Adding a transversus abdominis plane block to parenteral opioid for postoperative analgesia following trans-abdominal hysterectomy in a low resource setting: a prospective, randomised, double blind, controlled study.

BACKGROUND: The current gold standard treatment for acute postoperative pain after major abdominal surgery is multimodal analgesia using patient controlled analgesia delivery systems. Patient controlled analgesia systems are expensive and their routine use in very low income countries is not practical. The use of ultrasound in anaesthesia has made some regional anaesthesia blocks technically easy and safe to perform. This study aimed to determine whether adding an ultrasound guided transversus abdominis plane block as an adjunct to the current parenteral opioid based regimen would result in superior pain relief after a trans abdominal hysterectomy compared to using parenteral opioids alone.

METHODS: Thirty-two elective patients having trans abdominal hysterectomy were recruited into a prospective randomised double-blind, controlled study comparing a bilateral transversus abdominis plane block using 21 ml of 0.25% bupivacaine and 4.0 mg dexamethasone with a sham block containing 21 ml 0.9% saline. Sixteen patients were allocated to each group. Anaesthesia and postoperative analgesia was left to the attending anaesthetist's discretion. Primary outcome was visual analogue scale for pain at 2 h and 4 h. Secondary outcomes were time to first request for analgesia, visual analogue scale for comfort and bother. The data were analysed using the Statistical Package for Social Sciences (SPSS version 16).

RESULTS: There was no statistically significant difference in the demographics of the two groups regarding weight, height, physical status and type of surgical incision. There was a statistically significant difference in visual analogue scale for pain at 4 h during movement with lower pain scales in the test group (p = 0.034). Women in the control group had an average pain free period of 56.8 min (median 56.5 min) before requesting a rescue analgesic compared to 116.5 min (median 103 min) in the study group. The between group difference in the average total analgesia duration was statistically significant at the 0.05 level (p = 0.005).

CONCLUSION: The addition of a bupivacaine-dexamethasone transverse abdominis plane block to intramuscular opioid does produce superior acute post-operative pain relief following a hysterectomy. However a single-shot block has a limited duration of action, and we recommend a repeat block.

TRIAL REGISTRATION: Clinical trials registration was obtained PACTR201501000965252. http//www.pactr.org/ATMWeb/appmanager/atm/atmregistry?_nfpb=true&_windowLabel=BasicSearchUpdateController_1&BasicSearchUpdateController_1_actionOverride=%2Fpageflows%2Ftrial%2FbasicSearchUpdate%2FviewTrail&BasicSearchUpdateController_1id=965. The trial was registered on the 12th Dec 2014.