In vitro chondrotoxicity of bupivacaine at low concentrations in cultured canine articular chondrocytes

Abstract

Bupivacaine is a long-acting local anesthetic that is used in various anesthetic and/or analgesic protocols, including intra-articular injection for pain management during orthopedic procedures. The purpose of this study was to evaluate the in vitro chondrotoxicity of bupivacaine at concentrations similar to in vivo synovial fluid concentrations in canine articular chondrocytes. A controlled in vitro experimental study was used. Third passage (P3) chondrocytes in monolayer culture were treated with bupivacaine at 0.25%, 0.125%, 0.062%, 0.031% and 0.016% (2.5, 1.25, 0.62, 0.31 and 0.16 mg/ml, respectively). The control was treated with only growth medium. Chondrocyte viability was evaluated after 1, 6 and 24 hr using the live/dead assay; 3-(4,5-dimehylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay; and Cell Counting Kit-8 (CCK-8) assay. Bupivacaine at 0.125% and 0.25% significantly decreased chondrocyte viability compared to the control at all treatment time-points (P < 0.001). Bupivacaine at 0.062% was chondrotoxic at all treatment time-points with the MTT assay (P < 0.001) but only after 6 and 24 hr with the live/dead and CCK-8 assays (P < 0.001). After 24 hr, 0.031% bupivacaine caused cell clustering with the live/dead assay and significantly decreased cell viability with the MTT (P < 0.001) and CCK-8 (P = 0.001) assays. Bupivacaine at 0.016% did not significantly decrease cell viability at any of the treatment time-points. These findings indicate that bupivacaine has in vitro chondrotoxic effects on canine articular chondrocytes at concentrations that are similar to in vivo synovial fluid concentrations, especially with prolonged exposure.