Effects of thiopental and ketamine on cardiac function during moderate hemorrhage in chronically instrumented rats

This study was designed to assess the effects of thiopental and ketamine on cardiac function after a blood loss of 2 ml/100 g of body weight. In nine Sprague-Dawley rats, a catheter was placed in the abdominal aorta, a pulsed Doppler probe was positioned around the thoracic aorta, and a wall-thickness probe was sutured onto the left ventricle. On three occasions, all rats were studied awake, during thiopental anesthesia, and during ketamine anesthesia. In awake rats, a 30% blood loss resulted in an immediate, transient hypotension (49%) and a prolonged decrease in cardiac output (39%) and stroke volume (28%). No significant changes were observed in the wall-thickening fraction, which is an index of cardiac contractility, and in the heart rate. The effect of thiopental on cardiovascular responses to moderate hemorrhage was minimal. Although ketamine did not affect the hypotensive response to moderate hemorrhage, it did accentuate systemic vasoconstriction and cardiac depression as indicated by a decrease in cardiac output (57%), stroke volume (49%), and wall thickness (47%).