Is cerebral blood flow/metabolic mismatch during rewarming a risk factor after profound hypothermic procedures in small children?

Abstract

The relation between cerebral blood flow and oxygen consumption wasstudied in six children during cardiac operations with profoundhypothermia. A combination of topical cooling and core cooling was used toreduce the nasopharyngeal temperature to 15 degrees C. The alpha- statprinciple for pH management was used. Blood flow and oxygen consumptiondecreased significantly with temperature. At a nasopharyngeal temperatureof 15 degrees C, blood flow was reduced to 25% of the awake level,corresponding to 34% of the asleep value obtained 15-30 min afterintubation. Oxygen consumption decreased to 25% of the asleep value. Duringstable profound hypothermia, venous saturation in the jugular bulb was atthe same level as 15 min after intubation (70%). Markedly lower values wereobserved during topical cooling, and particularly during rewarming (down to21%), indicating a mismatch between cerebral blood flow and oxygenconsumption. The speed of rewarming correlated with the fall in venousoxygen saturation (rs = 0.82, P less than 0.05). It is suggested thatperiods of cerebral blood flow/metabolic mismatch during topical coolingand rewarming may explain postoperative cerebral dysfunction after deephypothermic procedures. A moderate speed of rewarming is advocated.