A comparative study between the use of dexmedetomidine vs. dexamethasone as adjuvants to bupivacaine in ultrasound-guided transversus abdominis plane block for postoperative pain relief in patients undergoing lower abdominal surgeries

Background & objective: Transversus abdominis plane (TAP) block using local anesthetics is associated with relatively shorter duration of action, and thus additional analgesic drugs are required in the postoperative period. We compared the efficacy and duration of postoperative analgesia achieved with using dexmedetomidine or dexamethasone as adjuvants to bupivacaine in TAP block for lower abdominal surgeries. Methodology: We enrolled 45 adult patients aged from 20-60 y, and randomly divided them into three equal groups. Group A received ultrasound guided TAP block with 0.25% bupivacaine 20 ml plus 4 mg dexamethasone on each side. Group B received 0.25% bupivacaine 20 ml plus dexmedetomidine 0.5 mu g/kg on each side, and Group C (control group) patients received only 0.25% bupivacaine 20 ml on each side. Postoperative pain was assessed with VAS on arrival in post-anesthesia care unit (PACU), at 2 h, 6 h, 12 h, 18 h, and at 24 h postoperatively. Duration of analgesia was the time from drug injection to the time of first rescue of analgesia was recorded. Results: Mean duration to first dose of rescue analgesia among patients of dexmedetomidine group (Group B) was significantly prolonged as compared to dexamethasone group and bupivacaine only group. Regarding postoperative pain scores there were no statistically significant difference between the three groups; except at 6 h between the A and B groups and the control group. Both dexamethasone group and dexmedetomidine group showed better pain control than bupivacaine only at 6 h interval. Conclusion: Dexmedetomidine added to bupivacaine in ultrasound-guided transversus abdominis plane block for postoperative pain relief in patients undergoing lower abdominal surgeries prolongs the time to initial postoperative pain presented by time to first rescue analgesic demand than dexamethasone added to bupivacaine; the shortest time to first rescue analgesic was observed in bupivacaine alone group. Abbreviations: TAP: Transversus abdominis plane block; LA: Local anesthetic; PACU: Post anesthesia care unit; VAS: Visual Analogue Scale; ASA: American Society of Anesthesiologists; SD: Standard deviation; IQR: Inter quartile range.