Anesthesia and cardiopulmonary bypass technique in calves and sheep

The number of research institutions using calves and sheep as models for open heart surgical procedures is increasing. The Artificial Heart Laboratory of the University of Utah has developed an effective protocol for thoracic procedures in these animals. Routine barbiturate induction and maintenance with fluothane and a pressure-regulated ventilator have minimized anesthetic problems. A membrane oxygenator with blood flows of 50 to 75 ml/kg body weight/min. seems to give adequate circulatory support during heart-lung bypass. Although animals implanted with total artificial hearts do not have problems with arrhythmias, changes in pulmonary function and peripheral vascular tone can alter their cardiac performance. The judicious use of ventilatory support and specific vasoactive drugs can significantly improve the animal's intraoperative blood pressure and postoperative arterial gases. A summary of the techniques and drugs which were used successfully in 187 of 189 animals during a 2 year period are presented.