Analgesic Equivalence of NSAIDs and a Weak Opioid in Acute Postoperative Pain Following Minimally Invasive Surgery Under Balanced General Anesthesia: A Pilot Randomized Controlled Trial

Background: Non-steroidal anti-inflammatory drugs (NSAIDs) and weak opioids such as tramadol are cornerstones of multimodal analgesia, particularly in settings with limited access to potent opioids. However, cross-class equianalgesic data comparing these agents remain scarce. This pilot randomised controlled trial aimed to explore the analgesic equivalence of ketorolac, diclofenac, and tramadol administered as premedication in patients undergoing minimally invasive surgery. Methods: In this double-blind, parallel-group pilot trial, 30 patients scheduled for elective minimally invasive surgery (28 laparoscopic cholecystectomies, 2 laparoscopic abdominal wall repairs) under balanced general anaesthesia were randomised to receive intravenous tramadol 150 mg, ketorolac 60 mg, or diclofenac 150 mg 45 minutes before skin incision. The primary outcome was pain intensity measured using the Numerical Rating Scale (NRS, 0-10) at recovery room arrival (T0) and at 30 (T1), 60 (T2), and 90 (T3) minutes thereafter. Secondary outcomes included Verbal Rating Scale (VRS) scores, rescue morphine consumption, and safety. Between-group comparisons were performed using Kruskal-Wallis tests with Dunn post-hoc corrections; within-group trajectories were analysed using Friedman tests. Effect sizes were estimated with epsilon-squared and Kendall's W. Results: All 30 patients completed the study. At T0 and T1, NRS scores were higher in the ketorolac group (median 1.5 and 3, respectively) compared with tramadol and diclofenac (both median 0 at T0; T1: tramadol 1, diclofenac 2; p < 0.05 for both). However, by T2 and T3, all three groups converged to a median NRS of 2 (p > 0.05 for between-group differences). Rescue analgesia requirements at T1 were 0/10 (tramadol), 3/10 (ketorolac), and 2/10 (diclofenac), with no statistically significant differences (p = 0.19). No hypersensitivity reactions occurred. Within-group analyses showed consistent pain trajectories, with Kendall's W ranging from 0.31 (ketorolac) to 0.64 (tramadol). Conclusions: In this pilot study, equianalgesic doses of tramadol, ketorolac, and diclofenac provided comparable postoperative pain control over 90 minutes following minimally invasive surgery. All agents were well tolerated. These findings support the feasibility of a larger definitive trial and offer clinically useful guidance for analgesic selection in resource-limited settings. Keywords: Analgesic equivalence, NSAIDs, tramadol, ketorolac, diclofenac, postoperative pain, minimally invasive surgery, pilot randomised controlled trial