Surgical transversus abdominis plane block with liposomal bupivacaine at cesarean: a pilot randomized trial

Abstract

Background

Post-cesarean pain control is challenging. In addition to intrathecal morphine, recent studies have shown that liposomal bupivacaine administered via conventional transversus abdominis plane block reduces post-cesarean opioid utilization. However, whether administration of liposomal bupivacaine via a surgical approach also reduces opioid utilization is unknown.

Objective

To investigate whether administration of liposomal bupivacaine via surgical transversus abdominis plane (TAP) block reduces the cumulative dose of opioids administered in the first 48 hours post-cesarean among participants who also receive intrathecal morphine.

Study design

This was a pilot single-blind randomized controlled trial of 60 parturients undergoing cesarean at a community tertiary referral hospital staffed by academic physicians. Immediately prior to fascial closure during cesarean delivery, a total of 80 mL of dilute bupivacaine plus liposomal bupivacaine or dilute bupivacaine alone was injected via surgical transversus abdominis plane block (40 mL on each side). The primary outcome was median cumulative opioid dose received within the first 48 hours post-cesarean measured in morphine milligram equivalents. Opioid utilization at other time points, pain scores, and participant satisfaction were also assessed. A sample size of 60 was determined to be adequate to inform a potential future adequately powered randomized trial. The primary outcome of morphine milligram equivalents and pain scores were compared via Wilcoxon-rank sum test.

Results: Between October 11, 2021 and August 29, 2022, 60 participants were randomized and analyzed

: 31 were allocated to liposomal bupivacaine plus regular bupivacaine (intervention) and 29 were allocated to regular bupivacaine alone (control). Participants allocated to intervention used a median cumulative dose of 2 morphine milligram equivalents of opioids (interquartile range 0-24) in the first 48 hours compared to 8 morphine milligram equivalents (interquartile range 0-40) among participants allocated to control (P=0.236). The percent of participants who used less than or equal to 15 morphine milligram equivalents of opioids was 61% in the intervention arm and 41% among controls (P=0.123), and the percent who used zero opioids was 45% in the intervention arm and 34% among controls (P=0.399). The total number of opioid pills prescribed at discharge was fewer among the intervention arm (P=0.029). Patient satisfaction with the intervention and control was similar.

Conclusion

This pilot suggests that liposomal bupivacaine administered via surgical transversus abdominis plane block is worth critical evaluation as an adjunctive analgesic modality in an adequately powered randomized trial.