone ⁄ mild 10 (42%) 10 (42%) 5 (22%) 6 (26%) 6 (27%) 9 (41%)Moderate ⁄ severe 14 (58%) 14 (58%) 18 (78%) 17 (74%) 16 (73%) 13 (59%)

VAS* 40.3 (20.3) 37.2 (16.0) 47.6 (21.5) 44.1 (18) 50.1 (24.8) 45.0 (20.5)VAS (both drugs combined) 39.2 (18.5)† 46.9 (19.7) 47.6 (23.5)

*Visual analogue scale.†p = 0.003; 95% CI for difference 2.8–12.6.



There were no statistically significant differences in

heart rate or systolic ⁄ diastolic blood pressure between

treatments or between groups. One subject suffered a self-

limiting bradycardia (< 50 beats.min)1) during insertion

of the nasal tracheal tube on each visit. There was a small

(non-significant) increase in baseline mean heart rate

following administration of cocaine (3 beats.min)1; 95%

CI )1.7–7.8 beats.min)1) and a decrease following

administration of Co-phenylcaine Forte ()1.5 beats.

min)1; 95% CI )6.5–3.5 beats.min)1). Three subjects

experienced moderate epistaxis, one in the cocaine group

and two in the Co-phenylcaine Forte group (NS).

Discussion

This study has shown that, following aerosolised topical-

isation with cocaine 5% or Co-phenylcaine Forte, and

coating of all tubes with 2% lidocaine, placement of a

6-mm nasopharyngeal airway and subsequent ‘dilation’ is

associated with significant pain in unpremedicated vol-

unteers. Pain scores were at the upper limit of accept-

ability for placement of the smallest tubes and increased

with the larger tubes, with the added volume of the cuff

material appearing to be responsible for the similarity in

pain scores between the 7-mm airway and the 6.5-mm

nasotracheal tube. Subjects were not, however, blind to

the sizes of the tubes.

Pain scores were very similar with each drug though

neither provided reliable analgesia with this technique. In

particular, subjects reported that the sensation of pressure

was not abolished. Post-hoc power analysis using the SD

of the difference in pain scores shows a power of 80%

to detect a 10-mm change in pain scores between the

agents. Since all the analgesic trends were in favour of

Co-phenylcaine Forte, it is probable that cocaine offers

no analgesic benefit in this context. Surgeons and

anaesthetists have traditionally used nasal cocaine because

of its combined properties of vasoconstriction and local

anaesthesia. There are, however, several problems asso-

ciated with its use. In patients with cardiovascular disease,

the tachycardia, vasoconstriction and increase in blood

pressure are undesirable [10]. Cocaine use has been

shown to cause coronary artery vasoconstriction [11] and

the reduction in the myocardial oxygen supply ⁄ demand

ratio increases the chance of myocardial ischaemia.

Co-Phenylcaine Forte is a pre-prepared mixture of

phenylephrine 0.5% and lidocaine 5%, presented as a

metered dose aerosol. It is an effective alternative to

cocaine for flexible nasendoscopy and other procedures

[7, 12–14]. Phenylephrine causes hypertension and bra-

dycardia, though when the cardiovascular effects of a

1-ml nasal dose of Co-phenylcaine Forte forte in healthy

volunteers were examined by Stott et al. they found a

small increase in heart rate and blood pressure when

compared with the administration of the same dose of

lidocaine alone [15]. In the young fit individuals who

were recruited to our study, we did not observe any

cardiovascular instability in either treatment group apart

from the single subject who experienced bradycardia with

both drugs. However, our study was not designed with

sufficient power to differentiate the cardiovascular effects

of cocaine and Co-phenylcaine Forte, nor can we

distinguish between the direct effects of each agent and

the autonomic responses to the procedures performed.

The cardiovascular effects in an older population may be

quite different due to altered vascular compliance or

ischaemic heart disease. Finally, there are economic

benefits associated with using Co-phenylcaine Forte over

cocaine, particularly when the extra costs of dispensing

and storing a controlled drug are added (Miss K. Grimble,

Link Pharmacist, personal communication).

When difficulty with the airway is anticipated, awake

intubation is widely recommended, yet there is little

evidence to guide clinicians on which techniques for

preparing the airway to choose. Serial dilation of the nose

is a recognised technique [16], but it was associated with

unsatisfactory analgesia when assessed in this study. We

deliberately used a small aerosol dose because of concerns

over toxicity, especially regarding cocaine. Larger doses

of aerosolised Co-phenylcaine Forte might result in

improved analgesia, and total lidocaine doses up to

9 mg.kg)1 have been reported for awake intubation with

acceptable plasma levels [17]. Since only a small number

of patients in any one unit require awake intubation, we

believe that volunteer studies of this type could be used to

compare the efficacy of different local anaesthetic tech-

niques, drugs and equipment.

Acknowledgements

The study was financed by a grant from Keymed

Scientific Instruments, Southend-on-Sea, Essex, the

NHS Department of Anaesthesia and the Queens Medical

Centre Simulator Fund (inconvenience payments to

volunteers). Co-phenylcaine Forte was supplied free of

charge by Paedpharm Pty Ltd, East Perth, WA, Australia.

Tracheal tubes and airways were provided by Portex Ltd,

Hythe, Kent.

References

1 American Society of Anesthesiologists. Practice guidelines

for management of the difficult airway. A report by the

American Society of Anesthesiologists Task Force on

Management of the Difficult Airway. Anesthesiology 1993;

78: 597–602.



2 Gray AJG, Hoile RW, Ingram GS, Sherry K. The Report of

the National Confidential Enquiry into Perioperative Deaths

1996 ⁄ 1997. London: NCEPOD, 1998.

3 Stone DJ, Gal TJ. Airway management. In: Miller RD, ed.

Anesthesia, 5th edn. New York: Churchill Livingstone,

1999: 1414–48.

4 Janssens M, Hartstein G. Management of difficult intuba-

tion. European Journal of Anaesthesiology 2001; 18: 3–12.

5 Simmons ST, Schleich AR. Airway regional anesthesia for

awake fiberoptic intubation. Regional Anesthesia and Pain

Medicine 2002; 27: 180–92.

6 Kundra P, Kutralam S, Ravishankar M. Local anaesthesia for

awake fibreoptic nasotracheal intubation. Acta Anaesthesio-

logica Scandinavica 2000; 44: 511–16.

7 Latorre F, Otter W, Kleeman PP, Dick W, Jage J. Cocaine

or phenylephrine ⁄ lignocaine for nasal fibreoptic intubation?

European Journal of Anaesthesiology 1996; 13: 577–81.

8 Jenkins SA, Marshall CF. Non-invasive local anaesthesia for

nasal intubation. Anaesthesia and Intensive Care 1998; 26:

596.

9 Altman DG. Practical Statistics for Medical Research, 1st edn.

London: Chapman & Hall, 1991.

10 Hardman JG, Limbird LE, Gilman AG, eds. Goodman and

Gilman’s Pharmacological Basis of Therapeutics, 10th edn.

New York: McGraw-Hill, 2002.

11 Lange RA, Cigarroa RG, Yancy CW et al. Cocaine-in-

duced coronary artery vasoconstriction. New England Journal

of Medicine 1989; 321: 1557–62.

12 Gross J, Hartigan M, Schaffer D. A suitable substitute for 4%

cocaine before blind nasotracheal intubation: 3% lido-

caine)0.25% phenylephrine nasal spray. Anesthesia and

Analgesia 1984; 63: 915–18.

13 Lennox P, Hern J, Birchall M, Lund V. Local anaesthesia in

flexible nasendoscopy. A comparison between cocaine and

Co-Phenylcaine. Journal of Laryngology and Otology 1996;

110: 540–2.

14 Jonathan DA, Violaris NS. Comparison of cocaine and

lignocaine as intranasal local anaesthetics. Journal of

Laryngology and Otology 1988; 102: 628–9.

15 Stott SA, Michels AMJ, Sanders DJ, Riley RH. The

cardiovascular effects of nasal Co-Phenylcaine forte spray.

Australian Journal of Hospital Pharmacy. 1995; 25: 417–9.

16 Sanchez A, Trivedi N, Morrison D. Preparation of the

patient for awake intubation. In: Benumof JL, ed. Airway

Management: Principles and Practice. St. Louis: Mosby, 1995:

160–1.

17 Reasoner DK, Warner DS, Todd MM, Hunt SW, Kirchner

J. A comparison of anesthetic techniques for awake

intubation in neurosurgical patients. Journal of Neurosurgical

Anesthesiology 1995; 7: 94–9.

FORUM

Effect of supplemental pre-operative fluid on postoperative

nausea and vomiting*

S. Z. Ali,1 A. Taguchi,2 B. Holtmann3 and A. Kurz4†

1 Fellow, Division of Critical Care Medicine, 2 Fellow and 4 Associate Professor and Director, Division of Clinical

Research, 3 Associate Professor, Department of Anaesthesiology, Washington University School of Medicine, 660 S Euclid

Ave, Campus Box 8054, St. Louis, MO 63110, USA

Summary

In a prospective, double-blind, randomised controlled trial, we studied the effects of pre-operative

fluid load on post-operative nausea and vomiting. Eighty patients attending for laparoscopic

cholecystectomy or gynaecological surgery were randomly allocated to receive 2 ml.kg)1 (cons-

ervative) or 15 ml.kg)1 (supplemental) Hartmann’s solution intravenously, shortly before induction

of anaesthesia. During the operation, fluid management was identical in both groups. During

the first post-operative 24 h, post-operative nausea and vomiting occurred in 29 patients (73%) in

the conservative fluid group and nine patients (23%) in the supplemental fluid group (p ¼ 0.01).

Supplemental pre-operative fluid is an inexpensive and safe therapy for reducing post-operative

nausea and vomiting.

Keywords Complications: post-operative nausea and vomiting. Fluid therapy. Hypovolemia.



Correspondence to: Prof. A. Kurz


�Present address: Professor and Chairman, Department of Anesthesi-

ology, University of Berne, 3010 Berne, Switzerland.

*Presented in part at the American Society of Anesthesiologists’ Annual

Meeting, New Orleans; October 2001.


The incidence of post-operative nausea and vomiting

(PONV) in adults remains high despite new anaesthetic

drugs and anti-emetics [1–4]. Post-operative nausea and

vomiting is a leading cause of unexpected admission to

hospital following planned day surgery [5]. It has been

suggested that additional oxygen reduces the incidence of

PONV [6, 7], perhaps by increasing oxygenation of the

gut and thus preventing the subtle intestinal ischaemia

which may be caused by anaesthesia or surgery [8, 9].

However, additional oxygen may fail to show its

beneficial effect in low perfusion states. Most surgical

patients are hypovolemic due to overnight fasting and

bowel preparation without adequate pre-operative fluid

replacement. Consequently, euvolemia is often not

re-established until the post-operative period. Although

the incidence of post-operative nausea can be reduced

by peri-operative administration of plasmalyte [10] and

hetastarch [8, 9], studies of supplemental intravenous

fluids produce conflicting results with respect to PONV,

some showing minor gain mainly after discharge [10–12]

and others showing no effect [13, 14].

There are no prospective, randomised, double-blind

studies with Hartmann’s solution as a supplemental pre-

operative fluid. The aim of this study was to test the

hypothesis that supplemental administration of pre-opera-

tive Hartmann’s solution will decrease the incidence of

PONV.

Methods

With approval from the Clinical Ethics Committee at

Washington University Medical Center and written

informed consent, we studied 80 patients. All were ASA

physical status 1–2, aged 18–70 years, and scheduled

for laparoscopic or gynaecological surgery lasting at least

1 h. Patients were instructed to fast from the previous

midnight. We excluded patients who experienced nausea

and ⁄ or vomiting on the morning before surgery, were

taking anti-emetic drugs, or had documented disorders of

the cardiovascular, hepatic, renal, gastrointestinal, or

neurological systems. Patients scheduled for surgery at

noon or later were also excluded.

Patients were prospectively and randomly assigned to

one of two groups: those assigned to conservative fluid

management were given a pre-operative fluid load of

2 ml.kg)1 Hartmann’s solution, whilst patients assigned to

supplemental fluid were given 15 ml.kg)1. Randomisa-

tion was based on computer-generated codes that were

maintained in sequentially numbered opaque envelopes.

The fluid was administered in the pre-operative holding

area before induction of anaesthesia. The anaesthesia

provider, the post-operative study investigator and the

postanaesthesia care unit (PACU) nurses were blinded to

allocation of the groups, as were the patients.

An 18-G i.v. catheter was inserted in each patient and

2 mg midazolam given. Hartmann’s solution was then

administered according to the randomisation. Thiopental

(3–5 mg.kg)1), rocuronium (0.6–0.9 mg.kg)1) and fent-

anyl (1–3 lg.kg)1) were used for induction of anaesthesia.

A tracheal tube was placed and anaesthesia maintained

with sevoflurane (1.0–2.0%) in 70% nitrous oxide and

oxygen. Mechanical ventilation was controlled to main-

tain PE,CO2 near 4.7 kPa. Additional oxygen was given as

necessary to maintain SpO2 above 94%. A gastric tube was

positioned, left on low suction throughout surgery, and

removed just before the end of anaesthesia. Prophylactic

anti-emetics were not administered. Forced-air warming

was used to keep distal oesophageal temperature near

36 �C. The anaesthetic and intra-operative fluid manage-

ment was standardised. Intra-operative fluids were infused

at 5 ml.kg)1.h)1 for laparoscopic and 10 ml.kg)1.h)1 for

open abdominal procedures. Blood loss was replaced

with crystalloid in a 3 : 1 ratio. Variation in individual

requirements precluded giving each patient identical

amounts of anaesthesia. Fentanyl 50–100 lg, morphine

1–2 mg and ketorolac 30 mg were given incrementally

according to clinical signs. Monitoring included SpO2,

heart rate, blood pressure, ECG, oesophageal temperature,

capnography, tidal and minute volumes, and end-expir-

atory concentration of inhaled anaesthetic. Neuromuscu-

lar blockade was antagonised at the end of surgery with

0.05 mg.kg)1 neostigmine and 0.01 mg.kg)1 glycopyrro-

nium. Patients were given 100% oxygen during emer-

gence. Fentanyl, morphine and ketorolac were given for

post-operative analgesia as required, as above. Ondanse-

tron (4 mg i.v.) was used as a rescue anti-emetic when the

nausea score on a visual analogue scale (VAS; see below)

exceeded 50 mm and ⁄ or the patient vomited. Patients



stayed in the PACU for � 1 h, where they received

oxygen via nasal prongs at 2 l.min)1 to maintain SpO2

above 94%. They were then either sent to the step-down

unit for an additional hour before being discharged home,

or admitted to the hospital ward.

Appropriate morphometric characteristics, pre-opera-

tive laboratory values and historical factors that would

influence PONV were recorded, including a history of

PONV, motion sickness, medication, smoking and

alcohol abuse. Patients were asked to rate their nausea

on a 100-mm VAS at 15-min intervals throughout

recovery (0 ¼ no nausea; 100 ¼ the worst imaginable

nausea). A score of 50 mm or greater was considered

significant. Episodes of vomiting and the need for rescue

medication, and the time, dose, and route of all post-

operative drugs were noted. Patients were called at

home the next day and asked to rate their nausea and

report any vomiting since discharge (1–24 h). Nausea at

home was scored on the scale of 0 (none) to 100

(worst). Patients who were admitted to hospital after

surgery were questioned by an investigator to determine

severity of nausea and episodes of vomiting between

discharge from the PACU and the 24th post-operative

hour.

Sample size for this study was based on the following

assumptions: the expected risk of PONV in our patient

population was estimated with a simplified risk score.

This score counts the four major risk factors for PONV:

female gender, non-smoking status, a history of PONV

and use of post-operative opioids. Almost all patients

were expected to be females, 80% to be non-smokers,

20% to have a history of PONV, and almost all would

need post-operative opioids. This adds up to an average of

three risk factors per patient, which corresponds to 61%

risk of PONV [4]. Assuming two out of three patients

would suffer from PONV and expecting a reduction of

PONV by 50%, 40 patients per group would give 80%

power to show a significant difference between the

groups using an alpha of 0.05. Chi2 tests were used to

analyse the incidence of PONV. Unpaired, two-tailed

t-tests were used for normally distributed continuous data

and the Mann–Whitney rank-sum test for data that

were not normally distributed. A p-value < 0.05 was

considered statistically significant.

Results

Patients’ characteristics are shown in Table 1. Duration

of anaesthesia and use of i.v. fluids and drugs were similar

in the two groups (Table 2). There was no significant

difference between the haemodynamic variables during

the intra- and post-operative period. Fifty-two patients

(65%) were admitted to hospital, 25 in the conservative

management group (63%) and 27 in the supplemental

fluid group (68%). The incidence of nausea and vomiting

is shown in Table 3. Median (interquartile range [range])

VAS for nausea was higher in the conservative fluid group

than in the supplemental fluid group at 0–1 h (16 (0–32

[0–82]) vs. 0 (0–10[0–70]), respectively; p ¼ 0.013) and

over the 1–24-h study period (55 (30–70[0–100]) vs. 15

(0–55[0–100]), respectively; p ¼ 0.002). Twenty patients

(50%) in the conservative fluid group and eight (20%)

patients in supplemental fluid group required ondansetron

post-operatively (NS). There was no significant difference

in post-operative vomiting between the groups.

Discussion

The published material on the influence of peri-operative

fluids on PONV is inconsistent. While several favourable

effects could be demonstrated, the incidence of PONV

was not reduced in the studies of Keane et al. and Cook

et al. [13, 14]. Similarly, Spencer was unable to show a

significant difference in the early post-operative period

but showed a significant difference in the incidence of

nausea after 3 days [11]. In all the above studies,

supplemental fluid was administered intra-operatively.

Yogendran et al., who administered fluids before induc-

tion of anaesthesia, were unable to show a significant

difference in the early post-operative period but also

reported a decreased incidence of late post-operative

nausea [10]. In our study, there was no significant

difference in the incidence of nausea up to 1 h; however,

the VAS scores differed significantly in this early post-

operative period. As in the previous studies, we saw a

significant reduction in the incidence of PONV as well as

in the VAS scores during the 24 h following anaesthesia.

One difference in our study compared to previous work

is the magnitude of reduction of PONV (68%), compared

in the other studies – if there was an effect at all – to a

Table 1 Characteristics of patients randomly assigned to receive2 ml.kg)1 (conservative) or 15 ml.kg)1 (supplemental) Hart-mann’s solution before induction of anaesthesia. Values aremean (SD) or number (proportion).

Conservativen = 40

Supplementaln = 40

Age; years 41 (11) 39 (10)Weight; kg 82 (18) 75 (18)Females: males 36 : 2 34 : 2History of PONV 7 (18%) 6 (15%)Current smokers 7 (18%) 10 (25%)Type of surgery:

Laparoscopic 24 (60%) 23 (58%)Abdominal 16 (40%) 17 (42%)



reduction of 10–20% [10, 11]. While the other studies

were mainly of minor outpatient procedures, ours was in

patients undergoing laparoscopic and gynaecological sur-

gery. Also, these patients were at increased risk for PONV

because they were mainly females, non-smokers and

receiving post-operative opioids [4]. To our knowledge

this is the first study to identify such a strong effect of

supplemental fluids on early post-operative nausea.

The mechanism by which supplemental fluid therapy

reduces nausea remains unknown. However, peri-opera-

tive hypoperfusion of the gut mucosa and consequent

ischaemia might be one of the causes of PONV. Gut

ischaemia is common during anaesthesia and surgey [15–

20] and results in release of serotonin, which is one of the

most potent triggers of nausea and vomiting. Mythen &

Webb showed that peri-operative plasma volume expan-

sion reduced the incidence of abnormal intramucosal pH

in patients having elective cardiac surgery, and was

associated with improved outcome [9]. It was noted that

patients who maintained normal intramucosal pH had a

lower incidence of persistent PONV. Consistent with

these data is the finding that administration of additi-

onal oxygen decreases the incidence of PONV [6, 7].

However, even supplemental oxygen fails to increase

tissue oxygenation during hypovolaemia. Most of our

patients are hypovolaemic before induction of anaesthesia

secondary to overnight fasting, more so in those with

bowel preparation. Euvolaemia is often not re-established

until the post-operative period. Supplemental fluid load

before induction of anaesthesia most likely decreases the

volume deficit, thereby promoting euvolaemia. A posit-

ive effect on splanchnic perfusion might inhibit the

impending intestinal ischaemia. The observation that

females with orthostatic hypotension or with a blood

pressure decrease > 35% at induction of anaesthesia are

more prone to PONV supports this hypothesis [21, 22].

References

1 Koivuranta M, Laara E. A survey of postoperative nausea

and vomiting. Anaesthesia 1998; 53: 413–14.

Table 2 Duration of anaesthesia, and intravenous fluids and drugs given to patients randomly assigned to receive 2 ml.kg)1

(conservative) or 15 ml.kg)1 (supplemental) Hartmann’s solution before induction of anaesthesia. Values are mean (SD) or median(IQR [range]).

Conservative n = 40 Supplemental n = 40 p-value

Duration of anaesthesia; min 106 (48) 123 (41) 0.11Intravenous fluids:

Preoperative; ml 226 (212–240 [150–250]) 1215 (930–1500 [800–1700]) 0.001Intraoperative; ml 1100 (750–2200 [500–3500]) 1700 (1000–2500 [500–3600]) 0.12

Thiopental; mg 300 (250–375 [150–500]) 325 (250–400 [200–500]) 0.93Intraoperative analgesics:

Fentanyl; lg 200 (150–250 [100–500]) 250 (150–300 [100–750]) 0.56Morphine; mg 8 (6–10 [6–15]) 10 (9–11 [6–20]) 0.22Ketorolac; mg 30 (30–30 [30–60]) 30 (30–30 [15–30]) 0.19

Post-operative analgesics (0–1 h)Fentanyl; lg 100 (65–125 [0–150]) 50.0 (43.5–87.5 [0–100]) 0.08Morphine; mg 9.5 (4–11 [0–17]) 6 (2–11 [2–18]) 0.57Ketorolac; mg 30 (30–60 [30–60]) 30 (30–30 [30–30]) 0.53

Post-operative analgesics (1–24 h)Morphine; mg 24 (10–43 [0–48]) 10 (4–31 [2–58]) 0.14Ketorolac; mg 38 (15–60 15–90]) 45 (30–60 [30–75]) 1.00

Post-operative analgesics (0–24 h)Morphine; mg 23 (6.5–48 [0–51]) 14 (6–39 [2–76]) 0.39Ketorolac; mg 60 (45–75 [15–90]) 30 (30–60 [30–75]) 0.28

Table 3 Incidence of post-operative nausea and vomiting inpatients randomly assigned to receive 2 ml.kg)1 (conservative)or 15 ml.kg)1 (supplemental) Hartmann’s solution beforeinduction of anaesthesia. Values are number (proportion) ormedian (IQR [range]).

Conservativen = 40

Supplementaln = 40 p-value

0–1 h post-operativelyNausea n (%) 14 (35%) 5 (13%) 0.11Vomiting n (%) 3 (8%) 2 (5%) 0.97





2 Quinn AC, Brown JH, Wallace PG, Asbury AJ. Studies in

postoperative sequelae. Nausea and vomiting – still a prob-

lem. Anaesthesia 1994; 49: 62–5.

3 Kovac AL. Prevention and treatment of postoperative nausea

and vomiting. Drugs 2000; 59: 213–43.

4 Apfel CC, Laara E, Koivuranta M, Greim CA, Roewer N.

A simplified risk score for predicting postoperative nausea

and vomiting: Conclusions from cross-validations between

two centers. Anesthesiology 1999; 91: 693–700.

5 Wetchler BV. Postoperative nausea and vomiting in day-

case surgery. British Journal of Anaesthesia 1992; 69: 33S–39S.

6 Greif R, Laciny S, Rapf B, Hickle RS, Sessler DI. Sup-

plemental oxygen reduces the incidence of postoperative

nausea and vomiting. Anesthesiology 1999; 91: 1246–52.

7 Goll V, Akca O, Greif R et al. Ondansetron is no more

effective than supplemental intraoperative oxygen for pre-

vention of postoperative nausea and vomiting. Anesthesia and

Analgesia 2001; 92: 112–17.

8 Gan TJ, Mythen MG, Glass PS. Intraoperative gut hypop-

erfusion may be a risk factor for postoperative nausea and

vomiting. British Journal of Anaesthesia 1997; 78: 476.

9 Mythen MG, Webb AR. Perioperative plasma volume

expansion reduces the incidence of gut mucosal hypoper-

fusion during cardiac surgery. Archives of Surgery 1995; 130:

423–9.

10 Yogendran S, Asokumar B, Cheng DCH, Chung F. A

prospective randomized double-blinded study of the effect

of intravenous fluid therapy on adverse outcomes on out-

patient surgery. Anesthesia and Analgesia 1995; 80: 682–6.

11 Spencer EM. Intravenous fluids in minor gynecological

surgery: their effect on postoperative morbidity. Anesthesi-

ology 1988; 43: 1050–1.

12 Elhakim M, El-Sebiae S, Kaschef N, Essawi GH. Intra-

venous fluid and postoperative nausea and vomiting after

day-case termination of pregnancy. Acta Anaesthesiologica

Scandinavica 1998; 42: 216–19.

13 Keane PW, Murray PF. Intravenous fluids in minor surgery.

Their effect on recovery from anaesthesia. Anaesthesia 1986;

41: 635–7.

14 Cook R, Anderson S, Riseborough M, Blogg CE. Intra-

venous fluid load and recovery. A double-blind comparison

in gynaecological patients who had day-case laparoscopy.

Anaesthesia 1990; 45: 826–30.

15 Beuk RJ, Heineman E, Tangelder GJ, Kurvers HA, Bonke

HJ, Oude Egbrink MG. Effects of different durations of total

warm ischemia of the gut on rat mesenteric microcircula-

tion. Journal of Surgical Research 1997; 73: 14–23.

16 Gelman SE. Dillard , Bradley EL Jr. Hepatic circulation

during surgical stress and anesthesia with halothane,

isoflurane, or fentanyl. Anesthesia and Analgesia 1987; 66:

936–43.

17 Diebel LN, Dulchavsky SA, Wilson RF. Effect of increased

intra-abdominal pressure on mesenteric arterial and intestinal

mucosal blood flow. Journal of Trauma 1992; 33: 45–8.

18 Caldwell CB, Ricotta JJ. Changes in visceral blood flow

with elevated intraabdominal pressure. Journal of Surgical

Research 1987; 43: 14–20.

19 Annadata R, Sessler DI, Tayefeh F, Kurz A, Dechert M.

Desflurane slightly increases the sweating threshold but

produces marked, nonlinear decreases in the vasoconstriction

and shivering thresholds. Anesthesiology 1995; 83: 1205–11.

20 Matsukawa T, Kurz A, Sessler DI, Bjorksten AR, Merrifield

B, Cheng C. Propofol linearly reduces the vasoconstriction

and shivering thresholds. Anesthesiology 1995; 82: 1169–80.

21 Pusch F, Berger A, Wildling E, Tiefenthaler W, Krafft P.

The effects of systolic arterial blood pressure variations on

postoperative nausea and vomiting. Anesthesia and Analgesia

2002; 94: 1652–5.

22 Pusch F, Berger A, Wildling E et al. Preoperative orthostatic

dysfunction is associated with an increased incidence of

postoperative nausea and vomiting. Anesthesiology, 2002; 96:

1381–5.

FORUM

Orthopaedic theatre noise: a potential hazard to patients

M. R. Nott1 and P. D. B. West2

1 Consultant in Anaesthesia, and 2 Consultant in Audiological Medicine, Royal West Sussex Hospital, St Richard’s,

Chichester, PO19 4SE, UK

Summary

Potentially hazardous noise levels are generated in the course of major orthopaedic surgery. The

risk to staff is probably real but very small. We used a sound level meter to record maximum

and mean levels and found peak values which exceeded 100 dB(A). If sustained, there is a

possibility of significant inner ear damage and perhaps permanent troublesome tinnitus, especially

among elderly and already hearing-impaired patients. This could be eliminated by the use of

ear defenders or disposable earplugs.



Keywords Anaesthesia: general. Surgery: orthopaedic. ENT: hearing loss, tinnitus.

........................................................................................................

Correspondence to: Dr M. R. Nott



Noise has long been recognised as posing a threat to

hearing. Occupational noise induced hearing loss (NIHL)

became widespread as a consequence of the industrial

revolution and in 1886 the first account of deafness in

boilermakers appeared [1]. Hearing conservation pro-

grammes were introduced and interest in the causes of

noise widened to include those arising from medical

procedures. Measurements in the general operating

theatre environment [2] and in dental practice [3] have

been made previously but the use of noisy mechanical and

compressed air-powered tools in orthopaedic surgery is

comparatively recent.

Noise is measured logarithmically in decibels (dB) on a

scale such that an increase of 3 dB is equivalent to a

doubling of the noise dose. Exposure to 90 dB for 8 h is the

same as 105 dB for 15 min. The A-weighted scale, dB(A)

[4], is used in clinical practice as it filters out inaudible

frequencies to which the cochlea is insensitive.

Hearing is protected by the stapedius muscle which

attenuates transmission of loud sound to the cochlea by

rapid involuntary contraction [5]. This reflex is normally

activated by noise levels above 85 dB(A). Individuals vary

in their susceptibility but damage to the hair cells of the

inner ear has been reported following prolonged exposure

to noise over 90 dB(A) [6]. The stapedius is likely to be

paralysed by neuromuscular blocking agents. We were

concerned that the hearing of patients might be at risk

when the natural reflex mechanism was abolished.

Methods

We measured the noise levels in routine orthopaedic

surgery. The patients were undergoing general anaesthesia

for total hip or knee replacement and intramedullary

nailing, either insertion or removal, for fractures of the

femur or tibia. The study was approved by the hospital

ethics committee. Individual consent was not felt to be

needed because there were no changes to the normal

anaesthetic or surgical care of each patient.

Measurements of noise were made throughout each

operation or during related procedures using a Kamplex

SLM3 Type 2 (BS5969) precision sound level meter (P.C.

Werth Ltd, London, UK) placed on the pillow. The

instrument is calibrated annually in accordance with

standard procedures by Guymark UK Ltd (Cradley Heath,

UK). Time intervals were measured with a stopwatch. The

meter was set to record maximum sound first and then

‘slow response’ to approximate to the mean level. The

number and duration of sound bursts were noted. Impulse

noise caused by hammering when reaming a cavity or

fitting a prosthesis was recorded as the maximum reading.

Findings were combined to give the mean or median and

extreme range of values for each procedure.

Results

Noise levels were measured in 59 procedures involving

sawing, hammering, drilling and nailing. The usual

surgical instruments included an AO Universal saw and

Hall oscillating saw. The patients were 31 women aged

53–92 years (mean 75) and eight men aged 16–86 years

(mean 59).

The decibel scale is non-linear and therefore the peak

intensities are given as maxima or mean of these levels

within each group. Where the slow response setting of the

instrument had already provided a mean level in individual

patients, the value for the group is given as a median value.

The noisiest elective operation was total knee replace-

ment, at a maximum intensity of 101 dB(A) (mean 92.4),

only exceeded by the plaster saw at 104 dB(A) (mean

97.9), which in this case was recorded with the patient

awake (Table 1). These contrast with background noise at

50–60 dB(A) and ‘animated’ conversation at 83 dB(A).

Metallic bin lid closure, metal instruments placed on a

standard surgical trolley and compressed air line detach-

ment also rated highly (Table 2). The noisiest procedure

of all was removal of an intramedullary nail using a slap-

hammer, which peaked at 107 dB(A).

The knee replacements were performed by six different

surgeons. We found that the time taken for sawing varied

from 87 to 334 s (mean 208) and was shorter if the

surgeon was more experienced. Similarly, the number of

hammer blows used differed markedly, the insertion of

one intramedullary nail requiring 23 impacts.

Discussion

Previous studies of medical noise in dental practice where

high-speed gas turbine bone-cutting drills are used

concluded that the risk to staff was very slight indeed



[3]. However, there have been two reports of the early

signs of NIHL in 50% of those working in orthopaedic

theatres [7,8].

Noise induced hearing loss became a prescribed disease

in the United Kingdom in 1974 and the first stipulated

limits to daily personal noise exposure were published as

the Noise at Work Regulations 1989 [9]. These state that,

at the first action level, workers exposed to an average of

85 dB(A) or more over an 8-h day must have ear protection

if requested. Measurements of compressed air-powered

tools, in theatre although not during operations, have

shown that it is possible to exceed these levels [10]. The

second action level, exposure to an average of 90 dB(A) or

more, requires the provision of ear protection.

It is reasonable to assume that extreme values represent

the greatest risk to patients. We investigated the intensity

and duration of noise at or near one ear of the patients, and

report the maximum as well as mean or median values

found during actual surgery. Our results are similar to

values (with standard deviations) quoted for the AO

Universal attachment 98 (1.3) dB(A) or Hall surgical saw

89.3 (4.5) dB(A) [10] and are equal to 105 dB(A) reported

for air pipeline disconnection [11]. The period of intense

noise in each procedure was reassuringly brief. The time

required with various instruments before total noise

allowance exceeded the first action level has been

calculated to show that the longest permissible duration

for a plaster saw, the noisiest instrument in their report as

in ours, was 4.5 min [10]. The longest total time for

sawing in this study was just over 5.5 min, but with a

quieter instrument (Table 1), and the first action level

defined by the Noise at Work Regulations was unlikely to

have been breached.

What is the risk of a patient under general anaesthesia

sustaining a hearing deficit? Continuous low frequency

sound in the absence of the stapedius reflex is known to

produce a pronounced temporary threshold shift (TTS)

[12]. It has also been shown that TTS was significantly

greater on the paralysed side when subjects with a

unilateral lower motor neurone facial (Bell’s) palsy, which

usually affects the branch to stapedius, were exposed to

recorded shipyard noise at 102 dB(A) [3]. It is unclear

whether impulse noise is more [13] or less [5] damaging

than steady state noise. Stapedius does provide significant

protection against impulse noise [14] and can exhibit

fatigue in response to steady state noise [15]. Susceptible

individuals may suffer significant NIHL following a single

intense exposure, e.g. fireworks, but it would appear from

the impact noise levels reported here that the probability

of permanent hearing loss is small. Nevertheless, the risk

cannot be regarded as negligible as many patients under-

going joint replacement are elderly and likely to have a

pre-existing deficit, presbyacusis, which may increase the

possibility of additional damage. Neuromuscular blocking

drugs affect all striped muscles including stapedius, there-

fore the paralysed patient must surely be at greater risk

from impulse noise. Regional anaesthesia might be

thought to give protection but conscious patients must

also be regarded as vulnerable.

Tinnitus is a symptom that can be caused by noise and

may be more troublesome than marginal hearing loss. It is

difficult to quantify and its severity may be quite unrelated

to the extent of any cochlear damage. Seven per cent of

adults experience tinnitus severe enough to consult a

doctor [16] and the prevalence rises to 50–60% in workers

exposed to noise [15]. It is more frequent in the elderly and

is known to be triggered by relatively minor incidents

when there is an existing cochlear disorder [6]. A recent

report of two cases suggests that tinnitus can be exacerbated

by routine and, in terms of the total noise dose, quite trivial

Table 1 Peak and slow response sound levels and duration. Slow response time measurements were not obtained in all subjects.

OperationNo. ofpatients

Peak sound levels dB(A),mean (range)

Slow response sound levels dB(A),median (range of measurements);no. of patients

No. ofsaw bursts,mean (range)

Total duration,s mean (range)

Sawing, knee replacement 11 92.4 (86.5–101) 85 (75–95); 9 20 (10–29) 208 (87–334)Sawing, hip replacement 10 88.6 (81–89.5) 83.5 (60–88); 6 8 (6–11) 132 (85–158)Sawing, other 3 83.7 (82–87) 78 (77–87); 3 – –Hammering 14 87.6 (74–98) – – –Nailing 7 93 (83–107) – – –Drilling 10 81.6 (74–86) 75.5 (71–95); 10 – –Plaster saw 4 97.9 (92–104) 90 (85–95); 3 – –

Table 2 Environmental noise levels.

Procedure or event Peak level dB(A)

Quiet theatre 50–60Conversation, animated 83Instrument setting-up 94–104Bin lids closing 101.5–104Compressed air line detachment 105



supra-threshold tests [17]. Permanent tinnitus caused by

magnetic resonance imaging (MRI), where noise may

reach 93 dB(A) [18], has been seen by one of the authors

(P.D.B.W.) in two patients with pre-existing hearing loss.

This level is less than measured in our theatres. Safeguard-

ing the hearing of patients in dental surgery has already

been suggested [19] and it is current policy in many MRI

units to fit earplugs [20]. Similar measures might be taken

in all operating departments, using either industrial ear

defenders (e.g. ARCO Hollman Nicholls, Orpington) or

conventional ear plugs. We consider that there is some risk

and that the hearing of these patients should be protected.

References

1 Barr T. Enquiry into the effects of loud sounds upon the

hearing of boilermakers and others who work amid noisy

surroundings. Transactions of the Philosophical Society of Glasgow

1886; 17: 223–39.

2 Kam PCA, Kam AC, Thompson JF. Noise pollution in the

anaesthetic and intensive care environment. Anaesthesia

1994; 49: 982–6.

3 Coles RRA, Hoare NW. Noise-induced hearing loss and

the dentist. British Dental Journal 1985; 159: 209–18.

4 ISO. Acoustics – expression of physical and subjective

magnitudes of sound or noise in air, ISO 131. Geneva:

International Organization for Standardization, 1979.

5 Zakrisson J-E, Borg E, Liden G, Nilsson R. Stapedius reflex

in industrial impact noise: fatigability and role for temporary

threshold shift (TTS). Scandinavian Audiology 1980; 12

(Suppl): 326–34.

6 Ward WD. General auditory effects of noise. Otolaryngologic

Clinics of North America 1979; 12: 473–92.

7 Kamal SA. Orthopaedic theatres: a possible noise hazard?

Journal of Laryngology and Otology 1982; 96: 985–90.

8 Willett KM. Noise-induced hearing loss in orthopaedic staff.

Journal of Bone and Joint Surgery [British] 1991; 73-B: 113–5.

9 HMSO. The Noise at Work Regulations. Health and Safety

Executive, no. 1790. London: HMSO, 1989.

10 Dodenhoff RM. Noise in the orthopaedic operating

theatre. Annals of the Royal College of Surgeons of England

1995; 77(Suppl.): 8–9.

11 Hodge B, Thompson JF. Noise pollution in the operating

theatre. The Lancet 1990; 335: 891–4.

12 Zakrisson J-E, Borg E, Diamant H, Møller AR. Auditory

fatigue in patients with stapedius muscle paralysis. Acta

Otolaryngologica 1975; 79: 228–32.

13 Sulkowski WJ, Kowalska S, Lipowcza A. Hearing loss in

weavers and drop forge hammermen: comparative study on

the effects of steady state and impulse noise. In: Rossi G, ed.

Proceedings of the 4th International Congress on Noise as a Public

Health Problem, Vol. 1. Milan: Centre Richerchie e Studi

Amplifon, 1983: 171–84.

14 Rossi G. Acoustic reflex amplitude and response to con-

tinuous noise and impulse noises with the same energy

content. In: Rossi G, ed. Proceedings of the 4th International

Congress on Noise as a Public Health Problem, Vol. 1. Milan:

Centre Richerchie e Studi Amplifon, 1983: 185–91.

15 Alberti PW. Noise and the ear. In: Kerr AG, ed. Scott-

Brown’s Otolaryngology, 6th edn. Vol. 2: Adult Audiology

(Stephens D, ed.) Oxford: Butterworths, 1997.

16 Davis A. Hearing in Adults. The Prevalence and Distribu-

tion of Hearing Impairment and Reported Hearing

Disability in the MRC Institute of Hearing Research’s

National Study of Hearing. London: Whurr, 1995.

17 Coles R. Case study: a word of caution. British Society of

Audiology 2001; Newsletter 32: 20–2.

18 Shellock FG, Kanal E. Auditory effects of MR procedures.

In: Magnetic Resonance: Bioeffects, Safety, and Patient Manage-

ment. New York: Raven Press, 1994.

19 Ray CD, Levinson R. Noise pollution in the operating

room: a hazard to surgeons, personnel and patients. Journal of

Spinal Disorders 1992; 5: 485–8.

20 Brummett RE, Talbot JM, Charuhas P. Potential hearing

loss resulting from MR imaging. Radiology 1988; 169: 539–40.

FORUM

Transurethral vaporisation of the prostate and irrigating

fluid absorption

R. A. Gray,1 A. H. Moores,2 M. Hehir3 and M. Worsley4

1 Provisional Fellow, Anaesthetic Department, Toowoomba Hospital, Toowoomba, Queensland, Australia, 2 Specialist

Registrar, 4 Consultant, Department of Anaesthesia and Intensive Care, Stirling Royal Infirmary, Stirling, FK8 2AU,

Scotland, UK, 3 Consultant, Department of Urology, Stirling Royal Infirmary, Stirling, FK8 2AU, Scotland, UK

Summary

Transurethral vaporisation of the prostate gland (TUVP) is an emerging surgical alternative to

conventional electroresection (TURP). This study examined vesical pressure and fluid absorption



during TUVP in 35 patients with benign prostatic hypertrophy. The irrigating fluid was a solution

of glycine 1.5% and ethanol 1%. Intraoperative intravesical pressure was monitored continuously

and absorption of irrigating fluid was detected by ethanol analysis in expired breath. The incidence

of absorption during TUVP was 34%. Intravesical pressures were higher amongst patients who

went on to absorb than amongst patients who did not. Combining data from the current study and

from 35 patients in our previous investigation into TURP (Gray et al.: Anaesthesia 2001; 56:

461–4), urological trainees operated at higher mean pressure and for longer than their consultant

colleagues and their resections were significantly more likely to result in absorption. The incidence

of irrigating fluid absorption during trainees’ operations appeared to be less using TUVP than using

conventional TURP.

Keywords Prostate: transurethral resection. Complications: TUR syndrome.

........................................................................................................

Correspondence to: Dr M. Worsley



Several ‘minimally invasive’ alternatives to traditional

transurethral resection of the prostate gland (TURP) have

emerged in recent years. The search for alternatives has

been driven by a desire to reduce surgical complications and

anaesthetic requirement, generally at the expense of efficacy

[1,2]. These have included transurethral incision of the

prostate, transrectal and transurethral thermotherapy, cry-

otherapy, focused ultrasound, side-firing diffusing, incising

and contact laser techniques and electrovaporisation [3].

Transurethral electrovaporisation of the prostate gland

(TUVP) is the newest of these technologies [1,4]. It uses a

conventional current generator but a specially shaped

probe that delivers higher energies and higher current

density. TUVP is similar procedurally to TURP [2,5].

The probe is moved more slowly during resection while

vaporizing and resecting the prostate tissue. Early results

suggest it to be the most effective of the newer surgical

therapies, demonstrating an efficacy approaching that of

TURP in the treatment of benign prostatic hyperplasia

[2,5,6]. Peri-operative bleeding is less than during

conventional TURP [4], allowing treatment of selected

patients with coagulation problems and dispensation

with routine postoperative bladder irrigation by some

operators [5,7].

There remains considerable doubt as to the extent of

fluid absorption when vesical irrigation is used with these

new surgical therapies. Given a 46% incidence during

conventional TURP (as detected by the well-established

and highly sensitive expired breath ethanol method [8]),

it seems reasonable to assess absorption in these newer

therapies. Absorption during laser prostatectomy has been

investigated by expired breath ethanol [9] but TUVP has

not been studied in this way.

We have previously demonstrated a positive relation-

ship between exposure to excessive bladder pressure and

the individual risk factors for irrigant absorption during

TURP: operator experience, operation duration and mass

of resectate all covary with vesical pressure as risks for the

TUR syndrome [10]. In the current study, we used

similar techniques to investigate irrigating fluid absorption

during TUVP to establish its incidence and to establish

whether patterns of pressure exposure predispose to

absorption as during TURP.

Methods

Local institutional ethical approval was obtained. Using

previous work [10], we calculated 35 cases to be necessary

for a study of 85% power in detecting one estimated

standard deviation of pressure difference between patients

who absorb and patients who do not, with a type I error

of 5%. Patients scheduled for elective TUVP were

included in the study and written, informed patient

consent was obtained in every case. Patients with known

alcohol sensitivity or ASA grade III or worse were not

studied.

The study method was similar to that of our previous

investigation [10] in that patients were premedicated

with oral temazepam prior to spinal anaesthesia using

0.5% hyperbaric bupivacaine and conscious sedation

using small doses of intravenous midazolam if needed.

Systolic arterial pressure was maintained with fluids and

vasopressors.

Electrovaporisation was performed using the second

generation Karl Storz resection ⁄ vaporisation loops (the

pearly loop and the wedge electrode). The energy source

was an Eschmann DS402S diathermy unit using settings

of 200 watts cut and 80 watts coagulation. The operations

were consecutive and unselected, no attempt being made

to influence the experience of the operator.



Vesical pressure was transduced continuously through

an 18-gauge epidural catheter (SIMS Portex Ltd, Hythe,

Kent, England) placed suprapubically. All measurements

were made relative to the mid axillary line and were

analysed in 5-min epochs. The area under the pressure-

time curve was also calculated for each patient and

expressed as a ‘pressure-time (p-T) product’. Irrigating

fluid was a commercial solution of glycine 1.5% and

ethanol 1% (Baxter Healthcare Ltd, Thetford, Norfolk,

England) held 90 cm above the pubic tubercle and

evidence of absorption was sought at the end of each

5-min epoch by testing expired breath for ethanol

using a commercial analyser (Alcolmeter S-D2, Lions

Laboratories, Barry, Vale of Glamorgan, Wales) [8,9].

Patients were classified as ‘absorbers’ if ethanol was

detected in the breath at any time intra-operatively or

immediately postoperatively. Our methodology used this

sensitive technique to detect absorption but did not

attempt to quantify it, as we felt that once absorption was

detected we were ethically obliged to act to prevent its

continuation. Pressure measurements after detectable

absorption were therefore ignored for the analysis.

Statistical tests used were Student’s t-tests, and Chi-square

tests.

Results

We recruited 35 patients. None was symptomatic for the

TUR syndrome and there were no complications related

to our study technique.

Incidence of absorption

Of the 35 patients recruited, 12 (34%) were found to

have absorbed irrigating fluid. We did not detect the

prolonged operation time for TUVP reported by other

investigators [11, 12]. The mean (SD) duration of

resection in this study was 31.4 (14.3) min.

Pressure pattern and absorption

Overall, mean vesical pressure during resection was

higher in patients destined to absorb irrigating fluid

(20.1, SD 8.5 mmHg) than in patients who never

absorbed (15.4, SD 8.4 mmHg; p ¼ 0.0015). The

tendency to higher pressure was consistent throughout

the period of resection in this group (Fig. 1). The mean

of absorbers’ peak pressures for 5-min epochs (29.2, SD

10.7 mmHg) was likewise higher than those of non-

absorbers (24.4, SD 12.3 mmHg; p ¼ 0.010).

Operator experience

Absorption occurred in eight (42%) of the cases per-

formed by trainees, and four (25%) of the operations

performed by consultants (Table 1). This was not a

significant difference. Trainees’ operations were longer

(mean duration 31 min) than consultants’ (26 min,

p ¼ 0.035). The pressure characteristics according to

operator experience are shown in Table 2.

Non-Absorbers

Absorbers30

25

20

15

10

10 20 30 40 50

Pre

ssu

re (

mm

Hg

)

Time (minutes)

95%

Co

nfi

den

ce In

terv

als

5

0

Figure 1 The mean intravesical pressure by period of resectionin absorbing and non-absorbing patients. For the sake of clarity,confidence intervals are omitted once fewer than three patientsremain.

Table 1 Incidence of absorption by technique and by operator.*

Consultant operator* Trainee operator*

TURP TUVP TURP† TUVP†

Non-absorbers 16 (89%) 12 (75%) 4 (24%) 11 (58%)Absorbers 2 (11%) 4 (25%) 13 (76%) 8 (42%)

All values expressed as number of patients (% of column total).*Operator experience influences risk of absorption (p = 0.00047;v2 = 12.216). †Type of resection influences absorption in operationsperformed by trainees (p = 0.0368; v2 = 4.359). ‘TURP’ refers to datacollected by the authors and reported in Gray et al. [10].

Table 2 Mean vesical pressure by operator and by technique.

Consultant operator Trainee operator‡

TURP TUVP TURP TUVP

Non-absorbers 11.1 (5.0) 13.7 (6.2) 17.3 (7.8) 17.0 (7.3)Absorbers 18.8 (3.9) 18.6 (4.5) 19.4 (6.4) 20.6 (8.8)Overall mean 12.0 (5.4) 14.9 (6.1) 18.9 (6.5) 18.5 (7.9)

All values as mean (SD) in mmHg. ‡Mean pressures during resectionsperformed by trainees higher than during those performed by con-sultants (p = 0.0013 by Student’s t-test). No significant difference byoperative technique in either operative group. ‘TURP’ refers to datacollected by the authors and reported in Gray et al. [10].



Discussion

Incidence of absorption

Studies purporting to assess absorption during TUVP

have used relatively insensitive measures such as a change

in haematocrit, serum sodium reduction and symptom

reporting [5,6]. Volumes of absorbed fluid required to

produce hyponatraemia or symptoms are of the order of

1500 ml or more, but the alcohol absorption method

popularised by Hahn is more sensitive, detecting absorp-

tions of around 200 ml [13,14]. Thus, studies based on

alcohol labelling are more effective in demonstrating the

safety of prostate resection and irrigation techniques.

Shokeir et al. [6] and Grundy et al. [7] demonstrated

less evidence of absorption during TUVP than TURP.

However, both studies showed slight falls in serum

sodium from baseline levels indicating the possibility that

some absorption had indeed taken place during TUVP,

albeit less than during TURP.

This study demonstrates an incidence of absorption

during TUVP of 34%. This compares favourably with the

43% incidence in our TURP series, which used otherwise

similar methodology [10]. TUVP may carry less risk of

absorption than TURP, but clearly there is a risk of

absorption in both techniques. Comparison with histor-

ical data is not ideal, but as the methodology was identical

in both studies, the results retain validity. A prospective,

randomised controlled trial using alcohol labelling to

compare absorption between TURP and TUVP might

confirm the difference.

The mean (SD) time to first detectable absorption in

the present study was 14 (10.5) min, comparable to the

19 (10.6) min seen amongst TURP patients in our earlier

study [10]. The temporal pattern of absorption incidence

was otherwise similar to that seen during conventional

resection.

As in the TURP series, once absorption was detected,

steps were taken to minimise further absorption in order

to protect the patient from possible harm. No quantifi-

cation of the absorbed fluid was therefore possible, other

than to say that the minimum volume detectable by the

system (200 ml) had been absorbed.

Pressure pattern and absorption

The results of this study confirm that intravesical pressure

is the major risk factor for irrigating fluid absorption

during TUVP (Fig. 1). As during TURP, high mean

pressures were associated with absorption, but the higher

‘pressure exposure’ as expressed by the p-T product was

not found among the absorbers. This may be due to the

abandonment of data recording after absorption, which

reduces the measured p-T product in the absorbing group

but not in the non-absorbers.

Overall, within each operator group, similar patterns of

pressure and pressure exposure are seen during TUVPs as

during the previous TURPs. However, further compar-

ison with our TURP data [3] revealed a slightly higher

mean vesical pressure amongst non-absorbing patients in

the TUVP group than amongst non-absorbing TURP

patients. No other pressure differences could be demon-

strated between the subgroups of these study samples

(Table 3).

A lower incidence of absorption despite similar oper-

ating pressures suggests a degree of safety inherent in the

vaporisation technique. There is a non-significant trend

towards a lower incidence of absorption during TUVP

than during TURP. Our non-absorbing TUVP patients

had higher mean pressures than those in the TURP study.

Therefore, it may be that vaporisation prostatectomy is

more ‘forgiving’ of high pressures (see Table 3). Perhaps

impedance to irrigant flow across the prostatic bed is

greater during TUVP because vessel openings are likely

to be sealed during ‘vaporisation’, preventing the intra-

vascular component of the absorption syndrome. This

would be conceptually consistent with the observed

tendency to reduced blood loss [4].

Operator experience

Trainees operate for longer and at higher pressure than

experienced operators, regardless of the ablation modality

(Tables 2 and 3). Their operations carry a higher risk of

irrigant fluid absorption (Table 1).

In our previously reported TURP study [10], irrigant

absorption was found to be more prevalent in operations

performed by trainees. ‘Training TUVP’ may carry a

lower incidence of absorption (42%) than ‘training

TURP’ (76%). No such trend is evident in operations

performed by consultants (Table 1).

Table 3 Pressure parameters by technique.

Parameter TUVP TURP p-value**

Operation duration (min) 31.4 (14.3) 29.9 (14.4) NS

Mean vesical pressure (mmHg)–Absorbers 20.1 (8.5) 19.1 (7.7) NSNon-absorbers 15.4 (8.4) 12.4 (6.5) 0.015

Peak vesical pressure– (mmHg)Absorbers 29.2 (10.7) 33.8 (10.5) NSNon-absorbers 24.4 (12.3) 25.5 (12.1) NS

Pressure-Time product (mmHg, min)Absorbers 336 (254) 458 (237) NSNon-absorbers 415 (249) 307 (183) NS

‘TURP’ refers to data collected by the authors and reported in Gray et al.2000. –‘Mean Vesical Pressure’ refers to overall mean pressure for thesample. ‘Peak Vesical Pressure’ refers to the arithmetic mean of peakpressures for 5-min epochs. **All comparisons by Student’s t-test.



Of particular interest is the apparent reduction in

trainees’ absorption with the change to TUVP. This

improvement may represent safety intrinsic to prostate

vaporisation, or perhaps trainees find TUVP easier and

can resect a given prostate mass more quickly and at lower

pressure. The remarkable similarity of pressure indices by

operating technique (Tables 2 and 3) indicates that this

reduction in the incidence of absorption is not due to

lower pressure but perhaps to inherent safety of TUVP.

On the current data, we suggest that TUVP is a safer

technique for trainee resectionists than TURP. This

improvement was not seen in the TUVPs undertaken by

consultants. As TUVP was a new technique, it may be

that consultant operators were themselves undergoing a

training process, whereas during the previous TURP

series they were using a practised technique.

We have again demonstrated the significance of intra-

vesical pressure in the absorption of irrigating fluid during

prostate ablation. TUVP and other new ablative modalities

may have significant safety advantages over conventional

resection. The risk of fluid absorption is one part of the

side-effect spectrum that should be investigated thor-

oughly in these emerging technologies, if only because it is

eminently preventable. Urology trainees will benefit from

careful attention to low-pressure operating techniques and

active surveillance of bladder pressure in a manner such as

used in our study. Perhaps vaporisation prostatectomy

should be the technique of choice whilst learning.

References

1 Fitzpatrick JM. A critical evaluation of technological inno-

vations in the treatment of symptomatic benign prostatic

hyperplasia. British Journal of Urology 1998; 81 (Suppl. 1): 56–63.

2 Schatzl G, Madersbacher S, Lang T, Marberger M. The early

postoperative morbidity of transurethral resection of the

prostate and of 4 minimally invasive treatment alternatives.

Journal of Urology 1997; 158: 105–11.

3 Khoury S. Future directions in the management of benign

prostatic hyperplasia. British Journal of Urology 1992;

70 (Suppl. 1): 27–32.

4 Thomas KJ, Cornaby AJ, Hammadeh M, Philp T, Matthews

PN. Transurethral vaporization of the prostate: a promising

new technique. British Journal of Urology 1997; 79: 186–9.

5 Hammadeh MY, Fowlis GA, Singh M, Philp T. Transure-

thral electrovaporization of the prostate – a possible alter-

native to transurethral resection: a one-year follow-up of a

prospective randomized trial. British Journal of Urology 1998;

81: 721–5.

6 Shokeir AA, Al-Sisi H, Farage YM, El-Maaboud MA, Saeed

M, Mutabagani H. Transurethral prostatectomy. a pros-

pective randomized study of conventional resection and

electrovaporisation in benign prostatic hyperplasia. British


7 Grundy PL, Budd DWG, England R. A randomized con-

trolled trial evaluating the use of sterile water as an irrigation

fluid during transurethral electrovaporization of the prostate.

British Journal of Urology 1997; 80: 894–7.

8 Hahn RG, Ekengren JC. Patterns of irrigating fluid

absorption during transurethral resection of the prostate as

indicated by ethanol. Journal of Urology 1993; 149: 502–6.

9 Cummings JM, Parra RO, Boullier JA, Crawford K,

Petrofsky J, Caulfield JJ. Evaluation of fluid absorption

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sure and the TUR Syndrome. Anaesthesia 2001; 56: 461–4.

11 Hahn RG. Ethanol monitoring of irrigant absorption in

transurethral prostatic surgery. Anesthesiology 1988; 68:

867–73.

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absorption during TURP by marking the irrigating

solution with ethanol. Scandinavian Journal of Urology

and Nephrology 1986; 20: 245–51.

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marking the irrigating fluid with 1% ethanol. Acta

Anaesthesiologica Scandinavica 1989; 33: 146–51.

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as tracer. Scandinavian Journal of Urology and Nephrology 1989;

23: 103–8.

FORUM

To shape or not to shape…Simulated bougie-assisted

difficult intubation in a manikin*

I. Hodzovic,1 A. R. Wilkes2 and I. P. Latto3

1 Senior Lecturer, Department of Anaesthetics and Intensive Care Medicine, 2 Senior Research Fellow, Department of

Anaesthetics and Intensive Care Medicine and 3 Consultant Anaesthetist, University Hospital of Wales, Heath Park,

Cardiff, CF14 4XW, UK



Summary

Thirty anaesthetists attempted to place a derived ‘optimal’ curve bougie or a straight bougie in

the trachea of a manikin, in a randomised cross-over study. A Grade 3 Cormack and Lehane

laryngoscopic view was simulated. The anaesthetists were blinded to success (tracheal placement) or

failure (oesophageal placement). The success rates with the curved and straight bougies were 83 and

7%, respectively, giving a difference (95% confidence interval) of 77% (54–87%) between the two

bougies (p < 0.0001). On a separate occasion, under identical laboratory conditions, 30 anaesth-

etists attempted to place a straight coude (angled)-tipped bougie or a straight straight-tipped bougie

in the trachea of a manikin. The success rates with the coude- and straight-tipped bougies

were 43 and 0%, respectively, giving a difference (95% confidence interval) of 43% (21–61%)

between the two bougies (p < 0.001). These results suggest that bougies used to facilitate

difficult intubation should be curved and have a coude tip.

Keywords Equipment: gum elastic bougie. Intubation, tracheal.

........................................................................................................

Correspondence to: I. Hodzovic

*Abstract presentation of the ‘Tip study’ at a doctors’ update,

Belle Plagne France, 27–31 January 2003.

Accepted: 25 March 2003

The gum elastic bougie is widely used in clinical practice

in the UK. We recently noted that many anaesthetists do

not curve the bougie when using it in clinical practice.

There is, however, no information on whether it is

necessary to curve the bougie to improve the success rate

for passage of the bougie into the trachea. There is also no

information on the shape that anaesthetists consider to be

optimum when faced with a Grade 3 Cormack and

Lehane laryngoscopic view. The coude (angled) tip of the

bougie was introduced by Venn in 1973 [1]. There have

been assertions that the coude tip would be helpful in

facilitating intubation [2–5], but this has not been

verified.

We therefore decided to determine the proportion of

anaesthetists who would curve the bougie when faced

with a restricted laryngoscopic view; to derive a ‘optimal’

bougie curve using the bougie curves chosen by anaes-

thetists during a survey; and to investigate on a manikin

whether a curved bougie shape is more effective than a

straight bougie. In addition, we investigated whether the

coude (angled) tip of a multiple-use bougie is more

effective in facilitating passage into the trachea than the

straight (nonangled) tip of a bougie (Table 1).

Methods

The local research ethics committee considered that

ethical approval for this study was unnecessary.

A Laerdal Airway Intubation Trainer (Laerdal Medical

Ltd, Orpington, UK) was used in all experiments. Before

the start of each study, the manikin was arranged to

simulate a Grade 3 Cormack and Lehane laryngoscopic

view [6] (only the tip of the epiglottis could be seen) and

was not altered for the duration of the study. The

laryngoscope blade (Macintosh size 3) was fixed into

position using a retort stand and a clamp (Fig. 1). The

anaesthetists present in the department at the time of the

study were invited to participate. They were informed

what the study entailed and were given the opportunity

not to participate. None declined to take part. All had

at least one year’s experience of using bougies. Multiple-

use gum elastic bougies (Eschmann Healthcare Tracheal

Tube Introducer, SIMS Portex, Hythe, UK) were used

in each of the experiments. The randomisation code was

generated according to a program written using LABVIEW

(Version 2.2.1 National Instruments) running on a

PowerMac Macintosh (Apple) computer.

Shape survey

We surveyed anaesthetists at the University Hospital of

Wales in Cardiff and the Royal Gwent Hospital in

Newport. Thirty-five anaesthetists, 13 from the Univer-

sity Hospital of Wales and 22 from the Royal Gwent

Hospital, were asked whether they routinely shaped the

bougie when faced with a Grade 3 Cormack and Lehane

laryngoscopic view. We also recorded the name and

grade of anaesthetist; previous anaesthetic experience and

previous experience with a bougie (in years). The survey

was completed during the first two weeks of July 2002.

Each of the anaesthetists who said that they shaped the

bougie routinely was shown a Laerdal Airway Intubation

Trainer set to simulate a Grade 3 Cormack and Lehane



laryngoscopic view and asked to curve the experimental

bougie into what he ⁄ she considered to be the optimum

shape for intubation.

The experimental bougie was a coude-tipped, mul-

tiple-use gum elastic bougie that had two 1.38 mm

standard gauge copper wires twisted together and inserted

through the hollow lumen reaching to 5 cm from the tip

of the bougie. The moulded bougie maintained the

chosen shape. The bougie shape was photocopied onto

the back of the survey form and later transferred onto

drawing film paper. Twenty of 35 anaesthetists routinely

shaped the bougie. Shapes fell into three groups (Fig. 2): a

middle group with 10 bougie shapes and top and bottom

groups with 5 bougie shapes each.

Deriving ‘optimal’ shape

From the bougie shapes chosen by anaesthetists during

the survey, we went on to derive the ‘optimal’ bougie

shape. Six perpendicular lines were drawn across the

curvatures of each of the three groups, roughly equidis-

tant (Fig. 3). The perpendicular lines were used to derive

a bougie shape representative of each of the three groups.

The distance of each bougie shape in the group from the

bottom of the perpendicular line was measured using dial

calliper (Mitutoyo Dial Calliper) with an accuracy of

0.1 mm (Fig. 3). The mean distance was calculated and

marked on each of the perpendicular lines. A ‘mean’

shape of each of the three groups was drawn through the

mean distance marks on the six perpendicular lines drawn

across each of the groups of bougie shapes (Fig. 3). The

‘mean’ shape of the middle group was taken to be an

‘optimal’ bougie shape to be used in the next experiment.

Shape study

We invited 30 anaesthetists, 12 consultants and 18 train-

ees of various grades, to participate in the study that

Figure 1 The Laerdal Airway Management Trainer arranged tosimulate a Grade 3 Cormack and Lehane laryngoscopic view.

Table 1 The outline of the investigation.

InvestigationNo. ofanaesthetists

Shape survey: Do you shape the bougie? If so,how much?

35

Deriving the ‘optimal’ bougie shape 20‘Optimal’ shape vs. straight bougie shape(‘shape study’)

30

Straight bougie: coude tip vs. straight tip (‘tip study’) 30

Figure 2 Twenty bougie shapes trans-ferred onto drawing film paper. The‘hooked’ end represents the tip of thebougie.



compared simulated difficult intubation with a curved

gum elastic bougie, fixed in the ‘optimal’ shape, and a

straight bougie, both coude-tipped.

The Grade 3 Cormack and Lehane laryngoscopic view

was maintained for the duration of the study. Each

anaesthetist attempted placement of both the ‘optimal’

curve and straight bougies in the trachea in random order.

The randomisation code ensured that equal numbers of

anaesthetists used the ‘optimal’ curve and straight gum

elastic bougies first. Three ‘optimal’ curve bougies and

six brand new gum elastic bougies were used in rotation.

The investigator held either the straight bougie or the

‘optimal’ curve bougie and passed it to the anaesthetist,

who was not allowed to manipulate the laryngoscope or

change the shape of the bougies, alter the head position

or apply external laryngeal pressure. The anaesthetist

was asked to hold the bougies 20 cm from the tip. A

stopwatch was started when the anaesthetist took the

bougie. The anaesthetist placing the bougie was blinded

as to whether the bougie was placed in the trachea or in

the oesophagus. The investigator noted the placement by

observing the tracheal and oesophageal apertures of the

manikin from below. The time taken to place the bougie

was also recorded. Tracheal intubation over the bougie

was not attempted.

Tip study

In a separate study, 30 anaesthetists: 9 consultants, 19

trainees of various grades and 2 other anaesthetists whose

grades were not recorded, were invited to participate.

None declined to take part.

We closely followed the method from the previous

curved vs. straight bougie study. Placements in the trachea

of both a straight gum elastic bougie with coude tip and the

straight gum elastic bougie with straight tip was required.

Twelve brand new bougies were used in rotation, allowing

five uses for each bougie. The coude tip (angled 40�anteriorly and 3.5 cm in length) and the straight end of the

gum elastic bougies were used in this experiment. An

investigator held the straight bougie at the ends and passed it

to the anaesthetist, in random order, ensuring that equal

numbers of anaesthetists used coude-tipped and straight-

tipped bougie first. In this study, anaesthetists were allowed

to choose the position of holding the bougie as they would

in everyday practice. The investigator noted the final

placement of both the coude-tipped and straight-tipped

gum elastic bougies, the time taken to place the bougies and

the distance from the tip at which the bougie was held.

Statistical analysis

The primary outcome measure in both parts of the study

was the difference in the success rate of tracheal

placement between the two bougies. McNemar’s test

with Yates’s correction for continuity was used for

analysis; the result from this test was compared with the

Chi-squared distribution with one degree of freedom,

taking a value of p < 0.05 to denote statistical signifi-

cance. The secondary outcome measure for both studies

included the time taken to place the bougie. Comparisons

between the two groups, within each study, were made

with Wilcoxon’s signed rank test. In addition, for the

coude tip vs. straight tip study, the distances the bougies

were held from their tips in each group were also

compared using Wilcoxon’s signed rank test.

We also tested whether those anaesthetists who rou-

tinely shaped a bougie were more or less successful at

placing the ‘optimal’ curve bougie by using the Fisher’s

exact test.

Figure 3 A ‘mean’ shape for each of thegroups was drawn through the meandistance marks on the six perpendicularlines. The ‘mean’ shape of the middlegroup was adopted as an ‘optimal’bougie shape.



Finally, we wanted to investigate whether the length of

experience of the anaesthetists improved the incidence of

successful placement. Logistic regression was used to

analyse the data, with the type of bougie and experience

(in years) added as two explanatory variables.

STATVIEW Version 5 (SAS Institute Inc., Cary, NC,

USA) was used to analyse data using Fisher’s exact test,

logistic regression and Wilcoxon signed rank test.

McNemar’s Test was carried out in accordance with

Campbell & Machin [7].

Results

Shape survey

In total 35 anaesthetists, 16 consultants and 19 trainees,

were approached. Twenty surveyed anaesthetists (57%)

routinely shaped the bougie when faced with Grade 3

Cormack and Lehane laryngoscopic view and 15 (43%)

did not.

Derived ‘optimal’ shape

The derived shape of the experimental bougie is shown

(middle curve) in Fig. 3.

Shape study

The anaesthetists in the ‘shape study’ were much more

likely to place the bougie in the trachea if it was curved

than if it was straight (Table 2). Two anaesthetists

successfully placed both bougies in the trachea. Five

anaesthetists who placed the experimental curved bougie

in the oesophagus also placed the straight bougie in the

oesophagus.

The time taken for placement was marginally but

significantly shorter with the curved bougie (Table 2).

Whether the anaesthetist routinely shaped the bougie

when faced with the restricted laryngoscopic view did not

significantly affect the likelihood of successful placement

of the curved bougie (Table 3).

Analysis of the effect of experience on outcome

revealed that the type of bougie (curved or straight)

significantly improved the success rate for tracheal

placement (p < 0.0001), but experience (in years) did

not affect the result (p ¼ 0.39), nor was there significant

interaction between bougie shape and experience.

Tip study

Results of comparison of success rates of tracheal

placement of the coude tip vs. straight tip of a straight

bougie in the ‘tip study’ are shown in Table 4. The

distance held from the tip and the time taken for

placement were similar for both the coude-tipped and

straight-tipped bougies (Table 5). The most common

distance held from the tip (mode) was 20 cm for both the

coude-tipped and straight-tipped gum elastic bougies.

Discussion

Our survey showed that a significant proportion of

anaesthetists do not curve the bougie when faced with a

Table 2 Placement and time to placement of experimentalcurved and straight bougies, both with coude tip, duringsimulated laryngoscopy by 30 anaesthetists. Corresponding val-ues are number (proportion) and median (interquartile range[range]). Difference (95% CI) in proportions between the twobougies 77% (54–87%).

Curved bougie Straight bougie p-value

Tracheal 25 (83%) 2 (7%) < 0.0001Oesophageal 5 (17%) 28 (93%)Time to placement; s 10.5 (8–12[6–19]) 12 (10–16 [7–28]) = 0.05

Table 3 Effect on placement of whether the anaesthetists rou-tinely shaped the bougie when faced with Grade 3 laryngo-scopic view. Analysis is limited to results with the experimentalcurved bougie only. Values are number (proportion) whetheranaesthetist shaped the bougie had no significant effect on thesuccess of the placement. Difference (95% CI) in proportions14% ()16 to 38%).

Routinely shape Do not routinely shape p-value

18 ⁄ 30 (60%) 12 ⁄ 30 (40%)Tracheal 14 (78%) 11 (92%) = 0.62Oesophageal 4 (22%) 1 (8%)

Table 5 Distance from the tip at which the coude-tipped andstraight-tipped bougies were held by 30 anaesthetists duringsimulated layngoscopy and times to placement. Values aremedian (interquartile range [range]). No significant differencebetween bougies.

Coude tip Straight tip p-value

Distancefrom tip; cm

22.5 (20–25 [10–30]) 22.5 (20–30 [18–30]) = 0.92

Time toplacement; s

10.0 (8–14 [5–22]) 10.5 (8–14 [6–35]) = 0.99

Table 4 Placement of the coude-tipped and straight end gumelastic bougies during simulated laryngoscopy by 30 anaesthet-ists. Values are number (proportion). Difference (95% CI) inproportions between the two bougies 43% (24–61%).

Coude tip Straight tip p-value

Tracheal 13 (43%) 0 (0%) < 0.001Oesophageal 17 (57%) 30 (100%)



Grade 3 laryngoscopic view. The manikin studies clearly

demonstrated the superiority of the curved and coude

(angled) tip gum elastic bougies according to the success

rates for tracheal placement, when using simulated

difficult intubation in a model.

The survey found that 43% of anaesthetists did not

routinely shape the bougie when faced with a Grade 3

laryngoscopic view. In a previous study comparing

simulated difficult intubation with multiple- and single-

use bougies, 26% of anaesthetists did not shape the bougie

before placing it in the trachea of a manikin set to

simulate Grade 3 difficult intubation [8]. The gum elastic

bougie is used in many clinical situations in which it is

unnecessary to shape the bougie. Despite having a

Grade 1 laryngoscopic view, it may not be possible to

pass the tube because it is deflected by irregular teeth or

the tube may not be rigid enough to allow it to be steered

into the trachea. In these circumstances the gum elastic

bougie may not need to be curved. However, we were

surprised to find that, when faced with a restricted

laryngoscopic view, a large proportion of anaesthetists do

not routinely curve the bougie.

The derived experimental bougie was made of a

multiple-use gum elastic bougie, the hollow lumen of

which allowed the placement of copper wire reaching

5 cm from the tip. This gave moderate stiffness to the

proximal part of the experimental bougie and did not

interfere with the flexibility of the distal end. The

experimental bougie was capable of maintaining its shape.

Although the multiple-use gum elastic bougie seems to

have optimal characteristics, some have criticised it as

being too soft [9]. It appears that an improved design

might incorporate a moderately rigid proximal end but a

flexible, soft distal end thus maintaining the desired

bougie characteristics. What needs to be resolved is how

long the distal flexible segment should be and how rigid

the proximal segment should be. In addition the bougie

could be designed with the wire fixed in place or the wire

could be removed after tracheal placement of the tip of

the bougie. Furthermore the optimum length and angle

of the coude tip has not been investigated.

Our results clearly show that shaping the bougie

significantly increases the likelihood of successful place-

ment when faced with a Grade 3 Cormack and Lehane

laryngoscopic view. Previous studies evaluating the use of

the gum elastic bougie in a simulated or real-life difficult

intubation [10–13], did not describe the details of the

bougie technique used. As far as we are aware, Gataure’s

study was the only one to report the use of a gum elastic

bougie whose distal end was bent into an ‘appropriate

curve’ [14]. Only two anaesthetists (7%) in the ‘shape’

study placed the straight (but coude-tipped) bougie in the

trachea. Our findings confirm that it is difficult to place

the straight gum elastic bougie in the trachea if the glottis

cannot be seen. When faced with a restricted laryngo-

scopic view the gum elastic bougie is best used in a curved

shape.

Not a single anaesthetist in our study managed to place

the straight-tipped gum elastic bougie in the trachea,

emphasising the importance of the coude tip in facilitating

tracheal placement in a Grade 3 laryngoscopic view. Venn

designed a coude tip to the bougie [1], which was

introduced 24 years after Macintosh’s description of

‘a long gum-elastic catheter’ [15]. It was widely assumed

that the bougie with coude tip would be helpful in

facilitating tracheal intubation [4–6]. Mushambi & Iyer

[3] stressed the importance of using the coude-tipped

bougie for routine or difficult intubation, after finding

that 2 of 17 operating theatres in their hospital stored only

straight-tipped bougies. They emphasised the importance

of making sure that all anaesthetic machines are equipped

with a coude-tipped bougie. We also recommend that the

bougies used to facilitate difficult intubation should have a

coude tip.

The success rates for the tracheal placement of the

straight coude-tipped bougie in our two manikin studies

were quite different. In the ‘shape study’ only 2

anaesthetists (7%) placed the straight coude-tipped

bougie in the trachea, whereas in the ‘tip study’, this

was achieved by 13 anaesthetists (43%). The apparent

laryngoscopic view in both studies was the same (only

the tip of the epiglottis could be seen) and, once set, was

maintained throughout each of the studies. Participating

anaesthetists did not alter the presentation of the airway

in any way. However, the degree of difficulty of bougie

placement was likely to be different between the studies,

because of the rigidity of the Laerdal model and the

consequent difficulty in exactly replicating the set-up.

This may explain the difference in tracheal placement

figures for the straight noncurved coude tipped gum

elastic bougie between two studies. However, the

validity of the comparisons within each of the studies

was ascertained by the cross-over nature of the study

design and unaltered manikin position for the duration

of each study.

When faced with unexpected difficult intubation, most

anaesthetists in the UK would use a gum elastic bougie as

their first choice [16]. A telephone survey of English

emergency departments revealed that 99% of units kept

gum elastic bougies on their difficult airway equipment

trolleys [17]. A reliable bougie technique may be life-

saving in the management of difficult intubation. This

study clearly shows the superiority of the curved bougie

with a coude tip. The straight-tipped bougie is appropri-

ate for tracheal tube exchange but is less likely to facilitate

tracheal placement in difficult intubation. There is



certainly room for improvement in the design of the

currently available single-use bougie which is potentially

traumatic [18]. Some of the features of this study may be

incorporated in future developments.

Acknowledgement

We thank Emeritus Professor W. W. Mapleson for his

help in preparation of this manuscript.

References

1 Henderson JJ. Development of the ‘gum-elastic bougie’.

Anaesthesia 2003; 58: 103–4.

2 Hex Venn P. The gum elastic bougie. Anaesthesia 1993; 48:

274–5.

3 Mushambi MC, Iyer GA. Gum elastic bougies. Anaesthesia

2002; 57: 727.

4 Surendra Kumar D, Jones G. Is your bougie helping or

hindering you? Anaesthesia 2001; 56: 1121.

5 Sellers WFS. Gum elastic bougies. Anaesthesia 2002; 57: 289.

6 Cormack RS, Lehane J. Difficult tracheal intubation in

obstetrics. Anaesthesia 1984; 39: 1105–11.

7 Campbell MJ, Machin D. Medical Statistics. A Commonsense

Approach, 2nd edn. Chichester: Wiley, 1993.

8 Annamaneni R, Hodzovic I, Wilkes AR, Latto IP. Com-

paring simulated difficult intubation with multiple-use and

single-use bougies in a manikin. Anaesthesia 2003; 58: 45–9.

9 Cormack RS. Difficult tracheal intubation in obstetrics.

Anaesthesia 1985; 40: 389.

10 Cook TM. A new practical classification of laryngeal view.

Anaesthesia 2000; 55: 274–9.

11 Latto IP, Stacey M, Mecklenburgh J, Vaughan RS. Survey

of the use of the gum elastic bougie in clinical practice.

Anaesthesia 2002; 57: 379–84.

12 Nolan JP, Wilson ME. An evaluation of the gum elastic

bougie. Intubation times and incidence of sore throat.

Anaesthesia 1992; 47: 878–81.

13 Marfin AG, Hames KC, Pandit JJ, Popat MT. Comparison

of single-use plastic bougie and multiple-use gum elastic

bougie for tracheal intubation in simulated grade III difficult

intubation. Anaesthesia 2003; 58: 511–2.

14 Gataure PS, Vaughan RS, Latto IP. Simulated difficult

intubation. Comparison of the gum elastic bougie and the

stylet. Anaesthesia 1996; 51: 935–8.

15 Macintosh RR. An aid to oral intubation. British Medical

Journal 1949; 1: 28.

16 Turley A, Latto IP. Cardiff airway management audit.

Proceedings of Difficult Airway Society Annual Meeting,

Cardiff, November 1996.

17 Morton T, Brady S, Clancy M. Difficult airway manage-

ment in an English emergency department. Anaesthesia 2000;

55: 485–8.

18 Wilkes AR, Hodzovic I, Latto IP. Comparison of the peak

forces that can be exerted by multiple-use and single-use

bougies in vitro. British Journal of Anaesthesia 2002;

89: 671P.

FORUM

Effect of introducing the Modified Early Warning score on

clinical outcomes, cardio-pulmonary arrests and intensive

care utilisation in acute medical admissions*

C. P. Subbe,1 R. G. Davies,2 E. Williams,3 P. Rutherford4 and L. Gemmell5

1 Specialist Registrar in Thoracic Medicine, 2 Specialist Registrar in Anaesthetics, 3 Specialist Practitioner Critical Care

Outreach, 5 Director of Critical Care Services, Wrexham Maelor Hospital, Croesnewydd Road, Wrexham, LL13 4TX,

UK, 4 Senior Lecturer and Honorary Consultant, Department of Nephrology, University of Wales College of Medicine,

Gwenfro Technology Park, Wrexham, LL13 7YP, UK

Summary

The effects of introducing Modified Early Warning scores to identify medical patients at risk of

catastrophic deterioration have not been examined. We prospectively studied 1695 acute medical

admissions. All patients were scored in the admissions unit. Patients with a Modified Early Warning

score > 4 were referred for urgent medical and critical care outreach team review. Data was

compared with an observational study performed in the same unit during the proceeding year.

There was no change in mortality of patients with low, intermediate or high Modified Early



Warning scores. Rates of cardio-pulmonary arrest, intensive care unit or high dependency unit

admission were similar. Data analysis confirmed respiratory rate as the best discriminator in ide-

ntifying high-risk patient groups. The therapeutic interventions performed in response to abnormal

scores were not assessed. We are convinced that the Modified Early Warning score is a suitable

scoring tool to identify patients at risk. However, outcomes in medical emergency admissions are

influenced by a multitude of factors and so it may be difficult to demonstrate the score’s benefit

without further standardizing the response to abnormal values.

Keywords Early Warning scores; physiological deterioration, cardio-pulmonary arrest, critical

illness, intensive care, length of stay.

........................................................................................................

Correspondence to: Dr C. P. Subbe


*Some of the data has been presented at the Intensive Care Society state

of the Art Meeting in London, December 2001 as an oral presentation.


Suboptimal care of critically ill patients on general wards

may result in potentially preventable cardio-pulmonary

arrests [1]. Suboptimal care prior to intensive care unit

(ICU) admission may be associated with increased

mortality measured as either ICU or hospital mortality

[2].

Identifying patients at risk is possible, using simple

algorithms based on bedside observations that include

respiratory and mental function [3,4]. The Modified Early

Warning score is an algorithm that has been validated for

clinical use in medical emergency admissions [5]. Use of

the Modified Early Warning score on surgical wards has

been shown to decrease Acute Physiology and Chronic

Health Evaluation (APACHE) II scores on admission

to intensive care [6]. The Department of Health [7],

Intensive Care Society [8] and Royal College of Physi-

cians (London) [9] have recommended the Modified

Early Warning score as an aid in identifying patients at

risk on general wards. However, no prospective study has

examined the impact of introducing the Modified Early

Warning score as standard clinical management of medical

emergency admissions.

The primary aim of our study was to measure the effect of

introducing the Modified Early Warning score on the rates

of ICU and high dependency unit (HDU) admission,

cardio-pulmonary arrest and mortality. A secondary aim

was to collect physiological data from patients prior to

critical care admission, cardio-pulmonary arrest or death, in

order to improve the discrimination of the score.

Methods

The Research Ethics Committee of the North-East Wales

NHS Trust reviewed and approved the study. The study

was performed in the 56-bedded medical admissions

unit of a district general hospital serving a population

of 300 000 in North Wales between 1 February and

31 April 2001 (3 months).

Patients

Patients were referred to the medical admissions unit by

general practitioners or the Accident and Emergency

Department. Patients diagnosed with myocardial infarc-

tion were admitted directly to the coronary care unit. The

study examined all patients aged above 15 years but

excluded patients admitted for palliative care only and

patients admitted directly to other wards. Patients who

were admitted more than once during the study period

were entered only once, on their first admission.

Scoring tool

All medical admissions unit nursing staff were trained by

the investigators and the critical care outreach team to

collect bedside observations and to calculate the Modified

Early Warning score (Table 1). Blood pressure and pulse

rate were measured non-invasively (DINAMAPTM,

Critikon Inc, Tampa, FL). The pulse rate was recorded

manually in patients with arrhythmias. The respiratory

rate was counted over 1 min. The AVPU score (AVPU

denoting A ¼ patient Alert, V ¼ responsive to Voice, p ¼responsive to Pain and U ¼ Unresponsive) was recorded

using nail-bed pressure as a standardised stimulus for

pain where appropriate. Temperatures were measured

sublingually using Temp-PlusII� (IVAC-Corporation,

San Diego, CA). All medical staff caring for emergency

medical admissions were briefed concerning the Modified

Early Warning score, its interpretation and their role in

the management of a patient identified as being at risk

of deterioration. The nursing staff were instructed to alert

appropriate medical staff and the critical care outreach



team if the Modified Early Warning score was 5 or more.

Doctors were instructed to examine and assess patients as

soon as possible but not later than ‘within 60 minutes’

with regard to further therapy and possible transfer to

critical care.

Data

Basic demographic data and bedside observations on

admission were collected for all patients admitted to the

medical admissions unit. Two trained data collectors

gathered data from observation charts once each day.

Daily comparison of the collected data with hospital

admission lists ensured that all patients who met the

inclusion criteria were studied.

Data was collected on admission to medical HDU,

ICU and following cardio-pulmonary arrest or death.

Nursing staff on HDU and ICU who were trained for this

study prospectively recorded basic demographic data and

bedside observations from all medical admissions trans-

ferred to their unit from other wards. The investigators

collected additional data from hospital case notes inclu-

ding diagnosis, pre-existing illness, basic laboratory data,

social circumstances prior to admission and bedside

observations 24 h, 6 h and immediately prior to transfer

to critical care. Intensive care unit and hospital discharge

data were collected retrospectively from the hospital’s

Patient Administration System. Time from hospital to

ICU admission, length of stay on ICU and ICU mortality

were calculated. Data on cardio-pulmonary arrests were

collected in a standardised manner by the cardio-

pulmonary arrest service. The investigators collected all

additional data for these patients from hospital case notes

as if the patient had been admitted to critical care. Data

from patients who died on the medical admissions unit

were collected in the same way. Data on 30-day hospital

mortality were calculated from the Patient Administration

System.

Data sets for which no outcome (i.e. death or hospital

discharge) could be identified were excluded from

analysis.

Control group

Data from a prospective observational study published

previously [5] was used as a control group. This control

group was admitted to the same admissions unit during

February 2000.

Patients were classified on the basis of the Modified

Early Warning score as being at low risk (Modified Early

Warning score 0–2), intermediate risk (Modified Early

Warning score 3–4) or high risk (Modified Early Warning

score > 4) of catastrophic deterioration. Rates of admis-

sion to critical care, cardio-pulmonary arrests and death

were calculated for each risk band.

Statistical analysis

Data was analysed using the Statistical Package for Social

Sciences (Version 10, SPSS Inc., Chicago, IL). For

normally distributed data, results are given as means and

standard deviations (SD). For non-parametric data,

medians and interquartile ranges (IQR) are given.

Unpaired t-tests were used to compare mean variables

in control and intervention groups and the Mann–

Whitney U-test to compare medians in non-parametric

variables. The Chi-squared test and Fisher’s exact test

were used to compare categorical variables. A p-value of

less than 0.05 was considered significant.

Results

Patient outcomes

Admission, clinical and outcome data were available for

1695 patients. Demographic data of patients are summa-

rised in Table 2. Patients’ ages, sex and Modified Early

Warning scores were not significantly different between

the study and control groups. In the study group, 166

(9.7%) patients died, 9 (0.5%) patients were admitted to

ICU, 79 (4.6%) were admitted to the medical HDU and

40 (2.3%) patients had cardio-pulmonary arrests.

The rates of ICU and HDU admissions and in-hospital

mortality were similar in the study and control groups

(Table 3) and for the three levels of risk as classified by the

Table 1 Scoring for Modified EarlyWarning score. Points

3 2 1 0 1 2 3

Systolic bloodpressure; mmHg

< 70 71–80 81–100 101–199 ‡ 200

Heart rate; beats.min)1 < 40 41–50 51–100 101–110 111–129 ‡ 130Respiratory rate;breath.min)1

< 9 9–14 15–20 21–29 ‡ 30

Temperature; �C < 35 35–38.4 ‡ 38.5Neurological score Alert Reacting

to VoiceReactingto Pain

Unresponsive



Modified Early Warning score. Overall, mortality was

unchanged irrespective of risk band. There was an

increased incidence of cardio-pulmonary arrests in the

study group in patients with a Modified Early Warning

score of 3 or 4 (i.e. intermediate risk).

Intensive care utilisation

Only nine patients in the study group and six patients in

the control group were admitted to ICU. Patients were

admitted to ICU after 24 (IQR 12–84), hours in hospital

in the study group and after 24 (IQR 18–186) hours in

the control group (p ¼ 0.9). APACHE II scores on

admission were 15 (SD 8) in the study group and 23

(SD 7) in the control group (p < 0.06). Length of stay in

ICU was 2 (IQR 1–30) days in the study group and

4 (IQR 1–8) days in the control group (p ¼ 0.3). ICU

mortality was 33% in the study group and 67% in the

control group (p ¼ 0.21).

Physiological changes prior to death,

cardio-pulmonary arrest or critical

care admission

Data from patients dying, suffering cardio-pulmonary

arrest or being admitted to critical care (‘sick patients’)

were compared with admission data from all other patients

in the study (‘stable patients’). This ‘sick’ patient subgroup

had statistically significant lower blood pressure, higher

heart rates, higher respiratory rates and lower temperatures

on admission (Table 4). Most physiological parameters in

this patient group became more abnormal during the

course of their illness. For the last set of observations prior

to cardio-pulmonary arrest, death or critical care admis-

sion, the systolic blood pressure was 12 (9%) mmHg

lower, the pulse rate 17 (20%) beats.min)1 faster, the

respiratory rate 8 (41%) breaths.min)1 higher and the

temperature 0.2 (0.5%) �C lower than the mean

temperature in the ‘stable’ patients. For the ‘sick’ patients

the mean drop in blood pressure was 9 (SD 26) mmHg

from admission to the last measurement prior to death,

cardio-pulmonary arrest or critical care admission.

Discussion

Introduction of a scoring system using bedside observa-

tions and a simple protocol to trigger medical and critical

care review did not change outcomes in acute medical

admissions. More importantly, outcomes in the patient

group with the highest risk (Modified Early Warning

score > 4) were not improved.

The proportion of patients admitted to critical care did

not increase with the introduction of Modified Early

Warning score but there was a trend towards earlier ICU

admission. The increase in cardio-pulmonary arrests in

the study group might be explained by the low rate of

arrests in the smaller control group and a higher

proportion of sick patients in the study group, as

suggested by the difference in interquartile range of the

Modified Early Warning score in control and study

groups. Patients were not randomised for Modified Early

Warning score use and the control group was a historic

control from a shorter period of time than the study

period. It was felt that randomisation of patients within

the admissions unit would have been technically difficult.

Our medical admission unit is comparable to units in

other district general hospitals in England and Wales. The

Modified Early Warning score had previously been

validated in our unit. However, our study did not

standardise the response to high scores by medical and

nursing staff. Delayed responses, faulty assessment of

disease severity and inadequate treatment could have

contributed to the negative outcome of this study. Other

authors have found that suboptimal treatment prior to

Table 2 Demographic characteristics and bedside observationson admission. Values are means and standard deviations (SD) ormedians and interquartile ranges (IQR).

ParameterStudygroup

Controlgroup

n 1695 659Age; years (SD) 64 (19) 63 (SD 20)Sex; male ⁄ female; (%) 45 ⁄ 55 45 ⁄ 55Systolic arterial blood pressure; mmHg (SD) 139 (27) 139 (27)Pulse rate; beats.min)1 (SD) 86 (21) 87 (20)Respiratory rate; breath.min)1 (SD) 20 (6) 20 (5)Temperature; �C (SD) 36.5 (1.3) 36.7 (0.9)Modified Early Warning score; median (IQR) 2 (1–3) 2 (1–2)

Table 3 Distribution of outcomes stratified by Modified EarlyWarning scores on admission.

Modified EarlyWarning scorerisk band

Study group

No. of patientswith event ⁄no. of patientsin risk band (%)

Control group

No. of patientswith event ⁄no. of patients inrisk band (%)

p-values forChi-square$

or Fisher’sexact test*

Death0–2 70 ⁄ 1214 (6%) 28 ⁄ 491 (6%) 0.97$

3–4 59 ⁄ 348 (17%) 15 ⁄ 117 (13%) 0.29$

5–15 37 ⁄ 133 (28%) 10 ⁄ 51 (20%) 0.25$

ICU or HDU admission0–2 45 ⁄ 1214 (4%) 16 ⁄ 491 (3%) 0.66$

3–4 22 ⁄ 348 (6%) 7 ⁄ 117 (6%) 0.90$

5–15 18 ⁄ 133 (14%) 4 ⁄ 51 (8%) 0.45*

Cardio-pulmonary arrests0–2 20 ⁄ 1214 (2%) 3 ⁄ 491 (1%) 0.11*3–4 16 ⁄ 348 (5%) 0 ⁄ 117 (0%) < 0.016*5–15 4 ⁄ 133 (3%) 1 ⁄ 51 (2%) 1.0*



intensive care can be caused by failure of organisation, lack

of knowledge, failure to appreciate urgency, lack of

supervision and failure to seek advice [2]. Whilst the

Modified Early Warning score identifies sick patients and

encourages staff to appreciate the severity of their condi-

tion, we were not able to control any of the other factors

that might have adversely affected patient’s outcome.

Changes in physiological parameters prior to cardio-

pulmonary arrest have been previously described [1].

Our study shows that changes in blood pressure and pulse

rate are comparatively small and could potentially be

clinically missed. Relative changes in respiratory rate are

of a much greater magnitude and are therefore more

likely to be better at discriminating between stable

patients and patients at risk. Consistent recording of

respiratory rate was achieved in this study for most

patients in the medical admissions unit. This represents a

crucial first step in recognizing patients at risk.

We are convinced that the Modified Early Warning

score is a suitable scoring tool to identify patients at risk.

However, outcomes in medical emergency admissions are

influenced by a multitude of factors. To impact on

outcomes the Modified Early Warning score has to be

placed into an educational context of improved training

in emergency medicine of junior and senior medical and

nursing staff. Training can be delivered at the bedside

or in courses such as the ALERTTM course (The Open

Learning Centre, University of Portsmouth, Buckingham

Building, Portsmouth, PO1 3HE, UK). Systematic

feedback of adverse outcomes and near misses might

further enhance care and show the true potential of the

Modified Early Warning score in the management of

critically ill patients on general medical wards.

Acknowledgements

We would like to acknowledge the invaluable help of our

data collectors and data entry clerks Dawn Griffiths, Linda

Edge and Pat Autiero, and the contribution of the

medical and nursing staff participating in the study. We

would like to thank specifically the ward sisters Helen

Williams and Fiona Wilkinson for their trust, advice,

expertise and leadership. The study was supported by a

grant from the North-east Wales NHS Trust Research

and Development Fund.

References

1 Schein RM, Hazday N, Pena M, Ruben BH, Sprung CL.

Clinical antecedents to in-hospital cardiopulmonary arrest.

Chest 1990; 98: 1388–92.

2 McQuillan P, Pilkington S, Allan A et al. Confidential inquiry

into quality of care before admission to intensive care. British

Medical Journal 1998; 316: 1853–8.

Table 4 Parameters for patients in the study group who suffered cardio-pulmonary arrests, death and critical care admission comparedwith mean parameter of all other patients in the study group (‘stable patients’) (One-sample t-test). D describes the relative difference inpercent of parameters if compared to mean parameter on admission of the ‘stable patients’. Values are means (SD).

Parameter On admission24 h priorto event

6 h priorto event

Last set of observationsprior to event

Systolic blood pressure; mmHg (SD) 135 (30) 120 (16) 120 (31) 128 (35)n = 259 n = 24 n = 46 n = 176

>D; mmHg (%), p-values 5 ()4%) 20 ()14%) 20 ()15%) 12 ()9%)p < 0.005 p < 0.001 p < 0.001 p < 0.001

Mean systolic blood pressure of ‘stable’ patients: 140 mmHg 94 (26) 106 (20) 102 (20) 101 (27)n = 262 n = 24 n = 42 n = 178

Pulse rate; beats.min)1 (SD) 94 (26) 106 (20) 102 (20) 101 (27)n = 262 n = 24 n = 42 n = 178

D; beats.min)1 (%), p-values 10 (+ 12%) 22 (+ 26%) 18 (+ 21%) 17 (+ 20%)p < 0.001 p < 0.001 p < 0.001 p < 0.001

Mean pulse rate of ‘stable’ patients: 84 beats.min)1 24 (8) 27 (6) 27 (7) 27 (9)n = 252 n = 21 n = 39 n = 172

Respiratory rate; breaths.min)1 (SD) 24 (8) 27 (6) 27 (7) 27 (9)n = 252 n = 21 n = 39 n = 172

D; breaths.min)1 (%), p-values 5 (+ 27%) 8 (+ 44%) 8 (+ 42%) 8 (+ 41%)p < 0.001 p < 0.001 p < 0.001 p < 0.001

Mean respiratory rate of ‘stable’ patients: 19 breaths.min)1 36.3 (1) 36.6 (0.8) 36.2 (1.2) 36.4 (1.3)n = 258 n = 25 n = 39 n = 170

Temperature; �C (SD) 36.3 (1) 36.6 (0.8) 36.2 (1.2) 36.4 (1.3)n = 258 n = 25 n = 39 n = 170

D; �C (%), p-values 0.3 ()0.7%) 0 (0%) 0.4 ()1%) 0.2 ()0.5%)p < 0.001 p = 0.961 p < 0.056 p < 0.052

Mean temperature of ‘stable’ patients: 36.6 �C.



3 Lee A, Bishop G, Hillman KM, Daffurn K. The Medical

Emergency Team. Anaesthesia and Intensive Care 1995; 23:

183–6.

4 Morgan RJM, Williams F, Wright MM. An Early Warning

Scoring System for detecting developing critical illness.

Clinical Intensive Care 1997; 8: 100.

5 Subbe CP, Kruger M, Rutherford P, Gemmell L. Validation

of a modified Early Warning Score in medical admissions.

Quarterly Journal of Medicine 2001; 94: 521–6.

6 Stenhouse C, Coates S, Tivey M, Allsop P, Parker T.

Prospective evaluation of a Modified Early Warning Score to

aid earlier detection of patients developing critical illness on

a general surgical ward. British Journal of Anaesthesia 2000;

84: 663p.

7 Department of Health. Comprehensive Critical Care: a Review of

Adult Critical Care Services. London: Department of Health,

2000.

8 Intensive Care Society. Guidelines for the Introduction of

Outreach Services. London: Intensive Care Society,

2002.

9 Baudouin S, Evans T. Improving outcomes for severely ill

medical patients. Clinical Medicine 2002; 2: 92–4.

FORUM

A 5-lm filter does not reduce propofol-induced pain

C. Hellier,1 S. Newell,2 J. Barry3 and J. Brimacombe4

1 Registrar, 2 Consultant, 3 Consultant, 4 Professor, James Cook University, Department of Anaesthesia and Intensive

Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia

Summary

We assessed the effectiveness of a 5-lm filter in reducing propofol-induced pain and determined

whether any reduction is due to removal of contaminants or an alteration in flow characteristics.

A total of 120 unpremedicated women (ASA 1–3, aged 18–70 yr) were randomly allocated to one

of three equal-sized groups. In group A, propofol was drawn up and injected through an unfiltered

plastic cannula. In group B, propofol was drawn up through a 5-lm filter needle and injected

through an unfiltered plastic cannula. In group C, propofol was drawn up and injected through a

5-lm filter needle. Unmodified propofol from a 20-ml rubber topped vial at room temperature

was used. A 22-g cannula was inserted into the largest visible vein on the dorsum of the

non-dominant hand. Propofol was administered at 0.5 ml.s)1 and patients were asked about pain

every 10 s until unresponsive, by a blinded observer. The pain score for the patient was the taken as

the most severe pain documented. The frequency and severity of pain were similar among

groups. We conclude that a 5-lm filter does not reduce pain associated with injection of propofol

drawn from a vial with a rubber bung.

Keywords Anaesthetics: intravenous, propofol. Pain, mechanism.

........................................................................................................

Correspondence to: Prof. J. Brimacombe


Accepted: 12 March 2003

Propofol is frequently associated with pain on injection.

The aetiology is unknown, but may be related to a direct

irritant effect on the vessel wall, or an indirect effect via

the kinin cascade [1,2]. A previous study suggested that

using a 0.2-lm filter significantly reduces pain, perhaps by

removing glass particles [3]. A 5-lm filter, which is one

quarter the cost of a 0.2-lm filter, also removes glass

particles [4]. In this randomised, double-blind controlled

trail we assessed the effectiveness of a 5-lm filter in

reducing pain on injection. We also determined whether

any reduction in pain is due to removal of contaminants

or an alteration in flow characteristics during injection.

Methods

Following Ethics Committee approval and written

informed consent, we studied 120 unpremedicated

women ASA 1–3, aged 18–70 yr, scheduled to undergo



elective surgery. Patients were excluded if they were

allergic to propofol, had communication difficulties, or

were unsuitable for intravenous induction of anaesthesia.

A 22-g cannula (InsyteTM, Becton Dickinson and Co.,

UT) was inserted into the largest visible vein on the

dorsum of the non-dominant hand and flushed with 2 ml

normal saline. An intravenous infusion was not com-

menced and coinduction agents were not administered.

Unmodified propofol (Diprivan 1%, AstraZeneca, North

Ryde, Australia) from a 20-ml rubber topped vial at room

temperature was used. Patients were randomised (by

opening an opaque envelope) into three equal-sized

groups. In group A, propofol was drawn up and injected

through an unfiltered plastic cannula (InterlinkTM, Bec-

ton Dickinson and Co.). In group B, propofol was drawn

up through a 5-lm filter needle (W ⁄ 5 Filter needle,

Becton Dickinson and Co.) and injected through an

unfiltered plastic cannula. In group C, propofol was

drawn up and injected through a 5-lm filter needle.

Propofol was administered by an anaesthestist at

0.5 ml.s)1 and patients were asked by the same anaes-

thetist, ‘does it hurt’ at 10-s intervals. The anaesthetist was

blinded to the use of the filter needle. If the response was

affirmative, they were asked if it was mild or severe.

Patients were questioned until unresponsive. Any spon-

taneous comments or reports of pain were noted. The

pain score for the patient was taken as the most severe

pain documented. Sample size was selected to detect a

projected difference of 40% between the groups for a type

I error of 0.05 and a power of 0.8. Statistical analysis

was by ANOVA and Chi squared test, with p < 0.05 as

significant.

Results

Two patients were excluded from the analysis (procedural

error; tissued cannula). Demographic data and dose of

propofol were similar among groups (Table 1). The

frequency and severity of pain were found to be similar

amongst all three groups (Table 1).

Discussion

Our findings contrast with those of Davies [3] who

showed that a 0.2-lm filter reduced the frequency of pain

from 62% to 34%. Proposed mechanisms whereby a filter

could reduce pain include the removal of contaminants

such as glass (from glass vials that are cracked open) [4],

silicone lubricant (from disposable syringes) [5], or

particles of undissolved propofol [3]; or because the filter

alters the flow characteristics during injection thereby

reducing endothelial exposure to the aqueous phase of

propofol [3]. We hoped to determine the aetiology of any

pain reduction by including a group where the propofol

was drawn up through the filter, but injected without the

filter. If the aetiology was due to particle removal, there

should have been a reduction in both filter groups; if it

was due to altered flow characterises, there should only

have been a reduction when injected through the filter.

Our data show that neither mechanism is effective with a

5-lm filter. A limitation of our study is that we used vials

that were not cracked open and therefore did not produce

glass contamination. It is still theoretically possible that a

5-lm filter might reduce pain with glass vials that are

cracked open. There is evidence that a 5-lm filter

significantly reduces the amount of glass contamination

from glass vials that are cracked open [4].

We conclude that a 5-lm filter does not reduce pain

associated with injection of propofol drawn from a vial

with a rubber bung.

References

1 Tan CH, Onsiong MK. Pain on injection of propofol.

Anaesthesia 1998; 53: 468–76.

2 Picard P, Tramer MR. Prevention of pain on injection with

propofol: a quantitative systematic review. Anesthesia and

Analgesia 2000; 90: 963–9.

3 Davies AF, Vadodaria B, Hopwood B, Dexter T, Conn D.

Efficacy of microfiltration in decreasing propofol-induced

pain. Anaesthesia 2002; 57: 557–61.

4 Driscoll DF, Lawrence KR, Lewis K, Bistrian BR. Particle

size distribution of propofol injection from ampoules and

vials: The benefits of filtration. International Journal of

Pharmaceutical Compounding 1997; 1: 118–20.

5 Lomax D. Propofol injection pain. Anaesthesia and Intensive

Care 1994; 22: 500–1.

Table 1 Demographic data, propofol dose and pain scores.

No filter

Filter fordrawingup only

Filter fordrawingup andinjection

Age; yr* 41 (12) 42 (12) 42 (12)Weight; kg** 65 (57–75) 65 (58–78) 65 (55–76)Propofol; mg** 190 (160–200) 200 (173–200) 190 (153–200)Pain: nil ⁄ mild ⁄ severe– 7 ⁄ 12 ⁄ 21 7 ⁄ 16 ⁄ 16 6 ⁄ 11 ⁄ 22

Data are *mean (SD), **median (interquartile range) or –numbers.



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