Ultrasound-guided transversus abdominis plane block does not improve analgesia after elective caesarean section when intrathecal diamorphine is used-A randomised double-blind controlled trial

Context: Previous studies comparing transversus abdominis plane (TAP) block and opioids for postoperative analgesia for caesarean section under spinal anaesthesia have been performed in the absence of a long-acting intrathecal opioid or with intrathecal morphine. In our unit, we use spinal diamorphine for caesarean sections under spinal anaesthesia. We wished to establish whether the performance of ultrasound-guided TAP blocks should be introduced into routine practice. Materials and Methods: Following local ethics committee approval, 53 parturients presenting for elective caesarean section were recruited. All patients received a spinal anaesthetic with 0.5% heavy bupivacaine and 300 mcg diamorphine. The study was completed by 48 patients who were randomised to undergo postoperative TAP blocks with 20 mL to each side of either 0.25-0.5% bupivacaine (n = 23) or normal saline (n = 25). Standard postoperative analgesia comprised of regular diclofenac and paracetamol, and subcutaneous morphine on request via an indwelling subcutaneous cannula. A blinded investigator assessed each patient at 2, 6, and 24 h postoperatively. Results: There were no statistically significant differences in postoperative morphine requirements or visual analogue pain scores between the two groups. The incidence of side effects was similar. Conclusions: We conclude the ultrasound-guided TAP block does not improve analgesia following elective caesarean section under subarachnoid block with intrathecal diamorphine and its routine implementation during utilisation of a multimodal analgesic regimen may not be beneficial