Influence of age on bupivacaine cardiac arrhythmogenic effects

Abstract

The cardiotoxic effects of bupivacaine, a widely used local anesthetic, may be age-dependent because neonates and children tolerate a higher plasma concentration of bupivacaine after intravenous administration than adults. No studies have compared the toxicity profiles of the bupivacaine isomers in human neonates and children, but differences in the lethal dose have been observed between adult and younger rats. Here, we determined the age dependency of cardiac toxicity induced by racemic RS(±) bupivacaine and its levo S(−) isomer in hearts obtained from 2-and 16-week-old male Wistar rats (n=30 each) using a Langendorff ex vivo assay. We found that both RS(±) and S(−) bupivacaine significantly reduced heart rate and prolonged the PR interval and QRS complex duration. The effects of both compounds were significantly greater in older rats, and RS(±) bupivacaine had a greater effect than S(−) bupivacaine. Furthermore, RS(±) bupivacaine induced significantly more severe arrhythmias in 16-week-old than in 2-week-old rats. By contrast, the same concentration of S(−) bupivacaine was associated with mild arrhythmias in both age groups. Thus, although RS(±) bupivacaine induced greater cardiotoxicity than S(−) bupivacaine, the effects of both compounds were age related, with hearts from older animals showing more signs of toxicity.