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Outcomes and Safety Among Patients With Obstructive Sleep Apnea Undergoing Cancer Surgery Procedures in a Freestanding Ambulatory Surgical Facility

Szeto, Betsy MPH*; Vertosick, Emily A. MPH; Ruiz, Karin RT*; Tokita, Hanae MD*; Vickers, Andrew PhD; Assel, Melissa MS; Simon, Brett A. MD, PhD*; Twersky, Rebecca S. MD, MPH*

doi: 10.1213/ANE.0000000000004111
Perioperative Medicine: Original Clinical Research Report
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BACKGROUND: Patients with obstructive sleep apnea (OSA) may be at increased risk for serious perioperative complications. The suitability of ambulatory surgery for patients with OSA remains controversial, and several national guidelines call for more evidence that assesses clinically significant outcomes. In this study, we investigate the association between OSA status (STOP-BANG risk, or previously diagnosed) and short-term outcomes and safety for patients undergoing cancer surgery at a freestanding ambulatory surgery facility.

METHODS: We conducted a retrospective analysis of all patients having surgery at the Josie Robertson Surgery Center, a freestanding ambulatory surgery facility of the Memorial Sloan Kettering Cancer Center. Surgeries included more complex ambulatory extended recovery procedures for which patients typically stay overnight, such as mastectomy, thyroidectomy, and minimally invasive hysterectomy, prostatectomy, and nephrectomy, as well as typical outpatient surgeries. Both univariate and multivariable analyses were used to assess the association between OSA risk and transfer to the main hospital, urgent care center visit, and hospital readmission within 30 days postoperatively (primary outcomes) and length of stay and discharge time (secondary outcomes). Multivariable models were adjusted for age, American Society of Anesthesiologists score, robotic surgery, and type of anesthesia (general or monitored anesthesia care) and also adjusted for surgery start time for length of stay and discharge time outcomes. χ2 tests were used to assess the association between OSA risk and respiratory events and device use.

RESULTS: Of the 5721 patients included in the analysis, 526 (9.2%) were diagnosed or at moderate or high risk for OSA. We found no evidence of a difference in length of stay when comparing high-risk or diagnosed patients with OSA to low- or moderate-risk patients whether they underwent outpatient (P = .2) or ambulatory extended recovery procedures (P = .3). Though a greater frequency of postoperative respiratory events were reported in high-risk or diagnosed patients with OSA compared to moderate risk (P = .004), the rate of hospital transfer was not significantly different between the groups (risk difference, 0.78%; 95% CI, –0.43% to 2%; P = .2). On multivariable analysis, there was no evidence of increased rate of urgent care center visits (adjusted risk difference, 1.4%; 95% CI, –0.68% to 3.4%; P = .15) or readmissions within 30 days (adjusted risk difference, 1.2%; 95% CI, –0.40% to 2.8%; P = .077) when comparing high-risk or diagnosed OSA to low- or moderate-risk patients. Based on the upper bounds of the CIs, a clinically relevant increase in transfers, readmissions, and urgent care center visits is unlikely.

CONCLUSIONS: Our results contribute to the body of evidence supporting that patients with moderate-risk, high-risk, or diagnosed OSA can safely undergo outpatient and advanced ambulatory oncology surgery without increased health care burden of extended stay or hospital admission and avoiding adverse postoperative outcomes. Our results support the adoption of several national OSA guidelines focusing on preoperative identification of patients with OSA and clinical pathways for perioperative management and postoperative monitoring.

From the *Department of Anesthesiology and Critical Care, Josie Robertson Surgery Center

Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York.

Published ahead of print 30 January 2019.

Accepted for publication January 28, 2019.

Funding: A research reported in this publication was supported in part by the National Cancer Institute of the National Institutes of Health under Award Number R25CA020449, “Summer Research Experiences For Medical Students Supervised By Faculty Mentors” (B.S.).

The authors declare no conflicts of interest.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Reprints will not be available from the authors.

Address correspondence to Rebecca S. Twersky, MD, MPH, Department of Anesthesiology and Critical Care, Josie Robertson Surgery Center, Memorial Sloan Kettering Cancer Center, 1133 York Ave, Suite 312, Box 221, New York, NY 10065. Address e-mail to twerskyr@mskcc.org.

See Editorial, p

Obstructive sleep apnea (OSA) is a significant public health concern, affecting approximately 9%–43% of the general adult population, with estimates varying by age, gender, and other factors.1–5 Repeated upper airway obstruction may result in arterial desaturations, sympathetic activation, and systemic inflammation and could cause a variety of cardiovascular and respiratory conditions with increased mortality.6,7 OSA prevalence is reported to be even higher in the surgical population than in the general population8 with up to 80%–90% of surgical patients remaining undiagnosed.4,5 In the perioperative setting, depression of muscle activity of the upper airway after sedation or general anesthesia may exacerbate OSA symptoms, and patients may be at risk for increased perioperative complications including hypoxemia and airway obstruction, respiratory arrest, and death.9–16 Respiratory complications are further influenced by postoperative use of sedatives and opioids, residual muscle weakness, atelectasis, pain, and surgical trauma. Patients with OSA have been shown to be at increased risk for pulmonary and cardiac complications, have been more likely to use ventilatory support and intensive care, consume more economic resources, and have longer lengths of hospitalization.17,18 In addition, an increase in malpractice lawsuits related to OSA complications has been reported.19

To address these clinical concerns, several professional societies published guidelines identifying risks and mitigating strategies for the perioperative setting.5,20–22 The American Society of Anesthesiologists (ASA) 2014 updated practice guideline concluded that the literature is insufficient to offer guidance on which patients with OSA can be safely managed on an inpatient versus outpatient basis.21 The Society of Anesthesia and Sleep Medicine provides a detailed review of the updated evidence, focuses on preoperative evaluation, and, though not specific for ambulatory surgery, establishes the importance of properly screening at-risk patients and the benefit of positive airway pressure (PAP) therapy in the management of these patients.5 The STOP-BANG Tool, developed in 2008 by Chung et al23 to screen surgical patients for OSA, is a validated screening tool that identifies patients at high or moderate risk for OSA and may help reduce risk of perioperative complications.24 In surgical patients, a greater STOP-BANG score is associated with a greater probability of moderate to severe OSA.5

The suitability of ambulatory surgery for a patient with OSA remains controversial, and the evidence regarding safety is limited. Careful preoperative screening of patients to identify those at risk for OSA is an important first step to improve care. The Society for Ambulatory Anesthesia issued a consensus statement supporting that patients with known or presumed diagnosis of OSA, with optimized comorbid conditions and whose postoperative pain can be managed predominantly with nonopioid analgesics, can be considered for ambulatory surgery.20 They call for more evidence that assesses clinically significant outcomes (eg, delayed discharge, unanticipated hospital admission, readmission, or serious morbidity and mortality), rather than surrogate outcomes (eg, desaturation, hypoxemia, or supplemental oxygen). Most importantly, the impact of these recommendations on clinical perioperative outcomes in ambulatory surgery is unknown.

The Josie Robertson Surgery Center, of the Memorial Sloan-Kettering Cancer Center, is a freestanding surgical facility dedicated to outpatient procedures in patients with cancer. It is unique in performing more advanced, nontraditional outpatient cancer procedures compared to most freestanding surgical centers due in part to its overnight stay capability. PAP can be provided by day and evening shift respiratory therapists. Since opening in 2016, Josie Robertson Surgery Center has accumulated a large body of data and outcomes that offer an opportunity to provide additional evidence to evaluate consensus guidelines and examine the safety and suitability of ambulatory surgery for at-risk patients with OSA.

In this study, we investigate the association between OSA status (STOP-BANG low-risk, moderate-risk, or high-risk, or previous OSA diagnosis) and short-term outcomes and safety for patients undergoing a variety of cancer surgery procedures in a freestanding ambulatory surgery facility.

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METHODS

After obtaining approval for the study from the Memorial Sloan-Kettering Cancer Center Institutional Review Board and an institutional review board waiver on the requirement for written consent, we identified all patients who underwent surgical procedures at Josie Robertson Surgery Center between January 1 and December 31, 2016.

If patients had multiple procedures during the study period, the first procedure was included in the analysis and any subsequent procedures were excluded. Procedures were also excluded if the patient had an ASA score of 4 or the procedure used local anesthesia only. Data on patient age, gender, body mass index (BMI), ASA score, anesthetic technique, type of surgical procedure, operative time, length of stay, transfer to main hospital or other acute care facility, and subsequent urgent care center visits and hospital admissions or readmissions within 30 days were documented as part of routine care. OSA status was defined using the STOP-BANG score, with scores <3 categorized as low risk of OSA, scores of 3–4 as moderate risk of OSA, and scores ≥5 as high risk (Figure).

Figure.

Figure.

We have defined ambulatory extended recovery procedures as those that are more complex than typical outpatient surgeries and are scheduled to have a single overnight stay while still being considered as ambulatory surgery cases from a regulatory standpoint. These surgeries include mastectomy (unilateral, bilateral, and with or without immediate reconstruction); thyroidectomy and parotidectomy; and minimally invasive hysterectomy, prostatectomy, and nephrectomy. To facilitate the performance of more complex cancer surgeries in the ambulatory setting, care, including patient and procedure selection, education and expectation setting, as well as intraoperative and postoperative management, is highly protocolized. We developed specific enhanced recovery after surgery protocols for anesthesia care for these ambulatory extended recovery patients which include opioid-sparing approaches including regional blocks and multimodal analgesia as a component of general anesthesia, but the specific choice of anesthetic is left to the anesthesia team’s discretion. There is no specific intraoperative anesthesia OSA protocol.

Data are presented for both ambulatory extended recovery and traditional outpatient procedures. Postoperative length of stay in hours was defined as time from entry into the postanesthesia care unit (PACU) to discharge home for outpatient procedures and did not include patients who had a reoperation or were transferred to the main hospital. Discharge time was defined as hours and minutes since midnight on the day of discharge, and we excluded patients who had a reoperation, were transferred to the main hospital, or did not stay overnight.

All surgery patients wear a Real-Time Location System badge (Versus Technology Inc, Traverse City, MI). The badge is detected by sensors placed throughout the facility approximately 10 feet apart and provides continuous location updates to our facility visualization maps and database. The badge is collected from the patient at the time of discharge.

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Patient Identification and Obstructive Sleep Apnea Risk

All patients undergoing surgical procedures at Josie Robertson Surgery Center are screened preoperatively for OSA by a nurse practitioner within 1 month of the date of the surgery. Patients are asked whether they have been diagnosed with OSA, and if so, whether they own equipment, such as a continuous positive airway pressure (CPAP) machine or a mouth guard, and whether they use the equipment. If a patient has not been diagnosed with OSA, they are screened using the STOP-BANG tool. First, they are asked the 4 STOP questions (Figure). If they answer “No” to >2 questions, they are considered at low risk for OSA. If they answer “Yes” to ≥2 questions, the BANG questions are applied. As some patients with OSA go undiagnosed, patients identified as high risk as well as those with previously diagnosed OSA are distinguished on the operating room schedule with a custom icon to alert of this risk. This information is available to perioperative staff so preoperative nurses inquire about their PAP devices, anesthesia staff are aware of associated anesthesia risks, and respiratory therapists conduct postoperative assessment and monitoring. Because STOP-BANG also includes a moderate OSA risk category, we retrospectively stratified the high risk into moderate or high based on individual chart review. For the low-risk individuals on whom the BANG score was not initially applied, we did data checks based on the patient’s BMI, age, and gender and used those along with STOP score to confirm that there were no false negatives and did not miss any patients who would have been high risk. The scoring system outlined in the Figure is then used to determine if the patient is at low, moderate, or high risk for OSA.

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Primary and Secondary Outcomes

Our primary outcome was safety as defined by 3 outcomes: transfer from Josie Robertson Surgery Center after surgery, any Memorial Sloan-Kettering Cancer Center urgent care center visit within 30 days after surgery, and any readmission within 30 days after surgery. As a secondary outcome, we assessed length of stay for patients undergoing outpatient procedures and discharge time for patients undergoing ambulatory extended recovery procedures.

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Respiratory Outcomes

All patients who are diagnosed with OSA, or screened as moderate or high risk for OSA, are identified preoperatively and assessed by a respiratory therapist postoperatively. The respiratory therapist makes note of any postoperative respiratory events such as repeated desaturations <90% oxygen saturation measured by pulse oximetry in an unstimulated environment or obstruction (apnea or snoring) lasting 20 seconds, and records the need for CPAP, bilevel positive airway pressure (BiPAP), or continued mechanical ventilation.

All patients diagnosed with OSA who own a home device are encouraged to bring their device with them on the day of the surgery. The device is examined by the Biomedical Engineering Department for electrical integrity, and if approved, the patient is encouraged to use their own machine in the postoperative period. If the device is not approved or if the patient does not bring his or her device, a PAP device is provided by the facility for these patients. For patients who do not use a machine at home or who did not bring their device, the respiratory therapist monitors them and may place them on a PAP device if they experience postoperative respiratory events. We recorded the use of PAP devices on at-risk or diagnosed patients regardless of whether they used home equipment or not.

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Statistical Analysis

For this analysis, OSA risk was categorized as low or moderate risk of OSA versus high-risk or diagnosed OSA, as high-risk and diagnosed patients are identified to clinicians before surgery to alert them of possible increased risk. As a sensitivity analysis, we repeated all analyses comparing low-risk patients to moderate-risk, high-risk, and diagnosed patients with OSA. Wilcoxon rank sum tests were used to assess the association between OSA risk and length of stay for outpatient procedures and between OSA risk and discharge time for ambulatory extended recovery procedures. We also planned a multivariable linear regression model, adjusted for age, ASA score, robotic surgery, type of anesthesia (general or monitored anesthesia care), and surgery start time, to assess the impact of OSA risk on length of stay after controlling for factors known to be associated with length of stay or discharge time.

We assessed whether there was an association between OSA risk and the probability of transfer to the main hospital after surgery, urgent care center visit within 30 days after surgery, or hospital readmission within 30 days after surgery using χ2 tests. We then tested whether the association remained significant after adjusting for age, ASA score, robotic surgery, type of anesthesia, and procedure class (outpatient or ambulatory extended recovery) using multivariable logistic regression and reported the adjusted risk difference as the adjusted risk in the lower OSA risk group (low or moderate risk) subtracted from the adjusted risk in the higher OSA risk group (high-risk or diagnosed OSA). We also reported the absolute difference in risk of postoperative death within 30 days between patients at low or moderate risk of OSA and those at high risk or diagnosed with OSA with 95% CI. We did not have sufficient event numbers to perform a multivariable analysis for the outcome of death within 30 days of surgery.

We assessed whether there was a difference in intraoperative or postoperative opioid use in oral morphine milligram equivalents based on OSA status. Univariate and multivariable logistic regression models were used with the outcome of any versus no intraoperative or postoperative opioid use. We then assessed the association while adjusting for age, gender, BMI, surgical service, and procedure class. Patients with a reoperation on the same day were excluded from the comparison of postoperative opioid use as postoperative opioid use included opioid use after subsequent surgeries on the same day.

Among patients diagnosed with or at moderate or high risk for OSA, we reported the incidence of postoperative respiratory events with 95% CI. We also investigated whether the incidence of postoperative respiratory events or the use of a postoperative respiratory device was associated with risk of or diagnosis with OSA using χ2 tests. P values <.05 were considered statistically significant. All analyses were performed using Stata 15 (StataCorp, College Station, TX). This article adheres to the applicable Strengthening the Reporting of Observational Studies in Epidemiology reporting guidelines.

We estimated that this study would include close to 6000 patients and that the prevalence of OSA or high risk for OSA would be 10%. For an adverse outcome with a prevalence close to 5%, this would give a 95% CI narrower than ±2%, which was deemed to be sufficient precision. We did not specify clinical relevance a priori in terms of a noninferiority margin and this limits the strength of our conclusions.

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RESULTS

We identified a cohort of 5731 patients who underwent 6522 surgical procedures at Josie Robertson Surgery Center during the study period. We excluded 791 procedures from patients who had a second procedure as part of a planned breast reconstruction, 9 patients classified as ASA 4, and 1 patient who received only local anesthesia. A total of 5721 surgical patients were included in the analysis. In this cohort, 526 (9.2%) were at risk for OSA and included 233 (4.1%) patients previously diagnosed, 91 (1.6%) at moderate risk, or 202 (3.5%) high risk for OSA. Other patient characteristics are presented in Table 1.

Table 1.

Table 1.

Outcomes by OSA risk group are presented in Table 2. On univariate analysis, we found no evidence of a difference in length of stay by OSA risk among patients undergoing outpatient procedures (P = .2) or ambulatory extended recovery procedures (P = .3; Table 3). We found no evidence that patients at high risk or diagnosed with OSA were more likely to be transferred to the main hospital after surgery (P = .2; Table 3). Patients at high risk for OSA or diagnosed with OSA were more likely to have an urgent care center visit within 30 days of surgery (P = .027) and to be readmitted to the hospital within 30 days (P = .047; Table 3). As a sensitivity analysis, we repeated these analyses comparing low-risk to moderate-risk, high-risk, and diagnosed patients with OSA. The results of this sensitivity analysis had similar effect sizes and were consistent with the results of the main analysis (data not shown). There were 51 (0.9%) patients transferred to the main hospital after surgery at Josie Robertson Surgery Center. Top reasons for transfer were surgical bleeding (29%), other surgical issues (24%), and cardiac or neurological events (20%). Three patients (5.9%) were transferred for pulmonary events, and only one of these was diagnosed with OSA.

Table 2.

Table 2.

Table 3.

Table 3.

On multivariable analysis, we found no evidence of a difference in length of stay based on OSA risk for patients undergoing outpatient procedures (P = .8; Table 4). While there was a significant difference in discharge time in ambulatory extended recovery procedures, the discharge time for high-risk and diagnosed patients with OSA was only 15 minutes later (95% CI, 0.42–30 minutes, P = .044). We also saw no evidence of a difference in transfer rates or urgent care center visits (Table 4). While there was some evidence that readmission rates within 30 days were higher among diagnosed and high-risk patients than among low- or moderate-risk patients (adjusted risk difference, 1.2%; 95% CI, –0.40% to 2.8%; P = .077; Table 4), the CI does not include clinically meaningful differences. Again, results of the sensitivity analysis comparing low-risk to moderate-risk, high-risk, or diagnosed patients were consistent with the primary analysis. One patient who was at low risk of OSA died within 30 days of surgery, and there were no other deaths within 30 days of surgery in this cohort. The risk of postoperative death within 30 days was 0.02% higher in low or moderate OSA risk patients than in high-risk or diagnosed patients with OSA (95% CI, –0.02% to 0.06%) with the 95% CI excluding a >0.02% higher risk of 30-day postoperative death in high-risk or diagnosed patients with OSA.

Table 4.

Table 4.

We found no evidence of a difference in any use of intraoperative opioids or postoperative opioids on univariate (P = .5 and P = .2, respectively; Table 3) or multivariable analysis (P = .3 and P = .6, respectively; Table 4). A sensitivity analysis comparing low-risk to moderate-risk, high-risk, and diagnosed OSA showed results consistent with the main analysis.

While there was some evidence on univariate analysis that rates of adverse safety events were higher in high-risk and diagnosed patients with OSA, there were no clinically important differences seen on multivariable analysis based on the upper bounds of the CIs. OSA risk does not add predictive value in addition to other patient characteristics that differed by OSA risk such as type of procedure and ASA score.

Among the 526 patients diagnosed with OSA or at moderate or high risk for OSA, 13% (95% CI, 10%–16%) experienced a postoperative respiratory event. When comparing moderate-risk, high-risk, and diagnosed patients with OSA separately, we found no evidence of a difference in the rate of postoperative respiratory events between high-risk patients (N = 30 events, 15%) and diagnosed patients with OSA (N = 36 events, 15%, P = .9). The rate in the combined high-risk and diagnosed OSA group was significantly higher than the rate of postoperative respiratory events in moderate-risk patients (N = 2 events, 2.2%; P = .001). Nearly half of the patients with diagnosed OSA used a postoperative respiratory device after surgery (N = 113, 49%), as compared to only 13% (N = 27) of high-risk and 2.2% (N = 2) of moderate-risk patients (P < .0001). Notably, 60% (n = 94) of patients diagnosed with OSA who use a home device (n = 156) chose to use their device or a hospital device postoperatively regardless of the occurrence of postoperative events. Among the 77 (33%) patients diagnosed with OSA who did not use a home device, 19 (25%) were placed on a PAP after experiencing a postoperative OSA event.

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DISCUSSION

We investigated the association between OSA status and short-term outcomes and safety for patients undergoing a variety of outpatient and more complex ambulatory extended recovery cancer surgery procedures in a freestanding ambulatory surgery facility. After multivariable adjustment, there was no statistically significant association between the risk of OSA and length of stay, urgent care visits, readmission, or risk of transfer for either outpatient or ambulatory extended recovery procedures. Based on the upper bounds of the CIs, clinically significant increase in the risk of these adverse events associated with OSA is unlikely.

We did find an increase in postoperative respiratory events among high-risk and diagnosed patients with OSA, but these events did not delay discharge or increase postoperative transfers. Although we found 49% of diagnosed patients used a postoperative respiratory device, this measure is not reflective of the occurrence of postoperative events that occurred since all patients diagnosed with OSA who use a home device are encouraged to bring and use their home device postoperatively regardless of the occurrence of postoperative events, whereas all other patients are placed on a PAP device only if they experience a postoperative event. Memtsoudis et al26 commented in a recent editorial that the increasing prevalence of OSA may lead facilities to develop protocols based on insufficient scientific evidence that could increase resource utilization for implementation. Our data demonstrate the feasibility of managing at-risk patients with OSA without increasing the burden of extended hospitalization or readmission.

These outcomes can be considered to reflect the impact of applied consensus and evidenced-based guidelines advanced by professional societies5,20 in a real-world clinical setting. Our preoperative process includes STOP-BANG screening of all scheduled patients and assessing the optimization of comorbid conditions. In addition, all patients who were scheduled as ambulatory extended recovery were on clinical pathways that include multimodal analgesic therapies including limiting, but not eliminating, opioids. Our results provide additional evidence for following current guidelines and maintaining safe use of opioids in the at-risk OSA population. Although we did not measure whether patients who received opioids had greater frequency of respiratory events, no patients with OSA were transferred because of prolonged hypoxemia or respiratory complications.

Our findings confirm those of Stierer et al27 who found that, among 2139 ambulatory surgery patients, those with diagnosed or at high risk for OSA did not have an increased risk of unplanned hospital admission, life-threatening events such as reintubation, cardiac arrhythmia, or death, although they did report an increase in perioperative events such as difficulty of intubation resulting in additional anesthetic management. Notably, they used a questionnaire and demographic data to identify patients, whereas we systematically screened all patients using the STOP-BANG tool. Our larger study population, including more complex ambulatory surgery cases, extends conclusion by Stierer et al27 that patients with OSA may undergo ambulatory surgery without increased risk of major adverse outcome, although they may require additional perioperative interventions.

In our study sample, 4.1% were diagnosed with OSA and 3.5% screened high risk for OSA compared to higher estimates in the adult population.1–5 The lower prevalence of OSA among our population is likely due in part to the lower prevalence of males (16%) in our sample as male gender is a risk factor for OSA. Indeed, among our male population, 20% screened as high risk or had an OSA diagnosis, closer to general population estimates for males.1 Our at-risk patients had higher BMI, more patients scored as ASA 3, greater use of general anesthesia, longer duration of surgery, and increased proportion undergoing advanced robotic ambulatory surgery. Nevertheless, with proper preoperative optimization and perioperative management, these at-risk patients did not experience an increase in length of stay or adverse outcomes.

A 2016 study conducted among 404 ambulatory surgical oncology outpatients undergoing low-risk cystoscopy procedures found that patients who screened high risk for OSA had a longer length of stay compared to low-risk patients28 with a difference in median length of stay of approximately 30 minutes. Our study found no difference in length of stay between diagnosed or high-risk patients versus moderate- or low-risk patients, and this held true for both patients undergoing outpatient procedures as well as for patients undergoing more extensive ambulatory extended recovery procedures. Notably, this study was conducted on predominantly male (78%) urologic oncology patients compared to our predominantly female population (84%). It is unclear whether the patients who stayed longer required increased monitoring and use of PAP devices; however, our data demonstrate that even high-risk and diagnosed patients may be managed with CPAP/BiPAP without prolonging length of stay.

A 2003 retrospective analysis conducted by Sabers et al29 of 234 patients with polysomnography-confirmed OSA and 234 matched controls found no significant difference in the rate of unplanned hospital admission including readmission within 24 hours or other adverse events. Our study, with a larger sample size and different surgical population, drew similar conclusions regarding transfer to the main hospital after surgery (equivalent to unplanned admission), but we report a 0.8% transfer rate compared to their 24%. Our expanded quality outcome of readmissions within 30 days also showed no significant difference based on OSA status (Table 4).

Our findings regarding postoperative respiratory events confirm those of Fernandez-Bustamante et al,30 who reported that patients at high risk for OSA had similar rates of postoperative adverse respiratory events as those diagnosed with OSA. They also found, however, that patients at high risk for OSA had higher rates of some adverse events than diagnosed patients including reintubation, mechanical ventilation, and direct admission to the intensive care unit after surgery and with an absolute increase in high-risk patients of approximately 3% for all 3 outcomes. Despite this increased risk of adverse events, they did not find a clinically significant difference in length of stay (median 3 days for both at-risk and diagnosed OSA). Conversely, our study found that there was no evidence of an increase in length of stay, transfers, urgent care center visits, readmissions within 30 days, and rates of postoperative respiratory events for diagnosed and high-risk patients based on the effect size estimates and the upper bounds of the corresponding CIs. These differences may reflect that Fernandez-Bustamante et al30 studied an inpatient surgery population, while our study was conducted on ambulatory surgery patients.

Our study has several strengths. First, our large sample size of 5721 ambulatory oncologic surgery patients provided a diverse patient population and enabled us to adjust for a number of patient and surgical characteristics. Second, the use of respiratory therapists and clinical staff to provide PAP during the postoperative stay may have contributed to the uneventful postoperative course, especially for the high-risk and diagnosed patients with OSA. A previous study found that involvement of respiratory therapists in the postoperative care of patients diagnosed with or at risk for OSA helped prevent acute respiratory compromise in these patients.31 Furthermore, the involvement of respiratory therapists increased the reliability and validity of data collected on respiratory events and devices used through their direct observations. Finally, STOP-BANG screening is part of the routine preoperative evaluation for all patients at the Memorial Sloan-Kettering Cancer Center and is consistently and reliably implemented and electronically documented by our trained nurse practitioners.

This study also has several limitations. STOP-BANG screening has its limitations with sensitivity and specificity of 83.6% and 56.3%, respectively.23,24 However, it is likely that patients who have severe OSA, restricting their functional ability with associated comorbidities, would be scored as ASA 4 which triggers a presurgical testing staff consult with an anesthesiologist about patient suitability for Josie Robertson Surgery Center. We feel our results demonstrate the feasibility of universal screening for OSA and practical applications in the clinical setting.

As with all retrospective observational studies, there are limitations on drawing firm conclusions. Naturally, the ideal study would be to randomize patients with OSA to inpatient versus ambulatory care. However, this is less likely primarily because of insurance designations. Our estimate of the increase in risk of urgent care center visits associated with OSA is 2.9%. Even if treating patients with OSA as inpatients halved the risk of an OSA–related complication, this would mean a small absolute risk difference of about 1.5%. To detect this difference in a randomized trial would require about 8000 patients and would therefore be infeasible. Moreover, it is questionable whether this decrease in risk would be clinically relevant, that is, whether it would be worth treating 67 patients with OSA on an inpatient basis to prevent 1 OSA–related urgent care center visit. Nonetheless, there is room for reasonable disagreement as to the clinical relevance or otherwise of the observed difference in the study adverse events.

Patients who screened as low risk were not initially monitored directly by respiratory therapists unlike patients at higher risk or diagnosed. If a postoperative respiratory event occurred in a low-risk patient, respiratory therapists were notified by nurses and would then begin close monitoring of the patient. Thus, postoperative respiratory events may be underreported among low-risk patients. Conversely, outcomes such as length of stay, urgent care center visits, hospital readmissions, and transfers were systematically collected. Nevertheless, a limitation of our 30-day readmission and urgent care center visit outcomes is that those occurring outside our Memorial Sloan-Kettering Cancer Center system would not be automatically captured resulting in potential underreporting. In addition, respiratory therapists are not available after midnight, and thus, respiratory events and device use are potentially underreported for overnight patients. Nevertheless, all patients arrive in the PACU before the respiratory therapist leaves for the night and none were transferred after midnight for pulmonary or respiratory issues. Although data collection was not designed for study purposes but was part of routine care, our data are accurate and complete and this allows examination of a large cohort of patients with high external validity for other practices. The lack of OSA–related events requiring intervention while these patients continued under our care should lend further confidence to the safety of managing these patients in the ambulatory setting.

More recently, after the completion of this study, a detailed review on intraoperative management of patients with OSA has been published. This report suggested that patients with OSA are at increased risk for difficult intubation and mask ventilation and recommend precautions when using propofol, neuromuscular blocking agents, opioid medications, or benzodiazepine sedation for patients with OSA as they may be at increased risk for adverse effects from the use of these agents.22

Our results contribute to the growing body of evidence supporting that patients with moderate-risk, high-risk, or diagnosed OSA can safely undergo outpatient and advanced ambulatory oncology surgery without increased health care burden and adverse postoperative outcomes in a protocolized perioperative management environment. Our data support the thoughtful adoption of practices promoted by several national OSA guidelines focusing on preoperative identification of patients with OSA and clinical pathways for perioperative management and postoperative monitoring.

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DISCLOSURES

Name: Betsy Szeto, MPH.

Contribution: This author helped design the conceptual design, acquire the data, and prepare and revise the manuscript.

Name: Emily A. Vertosick, MPH.

Contribution: This author helped perform the data analysis and prepare and revise the manuscript.

Name: Karin Ruiz, RT.

Contribution: This author helped acquire the data and revise and edit the manuscript.

Name: Hanae Tokita, MD.

Contribution: This author helped revise and edit the manuscript.

Name: Andrew Vickers, PhD.

Contribution: This author helped design the conceptual design, analyze the data, and revise the manuscript.

Name: Melissa Assel, MS.

Contribution: This author helped design the conceptual design, analyze the data, and revise the manuscript.

Name: Brett A. Simon, MD, PhD.

Contribution: This author helped design the conceptual design and prepare and revise the manuscript.

Name: Rebecca S. Twersky, MD, MPH.

Contribution: This author helped design the conceptual design, acquire the data, and prepare and revise the manuscript.

This manuscript was handled by: Tong J. Gan, MD.

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