Effects of Ketamine HCl on Cardiopulmonary Function in Snakes

We determined the effects of ketamine HCI on cardiopulmonary function in 10 grey ratsnakes (Elaphe obsoleta), weighing 320 ? 150 g (mean ? SD). To establish normal values of cardiovascular response, we measured arterial blood pressure, carotid arterial blood flow, heart rates, breathing rates, and arterial blood gases in conscious snakes positioned both horizontally and in a 45* head-up tilt. Then we measured the same variables following intravascular administration of ketamine HCI (41 ? 6 mg/kg). Administration of ketamine produced significant tachycardia, hypertension, and decreases in breathing rates which were reflected in modest changes of arterial pH and respiratory gas pressures. Arterial oxygen saturation, however, exceeded 95% in both conscious and anesthetized snakes. Administration of ketamine produced nearly twofold increases in systolic, diastolic, mean, and pulse systemic arterial pressures of resting snakes in horizontal position. In response to head-up tilt, central arterial pressures decreased in anesthetized snakes but did not fall below levels that were regulated by reflexogenic increases in conscious snakes. Thus, administration of ketamine HCI to snakes produced significant hypertension but did not seriously compromise cardiovascular performance in response to gravitational stress.