BARBITURATE ANESTHESIA: AN ABNORMAL PHYSIOLOGIC SITUATION

¹ Departments of Physiology and Anesthesiology, The University of Texas Medical Branch and Shriners Burns Institute, Galveston, Texas

The cardiovascular responses to an anesthetic dose of pentobarbital were examined in unpremedicated, unanesthetized dogs. Catheter implantations and electrocardiograph electrode placement were performed under halothane anesthesia. Full recovery of the animal was allowed, after which unanesthetized controls were taken. Variables measured included systolic, diastolic and mean arterial blood pressures, central venous pressure, heart rate, initial ventricular impulse, cardiac output and arterial pO₂ , pCO₂ and pH. Stroke volume, pulse pressure and total peripheral resistance were calculated. Sodium pentobarbital (30 mg/kg) was then administered i.v. After stabilization, the cardiovascular responses were recorded at -hr intervals for a 2-hr period. Systolic blood pressure remained significantly depressed throughout the test period as did the initial ventricular impulse, stroke volume, pulse pressure, central venous pressure, pO₂, pH and body temperature. Heart rate and pCO₂ remained statistically significantly greater than control. Mean blood pressure showed only one significant change from control, that being a decrease. The peripheral resistance was significantly elevated from 1 hr on, and cardiac output had decreased significantly at the 1-hr time and remained depressed. In view of these drastic responses, it is felt that careful consideration must be given to the choice of agent, if an anesthetic is to be employed in cardiovascular experimentation. Even more preferable would be the use of unanesthetized animals.

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