Subgroup Analysis From a Multicenter, Randomized, Double-Blind, Controlled Trial of Liposomal Bupivacaine Transversus Abdominis Plane Block for Cesarean Births

Abstract

The use of transversus abdominis plane (TAP) block with long-acting liposomal bupivacaine (LB) after cesarean was shown to decrease opioid consumption in the primary analysis of a randomized, double-blind study (NCT03176459). Here, we present an analysis across subgroups to assess whether opioid-reducing benefits would differ in patients on the basis of baseline characteristics. Adult women with term pregnancies (37–42 weeks) who were scheduled to undergo elective cesareans using spinal anesthesia were randomized 1:1 to TAP with LB 266 mg plus bupivacaine HCl 50 mg or bupivacaine HCl 50 mg alone as part of a multimodal pain management protocol. Primary efficacy endpoint was postsurgical opioid consumption (morphine equivalent dosing [MED]) through 72 hours. Analysis was conducted for subgroups on the basis of age, race, body mass index (BMI), prior cesarean, discharge time, and medical anxiety history. The difference between groups in least squares means (LSM) was determined using an analysis of covariance model (with treatment as the main effect and age and height as covariates) and presented as the difference between the LB plus bupivacaine HCl and bupivacaine HCl–only groups. Demographics were similar across treatment groups (LB, n = 71; bupivacaine, n = 65). Total opioid consumption was numerically lower with LB plus bupivacaine HCl overall (LSM, 15.5 vs 32.0 mg, p = .01) and across most subgroups. The LSM treatment differences (95% CI) in mg MED across subgroups were as follows: younger than 35 years, –18.0 (–38.1, 2.2); older than 35 years, –2.3 (–22.1, 17.5); White, –8.3 (–24.5, 7.9); non-White, –23.3 (–54.2, 7.5); body mass index (BMI) less than 25 kg/m2, 13.2 (–7.5, 33.8); BMI 25 to less than 30 kg/m2, –16.8 (–42.4, 8.8); BMI 30 kg/m2 or greater, –9.7 (–28.8, 9.5); prior cesareans: –17.3 (–35.4, 0.7); no prior cesareans, –4.6 (–25.8, 16.7); discharged on or before Day 3, –10.5 (–29.1, 8.1); discharged on or after Day 4, –14.3 (–36.2, 7.7); anxiety history, –32.9 (–77.1, 11.2); and no anxiety history, –8.8 (–23.8, 6.3). This analysis suggests that TAP block use of LB plus bupivacaine HCl as part of a multimodal analgesia protocol has opioid-reducing benefits after cesarean birth in a broad population, with patients in subgroups based on age, race, prior cesarean, and anxiety history receiving incremental benefit.