Timing of Fascial Plane Blocks in Bariatric Surgery: Pre-Incision Administration Is Associated with Lower Early Pain and Opioid Consumption

Background: Fascial plane blocks reduce opioid consumption after bariatric surgery, but the optimal timing of administration remains unclear. We compared pre-incision versus end-of-surgery block timing. Methods: This was a retrospective observational cohort study of consecutive patients undergoing laparoscopic sleeve gastrectomy at a single centre. All patients received a left external oblique intercostal block plus a bilateral rectus sheath block with 0.25% bupivacaine, performed by the same two experienced anaesthesiologists either before incision or at the end of surgery. Ward staff who routinely recorded postoperative pain scores did not have access to the anaesthesia record and were therefore unaware of block timing. The primary outcome was the numeric rating scale (NRS) pain score at post-anaesthesia care unit (PACU) admission. Repeated pain scores were analysed using generalized estimating equations (GEE) with an exchangeable correlation structure and robust standard errors, adjusted for BMI, ASA status and anaesthesia duration, and group × time interaction was tested. Secondary outcomes included 24 h intravenous morphine milligram equivalents (IV-MME) and the 24 h Quality of Recovery-15 (QoR-15) score, analysed with adjustment for baseline. Results: Fifty-four patients were analysed (pre-incision n = 28, post-surgery n = 26). Median NRS at PACU admission was lower in the pre-incision group (4.5 [IQR 2.0–8.0] vs. 7.0 [IQR 7.0–8.0]; p = 0.008). In the adjusted GEE model, pre-incision timing was associated with a 1.53-point lower NRS across the postoperative period (95% CI −2.15 to −0.91; p < 0.001). The between-group difference attenuated over time, from −2.42 points (95% CI −3.72 to −1.12) at PACU admission to −0.81 points (95% CI −1.30 to −0.33) at 24 h, although the group × time interaction did not reach significance (p = 0.075). PACU rescue fentanyl (median 62 [IQR 25–106] vs. 150 [IQR 100–194] µg; p < 0.001) and 24 h PCA tramadol (median 120 [IQR 100–150] vs. 172 [IQR 141–199] mg; p < 0.001) were both lower in the pre-incision group; mean consumption was 44% and 26% lower, respectively, corresponding to a 35% lower mean total IV-MME. No statistically significant difference in quality of recovery was detected, and the estimate was imprecise; the baseline-adjusted 24 h QoR-15 difference was 5.3 points (95% CI −7.0 to 17.6; p = 0.391). An exploratory subdomain analysis suggested better physical comfort with pre-incision timing, but this did not survive correction for multiple comparisons. Conclusions: In this retrospective cohort, pre-incision administration of fascial plane blocks was associated with lower early postoperative pain and lower recorded opioid consumption than end-of-surgery administration, with no statistically significant difference in overall quality of recovery, although that estimate was imprecise. Because block timing was determined by operating-room logistics rather than by randomisation, and intraoperative opioid exposure could not be quantified, these associations require confirmation in a prospective randomised trial before they can guide practice.