SUBCHRONIC CENTRIFUGAL MECHANICAL ASSIST IN AN UNHEPARINIZED CALF MODEL

The purpose of this study was to determine whether the major centrifug al pumps currently in use in the United States (Medtronic, BioMedicus BioPump and Carmeda-coated BioPump, Sarns 3M centrifugal pump, and St. Jude Medical Lifestream) could function as left mechanical assist dev ices in the subchronic (72 h) unheparinized calf model. Calves were in strumented for left atrial to aorta ex vivo assist, and the pump flow was set at 3.5 +/- 0.4 L/min. Two calves (Sarns 3M and St. Jude) survi ved 72 h of pumping without clinical complications. The other 2 calves died at 62 and 66 h (Medtronic BioPump and Carmeda-coated BioPump, re spectively); both had pelvic limb paralysis. The seal of the Sarns 3M pump head ruptured after approximately 36 h of pumping and required re placement. On postmortem examination, pump-associated thromboembolic l esions were detected in 3 of the 4 calves in one or more of the follow ing organs: kidney, pancreas, abomasum, duodenum, ileum, spleen, and l umbar spinal cord. The calf with the Sarns 3M pump had no discernable lesions. Because of the clinical abnormalities and postmortem lesions in the unheparinized calf model, it was suggested that anticoagulation is necessary for conducting centrifugal mechanical assist studies in calves using presently available technology.