不同低温麻醉下体外循环对脑氧代谢的影响

Effects of Different Hypothermia on Cerebral Oxygen Metabolism During Cardiopulmonary Bypass

目的 观察不同低温麻醉下体外循环 (CPB)对脑氧代谢的影响。方法 心脏瓣膜置换手术患者 2 0例 ,随机分为浅低温组 (30℃ )和中低温组 (2 6℃ )。在α稳态下 ,通过桡动脉和颈内静脉球部血液的动态血气分析及乳酸浓度测定 ,计算全身动脉及颈内静脉的血氧含量、动 -颈内静脉血氧含量差、脑氧摄取率和动 -颈内静脉乳酸浓度差。结果 CPB开始后 ,两组的动脉血氧含量、动 -颈内静脉血氧含量差和脑氧摄取率迅速下降 (P <0 0 1,P <0 0 5 ) ,随着复温又迅速升高。在最低温度点时 ,组Ⅰ的动 -颈内静脉血氧含量差、脑氧摄取率高于组Ⅱ (P <0 0 5 ;P <0 0 1)。两组的乳酸浓度进行性升高 ,但各温度点的动 -颈内静脉血的乳酸浓度差无明显变化 (P >0 0 5 ) ,始终接近零值。停CPB时 ,两组的动 -颈内静脉血氧含量差仍明显低于转流前水平 (P <0 0 1)。结论 浅、中低温麻醉下的体外循环 ,均可满足CPB过程中的脑氧供需平衡 ,进一步的体温下降并未取得更好的保护效果。CPB结束后 ,脑氧代谢可能会继续升高 ,是否发生脑氧供需失衡值得进一步研究。

Objective To observe the effects of different hypothermia on cerebral oxygen metabolism during cardiopulmonary bypass(CPB).Methods 20 patients undergoing valvular replacements were randomly divided in two groups:shallow hypothermia group(30℃) and middle hypothermia group(26℃).Blood gas analysis and lactate concentration in arterial and internal jugular vein blood were monitored at 3 time points during operation,from which the arterial-internal jugular venous oxygen content difference(Ca-jvO 2),cerebral oxygen extraction ratio(ERO 2),cerebral lactate production(ADVL) were calculated.Results CaO 2,Ca-jvO 2 and ERO 2 of the two groups were significantly reduced(P<0 01,P<0 05) after initiation of CPB,but they increased during rewarming time.In group Ⅰ,Ca-jvO 2 and ERO 2 were higher(P<0 05,P<0 01) than those in group Ⅱ during CPB at the T 2 time point.The lactate concentration in arterial and jugular vein blood increased in both groups during CPB,but ADVL in two groups did not change significantly(P>0 05) at the same time points.Ca-jvO 2 at the T 3 time point was both lower(P<0 01) than that at the T 1 time point in the two groups.Conclusions Total cerebral oxygen balance of the two groups patients is maintained during CPB.But cerebral oxygen metabolism will further increased after CPB termination.However,whether it leads to cerebral oxygen unbalance,should be studied further.