A CALF MODEL FOR LEFT-VENTRICULAR CENTRIFUGAL MECHANICAL ASSIST

The increased use of centrifugal mechanical assist (CMA) for treatment of refractory postcardiotomy cardiogenic shock highlights the need fo r experimental testing to improve clinical results. This report descri bes the preoperative conditioning, anesthetic and surgical technique, and postoperative management of a reliable calf model refined in this laboratory for in vivo subchronic (96 h) testing of CMA. Holstein bull calves (2 to 3 months old; mean body weight, 78 kg; n = 35) were inst rumented for left ventricular CMA; 4 of these calves were sham-operate d controls. Anesthetic recovery and postoperative restraint were accom plished in a specially designed crate to which each calf was precondit ioned extensively. Younger calves were more readily conditioned and mo re tolerant of postoperative restraint than older calves. One calf die d of ventricular fibrillation intraoperatively. One calf that had been heparinized developed uncontrollable hemothorax and died 12 h postope ratively. One calf prematurely dislodged his aortic cannula 15 h posto peratively and exsanguinated. Six calves developed pelvic limb paresis or paralysis because of lumbar spinal cord thromboembolism by 36 h po stoperatively, and 3 of these calves were sacrificed by 42 h postopera tively. Fifteen calves required sedation in the first 12 h after the o peration. Tachycardia associated with bottle feeding occurred in 15 ca lves. Second-degree atrioventricular block was noted frequently during deep relaxation. Postmortem examination demonstrated the absence of s urgical wound and distant infection, security of cannulae in all but t he calf that prematurely dislodged the aortic cannula, absence of thro mbus formation at cannulation sites, and presence of thromboembolism i n 51% of the calves. The incidence of thromboembolic lesions was not i nfluenced by the need for chemical restraint, by the occurrence of fee ding-associated tachycardia, or by the presence of atrioventricular bl ock. There were no thromboembolic lesions in any of the sham-operated controls.