Respiratory Monitoring after Opioid-Sparing Bariatric Surgery in Patients with Obstructive Sleep Apnea (OSA)

Introduction with Aim: Postoperative respiratory depression can complicate a patient's recovery after surgery. A predictive score (PRODIGY) was recently proposed to evaluate the risk of opioid-induced postoperative respiratory depression. For the first time, we applied this score to a cohort of patients receiving bariatric surgery, stratified by Obstructive Sleep Apnea (OSA) status. In addition, we recorded continuous postoperative capnography to evaluate respiratory depression and apnea episodes (Respiratory Events, RE). Materials and Methods: The present study was approved by our IRB and comprised continuous surveillance of respiratory variables during postoperative recovery (in PACU) after robotic bariatric surgery. We utilized continuous capnography and pulse oximetry (Capnostream 35, Medtronic Inc., and Profox Respiratory Oximetry software). Preoperative preparation included OSA evaluation for all bariatric patients, additional sleep studies for severe OSA grades, and evaluation of risk for respiratory depression (low, intermediate, or high) using the published PRODIGY score. In addition, we evaluated patients by OSA status. All patients received multimodal intraoperative non-opioid anesthesia from the same team. After surgery, all patients received continuous respiratory surveillance in PACU (average duration exceeding 140 min). Respiratory depression events were scored using a modified list of the five standard published categories. Events were measured according to analysis of continuously recorded tracing of the compiled respiratory variables by observers kept blind from the study patient's group. Results: Of the 80 patients evaluated (18 male), 56 had obstructive sleep apnea and were using CPAP at home (OSA); 24 did not. OSA patients received CPAP via an oronasal mask or a nasal pillow pressure support immediately after arriving in PACU, utilizing their at-home settings. We encountered 115 respiratory depression events across 48 patients. The most frequent respiratory event recorded was a transient desaturation (as low as 85%), which usually lasted 20-30 sec and resolved spontaneously in 3 to 5 min; most episodes followed small boluses of IV opioid analgesia administered during recovery, on demand. All episodes resolved spontaneously without any nursing or medical intervention. OSA patients had significantly more events than non-OSA patients (1.84 (1.78-1.9) mean events vs. 0.50 (0.43-0.57) for non-OSA, p = 0.0002). The level of PRODIGY score (low, intermediate, or high), instead, was not predictive of the number of events when we treated this variable as continuous (p = 0.39) or categorical (high vs. low, p = 0.65, and intermediate vs. low, p = 0.17). Conclusions: We attribute these novel results, showing a lack of respiratory events requiring intervention, to opioid-free anesthesia, early CPAP utilization, and head-up positioning on admission to PACU. Furthermore, all these patients had light postoperative narcotic requirements. Finally, an elevated PRODIGY score in our patients did not sufficiently predict respiratory events, but OSA status alone did. Key Points Summary: We investigated the incidence of Respiratory Events (RE) in Obstructive Sleep Apnea patients after surgery (56 patients) and compared them to similar patients without OSA (24 patients). All patients received identical robotic-assisted surgery and low- or no-opiate anesthesia. Patients were pre-screened with the standard published PRODIGY scores and were monitored after PACU arrival with continuous oximetry and capnography (Capnostream 35 and Profox analysis). OSA patients showed more RE than non-OSA (1.8 vs. 0.5, p = -0.0002). However, patients with elevated PRODIGY scores did not develop more frequent RE compared to patients with low scores. We attribute these novel results to opioid-sparing anesthesia/analgesia and immediate CPAP utilization on admission to PACU.