A Pain-informed Predictive Model and Mediation Analysis for Postoperative Nausea after Metabolic Bariatric Surgery: Insights from the PAIN OUT Registry.

BACKGROUND

A validated prediction model and mediation analysis for postoperative nausea (PON) are essential to guide targeted prevention and treatment in metabolic bariatric surgery.

METHODS

This study analyzed 2,331 anonymized metabolic bariatric surgery cases from the PAIN OUT database. PON was assessed on the first postoperative day using a standardized questionnaire. Clinically significant PON was defined as a numeric rating scale ≥ 4, categorizing participants into PONCS (scores 4–10) and Control (scores 0–3) groups.

RESULTS

A total of 1,486 patients (63.7%) were assigned to the Control group and 845 (36.3%) to the PONCS group. Among 30 candidate predictors, the following were identified as independent predictive factors for PON: age (OR [95% CI]: 0.979 [0.970–0.987]), female gender (2.159 [1.738–2.682]), hypertension (0.785 [0.635–0.972]), diabetes (0.572 [0.420–0.779]), cancer (0.474 [0.259–0.869]), affective disorders (0.616 [0.497–0.763]), chronic pain (1.272 [1.011–1.600]), preoperative non-opioids (0.619 [0.430–0.890]), sleeve gastrectomy (1.710 [1.389–2.106]), and three postoperative interventions administered in the PACU—non-opioids (1.482 [1.183–1.855]), opioids (1.536 [1.219–1.936]), and regional nerve blocks (0.413 [0.274–0.622]). The model showed good discrimination (AUC = 0.709; 95% CI 0.687–0.730) and calibration. Internal validation yielded an optimism-corrected AUC of 0.708 (95% CI 0.687–0.730) and a calibration slope of 0.955. PACU-administered non-opioids, opioids, and regional nerve blocks mediated the effects of preoperative non-opioids use and chronic pain on the PON development.

CONCLUSION

The novel PON prediction model shows favorable performance in metabolic bariatric surgery patients, with PACU-administered non-opioids, opioids, and regional nerve blocks identified as modifiable mediators linking preoperative non-opioids use and chronic pain to PON development.