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Review article

Obstructive sleep apnoea in adults

peri-operative considerations

A narrative review

Roesslein, Martin; Chung, Frances

Author Information
European Journal of Anaesthesiology: April 2018 - Volume 35 - Issue 4 - p 245-255
doi: 10.1097/EJA.0000000000000765
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The prevalence of sleep-related breathing disorders (SBDs) has been increasing in recent years, mainly due to the worldwide rise in obesity and chronic diseases.1–4 Obstructive sleep apnoea (OSA), the most common SBD, is characterised by repetitive obstruction of the upper airway resulting in abnormal ventilation during sleep. Consequently, affected individuals often suffer from sleep fragmentation, hypersomnolence, abnormal gas exchange and also significant cardiovascular and metabolic morbidity.5–10

Surgical patients afflicted with OSA pose a challenge to their treatment providers, as they may be at an increased risk for peri-operative complications.11–19 Furthermore, the disorder may not have been diagnosed preoperatively, potentially aggravating the associated risks.20–22

This review is based on the sources of information currently available within the public domain. It intends to inform on the epidemiology, pathogenesis and diagnosis of OSA in adult surgical patients, and also examine recommended measures for appropriate peri-operative management, including preoperative assessment, selection of suitable intra-operative anaesthesia regimens and for the management of the extent and duration of postoperative monitoring and care.

Definition of obstructive sleep apnoea

The American Academy of Sleep Medicine defines OSA as a disorder with repetitive episodes of complete (apnoea) or partial upper airway obstruction (hypopnoea) during sleep, often resulting in the reduction of blood oxygen saturation and usually terminated by brief arousals.23 The number of these predominantly obstructive respiratory events per hour of sleep determines the apnoea-hypopnoea index (AHI).

The term OSA syndrome refers to the existence of excessive daytime sleepiness or other health consequences of OSA.24 It is considered a chronic disease6 associated with the following cardiovascular and metabolic pathologies:5,23 systemic hypertension, pulmonary hypertension, coronary artery disease, atrial fibrillation, cerebrovascular accidents and type 2 diabetes mellitus.

Epidemiology of obstructive sleep apnoea

Depending on the diagnostic and sample criteria, the prevalence in the general population is estimated to vary between 3 and 24%,25–28 but is generally much higher in patients undergoing surgery (24 to 41%),19,29,30 reaching up to 70% in certain groups such as those seeking bariatric surgery.31 In the majority of cases, the diagnosis has not been established and hence therapy has not been commenced.30,31

Pathogenesis of obstructive sleep apnoea

The pathophysiology of OSA is complex and the underlying mechanisms involve impaired airway anatomy, ineffective control and function of upper-airway dilator muscles and also low arousal thresholds in association with impaired ventilatory control. The fact that these mechanisms seem to affect the genesis of the disease in individual patients to different extents has led to the perception of the existence of different OSA phenotypes.32,33

Being overweight with BMI (≥25 kg m−2) and obese (BMI ≥ 30 kg m−2) seem to be of utmost importance in the development of the disease. This is reflected in the fact that about 70% of OSA patients are overweight or obese; the prevalence of OSA in the obese is about twice as high as in adults of normal weight.4,34 Unsurprisingly, therefore, weight loss has been shown to significantly reduce severity and symptoms of OSA.35

Nonobese patients may suffer from OSA if certain characteristics in craniofacial anatomy are present such as inferior positioning of the hyoid bone, retropositioning of the mandible, an increase in the craniocervical extension angle or craniofacial skeletal restrictions.33,36

Next in importance to alterations in the anatomy of the upper airway, a decreased activity of the involved dilating muscles may contribute to the progression of the disease. In addition, pathological sensory processing of the upper airway leading to decreased stability of ventilatory control seems to be relevant to the pathogenesis.32,33

Diagnosis of obstructive sleep apnoea

According to the International Classification of Sleep Disorders (ICSD-3), diagnosis of OSA requires the following:24

  1. A breathing disorder not caused by another sleep disorder or medical cause or medication or other substances, and
  2. AHI at least 15 or AHI at least 5 in combination with relevant comorbidities.

Patients meeting the diagnostic criteria for OSA have traditionally been classified as having mild, moderate or severe disease on the basis of AHI with symptoms and associated medical complications taken into account.37 While the AHI, with underlying respiratory events that have not been consistently defined, helps to differentiate degrees of OSA severity, it may oversimplify the complex pathophysiology of the disease.2,3 Additional indices from polysomnography (PSG) and/or oximetry such as oxygen desaturation index, cumulative duration of oxygen desaturation less than 90%, the lowest SpO2 and/or mean SpO2 may help to improve the predictive value for postoperative complications in OSA patients.38,39

Peri-operative complications of obstructive sleep apnoea

Surgical patients with OSA undergoing procedures that require the use of opioids and/or general anaesthesia have been demonstrated to have a higher rate of various complications throughout the peri-operative period, mostly evident during the postoperative phase (Table 1).12–19

Table 1
Table 1:
Postoperative complications

Several peri-operative and anaesthetic factors may contribute to these complications:

  1. Medication: drugs commonly used during general anaesthesia (hypnotics, opioids and muscle relaxants) have been shown to have a negative influence on the tone of the upper-airway dilating muscles, the protective airway reflexes, the central respiratory drive and arousability.40,41 Although direct evidence is still lacking, these effects may be of immediate relevance to OSA patients who display compromised upper airway stability and ventilatory control.42,43
  2. Anaesthesia and the patient's position can negatively affect longitudinal traction forces in the trachea, leading to increased pharyngeal closing pressure and collapse of the upper airway.40,44
  3. Narrowing of the upper airway caused by pharyngeal oedema following intubation, haematoma or protracted prone positioning of the patient;21,45
  4. Protracted postoperative supine positioning of the patient leading to decreased airway stability;46
  5. Peri-operative discontinuation of continuous positive airway pressure (CPAP) therapy;47 and
  6. Disruption of sleep architecture favouring apnoeic episodes at night with increased periods of rapid eye movement (REM) following surgery.48

Existing cardiovascular and metabolic comorbidities associated with OSA not only contribute to the peri-operative risk profile of these patients but also make it more difficult to attribute complications to OSA specifically.49–51

Pulmonary complications

In several studies, a diagnosis of OSA has been associated with challenging airway management, including difficult or impossible mask ventilation,52 intubation53–57 or both.58 Interestingly, OSA as a predictor of difficult mask ventilation combined with difficult laryngoscopy seems to be independent of BMI or Mallampati status.58

The reciprocity of this relation is underlined by the fact that patients with unexpected difficult intubation may have previously undiagnosed OSA.59

The risk for pulmonary complications associated with OSA extends into the postoperative period. A meta-analysis was able to associate OSA with a decrease in peripheral oxygen saturation [odds ratio (OR) 2.27; 95% confidence interval (95% CI) 1.20 to 4.26, P = 0.01] and even acute respiratory failure (OR 2.43; CI 1.20 to 4.26, P = 0.01).12

In a large observational study of almost six million cases, orthopaedic and surgical patients suffering from OSA had higher rates of aspiration pneumonia, re-intubation and acute respiratory distress syndrome.14 These findings were confirmed by a recent systematic review that found OSA to be a risk factor for postoperative pulmonary complications in nine out of 15 studies under investigation.18

Cardiovascular complications

The increased risk of OSA patients for peri-operative cardiovascular complications may be due to the haemodynamic, autonomic, inflammatory and metabolic effects of an abnormal breathing and arousal pattern.60

Although not all studies confirmed the significant impact of OSA on postoperative cardiac complications,18 severe undiagnosed OSA was associated with higher rates of cardiac arrest.61 In addition, a meta-analysis demonstrated a higher incidence of postoperative cardiac events, including myocardial ischaemia, arrhythmias and cardiac arrest (OR 2.07; 95% CI 1.23 to 3.50, P = 0.007) in OSA patients.12

Peri-operative mortality

The available data concerning the impact of OSA on peri-operative mortality are inconsistent. There is evidence of an increased, unchanged and even decreased associated risk, something that might be explained by studies with different control groups and different peri-operative management regimens, their use of monitoring and treatment of patients with OSA.16,17,62–64

In this context, some studies have even suggested that the effect of intermittent ischaemia/hypoxia associated with OSA on blood vessel collaterality and production of reactive oxygen species might potentially have protective effects, leading to preconditioning phenomena of the organs at risk.65,66

Preoperative management

Because the preoperative identification of OSA may help to decrease peri-operative complications,61,67,68 patients with suspected or proven OSA should be presented to the anaesthetist as soon as possible in order to facilitate the best peri-operative management.69 Factors that should be taken into consideration when evaluating a patient for OSA preoperatively are listed in Table 2.

Table 2
Table 2:
Elements of preoperative evaluation and screening for obstructive sleep apnoea

Preoperative screening for obstructive sleep apnoea

Polysomnography and related procedures

Full-night, attended, in-laboratory PSG is regarded as the gold standard in the diagnosis of sleep-related breathing disorders including OSA.24 PSG enables the diagnosis, determines the severity and phenotype of OSA, and allows specific therapy tailored to the underlying cause.32 However, the execution of PSG is associated with logistical and financial expenses and may delay the scheduled surgery.26,27,29 Hence, sleep testing using portable polychannel monitoring devices at home may be appropriate as an alternative in patients with high pretest probability (daytime sleepiness, nocturnal apnoea and snoring).70,71

Screening tools and questionnaires

Patients identified by screening tools as having a high risk for OSA have been shown to be at an increased risk for postoperative complications.29 Therefore, these patients may benefit from further diagnostic evaluation and treatment.72

While preoperative screening has not been shown to reduce complications per se, the recent Society of Anesthesia and Sleep Medicine Guideline on preoperative screening and assessment of patients with OSA indicates that it may guide peri-operative management of patients identified to be at risk towards targeted precautions and interventions.73

Screening tools that have been evaluated in surgical patients with comparable accuracy are the American Society of Anesthesiologists (ASA) checklist,74 the Berlin questionnaire,29,75 Peri-operative Sleep Apnoea Prediction (P-SAP) score76 and the STOP-Bang tool.77

The ASA checklist is categorised under headings: physical characteristics, history of apparent airway obstruction during sleep, and complaints of somnolence requiring a clinician for resolution.74 The sensitivity of the ASA checklist was found to be 79 and 87% at AHI cutoff levels of more than 15 and more than 30, respectively.29

The Berlin questionnaire is a self-reporting instrument validated initially in the primary care setting.75 It consists of questions on snoring, excessive daytime sleepiness, sleepiness while driving, hypertension and information on age, sex, weight, height and neck circumference. A study screening preoperative patients using the Berlin questionnaire determined that it identified preoperative patients with OSA (AHI >5) with a sensitivity of 69% and a specificity of 56%.29 The large number of questions and the rather complicated scoring system are drawbacks of this tool.

The Peri-operative Sleep Apnoea Prediction Score (P-SAP) comprises personal (age, sex, obesity) and clinical (snoring, diabetes mellitus Type 2, hypertension) variables together with qualitatively assessed airway measurements (large neck circumference, modified Mallampati class 3 or 4, reduced thyromental distance).76 Although the implications for the peri-operative setting remain to be elucidated, the score may have the advantage of detecting lower grades of OSA with a relatively high sensitivity depending on the threshold score.

The STOP-Bang tool was developed to screen for OSA quickly and concisely in a presurgical group. STOP is an acronym for the dichotomous OSA predictor variables Snoring, Tiredness, Observed apnoea during sleep and high blood Pressure.

The addition of four variables with the acronym Bang, BMI more than 35 kg m−2, Age more than 50 years, Neck circumference more than 40 cm and male sex, improved the sensitivity to 93%, and 100% at AHI cut-offs of more than 15 and more than 30 respectively.77 STOP-Bang has been validated in different groups, including surgical patients, sleep clinic patients and the general public.78 While lacking subtlety to exclude mild grades of OSA,79 a high score of 5 to 8 correlates well with the probability for moderate to severe OSA.80–82 One retrospective cohort study of over 5000 undergoing elective surgery revealed that the risk of unexpected intra-operative and early postoperative adverse events increased fivefold with STOP-Bang scores at least 5.83 A combination of a STOP score at least 2 and BMI more than 35 kg m−2 or male sex is also associated with a higher risk of OSA.82,84

The current guidelines with the exception of those of the Society of Ambulatory Anesthesia do not provide recommendations for specific screening tests.67,73,85 The set thresholds for screening tests have a direct impact on the sensitivity and specificity, with implications for missed diagnoses with the increased use of resources that entails. In addition, predictive performance is affected by the prevalence of OSA in the population to be screened. All these factors need to be taken into account when screening for OSA preoperatively.73

Preoperative evaluation

Assessing the peri-operative risk of the individual patient with OSA may be quite challenging for the attending anaesthetist. The guidelines of the ASA provide an example of a scoring system to assess this risk (Table 3) that is based on the severity of OSA, the invasiveness of surgery and anaesthesia and the projected requirement for postoperative opioids.67 This scoring system is neither evidence based nor clinically validated, but it may be helpful in the stratification of risk of the individual OSA patient based on the clinical scenario.

Table 3
Table 3:
Assessment of peri-operative risk for obstructive sleep apnoea (-suspected) patients

The recent Society of Anesthesia and Sleep Medicine Guideline recommends additional preoperative cardiopulmonary evaluation for a formal diagnosis of OSA in preoperative patients with evidence of uncontrolled systemic disease or problems with ventilation or gas exchange such as hypoventilation syndromes, severe pulmonary hypertension and resting hypoxaemia in the absence of other cardiopulmonary disease.73

Preoperative continuous positive airway pressure therapy

Pneumatic splinting of the airway by applying CPAP is regarded as the gold standard in the treatment for OSA.86 It improves daytime sleepiness, accident risk and quality of life in OSA patients. A majority of studies have also shown that it decreases the risk of several adverse cardiovascular outcomes associated with OSA such as hypertension and atrial fibrillation, especially when OSA was severe and adherence to therapy was good.10,20,87–92

The value of using CPAP prior to hospital admission to prevent postoperative complications is not unequivocally confirmed in published reports.11,13,93–96 As the efficacy of CPAP is proven in a nonsurgical setting, according to several clinical guidelines, its continued preoperative application is recommended and its initiation should be considered in severe cases.67,73 Recent studies show that the effects of CPAP in the preoperative period may extend postoperatively, reducing AHI and also length of stay.47,97

Pharmacological premedication

The administration of anxiolytic and/or sedating medication such as benzodiazepines may expose OSA patients to an additional risk for airway collapse and/or respiratory depression during a period when adequate monitoring may not be available.79

Studies on the use of alpha-2-agonists in this setting are limited in their design and do not show consistent results.43,98,99 One study comparing orally administered clonidine versus placebo in surgical OSA patients was able to demonstrate significantly higher values in the postoperative nadir of oxygen saturation in the clonidine group, possibly due to an analgesic, opioid-sparing effect.99 However, dexmetomidine, another alpha-2-agonist, has been shown to impair ventilatory control in conjunction with upper airway obstruction in healthy individuals without a history of snoring or obesity.98

Pharmacological premedication in OSA patients, irrespective of substance class, should only be applied with extreme caution and when adequate monitoring is available.

A potential algorithm of preoperative risk evaluation is shown in Fig. 1. The algorithm is based on the risk for OSA and whether effective therapy is in place in diagnosed patients. However, it has not been clinically validated and serves only as a guide to aid the clinical decision process. Adjustments need to be made for the individual patient, type of surgery, type of anaesthesia, requirements of postoperative opioids and the healthcare facility.

Fig. 1
Fig. 1:
Possible algorithm for the determination of preoperative measures (a) “Uncontrolled systemic conditions” include hypoventilation syndromes, severe pulmonary hypertension and resting hypoxaemia in the absence of other cardiopulmonary disease. The scales icons symbolise the consideration between proceeding to surgery versus referring the patient to preoperative diagnostic OSA testing, which will depend on the urgency of surgery versus severity of OSA and associated symptoms. ‘Low risk OSA’ or ‘High risk OSA’ may result according to the cut-off of the specific screening tools used.14,82,119,124,125,126

Intra-operative management

Anaesthesia technique

There are insufficient data available regarding the safety of anaesthetic drugs in OSA patients, but due to the mentioned side-effects of intravenous and volatile anaesthetics, the use of local or regional anaesthesia should be considered whenever possible.67 When conducting additional sedation or general anaesthesia, it may be advantageous to use anaesthetic drugs and opioids with a favourable pharmacokinetic profile, that is with a short context-sensitive half-time.79

Use of muscle relaxants

Data regarding the safety of using muscle relaxants in OSA patients are likewise insufficient. Because incomplete reversal of muscle relaxants increases the risk for postoperative pulmonary complications in surgical patients irrespective of OSA status,100 it is prudent to use short-acting muscle relaxants and/or antagonising drugs with a low profile of adverse side-effects in patients suspected or known to have OSA.

In this context, the use of suggamadex, a modified gamma-cyclodextrin able to completely and selectively reverse aminosteroid-induced neuromuscular blockade, may be advantageous, as it has been shown to decrease the incidence of postoperative respiratory complications and related costs in OSA patients in comparison to neostigmine.101

Airway management

In OSA patients according to current guidelines, general anaesthesia with a secured airway is favoured over deep sedation with the airway unsecured.67 Pharyngeal airway size is increased so in preparation for securing the airway anaesthetised OSA patients may benefit from being placed in the sniffing position with elevation of torso and head under close haemodynamic monitoring until the airway is secured. This position reduces the chance of pharyngeal collapse.102,103

When performing awake fibre-optic intubation, topical anaesthesia of the upper airway may impair protective reflexes and lead to airway obstruction after extubation.104,105 If heavy sedation is performed, the use of an oro- or nasopharyngeal airway or CPAP should be considered.67

Postoperative management

Postoperative analgesia

Current data do not permit a consensus as to whether withholding or minimising opioid use leads to fewer postoperative complications irrespective of OSA status.106 However, a prospective observational study found that the cumulative opioid dose during the first 72 h after surgery was one of the factors associated with worsening breathing disorder during sleep as measured by AHI.107

Interestingly, it has been shown that intermittent hypoxia and sleep disruption – both common in postoperative OSA patients – may enhance pain, while intermittent hypoxia may amplify opioid-mediated analgesic effects.42,108 This reflects the complex nature of individual OSA phenotypes, which are influenced by different levels of chemoreflex responsiveness and arousal thresholds.109,110 Accordingly, it seems prudent to individualise therapy and titrate the systemic and neuraxial administration of opioids in these patients.111 A multimodal approach including local anaesthetics, nonopioids and co-analgesics reduces the demand for postoperative opioids and should therefore be considered in this situation. 67,112


The fact that OSA patients are at an increased risk of hypoxaemia in the early postoperative period may justify the continuous administration of supplementary oxygen until basal levels of oxygen saturation have been reached while breathing room air.48,107 This measure was found to improve oxygenation and decrease AHI in OSA patients without increasing the duration of apnoea-hypopnoea events.113

There are potential risks, however, if oxygen therapy masks apnoea or hypoventilation leading to atelectasis or retention of carbon dioxide. It may be advisable to decrease the level of inspired oxygen as much as adequate saturation allows and monitor adequate ventilation, for example by capnography.114

Postoperative continuous positive airway pressure therapy

A limited number of studies have evaluated the role of postoperative CPAP therapy in OSA patients. A recent prospective, randomised crossover trial in morbidly obese patients with high OSA prevalence demonstrated that overall, postoperative AHI was reduced and opioid-mediated AHI increase was mitigated by CPAP.51 Similarly, a meta-analysis showed that postoperative CPAP therapy decreased AHI and length of hospital stay.47 However, the study failed to demonstrate a significant reduction in postoperative complications due to its relatively small sample size, the overall low incidence of complications and suboptimal CPAP adherence.47 A large retrospective matched-cohort study, however, did demonstrate an increased risk for cardiovascular complications (including cardiac arrest, acute coronary syndrome, cerebrovascular accident and atrial fibrillation/flutter) in undiagnosed OSA patients compared with those who were prescribed CPAP.61 This has been corroborated by a recent study that demonstrated that surgical patients with untreated OSA suffered from more adverse events including myocardial infarction and reintubation than those who were treated with CPAP.68 The advantages of noninvasive positive pressure ventilation over supplementary oxygen in the postoperative period were seen in obese patients with a high prevalence of OSA.115

Measures such as nasal high-flow therapy or incentive spirometry may also prove beneficial in this context but require further investigation.116–118

Current guidelines do recommend immediate postoperative resumption of CPAP therapy – if feasible – or even initiation in patients with recurring respiratory events.67,73,85

Postoperative monitoring

Although OSA patients are at an increased risk for postoperative complications 14–16,119,120 and may benefit from postoperative monitoring,121 it is unclear to what extent and duration it should be sustained.67 This is of interest considering the increasing appearance of these patients in the peri-operative setting against a background of limited healthcare resources.15 In this context, neither using a telemetry-system nor transfer to a monitored setting have shown clear benefit in OSA patients.67 One study indicated that the implementation of a surveillance system using pulse oximetry was associated with a decrease in the number of respiratory events and transfers to an ICU.122 Another investigation demonstrated that patients at risk for OSA who have respiratory events (apnoea, bradypnoea, decreased oxygen saturation) in the immediate postoperative period are at an increased risk for further respiratory complications.123 On the basis of these findings, Fig. 2 shows a possible algorithm for the postoperative management of OSA patients. The algorithm, which has not been clinically validated, is meant only as a guide to clinical decision making. Adjustments need to be made for the individual patient, type of surgery, type of anaesthesia, requirements of postoperative opioids and the healthcare facility.

Fig. 2
Fig. 2:
Possible algorithm for the postoperative management of OSA patients (adapted from14,82,119,125). OSA-RS, peri-operative OSA risk score as per definition by the ASA guidelines (Table 3);67 PAP, positive airway pressure. (a) PACU: post anaesthesia care unit or comparably staffed and monitored setting. (b) Based on patient status, invasiveness of surgery and anaesthesia and projected demand for opioids. (c) Relevant critical events indicative of increased risk for further complications include:123 SpO2 < 90%, bradypnoea < 8 breaths min−1, apnoea ≥10 s; pain-sedation mismatch [visual analogue scale (VAS) > 5 and Richmond Agitation-Sedation Scale (RASS) ≤‘-3’]. (d) For the duration of increased risk for OSA-related postoperative complications including the option of immediate (non) invasive ventilatory support ‘Low risk OSA’ or ‘High risk OSA’ may result according to the cut off of the specific screening tools used.


OSA in surgical patients is increasing in prevalence and is associated with an increased risk for various peri-operative complications. Many affected patients are not diagnosed and, hence, therapeutic measures are not in place preoperatively.

Even though the level of evidence for any single intervention is limited, there is broad agreement among expert clinicians that diligent peri-operative management of affected patients may limit the risk for potential complications. This includes early diagnosis and risk evaluation, peri-operative continuation or even commencement of therapy, appropriate anaesthetic regimen including choice of medication and airway management and adequate postoperative monitoring.

While current guidelines do exist, many important questions concerning the peri-operative management of affected patients remain to be elucidated:

  1. To what degree do factors associated with patient, surgery and anaesthesia determine the peri-operative risk of the individual OSA patient?
  2. Which of these factors justifies preoperative optimisation and potential delay of surgery? Would this approach benefit the patient and be cost-effective?
  3. What phenotype characteristics determine pain and opioid responsiveness in the individual OSA patient?
  4. What criteria may be predictive of postoperative complications beyond the immediate recovery period?
  5. How can medical and legal burdens concerning the appropriate use of patient-owned devices in a hospital setting be overcome?

Further work is needed to provide a stronger foundation for current and future recommendations concerning the peri-operative safety in patients with sleep-related breathing disorders.

Acknowledgements relating to this article

Assistance with the review: none.

Financial assistance and sponsorship: none.

Conflicts of interest: MR has received nonrecurring compensation in 2015 for consultatory work for Covidien AG, Switzerland.

FC has received research grant support from Ontario Ministry of Health and Long-Term Care Innovation Fund, University Health Network Foundation, ResMed Foundation, Acacia Pharma and Medtronics. STOP Bang questionnaire: proprietary to University Health Network.


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