Prevalence of antiemetic administration after abdominal surgery with or without a regional anesthesia under general anesthesia in a nation-wide population-based study

The difference in the effect of regional anesthesia (RA; peripheral nerve block or epidural anesthesia) combined with general anesthesia (GA) and that of GA alone on postoperative nausea and vomiting (PONV) remains unclear. We used a national Japanese clinical database to evaluate whether the PONV incidence differed between GA with RA and GA alone during abdominal surgery. In this retrospective nation-wide cohort study, we compared the outcomes of patients who received GA with RA with those of patients who received GA alone during abdominal surgery between April 2016 and October 2019. The primary outcome was PONV, which was defined as antiemetic use within 2 days of surgery. Covariates were used to stabilize the inverse probability of treatment weighting. Univariate and multivariate Cox proportional hazard regression analyses were performed. E-values, subgroup definition, and restricted mean survival time were used for sensitivity analyses. Among the 566,819 patients who met the eligibility criteria, 249,433 received GA-RA and 317,386 received GA alone. Overall, 148,105 patients (59.4%) in the GA-RA group and 132,819 (41.8%) in the GA-alone group developed PONV. The weighted hazard ratios of the univariable and multivariable models for PONV were 1.25 (95% CI, 1.24 to 1.26; P < .001) and 1.20 (95% CI, 1.19 to 1.21; P < .001), respectively, for GA-RA and GA alone. Sensitivity analyses confirmed the robustness. GA-RA is associated with a slight increase in PONV. Therefore, opioids may be used sparingly when combined with RA.