Ethnic Differences in Analgesic Efficacy and Safety of Liposomal Bupivacaine Among Asian and Caucasian Surgical Patients: A Retrospective Matched-Cohort Analysis

Background: Extended-release local anesthetics allow for prolonged analgesia after a single administration. Although Asians demonstrate different pain thresholds than Caucasians, whether they have different postoperative local anesthetic analgesic effects has not been elucidated. Objective: We aimed to compare the postoperative analgesic efficacy of liposomal bupivacaine on Asian and Caucasian adults, and the incidence of local anesthetic systemic toxicity (LAST) syndrome. Methods: We conducted a retrospective, assessor-blinded cohort study of adult patients who received liposomal bupivacaine for surgery between 2012 and 2018. Asians and Caucasians were matched in a 1:1 ratio by clinical characteristics and surgery type. The primary outcome was pain management, defined as average pain score and opioid consumption during the initial 72 postoperative hours. The secondary outcome was the incidence of LAST syndrome. Reviewers were blinded to the ethnicity of the patient. Results: After 1:1 propensity score matching, 130 Asians and 129 Caucasians were analyzed. All confounding variables were balanced, except for higher body mass index in the Asian group. Pain scores were lower (adjusted mean difference of -0.50 [97.5% CI, -0.98, -0.01]; superiority p = 0.011) and opioid consumption was not greater (geometric means ratio, 0.61 [97.5% CI, 0.36, 1.04]; non-inferiority p ＜ 0.001) in Asian patients compared to Caucasian patients. Only one Caucasian patient was judged as having a potential case of LAST syndrome. The length of hospital stay and the incidence of additional complications were not different between the groups. Conclusion: Asian adults receiving liposomal bupivacaine as part of multimodal perioperative analgesia demonstrated lower pain scores compared to matching Caucasians, despite not having greater opioid consumption.