The Circulatory Arrest Recovery Ammonia Problem (CARAP) Hypothesis

Brain injury remains an ongoing concern for patients requiring cardiopulmonary bypass (CPB) surgery. Observations in a neonatal pig model of build-up of blood ammonia levels may be a significant unrecognized source of metabolic stress in these surgeries. Ammonia entering the brain upon restarting the CPB pump appears highly correlated with the level of hypothermia and glutamine/glutamate appears highly correlated with brain lactate levels. These changes are also strongly dependent on the choice of surgical parameters such the use of deep hypothermia cardiac arrest (whereby all blood flow is stopped) versus antegrade cerebral perfusion (whereby brain blood flow is maintained).