SLR - February 2011 - Megan Lynam
Reference: Baker JF, Byrne DP, Walsh PM, & Mulhall KJ (2010). Human Chondrocyte Viability after Treatment with Local Anesthetic and/or Magnesium: Results from an In Vitro Study. Arthroscopy: The Journal of Arthroscopic and Related Surgery, Epub ahead of print, 15 Oct 2010.
Scientific Literature Review
Reviewed by: Megan Lynam, DPM, MS
Residency Program: Cambridge Health Alliance in Cambridge, MA
Podiatric Relevance:
In recent literature, articles have been published demonstrating that certain types of local anesthetics, such as bupivacaine, may be more toxic to chondrocytes compared to other local anesthetics. This effect is of particular importance considering, as podiatric physicians, we perform numerous intra-articular injections in both the office and the operating room. Intra-articular local anesthetics, with or without arthroscopy, may have a devastating effect on cartilage. Magnesium sulfate has been shown to increase effectiveness of chondrocyte metabolism. This article studies and hypothesizes a possible method to decrease the chondrocytotoxicity of local anesthetic by adding alternative substitutes such as magnesium.
Methods:
The study subjects included a monolayer human chondrocyte cell line. The local anesthetics used in the study were 2% lidocaine, 0.5% levobupivacaine, 0.5% bupivacaine, and 0.75% ropivacaine. Each of the four types of local anesthetic was treated with the conditions of Magnesium in 10%, 20%, or 50% concentrations. Six wells of the monolayer cell cultures were used for each magnesium concentration and local anesthetic combination. After a 15 minute treatment, the cells were cultured for 24 hours with the test solutions replaced with normal cell media. Controls included cells in culture media, cells with 10%, 20%, or 50% Magnesium, and cells treated with normal saline. A cell proliferation assay measured by light spectrometry was used to assess viability by using a tetrazolium compound, which produces formazan. The color changes are based on the amount of formazan produced and correlate directly to the number of viable cells and mitochondrial activity. Treated cell viability was compared to the control cells.
Results:
The various concentrations of magnesium were not statistically significantly different when compared to the normal saline or untreated cells. The addition of magnesium to the various local anesthetics described above appeared to have more viable chondrocytes compared to the local anesthetics without magnesium. 0.5% levobupivacaine with the addition of any concentration of magnesium had statistically significant less viable chondrocytes compared to the 2% lidocaine with 20% magnesium and 0.75% ropivacaine with 10% magnesium.
Conclusions:
By supplementing the local anesthetics with magnesium, chondrocyte toxicity may be reduced. This study was performed in vitro, but the clinical and practical applications apply to intra-articular local anesthetic injections. The ideal magnesium concentration to be combined with local anesthetics should be explored further since magnesium in high concentrations is not a benign drug.