Modified ultrafiltration may not improve neurologic outcome following deep hypothermic circulatory arrest

Objective: Modified ultrafiltration (MUF) improves systolic blood pressure and left ventricular performance, as well as lowering transfusion requirements, after cardiopulmonary bypass (CPB). MUF has also been shown to enhance acute cerebral metabolic recovery after deep hypothermic circulatory arrest (DHCA), but whether this improves neurologic outcome is unknown. Methods: Sixteen neonatal piglets underwent CPB and 90 min of DHCA. The hematocrit was maintained between 25 and 30%. Alpha-stat blood gas management was used. After separation from CPB, animals were randomized to 15 min of MUF (n=8) or no intervention (n=8). Neurologic injury was assessed with behavior scores and histologic examination. Standardized behavior scores were obtained on post-operative days 1, 3, and 6 (0=no deficit to 95=brain death). The percentage of injured neurons by hematoxylin and eosin staining and the degree of reactive astrocytosis by glial filbrillary acidic protein (GFAP) immunohistochemistry were assessed to determine histologic scores in the neocortex and hippocampus (0=no injury to 4=diffuse injury). Results: There were no statistically significant differences between groups during CPB. After MUF, the hematocrit was significantly higher (40%±5.7 vs. 28%±3.9, P0.1). There was resolution of deficits by day 6 in all animals. Neuronal injury was present in 81% (13/16) of the animals with no statistically significant differences between groups in incidence or severity. Conclusions: Use of MUF after DHCA does not prevent neuronal injury or improve neurologic outcome in this neonatal swine model.