Lidocaine patches for postcesarean pain control in obese women: a pilot randomized controlled trial.

Background: Obesity increases the risk of opioid-related morbidity. Lidocaine patches have been shown to reduce postoperative pain after noncesarean surgeries.

Objective: This study aimed to determine whether the application of lidocaine patches around the cesarean incision in women with obesity reduces the total dose of opioids administered in the first 24 hours after cesarean delivery.

Study Design: This was a pilot single-blind randomized controlled trial of 61 women with obesity undergoing cesarean delivery at a community tertiary referral hospital staffed by academic physicians. After cesarean delivery, the allocated patches (either 5% lidocaine patches or placebo patches) were applied superior and lateral to the incision dressing and remained in place for 12 hours. The average cumulative opioid dose received within the first 24 hours after cesarean delivery was measured in morphine milligram equivalents. We also assessed pain and patient satisfaction. A sample size of 60 (30 per group) was determined to be adequate to inform a future appropriately powered randomized controlled trial. The primary outcome of morphine milligram equivalents was compared using the Student t test, and pain scores were compared using the Wilcoxon rank sum test.

Results: Of the 146 women screened between February 2019 and September 2019, 61 consented and were analyzed: 30 women were allocated to lidocaine patch and 31 were allocated to placebo (hydrocolloid patch). Women who were allocated to the lidocaine patch used an average of 87.0 (standard deviation, 35.8) morphine milligram equivalents of opioids in the first 24 hours compared with an average of 83.9 (standard deviation, 27.5) morphine milligram equivalents among women who were allocated to the placebo patch (P=.702). Women who were allocated to the lidocaine vs placebo patches reported median pain scores of 3.0 (interquartile range, 2.1-4.9) and 3.5 (interquartile range, 2.5-5.0), respectively (P=.217). The time to the first dose of opioids, total number of opioid doses, and total morphine milligram equivalents in 48 hours and for the entire hospital stay did not differ. Patient satisfaction with both patches was high and not statistically different.

Conclusion: This pilot suggests that 5% lidocaine patches applied superior and lateral to the cesarean incision are not effective at reducing the average total dose of morphine milligram equivalents administered in the first 24 hours after cesarean delivery among women with obesity, and they did not seem to improve median pain scores. An appropriately powered randomized trial would not be expected to demonstrate reduction in opioid use or pain.