Reduction of Environmental Temperature Mitigates Local Anesthetic Cytotoxicity in Bovine Articular Chondrocytes

The purpose of this study was to assess whether reducing environmental temperature will lead to increased chondrocyte viability following injury from a single-dose of local anesthetic treatment. Bovine articular chondrocytes from weight bearing portions of femoral condyles were harvested and cultured. 96-well plates were seeded with 15,000 chondrocytes per well. Chondrocytes were treated with one of the following conditions: ITS Media, 1x PBS, 2% lidocaine, 0.5% bupivacaine, or 0.5% ropivacaine. Each plate was then incubated at 37°C, 23°C, or 4°C for one hour and then returned to media at 37°C. Chondrocyte viability was assessed 24 hours after treatment. Chondrocyte viability is presented as a ratio of the fluorescence of the treatment group over the average of the media group at that temperature (ratio ± SEM). At 37°C, lidocaine (0.35 ± 0.04) and bupivacaine (0.30 ± 0.05) treated chondrocytes show low cell viability when compared to the media (1.00 ± 0.03) control group (p < 0.001). Lidocaine treated chondrocytes were significantly more viable at 23°C (0.84 ± 0.08) and 4°C (0.86±0.085) than at 37°C (p < 0.001). Bupivacaine treated chondrocytes were significantly more viable at 4°C (0.660 ± 0.073) than at 37°C or 23°C (0.330 ± 0.069) (p < 0.001 and p = 0.002 respectively). Reducing the temperature from 37°C to 23°C during treatment with lidocaine increases chondrocyte viability following injury. Chondrocytes treated with bupivacaine can be rescued by reducing the temperature to 4°C.

Key points

• Confirm that local anesthetics, specifically bupivacaine and lidocaine, are toxic to chondrocytes in monolayer
• Chondrocyte viability significantly improved for chondrocytes treated with bupivacaine when the environment was cooled to 23°C.
• Chondrocyte viability significantly improved for chondrocytes treated with bupivacaine or lidocaine when the environment was cooled to 4°C
• It is the recommendation of the authors that physicians should be wary of the risks of injecting local anesthetics into the intra-articular space.
• Active cooling of the joint could potentially protect the articular cartilage from insult following treatment with local anesthetics.

Key words: Clinical hypothermia, local anesthetics, articular cartilage, osteoarthritis, chondrolysis