Schwartz A E, Kaplon R J, Young W L, Sistino J J, Kwiatkowski P, Michler R E
Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, New York, New York.
Anesthesiology. 1994 Oct;81(4):959-64. doi: 10.1097/00000542-199410000-00023.
Neurologic injury after cardiopulmonary bypass (CPB) is a frequent and devastating complication of cardiothoracic surgery. Disordered cerebral hemodynamics during CPB has been implicated as an important factor in the etiology of these injuries. Evidence of disordered cerebral hemodynamics includes reports of a progressive time-dependent decrease in cerebral blood flow (CBF) during stable full-flow CPB. Low-flow hypothermic CPB has become a preferred technique for the management of pediatric patients undergoing surgical repair of complex cardiac lesions. Because CBF is already substantially reduced with the onset of low-flow CPB, we determined if a similar progressive decline in CBF occurs during the low-flow state.
After induction of general anesthesia in seven baboons, CPB was instituted. alpha-Stat management of arterial blood gases was used. Animals were cooled at a pump flow rate of 2.5 l.min-1.m-2 until tympanic membrane temperature decreased to 18 degrees C. CPB flow was then reduced to 0.5 l.min-1.m-2 and maintained constant for at least 77 min. Thereafter, CPB flow was increased to 2.5 l.min-1.m-2 and baboons rewarmed to normal temperature. CPB was discontinued after return of cardiac function. CBF was measured before, during and after CPB by washout of intraarterial xenon 133.
Low-flow CPB resulted in a decrease in CBF to about 50% of the prebypass rate and about 30% of the value measured during full-flow CPB. Sequential measurements of CBF at 30-min intervals during low-flow CPB showed no time-dependent change in cerebral perfusion.
Although systemic flow is reduced to 20% of full-flow during low-flow CPB, CBF reduced by half is disproportionately preserved relative to systemic flow. Furthermore, there is no time-dependent change in CBF under these low-flow conditions.
体外循环（CPB）后的神经损伤是心胸外科手术常见且严重的并发症。CPB期间脑血流动力学紊乱被认为是这些损伤病因中的一个重要因素。脑血流动力学紊乱的证据包括在稳定的全流量CPB期间脑血流量（CBF）随时间逐渐下降的报道。低流量低温CPB已成为接受复杂心脏病变手术修复的儿科患者管理的首选技术。由于低流量CPB开始时CBF已经大幅降低，我们确定在低流量状态下是否会出现类似的CBF逐渐下降。
对7只狒狒进行全身麻醉诱导后开始CPB。采用α-稳态动脉血气管理。动物以2.5 l·min⁻¹·m⁻²的泵流量降温，直到鼓膜温度降至18℃。然后将CPB流量降至0.5 l·min⁻¹·m⁻²并维持至少77分钟。此后，将CPB流量增加至2.5 l·min⁻¹·m⁻²，狒狒复温至正常体温。心脏功能恢复后停止CPB。在CPB前、期间和之后通过动脉内氙133洗脱测量CBF。
低流量CPB导致CBF降至体外循环前速率的约50%，全流量CPB期间测量值的约30%。在低流量CPB期间每隔30分钟连续测量CBF，结果显示脑灌注没有随时间变化。
尽管在低流量CPB期间全身流量降至全流量的20%，但相对于全身流量，CBF减半的情况得到了不成比例的保留。此外，在这些低流量条件下CBF没有随时间变化。
