Propofol does not affect the canine cardiac conduction system under autonomic blockade

Purpose: To determine the effects of propofol on the cardiac conduction sys tem in dogs with pharmacological autonomic blockade. Methods: In eight mongrel dogs receiving 6 mg.kg(-1).hr(-1) propofol and ve curonium under pharmacological autonomic blockade with atropine and propran olol the infusion rates of propofol were increased from 6, (baseline), to 1 2, 18 and 24 mg.kg(-1).hr(-1) at 60-min intervals. An electrophysiological study assessed sinus rate, sinus node recovery time corrected sinus node re covery time, intraatrial conduction time, AV nodal effective refractory per iod, Wenckebach cycle length and AV conduction times. Electrocardiographica l variables and arterial pressures were also measured, All measurements wer e repeated at 30 min after the beginning of each infusion of propofol, Results: Propofol did not produce direct effects on the electrophysiologica l or electrocardiographical variables at any infusion rates. Heart rates di d not change at higher infusion rates in the presence of decreases in arter ial pressures. Conclusion: Propofol did not affect the cardiac conduction system in the pr esence of autonomic blockade, Thus, the direct cardiac effects of propofol do not play a causative role in the genesis of propofol-associated bradyarr hythmias.