Cook D J, Proper J A, Orszulak T A, Daly R C, Oliver W C
Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
J Cardiothorac Vasc Anesth. 1997 Jun;11(4):415-9. doi: 10.1016/s1053-0770(97)90047-1.
The purpose of this study was to examine the effect of cardiopulmonary bypass flow rate on cerebral blood flow and cerebral metabolic rate for oxygen during hypothermic (27 degrees C) cardiopulmonary bypass.
DESIGN, SETTING, AND PARTICIPANTS: The investigation was a prospective, randomized study in a tertiary care hospital setting. The 30 participants were volunteer adult cardiac surgical patients at a single institution.
The N2O saturation method of Kety and Schmidt was used to determine global cerebral blood flow and metabolic rate during four periods: prebypass, cardiopulmonary bypass (CPB) (27 degrees C) flow rates of 2.3 and 1.2 L/min/m2, and 30 minutes post-CPB. Anesthesia consisted of fentanyl and midazolam; pH management was alpha-stat, and mean arterial pressure was maintained at 50 to 70 mmHg throughout CPB.
In the context of an unchanged mean arterial pressure, the pump flow did not affect cerebral blood flow or metabolic rate during hypothermic CPB. Systemic venous oxygen saturation was also maintained during reduced flow at 27 degrees C. Hemodilution during hypothermic CPB maintained cerebral blood flow at prebypass levels. In the postbypass period, persistent hemodilution resulted in an elevated cerebral blood flow.
Brain oxygenation is well maintained at lower than conventional pump flow levels during CPB. There may be practical advantages to reduced flows during hypothermia, and flow reductions do not appear to adversely affect cerebral blood flow or metabolism.
本研究旨在探讨在低温（27摄氏度）体外循环期间，体外循环流量对脑血流量和脑氧代谢率的影响。
设计、地点和参与者：本研究为在三级医疗中心进行的一项前瞻性随机研究。30名参与者为一家机构的成年心脏手术志愿患者。
采用凯蒂和施密特的N2O饱和法，在四个阶段测定全脑血流量和代谢率：体外循环前、体外循环（CPB）期间（27摄氏度）流量为2.3和1.2 L/min/m2时，以及体外循环后30分钟。麻醉采用芬太尼和咪达唑仑；pH管理采用α稳态，在整个体外循环期间平均动脉压维持在50至70 mmHg。
在平均动脉压不变的情况下，低温体外循环期间泵流量不影响脑血流量或代谢率。在27摄氏度低流量期间，全身静脉血氧饱和度也得以维持。低温体外循环期间的血液稀释使脑血流量维持在体外循环前水平。在体外循环后阶段，持续的血液稀释导致脑血流量升高。
在体外循环期间，低于传统泵流量水平时脑氧合仍能得到良好维持。低温期间降低流量可能具有实际优势，且流量降低似乎不会对脑血流量或代谢产生不利影响。
