Over the last few decades, there has been increasing concern that a majority of patients with obstructive sleep apnea are undiagnosed and that untreated obstructive sleep apnea is an important contributing factor to increased postoperative complications. Because of convincing evidence of an association between sleep apnea and cardiovascular illness, complications related to cardiac and vascular procedures have been the focus of considerable attention. Such procedures are performed with extraordinary frequency. According to the most recent CDC data (http://www.cdc.gov/nchs/fastats/inpatient-surgery.htm), in 2010, there were 51 million inpatient procedures of all types performed in the US. Of these, 1 million were cardiac catheterizations, 500,000 balloon angioplasties, 454,000 coronary stent placements, and 395,000 coronary artery bypass surgeries.
Several studies have demonstrated a high prevalence of sleep disordered breathing in patients undergoing cardiovascular interventions, but data demonstrating an impact on perioperative complications have been surprisingly inconclusive. Abdelsattar et al.1 reported a large cohort study which included 2,646 general and vascular surgical patients with a suspected or confirmed diagnosis of OSA of whom 1,465 were untreated. Untreated OSA was independently associated with more cardiopulmonary complications (risk-adjusted rates 6.7% versus 4.0%; adjusted odds ratio [aOR] = 1.8, p = 0.001), particularly unplanned reintubations (aOR = 2.5, p = 0.003) and myocardial infarction (aOR = 2.6, p = 0.031). A systematic review and meta-analysis reported by Kaw et al.2 identified 13 studies (3,942 total patients) with data available for quantitative synthesis. OSA was associated with increased incidence of postoperative desaturation, respiratory failure, postoperative cardiac events, and ICU transfers.
On the other hand, Memtsoudis et al.3 found an increase in complications but no impact of OSA on in-hospital mortality in an analysis of nationwide hospital discharge data. Another large national study demonstrated an independent association between OSA and cardiopulmonary complications but found no association with an increased rate of in-hospital death. Sleep-disordered breathing had an inconsistent impact on length of stay.4
Other studies have failed to demonstrate an increased risk of complications, perhaps as a result of limited statistical power. Such is the case with the paper by Foldvary-Schaefer et al.5 in this issue of the Journal of Clinical Sleep Medicine. This study, performed at 2 elite medical centers did identify an extraordinarily high prevalence of OSA among their cohort of patients with cardiovascular disease. Almost 74% had sleep apnea (based on an AHI > 5/h of sleep), with 27% of the sample having severe OSA (AHI > 30/h). The authors note that respiratory events were “predominantly” obstructive in type, with no Cheyne-Stokes breathing pattern noted in any of the study participants. Previously diagnosed subjects not using CPAP were not excluded. The study ended up enrolling 107 subjects, which was less than anticipated, due to unexpected difficulties with technical issues (data transfer).
Despite this remarkably high prevalence of sleep apnea, no increase in several key postoperative complications was identified. Clearly, this study had an insufficient number of patients to recognize uncommon associations. The study does highlight challenges of introducing a Sleep Medicine assessment in the clinical care of surgical cardiac patients, despite involvement of highly experienced Sleep Medicine practitioners. For example, no participant was treated with CPAP postoperatively. The unstated value of this report is the demonstration that expectant management of these patients (even without PAP therapy) can be very effective in the prevention of complications.
The benefit of perioperative PAP therapy is far from certain. Zarbock et al.6 reported a prospective, randomized, controlled trial of prophylactic CPAP in 2009. CPAP of 10 cm H2O used for at least 6 h was compared to 10 minutes every 4 h. There was a significant decrease in hypoxemia, pneumonia, reintubation rate, and readmission to the ICU. In 2013, Liao et al.7 reported a randomized open-label controlled clinical trial of perioperative auto-titration PAP in surgical patients with obstructive sleep apnea. APAP successfully lowered the AHI but there was no difference in the incidence of complications. Mutter et al.8 reported a matched cohort study in which diagnosis and management of OSA resulted in a decrease in cardiovascular complications, improved arterial oxygenation, decreased pulmonary complications (pneumonia and reintubation), and reduced re-admission to ICU. Most recently, Nagappa et al.9 conducted a systematic review and meta-analysis and reported no significant difference in post-op events between CPAP and no CPAP.
In summary, there are few if any large-scale, adequately controlled, prospective studies of the association between sleep disordered breathing and postoperative complications. However, there is extensive evidence from smaller studies. Furthermore, it is widely recognized that anesthetic agents, sedatives, and narcotics can exacerbate upper airway collapse and blunt the arousal response. Consequently and appropriately, it has become standard practice to closely monitor patients with a confirmed or nascent diagnosis of sleep apnea syndrome. Because such practice is now widespread, it is unlikely that a randomized controlled trial investigating the perioperative dangers associated with sleep apnea would be viewed favorably by an institutional review board.
We should not conclude that efforts to identify patients at risk are not useful. Rather, we should assume that all patients undergoing cardiovascular procedures have a high likelihood of undiagnosed sleep apnea and we should manage them accordingly. The Practice Guidelines recently published by the American Society of Anesthesiologists provide a substrate for decision making.10 Every reasonable effort should be made to diagnose OSA preoperatively to facilitate effective treatment with positive airway pressure. All patients who are identified as having a potential increased risk of sleep disordered breathing should be treated expectantly and perhaps prophylactically.
The authors have indicated no financial conflicts of interest.
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Abdelsattar ZM, Hendren S, Wong SL, et al., authors. The impact of untreated obstructive sleep apnea on cardiopulmonary complications in general and vascular surgery: a cohort study. Sleep. 2015;38:1205–10. [PubMed]
Kaw R, Chung F, Pasupuleti V, et al., authors. Meta-analysis of the association between obstructive sleep apnoea and postoperative outcome. Br J Anesth. 2012;109:897–906.
Memtsoudis SG, Stundner O, Rasul R, et al., authors. The impact of sleep apnea on postoperative utilization of resources and adverse outcomes. Anesth Analg. 2014;118:407–18. [PubMed Central][PubMed]
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Foldvary-Shaefer N, Kaw R, Collop N, et al., authors. Prevalence of undetected sleep apnea in patients undergoing cardiovascular surgery and impact on postoperative outcomes. J Clin Sleep Med. 2015;11:1083–9.
Zarbock A, Mueller E, Netzer S, et al., authors. Prophylactic nasal continuous positive airway pressure following cardiac surgery protects from postoperative pulmonary complications: a prospective, randomized, controlled trial in 500 patients. Chest. 2009;135:1252–9. [PubMed]
Liao P, Luo Q, Elsaid H, et al., authors. Perioperative auto-titrated continuous positive airway pressure treatment in surgical patients with obstructive sleep apnea: a randomized controlled trial. Anesthesiology. 2013;119:837–47. [PubMed]
Mutter TC, Chateau D, Moffatt M, et al., authors. A matched cohort study of postoperative outcomes in obstructive sleep apnea: could preoperative diagnosis and treatment prevent complications? Anesthesiology. 2014;121:707–18. [PubMed]
Nagappa M, Mokhlesi B, Wong JU, et al., authors. The effects of continuous positive airway pressure on postoperative outcomes in obstructive sleep apnea patients undergoing surgery: a systematic review and meta-analysis. Anesth Analg. 2015;120:1013–23. [PubMed]
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