Associations Between Opioid Timing and Postoperative Desaturation Burden Following Metabolic Bariatric Surgery.

INTRODUCTION

Opioid‑induced respiratory depression (OIRD) is a serious, often underrecognized complication after bariatric surgery, with obesity and obstructive sleep apnea (OSA) as key contributors. The objective was to determine how perioperative opioid timing influences postoperative oxygen desaturation in patients undergoing bariatric surgery.

METHODS

Retrospective analysis of 312 patients undergoing robotic-assisted Roux-en-Y gastric bypass or sleeve gastrectomy (2022-2025). Continuous SpO₂, acoustic respiratory rate, and pulse rate were recorded for 14.4 h post‑PACU discharge. Desaturation was defined as either a ≥ 3% decrease in SpO₂ lasting ≥ 30 s or an absolute SpO₂ ≤ 89%. Opioid use was reported in morphine‑milligram equivalents (MME) intra‑operatively, in PACU, and in 2‑hour postoperative intervals.

RESULTS

Median age was 45 years, BMI 42.5 kg/m2, 87.8% female, and 66% had OSA. Mean desaturation events 8.2(SD 22.3); nadir SpO₂ averaged 73%. Intra‑operative MME (mean 10.0 ± 14.1) correlated with lower mean postoperative SpO₂ (ρ = ‑0.159, p = 0.006). In adjusted analysis, intra‑operative MME was associated with desaturation burden (IRR = 1.026; 95% CI 1.001-1.053; p = 0.048), while PACU MME was not (IRR = 1.017; p = 0.50). Total postoperative MME was not associated (IRR = 1.004; p = 0.86). Male sex independently increased desaturation risk (IRR = 3.50); age (IRR = 1.03) and OSA severity (IRR = 1.51) trended in the same direction without reaching significance. CPAP reduced odds only in 10‑12 h window (OR = 0.36; p = 0.022).

CONCLUSION

Intra‑operative opioids may contribute to greater postoperative desaturation, while later opioids do not. Male sex further increases risk, with age and OSA severity trending similarly. Findings support continuous monitoring during the first postoperative night.

KEY POINTS: Early perioperative opioids increase postoperative desaturation burden Intraoperative opioids were associated with postoperative desaturation Male sex independently increases desaturation risk; age and OSA severity trend similarly Continuous overnight monitoring reveals clinically silent hypoxemia.