The effect of prolonged pentobarbital anaesthesia on cardiac electrophysiology and inotropy of the dog heart in situ.

The effect of prolonged pentobarbital anaesthesia was tested on the dog heart in situ by means of His bundle electrography and programmed electrical stimulation, monophasic action potential recordings from the right ventricle and measurements of peak dp/dt obtained by Millar tip transducer in the left ventricle. Sixteen dogs were used. Immediately after catheterization during anaesthesia, a slight decreased heart rate, a reduction in the conduction velocity and an increase in the functional refractory period of the atrioventricular node occurred. From 15 to 30 min. after catheterization we observed no change in cardiac electrophysiology during the 8 hrs observation period. A slight decrease in contractility, however, appeared towards the end of the period. We conclude that dogs anaesthetized with pentobarbital could serve as a suitable model for testing drug effect on cardiac electrophysiology and contractility. The limitations of the model area are discussed.