Preoperative versus postoperative rectus sheath block for acute postoperative pain relief: a retrospective cohort study

Background: Although rectus sheath block (RSB) is routinely used in laparoscopic surgeries to reduce mid-abdominal pain, it is unclear whether RSB should be performed before or after surgery. In this study, we investigated the optimal timing for RSB in patients undergoing laparoscopic surgery. Methods This retrospective cohort study analyzed patients who underwent RSB during laparoscopic procedures at our hospital between January 2013 and December 2018. The primary outcome was the first analgesia request within 24 h after the end of anesthesia. The patients were divided into preoperative RSB (pre-RSB) and postoperative RSB (post-RSB) groups. A multivariable Cox proportional hazards regression model was used to analyze analgesia requests in the unmatched and propensity-score (PS)-matched patient populations. Results We analyzed the findings for 609 of 14284 patients (pre-RSB group, 227 patients; post-RSB group, 382 patients). After PS matching, 97 patients were assigned to both groups. Although the time from extubation to the first analgesic request was not significantly different between the two groups (322 versus 294 min, P = 0.57), the patients in the pre-RSB group showed a lower risk of postoperative first analgesic administration after PS matching (adjusted hazard ratio, 0.71; 95% confidence interval, 0.53–0.95; P = 0.023). Conclusions Among patients undergoing laparoscopic surgery, the pre-RSB group tended to show a longer time to the first analgesic request. Patients in the pre-RSB group showed a lower risk of analgesic administration within 24 h than those in the post-RSB group. Thus, it may be preferable to perform RSB preoperatively. Trial registration: This study was registered with the University Hospital Medical Information Network-Individual Case Data Repository (UMIN000047494).