A comparison of analgesic efficacy between oblique subcostal transversus abdominis plane block and intravenous morphine for laparascopic cholecystectomy. A prospective randomized controlled trial.

Background: The ultrasound-guided oblique subcostal transversus abdominis plane (OSTAP) block provides a wider area of sensory block to the anterior abdominal wall than the classical posterior approach. We compared the intra-operative analgesic efficacy of OSTAP block with conventional intravenous (IV) morphine during laparoscopic cholecystectomy.

Methods: Forty adult patients undergoing laparoscopic cholecystectomy under standard general anesthesia, were randomly assigned for either bilateral OSTAP block using 1.5 mg/kg ropivacaine on each side (n = 20) or IV morphine 0.1 mg/kg (n = 20). The intra-operative pulse rate, systolic and diastolic blood pressure and mean arterial blood pressure were monitored every five minutes. Repetitive boluses of IV fentanyl 0.5 µg/kg were given as rescue analgesia when any of the above-mentioned parameters rose more than 15% from the baseline values. Time to extubation was documented. Additional boluses of IV morphine 0.05 mg/kg were administered in the recovery room if the recorded visual analogue score (VAS) was more than 4. Nausea and vomiting score, as well as sedation score were recorded.

Results: The morphine group required more rescue fentanyl as compared to the OSTAP block group but the difference was not significant statistically. Time to extubation was significantly shorter in the OSTAP block group (mean [SD] 10.4 [2.60] vs 12.4 [2.54] min; P = 0.021). Both methods provided excellent analgesia and did not differ in postoperative morphine requirements. No between-group differences in sedation score and incidence of nausea and vomiting were demonstrated.

Conclusions: Ultrasound-guided OSTAP block has an important role as part of balanced anesthesia. It is as efficacious as IV morphine in providing effective analgesia during laparoscopic cholecystectomy.