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.

Background: 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.

Methodology: 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.

Results: 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 123.8 min (SD = 56.5), and mean length of hospital stay was 4.7 days (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 0.5 h) with a score of 3.5 out of 10 and the level decreased steadily over the next 20 h starting from 4 h 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 2 h [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 1 h [2.7 (SD = 1.9) vs. 3.7 (SD = 2.1), p = 0.02]; 2 h [2.7 (SD = 1.6) vs. 3.7 (SD = 2.0), p = 0.01]; 4 h [2.2 (SD = 1.5) vs. 2.9 (SD = 1.7), p = 0.04], 6 h [1.9 (SD = 1.4) vs. 2.5 (SD = 1.6), p = 0.04] and 12 h [1.5 (SD = 1.5) vs. 2.2 (SD = 1.4), p = 0.03]. Mean dose of tramadol used as rescue analgesia in 24 h duration was lower in the diclofenac group as compared to bupivacaine group [13.8 mg (SD = 24.9) vs. 36.2 mg (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].

Conclusion: 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.