Nollert G, Möhnle P, Tassani-Prell P, Reichart B
Department of Cardiac Surgery, Klinikum Grosshadern, University of Munich, Germany.
Circulation. 1995 Nov 1;92(9 Suppl):II327-33. doi: 10.1161/01.cir.92.9.327.
Neuropsychological deficits after cardiac surgery are attributed to the side effects of cardiopulmonary bypass (CPB). To protect the brain from ischemic damage, the influences of temperature, blood pressure, blood gases, acid-base status, and hemodilution on cerebral oxygenation have to be elucidated and quantified.
Forty-one consecutive patients were investigated during cardiac surgery while on CPB. Operative management included moderate hypothermia of 26 degrees C and the alpha-stat pH management. With near-infrared spectrophotometry, changes in oxygenated hemoglobin (HbO2, representing oxygen delivery) and oxidized cytochrome a,a3 (CtO2, cellular oxygenation) in brain tissue were obtained noninvasively. In addition, venous saturation of the brain was measured via a catheter in the jugular bulb (SBJO2). The influence of operative management parameters on cerebral oxygenation was calculated by univariate and multiple regression analyses.
Before and after CPB there was no significant multivariate determinant of cerebral oxygenation. During CPB, HbO2 depended solely on PCO2 (P < .01; r = .89). CtO2 was determined by pH (P < .01), esophageal temperature (P < .01), PCO2 (P < .01), and Hb (P < .01). These parameters explained nearly all changes of the cytochrome measurements during CPB (r = .99). Arterial PCO2 (P < .01) and pH (P < .01) influenced brain venous oxygen saturation (SBJO2; r = .98).
Cerebral oxygenation is autoregulated during cardiac surgery before and after CPB. During CPB, Hb, temperature, pH, and PCO2 determined at least 85% of all changes in cerebral oxygenation. The main causes of impaired cerebral oxygenation are the decrease in Hb with hemodilution, vasoconstriction due to hypocapnia, and the leftward shift of the Hb binding curve in alkalosis and hypothermia.
心脏手术后的神经心理学缺陷归因于体外循环（CPB）的副作用。为保护大脑免受缺血性损伤，必须阐明并量化温度、血压、血气、酸碱状态和血液稀释对脑氧合的影响。
对41例连续接受心脏手术且处于CPB期间的患者进行研究。手术管理包括26℃的中度低温和α-稳态pH管理。使用近红外分光光度法，无创获取脑组织中氧合血红蛋白（HbO2，代表氧输送）和氧化细胞色素a,a3（CtO2，细胞氧合）的变化。此外，通过颈静脉球导管测量脑静脉血氧饱和度（SBJO2）。通过单因素和多因素回归分析计算手术管理参数对脑氧合的影响。
CPB前后，脑氧合无显著的多因素决定因素。在CPB期间，HbO2仅取决于PCO2（P <.01；r =.89）。CtO2由pH（P <.01）、食管温度（P <.01）、PCO2（P <.01）和Hb（P <.01）决定。这些参数几乎解释了CPB期间细胞色素测量的所有变化（r =.99）。动脉PCO2（P <.01）和pH（P <.01）影响脑静脉血氧饱和度（SBJO2；r =.98）。
在心脏手术的CPB前后，脑氧合是自动调节的。在CPB期间，Hb、温度、pH和PCO2决定了至少85%的脑氧合变化。脑氧合受损的主要原因是血液稀释导致的Hb降低、低碳酸血症引起的血管收缩以及碱中毒和低温时Hb结合曲线的左移。
