Research Article Open Access

An Observational Study of the Pharmacokinetics of Adductor Canal Block using Liposomal Bupivacaine in Total Knee Arthroplasty

Abstract

Background: Periarticular Local Infiltration of Analgesia (LIA) and regional nerve block using Adductor Canal Block (ACB) have been described as effective in managing postoperative pain for Total Knee Arthroplasty (TKA). It has been shown that combining ACB with LIA can significantly reduce pain scores and postoperative consumption of morphine compared with LIA alone. However, this may raise concerns about the potential risk of Local Anesthetic Systemic Toxicity (LAST), especially with the large doses of total local anesthetic used in both LIA and ACB.

Objectives: The purpose of this study was to evaluate the plasma level of bupivacaine over a 72-hour period following ACB using 66.5 mg of Liposomal Bupivacaine (LB) in patients undergoing TKA with LIA using 300 mg ropivacaine. This study aims to provide some pharmacokinetic data of LB in ACB for future dose defining study on LB in ACB together with LIA.

Design: Prospective observational study.

Setting: Ethical approval for this study (Reference Number UW 20 -589) was provided by the Ethical Committee, Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster, Queen Mary Hospital, Hong Kong (Chairman Prof. Brian Liang) on 6 October 2020

Patients: Ten patients underwent primary, unilateral, simple revision TKA were included in the study from December 2020-February 2022.

Main outcome measures: The primary outcomes were the time to peak plasma concentration (Tmax) of bupivacaine and the peak plasma concentration (Cmax) of bupivacaine. The secondary outcome was the presence of LAST.

Results: Tmax of bupivacaine was 48 hours while Cmax of bupivacaine was 88 mcg/L, this value was far below 2000 mcg/L, the defined toxic plasma concentration of bupivacaine.

Conclusion: The report's only validity resides with the dataset describing Tmax and Cmax of LB in a small cohort underwent TKA. Despite there was large variation of Cmax, we did not identify plasma bupivacaine levels within toxic ranges especially with such relatively small dose of LB administered. Therefore, there is still room for increasing the dose of LB used in ACB for TKA patients with LIA using high dose of ropivacaine.

Trial registration: The clinical trial was registered at ClinicalTrials.gov with registration number NCT04916392.

Will Shing Him Chan1, Timmy Chi Wing Chan1*, Henry Chi Yeung Mak1, Manson Tak Hei Chan1, Clement Hoo Chun Cheung1, Susan Wai Sum Leung3, Steve Po Yam Li3, Stanley Sau Ching Wong2, Chi Wai Cheung2

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