UNIVERSITY-OF-WISCONSIN CEREBROPLEGIA IN A PIGLET SURVIVAL MODEL OF CIRCULATORY ARREST

Background. Previous acute studies in immature piglets at our institut ion have demonstrated improved recovery of cerebral blood now, intrace llular pH, and high-energy phosphates with the administration of multi dose University of Wisconsin solution as cerebroplegia during a period of deep hypothermic circulatory arrest (HCA). In an effort to define further the clinical applicability of this technique, we have develope d a survival model of swine cardiopulmonary bypass (CPB) and HCA. Meth ods. 12 Yorkshire pigs (age 4 to 5 weeks) were placed on CPB via the r ight femoral artery and right atrium. Animals were cooled to a rectal temperature of 15 degrees C and submitted to 90 minutes of HCA. Group UW (n = 6) received a single infusion of 50 mL/kg of 4 degrees C Unive rsity of Wisconsin solution delivered antegrade to the cerebral circul ation. The control group (n = 6) received no intervention. Animals wer e reperfused, rewarmed to 35 degrees C, and weaned from CPB. Neurologi c assessments using neurologic deficit scoring (0 = normal, 500 = brai n death) and overall performance categories (1 = normal, 5 = brain dea th) were performed at 24-hour intervals for 5 days. On the 5th postope rative day all brains were perfusion-fixed and examined for histologic evidence of neuronal injury (0 = normal, 5 = severe injury). Results. All animals were extubated 18 to 20 hours postoperatively. There was no significant difference between the mean neurologic score of the two groups. The mean day 5 neurologic deficit score was 108 for the UW gr oup and 68 for the control group (p > 0.05). The day 5 overall perform ance category was 2.8 for the UW group and 2.0 for the control group ( p > 0.05). Three of the UW animals but none of the control animals exp erienced generalized seizures. Histologic examination revealed more se vere damage in UW animals, primarily in the cerebral cortex. Injury wa s more widespread in UW animals, involving cerebellum and hippocampus. The mean histologic injury score was 3.8 for UW animals and 2.4 for t he control group (p = 0.06). Conclusions. A clinically relevant surviv al model of CPB with HCA in immature swine is feasible. Cold UW soluti on as single-dose cerebroplegia is not beneficial, and may be injuriou s to the immature swine brain subjected to CPB and HCA. Further studie s are indicated to determine optimal composition and administration of cerebroplegic solutions.