Background: Caudal block is the most frequently used regional anesthetic for pediatric analgesia, technique with the disadvantage of limited duration of action associated with an undesired motor blockade and other complications. Recently, the transversus abdominis plane (TAP) block has been described as an effective technique to reduce postoperative pain intensity and morphine consumption after lower abdominal surgery. Materials & Methods: This prospective, randomized, controlled study included 40 children aged between 1 to 10 years, scheduled for elective lower abdominal surgery and divided into two groups in a double-blinded randomized manner. Group A (n=20): received single caudal dose with isobaric bupivacaine 0.25% (1.25ml/kg) and Group B (n=20): received an ultrasound guided TAB block with isobaric bupivacaine 0.25% (0.3ml/kg). The primary outcomes were the time to first analgesia in minutes and the analgesic doses (intravenous acetaminophen and rectal diclofenac) required during the first 24 h postoperatively. The secondary outcome measures included FLACC pain scale score and intraoperative hemodynamic variables. Results: No significant difference between two groups regarding demographic data and intraoperative hemodynamic values. Group B (TAP block) had a significantly longer time to first analgesia (638.50 ± 63.8 vs 268.53 ± 58.15 min) and required significantly lower doses of acetaminophen (320.5 ± 151.05 vs 653.05 ± 105.52 mg) and rectal diclofenac (0, 0, 0 vs. 0, 0, 25 mg) than group A (Caudal block). FLACC pain scale score was significantly lower in group B than in group A (P < 0.05) at 2, 4, 6, 8, 10, 12, 16, 18, 20, and 24 h postoperatively. Conclusion: TAP block provided superior analgesia compared with single dose caudal block injection with isobaric bupivacaine 0.25% in the first 24hours after surgery
