Tanaka J, Shiki K, Asou T, Yasui H, Tokunaga K
Division of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
J Thorac Cardiovasc Surg. 1988 Jan;95(1):124-32.
We evaluated effects of hypothermic cardiopulmonary bypass on the cerebral circulation and metabolism of six dogs over a temperature range of 37 degrees to 20 degrees C under alphastat acid-base regulation (uncorrected for body temperature). Cerebral metabolic rate for oxygen was determined from the difference between arterial and sagittal sinus blood oxygen contents, and direct cerebral blood flow measurements of the venous outflow from the isolated sagittal sinus. After core cooling at a constant perfusion flow rate of 80 ml/kg/min, cerebral blood flow significantly reduced to 10.0 +/- 1.1 ml/100 gm/min at 20 degrees C (20% +/- 2% of that at 37 degrees C) because of an increase in the cerebral vascular resistance (339% +/- 48%). Cerebral metabolic rate for oxygen reduced to 18% +/- 2%. The upper body vascular resistance decreased to a greater extent than the lower body resistance (37% +/- 4% versus 82% +/- 12%). In the selective cerebral perfusion system at 20 degrees C, when perfusion pressure (mean carotid arterial pressure minus central venous pressure) was lowered from 90 mm Hg by graded reduction of the perfusion flow rate, cerebral blood flow remained constant down to a perfusion pressure of 40 mm Hg, then steeply declined. Cerebral metabolic rate for oxygen also kept a constant level down to 30 mm Hg, then fell abruptly. Definite autoregulatory response was detected even in profound hypothermic nonpulsatile cardiopulmonary bypass. These results suggest that cerebral perfusion flow should be regulated so as to keep the perfusion pressure within the range of cerebral autoregulation to prevent cerebral ischemia or hyperperfusion, especially during selective cerebral perfusion for operations on the aortic arch.
我们评估了在α稳态酸碱调节（未校正体温）下，低温体外循环对6只犬在37℃至20℃温度范围内脑循环和代谢的影响。通过动脉血与矢状窦血氧含量之差测定脑氧代谢率，并通过测量分离的矢状窦静脉流出的脑血流量进行直接测定。在以80ml/kg/min的恒定灌注流速进行核心降温后，由于脑血管阻力增加（339%±48%），脑血流量在20℃时显著降至10.0±1.1ml/100g/min（为37℃时的20%±2%）。脑氧代谢率降至18%±2%。上身血管阻力比下身血管阻力下降幅度更大（37%±4%对82%±12%）。在20℃的选择性脑灌注系统中，当通过分级降低灌注流速使灌注压力（平均颈动脉压减去中心静脉压）从90mmHg降低时，脑血流量在灌注压力降至40mmHg之前保持恒定，然后急剧下降。脑氧代谢率在灌注压力降至30mmHg之前也保持恒定水平，然后突然下降。即使在深度低温非搏动性体外循环中也检测到明确的自动调节反应。这些结果表明，应调节脑灌注流量，以使灌注压力保持在脑自动调节范围内，以防止脑缺血或灌注过多，尤其是在主动脉弓手术的选择性脑灌注期间。
