Cardiovascular and antiarrhythmic effects of esmolol in children.

This prospective study evaluated the cardiovascular and antiarrhythmic effects of esmolol, an intravenous beta-blocker with an extremely short half-life. Twenty patients (aged 2 to 16 years) underwent diagnostic electrophysiologic studies at rest and during beta-blockade induced with esmolol. An initial dose of 600 micrograms/kg was infused for 2 minutes and followed by an infusion of 200 micrograms/kg per minute. The dosage was increased by 50 to 100 micrograms/kg per minute every 5 to 10 minutes until a reduction of greater than 10% in either heart rate or mean blood pressure was seen. The dosage required to achieve beta-blockade ranged from 300 to 1000 micrograms/kg per minute (mean 550 micrograms/kg per minute). Electrophysiologic effects included a decrease in the rate of sinoatrial node discharge and delay in conduction through the atrioventricular node. There was no effect on His-Purkinje conduction. Atrial and ventricular effective refractory periods were unchanged. In six patients with supraventricular tachycardia, esmolol prevented induction of tachycardia in four and slowed the rate of the tachycardia in two. In four patients with ventricular tachycardia, clinical findings were improved in three and unchanged in one. Heart rate and blood pressure returned to near baseline values 10 minutes after the esmolol infusion was stopped. Adverse ventricular electrophysiologic effects were observed in two patients with biopsy evidence of myocarditis. No other adverse effects were seen. We conclude that the effects of esmolol in children are similar to those of other beta-blockers and that it is useful in the evaluation and management of pediatric tachyarrhythmias. The weight-adjusted dosage required to induce beta-blockade in children is larger than the adult dosage, and the effects of esmolol dissipate rapidly.