A Calf Model for Left Ventricular Centrifugal Mechanical Assist

Abstract

The increased use of centrifugal mechanical assist (CMA) for treatment of refractory postcardiotomy cardiogenic shock highlights the need for experimental testing to improve clinical results. This report describes 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 instrumented for left ventricular CMA; 4 of these calves were sham-operated controls. Anesthetic recovery and postoperative restraint were accomplished in a specially designed crate to which each calf was preconditioned extensively. Younger calves were more readily conditioned and more tolerant of postoperative restraint than older calves. One calf died of ventricular fibrillation intraoperatively. One calf that had been heparinized developed uncontrollable hemothorax and died 12 h postoperatively. One calf prematurely dislodged his aortic cannula 15 h postoperatively and exsanguinated. Six calves developed pelvic limb paresis or paralysis because of lumbar spinal cord thromboembolism by 36 h postoperatively, and 3 of these calves were sacrificed by 42 h postoperatively. Fifteen calves required sedation in the first 12 h after the operation. Tachycardia associated with bottle feeding occurred in 15 calves. Second-degree atrioventricular block was noted frequently during deep relaxation. Postmortem examination demonstrated the absence of surgical wound and distant infection, security of cannulae in all but the calf that prematurely dislodged the aortic cannula, absence of thrombus formation at cannulation sites, and presence of thromboembolism in 51% of the calves. The incidence of thromboembolic lesions was not influenced by the need for chemical restraint, by the occurrence of feeding-associated tachycardia, or by the presence of atrioventricular block. There were no thromboembolic lesions in any of the sham-operated controls.

Perioperative Management of Calves Undergoing Implantation of a Left Ventricular Assist Device

“…Advantages associated with the use of the calf for this study of a LVAD and bypass circuits include the size of its thoracic cavity and vasculature, and the ready adaptation to restraint and handling. The implantation and function of various other left ventricular assist devices in calves have been reported 4–10 …”

“…The implantation and function of various other left ventricular assist devices in calves have been reported. [4][5][6][7][8][9][10] Factors that must be managed to produce a good outcome when anesthetizing calves for cardiopulmonary bypass and aortic surgery include bloat, regurgitation and aspiration of rumen contents, ischemia-induced peripheral myoneuropathy, cardiac arrhythmias, pulmonary dysfunction, hemodilution and severe hemorrhage. [11][12][13][14][15] Maintenance of anesthesia during partial cardiopulmonary bypass, restraint during the postoperative period, and the provision of adequate postoperative analgesia are all additional challenges.…”

Estudos de técnicas de texturização e biolização, e desempenho biológico in vitro e in vivo em membrana para um dispositivo de assistência ventricular e coração artificial totalmente implantáveis

“…A faixa etária determinada do modelo animal foi estabelecida de maneira a manter uma equivalência com o porte de um ser humano. Assim, não sendo necessária nenhuma adaptação de instrumental, bem como de parâmetros de fluxo para o bombeamento (Mann, 1996).…”