控制性降压及过度通气对脑动静脉氧饱和度和乳酸的影响

Effects of induced hypotension and hyperventilation on cerebral arteriovenous oxygen saturation and lactate concentration

目的：研究控制性降压及过度通气对脑动静脉氧饱和度和乳酸的影响。方法：３０例行择期颅脑幕上肿瘤切除术的患者，术中给予安氟醚控制性降压，使平均动脉压（ＭＡＰ）维持（１０．００±０．６７）ｋＰａ１ｈ；过度通气，动脉血二氧化碳分压（Ｐａ－ＣＯ２）维持４．１３～４．３５ｋＰａ。分别于麻醉前，气管插管后５ｍｉｎ，开颅后５ｍｉｎ，术中降压１ｈ和术终同时抽取动脉血和颈内静脉血行血气分析和乳酸测定，对开颅超过３ｈ的１４例患者则于３ｈ后再抽取１次动静脉血样。结果：动脉血氧饱和度（ＳａＯ２）始终高于９５％。颈内静脉血氧饱和度（ＳｊｖＯ２）基础值为（７０．８０±５．８３）％，诱导插管后ＳｊｖＯ２较麻醉前显著升高；但自诱导插管后至术终不同时间点之间ＳｊｖＯ２无显著差异。动静脉乳酸差值（Ａ－ＶＤＬ）基础值为－（０．１３±０．２８）ｍｍｏｌ／Ｌ，随手术的进行有缩小的趋势，但在因各种原因所导致的脑缺血时，Ａ－ＶＤＬ仍可增加。结论：在采用安氟醚控制性降压和过度通气的颅脑手术中，ＳｊｖＯ２和Ａ－ＶＤＬ的监测各有其自身意义，不能互相代替。

Objective: To study the effect of induced hypotension by enfluane combined with hyperventilation on cerebral metabolism. Methods: Thirty patients with signs of intracranial hypertension were studied during elective craniotomy for supratentorial tumor resection. After the dura was opened, the hypotension was induced by increasing enfluane concentration to achieve an intraarterial pressure of (10.00±0.67) kPa for 1 h. The arterial carbon dioxide pressure(PaCO 2) was maintained between 4.13 ～ 4.30 kPa during the anesthesia. Arterial and jugular venous blood samples were obtained simultaneously for determination of blood gases, oxygen saturation, hemoglobin, and lactate concentration. The measurements were made before anesthesia induction,5 min after endotracheal intubation,5 min after dural opening,at 1 h of induced hypotension, and at the end of operation. In 14 patients, the craniotomy lasted for more than 3 h and then at the third hour, the arterial and jugular venous blood samples were drawn. Results: The arterial oxygen saturation(SaO 2) was always greater than 95% and remained constant throughout the study. Baseline jugular venous saturation(SjvO 2) was (70.80±5.83)%, and increased significantly after endotracheal intubation,but didn’t change during surgery. The initial difference between the arterial and jugular venous blood lactate concentration(A VDL) was -(0.13±0.28) mmol/L. During surgery, the A VDL tended to decrease,however, an increased A VDL might still be present in several cases of cerebral ischemia, while arterial lactate concentration was increased. Conclusion: The results suggest that the SjvO 2 and A VDL monitoring,which cannot be replaced each other, may be of clinical value during neurosurgical operation with hyperventilation and induced hypotension by enfluane.