A Double-Blind, Randomized Controlled Trial of Pre-incision Wound Infiltration Using Diclofenac Versus Bupivacaine for Post-operative Pain Relief in Open Thyroid and Parathyroid Surgery.

Abstract

Pre-incision wound infiltration using NSAID is an alternative method to manage post-operative pain in surgery. It is postulated that NSAID delivered peripherally exerts efficient analgesic and anti-inflammatory effect with minimal systemic complication. This study explored the efficacy of using diclofenac for wound infiltration in open thyroidectomy and parathyroidectomy as compared to conventional agent, bupivacaine. The study was designed as a double-blind, randomized controlled trial involving 94 patients who underwent open thyroidectomy or parathyroidectomy in Hospital Pulau Pinang, Malaysia, from November 2015 to November 2016. The study compared the efficacy of pre-incision wound infiltration of diclofenac (n = 47) versus bupivacaine (n = 47) in post-operative pain relief. Wound infiltration is given prior to skin incision. Mean pain score at designated time interval within the 24-h post-operative period, time to first analgesia, total analgesic usage and total analgesic cost were assessed. Ninety-four patients were recruited with no dropouts. Mean age was 49.3 (SD = 14.2) with majority being female (74.5%). Ethnic distribution recorded 42.6% Chinese, 38.3% Malay, followed by 19.1% Indian. Mean duration of surgery was 123.8min (SD = 56.5), and mean length of hospital stay was 4.7days (SD = 1.8). The characteristics of patient in both groups were generally comparable except that there were more cases of total thyroidectomy in the diclofenac group (n = 31) as compared to the bupivacaine group (n = 16). Mean pain score peaked at immediate post-operative period (post-operative 0.5h) with a score of 3.5 out of 10 and the level decreased steadily over the next 20h starting from 4h post-operatively. Pre-incision wound infiltration using diclofenac had better pain control as compared to bupivacaine at all time interval assessed. In the resting state, the mean post-operative pain score difference was statistically significant at 2h [2.1 (SD = 1.5) vs. 2.8 (SD = 1.8), p = 0.04]. During neck movement, the dynamic pain score difference was statistically significant at post-operative 1h [2.7 (SD = 1.9) vs. 3.7 (SD = 2.1), p = 0.02]; 2h [2.7 (SD = 1.6) vs. 3.7 (SD = 2.0), p = 0.01]; 4h [2.2 (SD = 1.5) vs. 2.9 (SD = 1.7), p = 0.04], 6h [1.9 (SD = 1.4) vs. 2.5 (SD = 1.6), p = 0.04] and 12h [1.5 (SD = 1.5) vs. 2.2 (SD = 1.4), p = 0.03]. Mean dose of tramadol used as rescue analgesia in 24h duration was lower in the diclofenac group as compared to bupivacaine group [13.8mg (SD = 24.9) vs. 36.2mg (SD = 45.1), p = 0.01]. The total cost of analgesia used was significantly cheaper in diclofenac group as compared to bupivacaine group [RM 3.47 (SD = 1.51) vs. RM 13.43 (SD = 1.68), p < 0.01] or [USD 0.83 (SD = 0.36) vs. USD 3.21 (SD = 0.40), p < 0.01]. Pre-incision wound infiltration using diclofenac provides better post-operative pain relief compared to bupivacaine for patient who had underwent open thyroidectomy or parathyroidectomy. Diclofenac is cheap and easily available in the limited resource setting. This approach offers a superior alternative for post-operative pain relief as compared to bupivacaine.