Sevoflurane reduces the cardiac toxicity of bupivacaine compared with propofol in rabbits: an experimental study using early electrocardiographic detection and measurement of toxic plasma concentration.

Background: The effect of both propofol and sevoflurane on bupivacaine cardiac toxi-city has not been conclusively defined. The goal of this study was to investigate the effects of propofol vs sevoflurane general anesthesia (GA) on bupivacaine-induced arrhyth-mias.

Material and methods: Ten rabbits were randomized to two groups: propofol- or sevoflurane-based GA. At the maintenance stage of anesthesia heart rate and QRS/QT durations were recorded as "baseline" and an intravenous (i.v.) bupivacaine 0.25% infusion at the rate of 1.0 mg kg -1 min -1 was initiated. Blood samples were obtained when predefined electrocardiographic (ECG) changes were observed and when the heart rate (HR) reached 75%, 50%, and 25% of the baseline and 0 bpm.

Results: The mean time to first predefined ECG changes was 131 ± 25.02 s for the propofol group and 223 ± 34.11 s for the sevoflurane group ( P = 0.001). Time of progression of bradycardia in both groups was evaluated as a percentage of the initial HR for the understanding of the dynamics of changes during the local anesthetic systemic toxicity (LAST). The 25% HR time was shorter for the propofol group (480 ± 117 vs. 673 ± 146 s, P = 0.05). Time to asystole was shorter in the propofol group (110.7 ± 22.22 vs. 226.6 ± 98.61 s, P = 0.047). Mean serum bupivacaine concentration was lower for the propofol group during the occurrence of the first ECG changes (2.542 ± 1.415 vs. 6.997 ± 2.197 mg mL -1 , P = 0.005) and asystole (110.7 ± 22.22 vs. 226.6 ± 98.61 mg mL -1 , P = 0.047).

Conclusions: It seems that sevoflurane-, but not propofol-based anesthesia reduces the risk of LAST during GA combined with peripheral nerve blocks. Sevoflurane-based anesthesia may protect the myocardium from the toxic effects of bupivacaine.