Cerebral hemodynamics after low-flow versus no-flow procedures

Temperature induces depression of cerebral perfusion and cerebral oxygen metabolism in particular, and this seems to explain why a reduced pump flow above a critical level is well tolerated during hypothermic cardiopulmonary bypass with apparent full metabolic recovery afterward. It only partly explains why a longer period of hypothermic circulatory arrest leads to a protracted recovery of cerebral perfusion and cerebral metabolism. This review suggests there is evidence that energy metabolism can easily be compromised during and after rewarming after hypothermic cardiopulmonary bypass with low flow and with circulatory arrest. Although data indicate that cerebral metabolism and cerebral energy state are better after low flow than after circulatory arrest, the risk of energy crises appears imminent with both techniques.