Obstructive Sleep Apnea and Ambulatory Surgery: Who Is Truly at Risk?

See Article, p Obstructive sleep apnea (OSA) is a common condition in the general population, with an estimated prevalence of 22% (range, 9%–37%) in men and 17% (range, 4%–50%) in women.1 The rates of OSA are not only more prevalent in males but also increase with age and body mass index. Unfortunately, in many patients, OSA still remains undiagnosed, which is a major concern in the surgical population undergoing both ambulatory and inpatient procedures.2 The danger is real because OSA is associated with a 3- to 4-fold higher risk of difficult intubation or mask ventilation.3 It is also well established that surgical patients with OSA may have multiple comorbidities and are at an increased risk for perioperative complications such as a need for respiratory interventions, prolonged length of hospital stay, and perioperative mortality.4,5 In fact, a recent, large systematic review of 61 studies with >400,000 OSA patients and 8.5 million non–OSA patients suggests that the presence of OSA is associated with an increased risk of postoperative complications.6 A recent 2018 Guideline from the Society of Anesthesia and Sleep Medicine by Memtsoudis et al7 regarding intraoperative management of adult patients with OSA outlines recommendations for various aspects of perioperative care; these recommendations include screening patients for OSA, using positive-pressure airway therapy, and carefully selecting anesthetic drugs, analgesics, and anesthesia type. The Society for Ambulatory Anesthesia (SAMBA) Consensus Statement on preoperative selection of adult patients with OSA by Joshi et al8 specifically addresses the ambulatory patient population. Published in 2012, the authors conducted a systematic review of the literature and came to a conclusion that patients with a known diagnosis of OSA and optimized comorbid medical conditions can be considered for ambulatory surgery if they are able to use a continuous positive airway pressure device in the postoperative period. Patients with a presumed diagnosis of OSA, based on screening tools such as the Snoring, Tiredness, Observed apnea, Blood Pressure, Body mass index, Age, Neck circumference, and Gender (STOP-BANG) Questionnaire,9 and with optimized comorbid conditions, can also be considered for ambulatory surgery, given that postoperative pain can be managed predominantly with nonopioid analgesic techniques. On the other hand, the authors concluded that OSA patients with nonoptimized comorbid medical conditions may not be good candidates for ambulatory surgery. This SAMBA Consensus Statement specifically recommended the use of the STOP-BANG criteria for preoperative OSA screening and comorbid conditions during the patient selection process. Finally, the American Society of Anesthesiologists put forward the Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea.10 Published in 2014, it addresses patient selection for inpatient versus outpatient (OP) setting, essentially concluding that there is a lack of strong evidence to provide guidance regarding triaging these patients, although it acknowledged that OSA patients are at an increased perioperative risk. In the retrospective study by Szeto et al11 published in this issue of Anesthesia & Analgesia, entitled “Outcomes and safety among patients with OSA undergoing cancer surgery procedures in a free-standing ambulatory surgical facility,” the authors address an important and controversial topic of whether patients undergoing cancer surgery in the ambulatory setting with a known diagnosis of OSA or who are likely to have OSA based on STOP-BANG Questionnaire results are at an increased risk for developing complications. The STOP-BANG scoring algorithm for general population identifies patients with a low risk of OSA with “Yes” to 0–2 questions, moderate risk with “Yes” to 3–4 questions, and high risk with “Yes” to 5–8 questions.12 The authors used data from their free-standing ambulatory surgery facility and included patients who underwent typical OP cancer surgeries as well as those who had more complex cancer procedures that required a planned overnight stay (ie, “ambulatory extended recovery” [AXR]). Surgical specialties included breast, gastric mixed tumor, gynecology, head and neck, plastics, and urology. Their study sample contained a total of 5721 patients, of whom 526 patients (9.2%) were previously diagnosed with OSA or were at high or moderate risk for OSA based on the STOP-Bang Questionnaire score. They tested for the association of OSA risk with several important patient outcomes such as length of stay (LOS), adverse respiratory events, a need for a transfer to the main hospital, Urgent Care facility visits postdischarge, and hospital readmission within 30 days. For the purposes of the analysis, the authors separated their study population into 2 groups: those who have an OSA diagnosis or are high risk for OSA and those who are moderate or low risk for OSA. This study raises several important issues for the anesthesia provider. One major concern is that ambulatory patients with OSA will have an increased rate of perioperative complications due to OSA or associated comorbidities.3 However, in this study, the authors demonstrate that the LOS did not differ for high-risk or diagnosed OSA patients compared to those who are moderate or low risk, and the same was true for both OP and AXR groups. Not surprisingly, the authors found a higher incidence of postoperative respiratory events, such as repeated desaturations (<90% oxygen saturation measured by pulse oximetry [Spo2] in an unstimulated environment or obstruction [apnea or snoring] lasting 20 seconds) in the high-risk or diagnosed OSA patients, but the rates of Urgent Care facility visits or 30-day hospital admission were similar between the 2 groups. Also, even though high-risk and diagnosed OSA patients had a significantly longer postoperative AXR stay, the actual difference was only 15 minutes, which may not be clinically significant. In addition, and perhaps not surprisingly, the rate of postoperative events was higher in the high-risk/diagnosed OSA patients compared to moderate-risk patients (15% and 2.2%, respectively). Based on these data, the authors concluded that it is safe for patients who are moderate, high risk, or who are diagnosed with OSA to undergo typical OP and more complex ambulatory cancer procedures without a significant increase in complication rates or increased LOS. This study adds to our current knowledge in several ways. The authors included both traditional OP procedures and more complex cancer surgeries that required an extended stay, specifically demonstrating that patients who are high risk or diagnosed with OSA can safely undergo more complex ambulatory procedures. The study also explores meaningful patient outcomes that can impact efficiency, patient satisfaction, and quality of care. Finally, the authors have implemented specific clinical pathways and enhanced recovery protocols that emphasize opioid-sparing analgesia, patient education, and other intraoperative management strategies. The authors demonstrate that applying the principles outlined in the aforementioned professional society guidelines for the management of patients with suspected or diagnosed OSA may lead to improved outcomes. For example, they used the STOP-BANG Questionnaire for all patients, made attempts to optimize their existing medical conditions, and used multimodal analgesia techniques while minimizing opioid use postoperatively. It is worth noting, however, that opioid use was still very high intraoperatively (97%–99%) and postoperatively (58%–63%), making room for future efforts to reduce or eliminate perioperative opioid use when appropriate. We would hope that highly protocolized management of these patients will lead to better outcomes. Also, patients were evaluated by a respiratory therapist who was available on-site to assess for a need for positive-pressure ventilatory support postoperatively and to monitor their postoperative respiratory recovery. It appears that the involvement of respiratory therapists was important to ensure proper and timely management of respiratory compromise in high-risk patients. In addition, all patients wore a Real-Time Location System badge (Versus Technology Inc, Traverse City, MI) to help provide continuous location updates of each patient, contributing to greater accuracy of times recorded for different phases of care. Another key point regarding the low rate of adverse outcomes seen in this study is that among the 233 patients with diagnosed OSA, 65% had home devices with the majority of them being compliant with home device use. A recent review on the polysomnographic parameters for predicting postoperative adverse events in patients with OSA indicated that complications may be more likely to occur in the category of moderate-to-severe OSA with apnea hypopnea index ≥15 events per hour.13 In this study, 527 patients were high risk or diagnosed OSA, yet the number of patients with moderate-to-severe OSA with apnea hypopneas index ≥15 events per hour is not known and could be substantially smaller. The authors showed that although greater frequencies of postoperative respiratory events were reported in high-risk or diagnosed OSA patients, the rate of hospital transfer was not significantly different between the groups (P = .10). Because the P value is .1, the results could be significant with a larger sample size. It is important to point out a few important limitations of this study. One drawback is that the study describes the experience of a single facility, which predisposes it to patient selection bias and susceptibility to institution-specific surgical and anesthetic practices that may not be reflective of national practices. The sample size was also relatively small and limited to a few surgical subspecialties, potentially making it subject to various patient, anesthesia, and procedure-related confounding factors. In addition, as the authors themselves acknowledge, the prevalence of OSA in the study was low, with 4.1% diagnosed and 3.5% screened high risk, compared to a general population or surgical population where the rates are cited as high as ≥25%, depending on gender.1,3 Their study group was recruited on the basis of likely presence of OSA (presumably on the basis of a sleep study) or OSA risk identified from questionnaire data. This group will include many patients with trivial OSA and a large number (given the low specificity of STOP-Bang and other questionnaires) with no OSA at all. However, within this large group will exist patients with high arousal thresholds, lengthy obstructive events, and substantial associated hypoxemia who are likely to be at considerably greater risk if exposed to postoperative opioids or sedatives. In fact, the study by Szeto et al11 contained a relatively low percentage of males, perhaps due to a large number of gynecological procedures performed at their facility. Yet, despite the fact that at-risk patients had higher body mass index (BMI), were more likely to have multiple comorbidities, longer surgery, and general anesthesia, the overall outcomes were similar between the 2 OSA study groups. Part of the reasons that only 3.5% of cancer patients were screened high risk is that the authors used a 2-step–modified nonvalidated approach to STOP-BANG scoring. The authors asked the 4 STOP questions first. The BANG questions were only applied subsequently if patients answered “Yes” to ≥2 questions of STOP. If patients had only 1 positive answer on STOP, these patients were not considered at risk for OSA. However, they may actually not be low risk as they may be obese, male or >50 years even with just 1 positive answer to STOP questions. The authors automatically misclassified these patients as low risk, resulting in only 3.5% of cancer patients being high risk for OSA. Another reason for no difference in outcomes between the 2 groups could be that the high risk or diagnosed OSA leads to early effective intervention, which decreases adverse outcomes, while the population of patients without high risk or diagnosed OSA includes patients with OSA who experience adverse outcomes because of failure to identify OSA.5 In addition, the authors used a single screening tool for OSA—STOP-Bang Questionnaire, which, while used frequently in clinical practice due to ease of administration and high predictive value, still does not have perfect sensitivity or specificity.9 The sensitivity for detecting any OSA in a surgical population at a cutoff score of ≥3 is 84%, while specificity is low at 43%, meaning a high false-positive rate.3 Based on the results of this study, the use of an OSA screening tool appears feasible in a busy ambulatory setting to help risk-stratify patients undergoing both simple and more complex procedures. Also, although helpful, it may not be practical or cost-effective to have respiratory therapist(s) present in an ambulatory facility to routinely monitor and intervene in patients who experience a respiratory event. As ambulatory surgery across the country has shown good track record in patient outcomes, there is an increasing pressure on anesthesia providers to include more complicated patients (eg, higher body mass index, OSA, airways challenges, multiple comorbidities) in an ambulatory surgery center.14 In summary, this study from a highly specialized single center demonstrates that with careful patient selection and appropriate resources, patients with a diagnosis or at high risk of OSA may safely undergo ambulatory surgery. Multicenter studies with larger sample size are needed to confirm these findings and to make a final clinical practice recommendation. We urge caution on this topic as one death is too many.15 Nonetheless, the boundary of patient inclusion in ambulatory surgery is being further stretched. DISCLOSURES Name: Richard D. Urman, MD, MBA. Contribution: This author helped analyze and interpret the data, draft the initial manuscript, and critically revise the manuscript. Conflicts of Interest: R. D. Urman received funding for unrelated research by Medtronic and honoraria from Merck, Acacia, and 3M. Name: Frances Chung, MBBS, FRCPC. Contribution: This author helped analyze and interpret the data, draft the initial manuscript, and critically revise the manuscript. Conflicts of Interest: None. Name: Tong J. Gan, MD, MBA, MHS, FRCA. Contribution: This author helped analyze and interpret the data, draft the initial manuscript, and critically revise the manuscript. Conflicts of Interest: T. J. Gan received honoraria from Acacia, Malinckrodt, Medtronic, and Merck. This manuscript was handled by: David Hillman, MD.

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