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Wound-edge protection devices for preventing surgical site
infection in abdominal surgery (Protocol)
Pinkney TD, McCall J, Dumville JC, Edwards FJ, Gheorghe A, Bartlett DC, Fletcher BR,
Calvert MJ
This is a reprint of a Cochrane protocol, prepared and maintained by The Cochrane Collaboration and published in The Cochrane
Library 2013, Issue 6
http://www.thecochranelibrary.com
Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
T A B L E O F C O N T E N T S
1HEADER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11CONTRIBUTIONS OF AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12DECLARATIONS OF INTEREST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12SOURCES OF SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iWound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
[Intervention Protocol]
Wound-edge protection devices for preventing surgical siteinfection in abdominal surgery
Thomas D Pinkney1 , John McCall2, Jo C Dumville3, Francesca J Edwards2, Adrian Gheorghe4, David C Bartlett5, Benjamin R Fletcher4, Melanie J Calvert6
1Academic Department of Surgery, University Hospitals Birmingham, Birmingham, UK. 2Department of Surgical Sciences, Dunedin
School of Medicine, University of Otago, Dunedin, New Zealand. 3Department of Nursing, Midwifery and Social Work, University of
Manchester, Manchester, UK. 4Primary Care Clinical Sciences, University of Birmingham, Birmingham, UK. 5NIHR Biomedical Unit
and Centre for Liver Research, University of Birmingham, Birmingham, UK. 6School of Health and Population Science, University of
Birmingham, Birmingham, UK
Contact address: Thomas D Pinkney, Academic Department of Surgery, University Hospitals Birmingham, Queen Elizabeth Hospital,
Mindelsohn Drive, Edgbaston, Birmingham, NG7 2UH, UK. thomas.pinkney@tiscali.co.uk.
Editorial group: Cochrane Wounds Group.
Publication status and date: New, published in Issue 6, 2013.
Citation: Pinkney TD, McCall J, Dumville JC, Edwards FJ, Gheorghe A, Bartlett DC, Fletcher BR, Calvert MJ. Wound-edge
protection devices for preventing surgical site infection in abdominal surgery. Cochrane Database of Systematic Reviews 2013, Issue 6.
Art. No.: CD010614. DOI: 10.1002/14651858.CD010614.
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
A B S T R A C T
This is the protocol for a review and there is no abstract. The objectives are as follows:
To compare the effects of WEPDs in the prevention of SSI in patients undergoing abdominal surgery.
B A C K G R O U N D
Surgical site infection (SSI) is an infection of the wound following
a surgical procedure. These infections can be categorised into su-
perficial (skin and subcutaneous tissue), deep incisional (fascia and
muscle) and organ space infection (involving manipulated internal
parts) (Mangram 1999). SSI is the most frequent cause of nosoco-
mial infection in surgical patients, accounting for 38% of all in-
fections (Mangram 1999) and its occurrence confers a significant
impact on patient mortality and morbidity rates as well as health-
care costs. A US study found that in over 750,000 episodes of sur-
gical hospitalisation, 1% resulted in a SSI (de Lissovoy 2009), and
similar estimates have been found in France (Astagneau 2009). A
UK-wide prevalence survey of over 75,000 patients showed that
3.7% to 5.4% of patients undergoing a surgical procedure devel-
oped a SSI (Smyth 2008). It should be noted that all these figures
are based on passive and retrospective surveillance and are reliant
on the accurate coding or recording of SSI signs and symptoms.
As such they are likely to significantly under-represent the true
incidence of this complication.
The risk of developing SSI has been shown to be multifactorial.
Surgical wound type is one such factor first categorised by the Na-
tional Research Council in 1964 (NRC 1964). Under this system
wounds may be classified as ’clean’, ’clean-contaminated’, ’con-
taminated’ and ’dirty’.
• Clean wounds are defined surgical wounds in which the
bronchi, gastrointestinal tract or genitourinary tract was not
entered. The incidence of SSI in clean wounds is less than 2%
1Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
and is most commonly due endogenous Staphylococcus aureus
present on the skin.
• Clean-contaminated wounds are defined as surgical wounds
in which the bronchi, gastrointestinal tract or genitourinary tract
was breached, but without unusual contamination. Elective
intestinal resection, pulmonary resection, gynaecologic
procedures and head-neck cancer operations that involve the
oropharynx are examples of clean-contaminated procedures. SSI
incidence for these procedures is in the range of 4% to 10%.
• Contaminated wounds are defined as fresh traumatic
wounds or surgical wounds where there has been a breach in
sterile technique or acute, gross spillage from gastrointestinal
tract or nonpurulent inflammation is encountered. Infection
rates in contaminated wounds exceed 10% even with antibiotic
prophylaxis.
• Finally dirty wounds are old traumatic wounds involving
abscesses or perforated viscera. Abdominal exploration for acute
bacterial peritonitis and intra-abdominal abscess are examples of
this class of surgical site infection (NNIS 2004; NRC 1964).
In addition to this stratification by contamination level, the site of
surgery and structures operated upon also play an important role
in the likelihood of developing a SSI. Abdominal surgery carries
one of the highest rates of SSI, particularly if the operation involves
the colon or rectum (Blumetti 2007; Smyth 2008). Recent studies
exploring the rate of SSI after open colorectal surgery have found
a very similar incidence of 25% (Blumetti 2007), 25.3% (Howard
2010) and 24.9% (Serra-Aracil 2011).
Other co-factors associated with an increased risk of SSI include a
compromised immune system (including diabetes, malnutrition,
immunosuppressive therapy or HIV), increased risk of endoge-
nous contamination (positively correlated to the duration of the
operative procedure) and type of operation (procedures involving
tissue with high concentrations of bacterial flora such as the bowel)
(NICE 2008).
SSI is associated with considerable morbidity, a reduction in qual-
ity of life and increased healthcare costs, placing a significant bur-
den on healthcare systems and individuals. In a study of 38,973 pa-
tients in Northern France over a three-year period, SSI was found
to be an independent predictor of mortality, with mortality due
to SSI reported in 78 patients (0.2%) (Astagneau 2001). In 2002
there were 8205 deaths in the US due to SSI, accounting for 8%
of all deaths caused by a nosocomial infection, with SSI listed as
one of the most common causes of multiple system organ failure
(Klevens 2007; Mangram 1999).
SSI has also been shown to significantly increase the duration and
cost of patient hospitalisation, predominantly due to re-operation,
additional nursing care and drug treatment costs (Mangram 1999;
Wilson 2004). In a case-controlled US study of 255 patient pairs,
it was found that in those patients with SSI, hospital discharge
was delayed by an average of 6.5 days (95% confidence interval
(CI) 5 to 8 days) with an additional direct cost of USD 3089 per
patient (Kirkland 1999). In a further Swiss study of 6283 surgical
procedures, 187 SSIs were reported, of which 168 were successfully
matched with a control patient. In patients with SSI, the mean
additional hospital cost was CHF 19,638 (95% CI CHF 8492 to
CHF 30784) and the mean additional length of hospitalisation
was 16.8 days (95% CI 13 to 20.6 days) (Weber 2008). In the UK,
length of stay is typically doubled and additional costs of GBP
814 to GBP 10,523 are incurred in patients with a SSI (Coello
2005; NICE 2008; Plowman 2001; Tanner 2009). The indirect
costs of SSI, due to loss of productivity, patient dissatisfaction
and litigation, and reduced quality of life, have been studied less
extensively.
As the majority of SSIs are the result of bacterial contamination of
a wound stemming from endogenous flora from the patients skin,
mucous membranes or hollow viscera, the idea of using a physical
barrier to cover the cut edges of the surgical wound has been
revisited several times over the last 40 to 50 years. This protection
can take the form of a wound-edge protection device (WEPD) or
’wound-guard’ which is inserted into the wound for the duration
of the operation.
This review aims to assess the clinical effectiveness of wound-edge
protection devices (WEPDs) in reducing the SSI rate in patients
undergoing open abdominal surgery.
Description of the condition
Whilst SSIs can be difficult to define - one review identified 41
different definitions and 13 SSI grading scales (Bruce 2001) - the
Centers for Disease Control and Prevention (CDC) have pub-
lished the following guidelines defining superficial and deep inci-
sional SSIs (Horan 2008).
A superficial SSI is defined as: an infection occurring within 30
days after the operation and only involving the skin and subcuta-
neous tissue of the incision that is associated with at least one of
the following.
• Purulent drainage, with or without laboratory
confirmation, from the surgical site.
• Organisms isolated from an aseptically obtained culture of
fluid or tissue from the surgical site.
• At least one of the following signs or symptoms of
infection: pain or tenderness, localised swelling, redness or heat,
and superficial incision is deliberately opened by the surgeon and
is culture-positive or not cultured. A culture-negative finding
does not meet this criterion.
• Diagnosis of SSI by the surgeon or attending physician.
A deep incisional SSI is defined as: infection that occurs within
30 days after the operative procedure if no implant is left in place,
2Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
or within one year if an implant is left in place, and the infection
appears to be related to the operative procedure and involves deep
soft tissues (e.g. fascial and muscle layers) of the incision associated
with one of the following.
• Purulent drainage from the deep incision, but not from the
organ/space component of the surgical site.
• A deep incision spontaneously dehisces (opens up) or is
deliberately opened by the surgeon and is culture-positive or not
cultured when the patient has at least one of the following
symptoms: fever or localised pain or tenderness.
• An abscess, or other evidence of infection involving the
deep incision is found on direct examination, during re-
operation, or by histopathologic or radiologic examination.
• Diagnosis of a deep incisional SSI by a surgeon or attending
physician.
Other systems have been used to diagnose or classify SSI includ-
ing the ASEPSIS system and providing these are validated and
predominantly based upon a clinical diagnosis of SSI they will be
included in this review. We will exclude purely bacteriological def-
initions of SSI because the current clinical guidelines (CDC 1999;
NICE 2008) specify definitions of SSI based predominantly on
clinical signs and because it is difficult to differentiate infection
from contamination when interpreting the positive results of swab
cultures (Gurevich 1995; Peel 1991).
Description of the intervention
Wound-edge protection devices (WEPDs), also known as ’wound
guards’, have been used in abdominal surgery for more than 40
years (Maxwell 1969). There are several different devices on the
market but they have the same basic design - a semi-rigid plastic
ring placed into the abdomen via the laparotomy wound to which
an impervious drape is circumferentially attached. This plastic
drape comes up and out of the wound onto the skin surface, thus
protecting the cut wound edges. WEPDs create a physical barrier
between the abdominal wound edges and viscera, visceral contents,
contaminated instruments and gloves, thereby preventing wound
contamination. A wound protector may also provide a degree of
mechanical retraction of the incisional edges.
Despite their potential for reducing SSIs when used intra-oper-
atively, by protecting the wound margins from contact with any
contaminated materials, they have never become common prac-
tice and they are not mentioned in the current UK clinical guide-
lines. It should be noted that WEPDs are distinct from ’adhesive
drapes’: the latter are plastic drapes adherent to the superficial sur-
face of the skin and they do not come into direct contact with the
internal wound margins, i.e. the cut edge of skin, fat and fascia/
muscle.
How the intervention might work
The proposed mechanism of action of a WEPD is two-fold.
Firstly, they create a physical barrier between the abdominal wound
edges and viscera, visceral contents, contaminated instruments and
gloves, thus reducing accumulation of endogenous and exogenous
bacteria on the wound edges. They also potentially reduce tissue
necrosis from long procedure exposure as well as performing a de-
gree of mechanical retraction which in turn may reduce the need
for handheld mechanical retraction and the tissue damage associ-
ated therein. Smaller versions of wound-edge protection devices
are also currently often used in laparoscopic-assisted resections of
colorectal malignancies to prevent seeding of tumour cells into
wound edges - this potential role is not relevant to this review.
It can be hypothesised that WEPDs may be particularly benefi-
cial in procedures with an increased risk of endogenous contam-
ination such as clean-contaminated, contaminated or dirty pro-
cedures where, by definition, there will be greater bacteriological
concentrations contained within the operative field.
The effectiveness of the physical barrier WEPDs provide over the
wound edges in reducing numbers of bacterial pathogens present
was first reported more than 40 years ago (Harrower 1968) and
corroborated more recently by Horiuchi 2010 who found that all
incision margin cultures from patients where a WEPD had been
used yielded no growth of organisms.
Why it is important to do this review
SSI places a significant burden on healthcare systems globally due
to increased hospitalisation, additional operative and nursing costs
and drug treatment requirements. SSI is associated with signifi-
cant morbidity and mortality and can have a significant impact
on individuals’ well being, causing persistent pain, cosmetically
unacceptable scars and restriction of movement (NICE 2008).
Guidelines concerning the prevention of SSI have been issued in
the UK by the National Institute for Health and Clinical Excel-
lence (NICE 2008) and in the USA by the Centers for Disease
Control and Prevention (CDC 1999). These recommendations
are based on systematic reviews of best available evidence, or when
minimal evidence is available the guideline development group’s
opinion of what constitutes good practice. Intra-operative guid-
ance includes the role of hand decontamination, sterile gowns and
drapes, and antiseptic skin preparation. The concept of a WEPD
is not discussed in these guidelines.
O B J E C T I V E S
To compare the effects of WEPDs in the prevention of SSI in
patients undergoing abdominal surgery.
M E T H O D S
3Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Criteria for considering studies for this review
Types of studies
Published or unpublished randomised controlled trials (RCTs)
that compare the use of an intra-operative WEPD with standard
care or comparing alternate types of WEPD in patients undergoing
abdominal surgery. We will include any RCT where the use of a
WEPD is the only systematic difference between trial arms.
Types of participants
Studies involving patients of any age undergoing abdominal
surgery.
Types of interventions
The primary intervention is the use of a WEPD. For the purpose of
this review, a WEPD is considered eligible if it covered the wound’s
cut edges with an impervious plastic sheet. We will exclude studies
evaluating adhesive drapes which, unlike WEPDs, adhere to the
superficial surface of the skin and do not come into direct contact
with the internal wound margins, i.e. the cut edge of skin, fat and
fascia/muscle.
Types of outcome measures
Primary outcomes
• Postoperative SSI: any standard definition of postoperative
SSI based on clinical findings (e.g. CDC criteria) diagnosed
within 30 days of operation. We will exclude purely
bacteriological definitions of SSI. We will not differentiate
between superficial, deep incisional and organ space infection.
• Adverse events relating to use of the WEPD, as defined and
categorised in individual studies.
Secondary outcomes
• Cost-effectiveness: including measures of resource use such
as duration of hospital stay, operation duration, use of antibiotic
or analgesic drugs, dressing costs and nursing time, all in relation
to the index admission for the operation during which the
intervention (WEPD/control) was used.
• Pain within 30 days of operation, measured using survey/
questionnaire/data capture process or visual analogue scale in
individual studies.
• Health-related quality of life (measured using a
standardised generic questionnaire such as EQ-5D, SF-36, SF-
12 or SF-6 or disease-specific questionnaire). We will not include
ad hoc measures of quality of life which are likely not to be
validated and will not be common to multiple trials. Measured
any time from the operation up to one year.
• Other wound complications such as wound dehiscence and
incisional hernia - measured within one year of operation.
• Mortality.
Search methods for identification of studies
Electronic searches
We will search the following electronic databases:
• the Cochrane Wounds Group Specialised Register (latest
issue);
• the Cochrane Central Register of Controlled Trials
(CENTRAL) (The Cochrane Library, latest issue);
• Ovid MEDLINE (1948 to latest issue);
• Ovid MEDLINE (In-Process & Other Non-Indexed
Citations, latest issue);
• Ovid EMBASE (1974 to latest issue);
• EBSCO CINAHL (1982 to latest issue).
We will combine the Ovid MEDLINE search with the Cochrane
Highly Sensitive Search Strategy for identifying randomised tri-
als in MEDLINE: sensitivity- and precision-maximising version
(2008 revision); Ovid format (Lefebvre 2011). We will use the
Ovid EMBASE filter developed by the UK Cochrane Centre
(Lefebvre 2011) and combine the CINAHL search with the trial
filters developed by the Scottish Intercollegiate Guidelines Net-
work (SIGN) (SIGN 2011). There will be no restrictions on the
basis of date or language of publication.
We will use the following search strategy to search CENTRAL:
1 (wound* adj protect*).tw.
2 wound edge protect*.tw.
3 (wound* adj guard*).tw.
4 wound drape*.tw.
5 ring drape*.tw.
6 ((drape or barrier) adj protect*).tw.
7 (ViDrape or Vi Drape or Steri Drape or SteriDrape or Alexis).tw.
8 or/1-7
9 exp Surgical Wound Infection/
10 exp Surgical Wound Dehiscence/
11 (surg* adj5 infect*).tw.
12 (surg* adj5 wound*).tw.
13 (surg* adj5 site*).tw.
14 (surg* adj5 incision*).tw.
15 (surg* adj5 dehisc*).tw.
16 (wound* adj5 dehisc*).tw.
17 wound complication*.tw.
18 exp Bacterial Infections/
19 exp Postoperative Complications/
20 or/9-19
4Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
21 8 and 20
We will search the following ongoing trials databases:
• Current Controlled Trials (http://www.controlled-
trials.com/);
• ClinicalTrials.gov (http://www.clinicaltrials.gov/);
• WHO International Clinical Trials Registry Platform
(ICTRP) (http://www.who.int/ictrp/en/).
Searching other resources
We will search the bibliographies of all retrieved and relevant publi-
cations identified by these strategies for further studies. We will not
perform handsearches for this review since they are conducted by
the Cochrane Wounds Group in order to populate the Cochrane
Central Register of Controlled Trials (CENTRAL), which will
be searched. We will also contact manufacturers regarding studies
for inclusion including: 3M (’Steri-drape’ wound edge protection
drape), Applied Medical (’Alexis’ device) and Medical Concepts
Development (MCD) (’Vi-Drape’ device).
Data collection and analysis
Selection of studies
Two review authors will independently assess the study titles and
abstracts against the review inclusion criteria. After this initial as-
sessment, we will obtain all studies that might potentially meet
these criteria in full. Two review authors will check the full pa-
pers for eligibility, with disagreements being resolved by discus-
sion and, where required, the input of a third review author. We
will extract details of the eligible studies and summarise them on
a data extraction sheet. Two review authors will extract data in-
dependently. If data are missing from reports, we will make at-
tempts to contact the study authors to obtain the missing infor-
mation. Studies published in duplicate will be included once, but
we will extract the maximum amount of data from the papers.
This process will be followed by all review authors, with at least
two review authors working independently. We plan to include a
study flow diagram as recommended by the PRISMA statement
(Liberati 2009) to illustrate the results of all searching activity and
the process of screening and selecting studies for inclusion in the
review.
Data extraction and management
Two review authors will extract all data independently. We will
extract the following data.
• Country of origin of trial.
• Type of surgery.
• Classification of surgical contamination.
• Eligibility criteria and baseline participant data.
• Details of the protector/treatment regimen received by each
group and any co-interventions.
• Primary and secondary outcome(s) (with definitions).
• Outcome data for primary and secondary outcomes (by
group).
• Duration of follow-up.
• Number of withdrawals (by group).
• Source of funding for trial.
Assessment of risk of bias in included studies
Two review authors will independently assess each included study.
We will undertake assessment using the Cochrane Collaboration
tool for assessing risk of bias (Higgins 2011). The ’Risk of bias’
tool considers six domains: sequence generation, allocation con-
cealment, blinding, incomplete outcome data, freedom from se-
lective reporting and other issues (e.g. fraud). Please see Appendix
1 for details of the criteria on which the judgement will be based.
We will complete a ’Risk of bias’ table for each eligible study; we
will combine these data into a ’Risk of bias’ summary figure where
judgements for each domain are tabulated by study. We will con-
sider all risk of bias domains equally, but for the purpose of the
proposed sensitivity analysis we will classify trials as being at over-
all high risk of bias if they are rated ’high’ for any one of three key
criteria, i.e. randomisation sequence, allocation concealment and
blinded outcome assessment.
Measures of treatment effect
We will present results with 95% confidence intervals (CI). We
will report estimates for dichotomous outcomes (e.g. infected: yes/
no) as risk ratios (RR) (Deeks 2002). We will report continuous
data (e.g. pain) as mean differences (MD) and we will calculate
overall effect sizes (with 95% CI). We will record the adverse events
reported and present this information narratively, we will report
the data as count data if available.
Dealing with missing data
The problem of missing data is common in trials, especially those
of poor quality. Excluding participants from the analysis after ran-
domisation, or ignoring participants lost to follow-up can, in ef-
fect, undo the process of randomisation and thus, potentially, in-
troduce bias into the trial. For our primary outcomes, SSI and
adverse events, we will assume that where randomised participants
are not included in an analysis, they did not have a SSI or other
adverse event(s)(that is they were considered in the denomina-
tor but not the numerator). Given the relatively small number of
SSI or adverse events anticipated, this seems the most appropri-
ate assumption. However, we will test this assumption in a sen-
sitivity analysis where we will assume participants excluded post-
randomisation to have developed the outcome (i.e. included in
both the numerator and the denominator). Where a trial does not
5Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
specify participant group numbers prior to dropout, we will only
present complete case data. We will present data for all secondary
outcomes as complete case analysis.
Data synthesis
We will explore both clinical and statistical heterogeneity and the
decision to include studies in a meta-analysis will depend on the
availability of treatment effect data and assessment of heterogene-
ity.
We will also summarise data for each comparison by compiling
’Summary of findings’ tables in GRADEprofiler: all outcomes will
be included. We will estimate control group event rates for pa-
tients at medium risk of SSI using the average risk of SSI in the
included studies; we will investigate the potential of estimating
control group event rates for patients at high risk of SSI using data
from studies with populations at particularly high risk, e.g. based
on surgery type.
Subgroup analysis and investigation of heterogeneity
We will assess statistical heterogeneity using the Chi² test (we will
consider a P value significance level of less than 0.1 to indicate het-
erogeneity). We will consider the I² statistic which examines the
percentage of total variation across studies due to heterogeneity
rather than to chance. Values of I² over 50% may represent sub-
stantial heterogeneity (Higgins 2003). In the absence of clinical
heterogeneity, we will perform a meta-analysis using a fixed-effects
model. Where there is likely clinical heterogeneity, we will apply
a random-effects model. Where possible we will assess the influ-
ence of the degree of contamination (clean/clean-contaminated/
contaminated/dirty) on the impact of wound protectors on SSI
rate.
Should data be available we will undertake subgroup analyses com-
paring open and laparoscopic surgery.
Sensitivity analysis
We will undertake a sensitivity analysis to investigate the effects of
removing studies at high risk of bias from the analysis, studies at
high risk of bias being those which do not adequately define ran-
dom sequence generation, allocation concealment methods and
blinding of outcome assessor. We will undertake a sensitivity anal-
ysis to investigate the way that missing data was dealt with as de-
tailed in the Dealing with missing data section.
’Summary of findings’ table
We will present the main results of the review in summary of
findings tables, which provide key information concerning the
quality of evidence, the magnitude of effect of the interventions
examined, and the sum of available data on the main outcomes,
as recommended by the Cochrane Collaboration (Schunemann
2011a). We plan to include the following main outcomes in the
summary of findings tables:
1. surgical site infection;
2. health-related QOL and cost-effectiveness
3. wound complications, adverse events.
The summary of findings table includes an overall grading of the
evidence related to each of the main outcomes, using the GRADE
approach (Schunemann 2011b).
A C K N O W L E D G E M E N T S
We would like to acknowledge Jenny Bellorini, the copy editor
of this protocol, the external peer referees (Anne-Marie Bagnall,
Malcolm Brewster, Beryl de Souza and Elmer Villanueuva) and the
Wounds Group Editors (Kurinchi Gurusamy and Dirk Ubbink).
R E F E R E N C E S
Additional references
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Astagneau P, Rioux C, Golliot F, Brucker G. Morbidity and
mortality associated with surgical site infections: results
from the 1997-1999 INCISO surveillance. Journal of
Hospital Infection 2001;48(4):267–74.
Astagneau 2009
Astagneau P, L’Hériteau F, Daniel F, Parneix P, Venier AG,
Malavaud S, et al.Reducing surgical site infection incidence
through a network: results from the French ISO-RAISIN
surveillance system. Journal of Hospital Infection 2009;72
(2):127–34.
Blumetti 2007
Blumetti J, Luu M, Sarosi G, Hartless K, McFarlin J, Parker
B, et al.Surgical site infections after colorectal surgery:
do risk factors vary depending on the type of infection?.
Surgery 2007;142(5):704–11.
Bruce 2001
Bruce J, Russell EM, Mollison J, Krukowski ZH. The
measurement and monitoring of surgical adverse events.
Health Technology Assessment Monograph 2001;5(22):1–194.
CDC 1999
Centers for Disease Control and Prevention (CDC).
Guideline for prevention of surgical site infection. Infection
Control and Hospital Epidemiology 1999;20:247–78.
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Coello 2005
Coello R, Charlett A, Wilson J, Ward V, Pearson A,
Borriello P. Adverse impact of surgical site infections in
English hospitals. Journal of Hospital Infection 2005;60(2):
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de Lissovoy 2009
de Lissovoy G, Fraeman K, Hutchins V, Murphy D,
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Deeks 2002
Deeks JJ. Issues in the selection of a summary statistic
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Statistics in Medicine 2002;21:1575–600.
Gurevich 1995
Gurevich I, Horan TC. Surgical site infections: simplifying
the definitions. Infection Control and Hospital Epidemiology
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Harrower 1968
Harrower HW. Isolation of incisions into body cavities.
American Journal of Surgery 1968;116:824–6.
Higgins 2003
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A P P E N D I C E S
Appendix 1. Appendix 1 - Assessment of risk of bias in included studies
1. Was the allocation sequence randomly generated?
Low risk of bias
The investigators describe a random component in the sequence generation process such as: referring to a random number table; using
a computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots.
High risk of bias
The investigators describe a non-random component in the sequence generation process. Usually, the description would involve some
systematic, non-random approach, for example: sequence generated by odd or even date of birth; sequence generated by some rule
based on date (or day) of admission; sequence generated by some rule based on hospital or clinic record number.
Unclear
Insufficient information about the sequence generation process to permit judgement of low or high risk of bias.
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2. Was the treatment allocation adequately concealed?
Low risk of bias
Participants and investigators enrolling participants could not foresee assignment because one of the following, or an equivalent
method, was used to conceal allocation: central allocation (including telephone, web-based and pharmacy-controlled randomisation);
sequentially numbered drug containers of identical appearance; sequentially numbered, opaque, sealed envelopes.
High risk of bias
Participants or investigators enrolling participants could possibly foresee assignments and thus introduce selection bias, such as allocation
based on: using an open random allocation schedule (e.g. a list of random numbers); assignment envelopes were used without appropriate
safeguards (e.g. if envelopes were unsealed or non opaque or not sequentially numbered); alternation or rotation; date of birth; case
record number; any other explicitly unconcealed procedure.
Unclear
Insufficient information to permit judgement of low or high risk of bias. This is usually the case if the method of concealment is not
described or not described in sufficient detail to allow a definite judgement, for example if the use of assignment envelopes is described,
but it remains unclear whether envelopes were sequentially numbered, opaque and sealed.
3. Blinding - was knowledge of the allocated interventions adequately prevented during the study?
Low risk of bias
Any one of the following.
• No blinding, but the review authors judge that the outcome and the outcome measurement are not likely to be influenced by
lack of blinding.
• Blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken.
• Either participants or some key study personnel were not blinded, but outcome assessment was blinded and the non-blinding of
others unlikely to introduce bias.
High risk of bias
Any one of the following.
• No blinding or incomplete blinding, and the outcome or outcome measurement is likely to be influenced by lack of blinding.
• Blinding of key study participants and personnel attempted, but likely that the blinding could have been broken.
• Either participants or some key study personnel were not blinded, and the non-blinding of others likely to introduce bias.
Unclear
Any one of the following.
• Insufficient information to permit judgement of low or high risk of bias.
• The study did not address this outcome.
4. Were incomplete outcome data adequately addressed?
Low risk of bias
Any one of the following.
• No missing outcome data.
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• Reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing
bias).
• Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups.
• For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a
clinically relevant impact on the intervention effect estimate.
• For continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing
outcomes not enough to have a clinically relevant impact on observed effect size.
• Missing data have been imputed using appropriate methods.
High risk of bias
Any one of the following.
• Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing
data across intervention groups.
• For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce
clinically relevant bias in intervention effect estimate.
• For continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing
outcomes enough to induce clinically relevant bias in observed effect size.
• ‘As-treated’ analysis done with substantial departure of the intervention received from that assigned at randomisation.
• Potentially inappropriate application of simple imputation.
Unclear
Any one of the following.
• Insufficient reporting of attrition/exclusions to permit judgement of low or high risk of bias (e.g. number randomised not stated,
no reasons for missing data provided).
• The study did not address this outcome.
5. Are reports of the study free of suggestion of selective outcome reporting?
Low risk of bias
Any of the following.
• The study protocol is available and all of the study’s pre-specified (primary and secondary) outcomes that are of interest in the
review have been reported in the pre-specified way.
• The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that
were pre-specified (convincing text of this nature may be uncommon).
High risk of bias
Any one of the following.
• Not all of the study’s pre-specified primary outcomes have been reported.
• One or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that
were not pre-specified.
• One or more reported primary outcomes were not pre-specified (unless clear justification for their reporting is provided, such as
an unexpected adverse effect).
• One or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta-analysis.
• The study report fails to include results for a key outcome that would be expected to have been reported for such a study.
Unclear
Insufficient information to permit judgement of low or high risk of bias. It is likely that the majority of studies will fall into this category.
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6. Other sources of potential bias
Low risk of bias
The study appears to be free of other sources of bias.
High risk of bias
There is at least one important risk of bias. For example, the study:
• had a potential source of bias related to the specific study design used; or
• has been claimed to have been fraudulent; or
• had some other problem.
Unclear
There may be a risk of bias, but there is either:
• insufficient information to assess whether an important risk of bias exists; or
• insufficient rationale or evidence that an identified problem will introduce bias.
C O N T R I B U T I O N S O F A U T H O R S
Thomas Pinkney conceived the review question, developed the protocol, coordinated development, completed the first draft, performed
part of the writing and editing of the protocol, made an intellectual contribution, advised on the protocol, approved the final draft
prior to submission and is guarantor.
John McCall conceived the review question, developed the protocol and coordinated development, completed the first draft, performed
part of the writing and editing of the protocol, made an intellectual contribution, advised on the protocol, approved the final version
prior to submission.
Jo Dumville conceived the review question, developed the protocol, completed the first draft of the protocol, performed part of the
writing and editing of the protocol, made an intellectual contribution, advised on the protocol, and approved the final version prior to
submission.
Francesca Edwards conceived the review question, developed the protocol, completed the first draft, performed part of the writing and
editing, made an intellectual contribution, advised on the protocol and approved the final version prior to submission.
Adrian Gheorghe developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual
contribution, advised on the protocol, and approved the final version prior to submission.
David Bartlett conceived the review question, developed the protocol, completed the first draft, performed part of the writing and
editing, made an intellectual contribution, advised on the protocol and approved the final version prior to submission.
Melanie Calvert developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual
contribution, advised on the protocol and approved the final version prior to submission.
Benjamin Fletcher developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual
contribution, advised on the protocol and approved the final version prior to submission.
Contributions of editorial base:
Nicky Cullum: edited the protocol; advised on methodology, interpretation and protocol content.
Kurinchi Gurusamy, Editor: advised on methodology and protocol content. Approved the final protocol prior to submission.
Sally Bell-Syer: coordinated the editorial process. Advised on methodology, interpretation and content. Edited and copy edited the
protocol.
Ruth Foxlee: designed the search strategy and edited the search methods section.
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D E C L A R A T I O N S O F I N T E R E S T
The authors Pinkney, Gheorghe, Bartlett, and Calvert are members of the trial management group for the ROSSINI Trial - a multicentre
UK randomised controlled trial assessing the efficacy of wound-edge protection devices in the reduction of surgical site infection for
adult patients undergoing laparotomy. This trial is independent research commissioned by the National Institute for Health Research
(NIHR) under the Research for Patient Benefit (RfPB) programme (PB-PG-1208-18234) and is not sponsored by industry. Mr Fletcher
works alongside the members of the trial management group at the University of Birmingham, but is not a member himself.
S O U R C E S O F S U P P O R T
Internal sources
• Department of Surgical Sciences, Dunedin School of Medicine, Otago University, New Zealand.
Salary
External sources
• NIHR/Department of Health (England), (Cochrane Wounds Group), UK.
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Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
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