Changes in heart rate and impulse conduction after a single dose of succinylcholine

The effect of 1 and 2 mg/kg b.w. succinylcholine on changes in cardiac rate and rhythm was studied in 40 fit, adult patients undergoing non-emergency surgery. Induction of anaesthesia consisted of atropine 0.007 mg/kg b.w., pancuronium 0.015 mg/kg b.w., thiopental 5 mg/kg and succinylcholine 1 or 2 mg/kg b.w. Succinylcholine 1 mg/kg b.w. intravenously resulted in a significant decrease in heart rate after 1 min. This decrease persisted after 2 min. The heart rate was unchanged 1 and 2 min after succinylcholine 2 mg/kg b.w. When the two groups were compared, no significant difference was found. No serious cardiac arrhythmias were seen. These results suggest that the larger single dose of succinylcholine is not more likely to cause severe bradycardia or asystole.