Key result
Bupivacaine plus fatty acids reduces sodium current block in human cardiac channels versus bupivacaine alone.
Why the study?
Do fatty acids reduce bupivacaine-induced sodium channel blockade in human cardiac sodium channels?
Do fatty acids reduce bupivacaine-induced sodium channel blockade in human cardiac sodium channels?
Fatty acids may antagonize bupivacaine cardiotoxicity through a direct modulatory effect on cardiac sodium channels, reducing bupivacaine-induced blockade.
Fatty acids may attenuate bupivacaine sodium channel block in vitro; leaves open clinical relevance to lipid rescue.
Theories regarding the mechanism of intravenous fat emulsion for bupivacaine cardiotoxicity include creation of an intravascular lipid sink into which the cardiotoxic drug is sequestered, an improvement of impaired cardiac metabolism, and restoration of cardiomyocyte function by increasing intracellular calcium. However, work in this area is inconclusive and a more mechanistic explanation is desirable. We used a heterologous expression system (HEK-293 cells) and voltage clamp techniques to study the electrophysiologic effects of bupivacaine, polyunsaturated, and saturated fatty acids on sodium current (I(Na)) in stable cell lines expressing human cardiac sodium channels. Linolenic (polyunsaturated) and stearic (saturated) fatty acids were selected for study as they are components of commonly used lipid infusions. Bupivacaine-induced significant tonic and use dependent I(Na) block, as expected. Linolenic and stearic fatty acids directly modulated I(Na), inducing primarily tonic block. Greater block was seen with linolenic acid as compared with stearic acid. Simultaneous exposure to bupivacaine and fatty acids reduced both the tonic and use dependent block compared with bupivacaine alone. Reduction of bupivacaine-induced I(Na) block was greatest in cells treated with linolenic acid. These results suggest that the salutary effects of intravenous fat emulsion may be, in part, due to a direct modulatory effect of fatty acids on cardiac sodium channels.
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Mottram et al. (2011) studied Bupivacaine cardiotoxicity. Linolenic and stearic fatty acids vs. Bupivacaine alone was evaluated on Sodium current (I(Na)) block. Simultaneous exposure to bupivacaine and fatty acids reduced both tonic and use-dependent sodium current block compared with bupivacaine alone in human cardiac sodium channels.
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