Jonassen A E, Quaegebeur J M, Young W L
Department of Anesthesiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
J Thorac Cardiovasc Surg. 1995 Oct;110(4 Pt 1):934-43. doi: 10.1016/s0022-5223(05)80160-6.
Transcranial Doppler sonography of the middle cerebral artery was used to determine whether cerebral perfusion was detectable in low flow states during operations with cardiopulmonary bypass in pediatric patients. Quantitative and qualitative differences in cerebral blood flow velocity after rewarming in patients treated with continuous low-flow bypass or deep hypothermic circulatory arrest were assessed. To determine whether the alterations in cerebrovascular resistance pattern observed in our patients undergoing profound hypothermia was more a function of perfusion technique than of minimum temperature during operation, a third group of patients treated with moderate hypothermia was studied. The three patient groups were the arrest group (N = 16), comprised of patients undergoing circulatory arrest at 18 degrees to 20 degrees C; the low-flow group (N = 16), patients treated with continuous low-flow (cardiac index 0.5 L/min per square meter) bypass at 18 degrees to 20 degrees C; and the moderate group (N = 5), patients treated with moderate hypothermia at 24 degrees to 28 degrees C. Flow velocity was detectable in all patients in the low-flow group, with mean arterial pressures as low as 15 mm Hg. Mean flow velocity was reduced after bypass as compared with prebypass values in both the arrest and low-flow groups (p = 0.0001). Mean flow velocity increased after bypass in the moderate group (p = 0.0001). A Doppler waveform pattern consistent with high cerebrovascular resistance was found in 67% of patients in the arrest group and 44% of those in the low-flow group. None of the patients in the moderate group exhibited such a pattern. Patients treated with profound hypothermia who underwent a period of cold full-flow reperfusion before rewarming did not exhibit this high resistance pattern after rewarming. The present findings indicate that profound hypothermia may evoke changes in the cerebral vasculature that result in decreased mean cerebral blood flow velocity after cardiopulmonary bypass rewarming. A period of cold full-flow reperfusion before rewarming may prevent these alterations and improve cerebral perfusion during rewarming.
采用经颅多普勒超声检查大脑中动脉，以确定小儿患者在体外循环手术的低流量状态下是否可检测到脑灌注。评估了接受持续低流量旁路或深低温循环停止治疗的患者复温后脑血流速度的定量和定性差异。为了确定在我们接受深度低温治疗的患者中观察到的脑血管阻力模式的改变更多是灌注技术的作用而非手术期间最低温度的作用，研究了第三组接受中度低温治疗的患者。三个患者组分别为：停止组（N = 16），由在18摄氏度至20摄氏度下接受循环停止的患者组成；低流量组（N = 16），在18摄氏度至20摄氏度下接受持续低流量（心脏指数0.5升/分钟每平方米）旁路治疗的患者；中度组（N = 5），在24摄氏度至28摄氏度下接受中度低温治疗的患者。低流量组所有患者均检测到血流速度，平均动脉压低至15毫米汞柱。与旁路前值相比，停止组和低流量组旁路后平均血流速度均降低（p = 0.0001）。中度组旁路后平均血流速度增加（p = 0.0001）。在停止组67%的患者和低流量组44%的患者中发现了与高脑血管阻力一致的多普勒波形模式。中度组患者均未表现出这种模式。在复温前接受一段时间冷全流量再灌注的深度低温治疗患者复温后未表现出这种高阻力模式。目前的研究结果表明，深度低温可能会引起脑血管变化，导致体外循环复温后脑平均血流速度降低。复温前进行一段时间的冷全流量再灌注可能会预防这些改变，并改善复温期间的脑灌注。
