SLEEP APNEA AND VENTILATORY DISORDERS IN ANESTHESIA (F CHUNG, SECTION EDITOR)

Perioperative Complications in Patients with ObstructiveSleep Apnea

Roop Kaw

Published online: 13 December 2013

� Springer Science + Business Media New York 2013

Abstract Recent literature is full of studies that have

brought forth several perioperative concerns in patients

with known or suspected obstructive sleep apnea. These

issues were first reported as independent observations or

case series, until data emerged from single centers and were

more recently confirmed from analysis of large databases of

hospitalized patients undergoing elective surgery. Among

these, the concerns raised most often are those of difficult

intubation and postoperative respiratory complications

requiring reintubation and mechanical ventilation; positive

airway pressure therapy, unplanned critical care service

admission or prolonged intensive care unit or hospital stay.

Others have reported cardiac events and unexpected/unex-

plained postoperative mortality. While all possible postop-

erative complications are not yet fully established or

understood, the prevention and management of these

complications may sometimes not be as challenging.

Keywords Perioperative � Anesthesia � Obstructive sleep

apnea � Continuous positive airway pressure � Sleep

disordered breathing � Polysomnography

Introduction

The prevalence of obstructive sleep apnea (OSA) among

patients undergoing elective surgery varies according to the

screening or diagnostic method of the study reporting it.

Recently, in the largest single academic registry of surgical

patients undergoing anesthesia, Ramachandran et al. [1]

reported a prevalence of 7 % patients with OSA. Similarly,

Memtsoudis et al. [2] reported a prevalence of sleep apnea

(billed diagnosis) in 1998 versus 2007 to be 0.4 and 2.7 %

for general surgical procedures and 0.4 and 5.5 % for

orthopedic procedures, respectively. Recent studies have

identified some of the specific risks among patients with

OSA in the surgical setting. Since patients with OSA are

prone to hypoxia especially during the night any added

insults during anesthesia induction or recovery, with

sedation or analgesia required in the perioperative setting,

can tend to exacerbate any hypoxia-related complication in

the postoperative period. This review examines the evi-

dence for these complications in detail and also discusses

some recommended strategies and interventions to mini-

mize possible adverse outcomes.

Difficult Intubation (DI)

Both anesthesia and sleep induce reductions in pharyngeal

dilator muscle activation and lung volume, thereby predis-

posing to upper airway obstruction. [3] Upper airway mus-

cular tone can be delayed (100–200 ms) or abolished during

inspiration in patients with OSA [4, 5]. In addition, upper

airway neuromotor responses are impaired in patients with

OSA relative to controls, and variability in collapsibility of

the upper airway between individuals cannot be explained by

structural loads alone [6]. Although DI has not been specif-

ically studied among patients with OSA, its major predictor,

as reported by Kheterpal et al. [7] among a cohort of 50,000

anesthetized patients, is body mass index (BMI)[30 kg/m2;

OSA and neck circumference[40 cm can also predict OSA

in the general population. The same can be said of clinical

predictors of DI such as the Mallampati score and short

R. Kaw (&)

Departments of Hospital Medicine and Anesthesiology

Outcomes Research, Cleveland Clinic, 9500 Euclid Avenue,

Cleveland, OH 44195, USA

e-mail: kawr@ccf.org

123

Curr Anesthesiol Rep (2014) 4:37–41

DOI 10.1007/s40140-013-0044-3

thyromental span [8]. Indeed, a close relationship has been

suggested between DI and the presence of OSA [9].

Strategies to Mitigate DI and/or Mask Ventilation

Isono et al. [10] reported passive closing pressures (PCLOSE)

among anesthetised OSA patients to be up to 9 cm H2O higher

than among non-OSA patients and recommended reduction

by about 10 cm of H2O. Proper positioning of the patient in the

sitting position can decrease the PCLOSE by 6 cmH2O and is

advantageous for mask ventilation. Similarly, the sniffing or

the ramp position will decrease the PCLOSE by 4 cmH2O,

also allowing both tracheal intubation and ventilation. Awake

intubation (with regional anesthesia and or sedation) and rapid

induction are preferred over slow induction when DI is sus-

pected [11]. Negative inspiratory pressure from spontaneous

breathing can induce negative constricting forces in the air-

way, which can progressively increase to -50 cm H2O and

cannot be possibly ameliorated by continuous positive airway

pressure (CPAP) during pharyngeal obstruction [12]. Pha-

ryngeal airway closure can be prevented by application of

10 cm of positive end expiratory pressure (PEEP) during

positive pressure ventilation in even the most severe cases of

OSA.

Postoperative Respiratory Failure

The other main concern among patients with OSA is post-

operative respiratory failure. In 1997, Ostermeier et al. [13]

reported three cases of sudden postoperative respiratory

arrest associated with epidural opioids in patients with sleep

apnea. All three patients died. Recently, looking at a large

inpatient database, Memtsoudis et al. [2] reported a five-

fold increase in intubation and mechanical ventilation after

orthopedic surgery (n *50,000) and two-fold increase after

general surgery (n *50,000) among patients with OSA

compared to controls. Our group confirmed a higher prev-

alence of postoperative respiratory failure in a meta-ana-

lysis of 3,942 patients with OSA (OR, 2.43; p = 0.003)

compared to controls [14] (Fig. 1). More recently, Mokhlesi

et al. [15], also using the NIS database, looked at postop-

erative outcomes among different surgical categories and

again found a higher need for emergent intubation and

postoperative mechanical ventilation unchanged across all

surgical categories. Interestingly enough, after adjusting for

the age, sex and Charleston comorbidity index, patients

without sleep-disordered breathing (SDB) requiring emer-

gent intubation had significantly worse outcomes compared

to those with SDB requiring emergent intubation. The need

for emergent intubation and mechanical ventilation was

higher on the day of surgery or the first postoperative day

compared to patients without SDB. Among possible

explanations for both of these findings provided by the

authors was that events requiring intubation and mechanical

ventilation in patients with SDB could be mostly related to a

rapidly reversible upper airway complication in the setting

of opioid and sedative use in the immediate postoperative

period or perhaps a lower threshold was used for intubating

patients with OSA or transferring them to the intensive care

unit (ICU). Both of these studies using the NIS data [2, 15]

were dominated by the orthopedic surgical cohort

(n *1,000,000) and showed a steadily increasing preva-

lence of OSA from the start of the study period to the end.

Early reports among patients with obesity hypoventilation

syndrome (OHS) undergoing elective surgery show that the

incidence of postoperative respiratory failure may be even

higher and that OHS is more likely to be unrecognized

before elective non-cardiac surgery when compared to OSA

[16]. Another subset of patients with OSA on chronic opiate

Study or Subgroup

Ahmad 2008Finkel 2009Gali 2009Gupta 2001Kaw 2006Kaw 2009Luizaga 2010Sabers 2003Vasu 2010

Total (95% CI)

Total eventsHeterogeneity: Chi² = 7.06, df = 6 (P = 0.31); I² = 15%Test for overall effect: Z = 2.93 (P = 0.003)

Events

01065

16014

33

Total

31661221101

37270

69234

56

1680

Events

1002

164010

24

Total

92117

472101185202

22234

79

3421

Weight

15.3%1.6%

12.8%31.5%29.4%

6.8%2.6%

100.0%

M-H, Fixed, 95% CI

0.09 [0.00, 2.41]9.62 [0.39, 236.37]

Not estimable3.13 [0.62, 15.87]

1.65 [0.56, 4.83]3.12 [1.03, 9.47]

Not estimable1.00 [0.06, 16.08]

13.63 [0.72, 258.43]

2.43 [1.34, 4.39]

OSA Non-OSA Odds Ratio Odds RatioM-H, Fixed, 95% CI

0.01 0.1 1 10 100Favours OSA Favours Non-OSA

Fig. 1 Postoperative respiratory failure as reported among patients with OSA undergoing elective surgery. From ‘‘In the December 2012 BJA …,’’

Br. J. Anaesth. (2012), 109 (6): vi, with permission from Oxford University Press

38 Curr Anesthesiol Rep (2014) 4:37–41

123

therapy has been shown to fail CPAP therapy more often

than those who are not chronically on opioids for pain

control [17••]. This has been attributed to the presence of

central sleep apnea during CPAP, a condition known as

complex sleep apnea, as well as poorly understood breath-

ing patterns.

Depending upon the definition used among the different

studies reported in the literature as well as their respective

sample size, postoperative respiratory failure has not been

consistently reported among patients with OSA. Moreover,

some of the single-center studies were originally initiated

as quality improvement (QI) projects and hence by design

report fewer postoperative respiratory complications than

others [18–21]. Among other reasons for variations in

reporting of postoperative complications between different

studies are whether OSA was diagnosed clinically by

screening or by a gold standard test and, especially among

the case control studies, whether the comparison was

against a group of ‘true controls’ (OSA excluded by formal

polysomnography).

Unanticipated ICU Transfer

Although ICU transfer has been used as an outcome measure

among patients with OSA who undergo surgery, it is not

always easy to track as patients are often sent to ICU over-

night for observation. After excluding studies [22] that made

specific mention of such practices, our meta-analysis showed

that the presence of OSA was significantly associated with

higher odds of ICU transfer [105/2,062 (5.09 %) versus

58/3,681 (1.57 %), respectively; OR 2.29, 95 % CI

1.62–3.24, p B 0.00001, (I2 = 57–68 %, p B 0.02] after

surgery. It is even harder to get this information from the two

recent studies reporting on a large number of surgical

patients as NIS data [12, 14] do not report use of advanced

services such as critical care, step down and telemetry ser-

vices when reporting or estimating charges. A recent study

using the STOP-BANG score as a predictor of postoperative

critical care admission reported OR of 2.2 (95 % CI 1.1–4.6;

p = 0.037), 3.2 (95 % CI 1.2–8.1; p = 0.017) and 5.1 (95 %

CI: 1.8–14.9; p = 0.002) for STOP-BANG scores of 4, 5

and C6, respectively [23].

Postoperative Mortality

Gami et al. [24], looking at autopsy reports, reviewed 112

reports of sudden death and found that almost half of the

patients with polysomnographically confirmed OSA died

during sleep hours (12 midnight to 6.00 am) compared to

21 % of those without OSA (RR: 2.57). More recently, the

same group of authors showed that OSA independently

predicted sudden cardiac death (SCD), and among these

patients, the lowest nocturnal oxygen desaturation and AHI

were independent predictors of SCD [4, 25]. A few studies

that have looked at postoperative mortality [14, 25] did not

find any association between OSA and mortality after

elective surgery. In fact, Mokhlesi et al. found lower

mortality among patients with OSA undergoing cardiac

(OR 0.54; 95 % CI 0.40–0.73; p \ 0.001), orthopedic (OR

0.65; 95 % CI 0.45–0.95; p = 0.03) and abdominal surgery

(0.38; 95 % CI 0.22–0.65; p = 0.001) compared to those

without OSA. The study used administrative data that limit

the validity of the OSA diagnosis as well as use of

advanced and critical care services; hence, the investigators

cannot provide any plausible explanation for this result and

advise cautious interpretation. Recently, Lockhart et al.

[26] did not find any difference in 30-day and 1-year

postoperative mortality among patients with OSA under-

going elective surgery compared to controls. However,

patients who screened as high risk for OSA by the Flemon,

STOP or STOP-BANG criteria revealed higher mortality at

1 year compared to the group that screened as low risk for

OSA, but no causal inferences can be made. This observed

lack of association between postoperative mortality and

OSA does not necessarily mean that death cannot be an

expected sentinel event in a postoperative patient with

OSA especially if exposed to additional insults such as a

failed airway, an unmonitored respiratory depression opi-

oid and/or sedative administration especially with PCA

infusions and others. Clearly the incidence of such events

in the perioperative setting when reported from the large

administrative databases is low enough to pass any statis-

tical rigor of association.

Perioperative Risk Reduction Strategies in Obstructive

Sleep Apnea (OSA)

Some patients present with DI and airway management

issues. Patients with known OSA using CPAP at home

should be advised to bring their machine to the hospital at

the preoperative visit. Patients who are noncompliant

should be encouraged to use it more consistently. In

patients with previously undiagnosed OSA and high clin-

ical suspicion of OSA based on preoperative assessment, if

significant use of opioids and sedation is anticipated based

on the type of the surgical procedure, consideration should

be given to inpatient surgery as opposed to ambulatory

surgery. Wherever possible regional anesthesia and blocks

are preferred and for general anesthesia, short-acting agents

such as desflurane and propofol are recommended. A

recent study on sleep apnea patients undergoing total joint

arthroplasty found that patients undergoing surgery under

neuraxial anesthesia had significantly lower rates of major

Curr Anesthesiol Rep (2014) 4:37–41 39

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complications compared to cases in which combined

neuraxial and general or general anesthesia was used

[27••]. When using general anesthesia, the possibility of DI

should be kept in mind, and preparation for induction and

intubation should follow the ASA difficult airway guide-

lines [28]. Full reversal of neuromuscular blockade (when

applicable) with use a nerve stimulator should be verified

prior to extubation [29]. These patients must be fully

awake, normothermic, hemodynamically stable, and

spontaneously breathing with an adequate respiratory rate

and tidal volume prior to breathing.

Multimodal analgesia involving the use of NSAIDS,

acetaminophen, tramadol, ketamine, pregabalin and COX-

2 inhibitors should be considered to minimize the use of

opioids in the postoperative setting [30]. OSA patients

receiving opioids are more likely than patients receiving

nonopiod analgesia to have perioperative oxygen desatu-

ration [31]. Patients undergoing ambulatory surgeries

should be observed for an extended period of time prior to

their discharge home [32]. Continuous pulse oximetry

monitoring is recommended in the postoperative setting in

patients at risk for respiratory complications of OSA.

Cautious use of supplemental oxygen is advised after

extubation until the patient is able to maintain his/her

baseline oxygen saturation on room air. If frequent or

severe airway obstruction or hypoxemia is noted in the

postoperative monitoring period, consideration should be

made to initiate CPAP of NIPPV.

The role of CPAP used perioperatively among patients

with OSA has not been well studied. Indirect evidence can be

obtained from patients undergoing bariatric surgery who

happen to have a higher prevalence of OSA and have often

had the chance to have a treatment plan initiated before sur-

gery. Although some series have reported higher postopera-

tive complication rates among bariatric surgical patients with

OSA, in others most patients were preoperatively diagnosed

and treated with PAP therapy; the presence or severity of

OSA did not lead to a higher postoperative complication rate.

[33]. Among patients with OSA cardioverted for atrial

fibrillation, those treated with CPAP were less likely to

develop recurrent atrial fibrillation within 12 months of car-

dioversion compared to patients without treatment with CPAP

[34]. A recent study randomized patients with a high Sleep

Apnea Clinical Score (SACS) undergoing elective orthopedic

surgery to standard care with auto-PAP and to standard care

alone. No differences in length of stay (p = 0.65) or sec-

ondary outcomes (including unplanned ICU transfer,

arrhythmia, MI or delirium) were observed between the two

groups [35••]. Some of the main limitations of this study,

were incomplete resolution of OSA as suggested by a median

residual AHI of 13.5 events/h, inability to distinguish central

sleep apnea from OSA and limited adherence in a hospital

setting. Conclusive evidence mandating empiric use of CPAP

perioperatively among patients not currently using it is still

lacking. More studies are needed.

Conclusions

Clinicians taking care of patients with OSA are often

intrigued and concerned about safe perioperative care.

Studies to date have shown that OSA is vastly underesti-

mated in the general population and often undiagnosed in

surgical patients; hence, it can lead to higher postoperative

morbidity. Early clinical recognition of OSA can definitely

help in designing a safer careplan.

Compliance with Ethics Guidelines

Conflict of Interest Roop Kaw declares that he has no conflict of

interest.

Human and Animal Rights and Informed Consent This article

does not contain any studies with human or animal subjects per-

formed by any of the authors.

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Curr Anesthesiol Rep (2014) 4:37–41 41

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