Background: Ultrasound-guided transversus abdominis plane (TAP) block has been used for analgesia in lower abdominal surgery. In the literature, there are inconsistent reports regarding the efficacy of TAP block in different open abdominal procedures. Therefore, we conducted this prospective randomised doubleblind study to evaluate the pattern of perioperative analgesia and to validate the efficacy of TAP block in patients undergoing lower abdominal surgery.

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45 patients undergoing thyroidectomy were randomly divided into three groups; A, B and C. The protocol for induction and maintenance of general anaesthesia was similar for all three groups. Group A patients received 10 ml of 0.5% bupivacaine infiltration five minutes before skin incision, and 10 ml of 0.9% saline infiltration at the end of surgery. In group B saline infiltration was done before surgical incision, and 10 ml of 0.9% bupivacaine was infiltrated at the end of surgery. In group C (control group) 10 ml of 0.9% saline was infiltrated both before and end of the surgery. Post-operative pain was evaluated at 30 min, 2, 4 and 24 hr after surgery by 10 mm visual analogue score (VAS). Time for first analgesic request and total amount of pethidine consumed in 24 hr were recorded. Group A patients made first analgesic request after 125.3±42.5 min, in group B was 207.0 ± 8.36 minutes and in group C was 34.5 ± 26.6 min. The difference between these groups was statistically significant P value < 0.05. By the end of 24 hr, total consumption of pethidine in group A was 125.3 ± 42.5 mg, in group B was 143.3 44.2 mg and in group C was 191.6 ± 54.6 mg. There was no statistically significant difference in total consumption of pethidine between group A and B. But the difference between C and two groups A and B was significant. Group C patients showed higher pain intensity on VAS both clinically and statistically. We conclude that preemptive 0.5% bupivacaine infiltration improved the quality of post operative analgesia, but larger sample size study is required to prove statistical significance.