INFLUENCE OF EXTRACEREBRAL TEMPERATURE ON CEREBRAL TEMPERATURE DISTRIBUTIONS DURING INDUCTION OF DEEP HYPOTHERMIA WITH SUBSEQUENT CIRCULATORY ARREST.

Local hypothermia protects cardiac cells for surgical arrest by reducing the consumption of metabolic substrate and by buffering hydrogen ions. For neonatal and pediatric cardiac surgical patients the operative field and blood vessels are too small to implement local cooling/arrest procedures. Surgeons have developed the technique of whole body hypothermic circulatory arrest (HCA) for these patients. The whole body is, in theory, brought to 12-14 degree C by surface and/or perfusion cooling (using cardiopulmonary bypass (CPB)), at which point the circulation is stopped for 30-60 min. Success with the pediatric technique has prompted extension of whole body HCA to adult cardiac and neurological surgical procedures. However, in both the pediatric and more susceptible adult patient, uneven cooling and rewarming of cells, especially in the brain, may lead to depletion of metabolic substrate, irreversible cell damage and postoperative complications. We present numerical (finite element) and experimental results designed to evaluate the protection of brain during HCA.