Reasoner D K, Warner D S, Todd M M, McAllister A
Department of Anesthesia, University of Iowa, Iowa City 52242.
Br J Anaesth. 1990 Aug;65(2):210-5. doi: 10.1093/bja/65.2.210.
It has been demonstrated in several species that a significant increase in cerebral blood flow (CBF) occurs when nitrous oxide is added to a volatile anaesthetic. This blood flow response could result from an increase in cerebral metabolic rate or from a direct effect of nitrous oxide on cerebral vessels. To investigate this, the cerebral metabolic rate for glucose (CMRglu) was determined autoradiographically in rats receiving isoflurane anaesthesia with or without nitrous oxide. An increase in anaesthetic depth from 0.5 to 1.0 MAC achieved with isoflurane alone caused a significant reduction in CMRglu (52 (SD11) mumol/100 g min-1 vs 39 (8)mumol/100 g min-1). In contrast, the addition of 70% nitrous oxide (0.5 MAC) to 0.5 MAC isoflurane anaesthesia (1 MAC total) left CMRglu unchanged (54 (4) mumol/100 g min-1). We conclude that 70% nitrous oxide does not alter cerebral metabolic rate when administered with 0.5 MAC isoflurane. Because CBF increases substantially under very similar conditions, our data indicate that the CBF effects of nitrous oxide, when administered with a volatile agent, were direct and mediated by factors other than changes in cerebral metabolic rate.
在多个物种中已证实，当将氧化亚氮添加到挥发性麻醉剂中时，脑血流量（CBF）会显著增加。这种血流反应可能是由于脑代谢率增加或氧化亚氮对脑血管的直接作用所致。为了对此进行研究，采用放射自显影法测定了接受异氟烷麻醉且有或无氧化亚氮的大鼠的脑葡萄糖代谢率（CMRglu）。仅使用异氟烷将麻醉深度从0.5 MAC增加到1.0 MAC会导致CMRglu显著降低（52（标准差11）μmol/100 g·min-1对39（8）μmol/100 g·min-1）。相比之下，在0.5 MAC异氟烷麻醉（总1 MAC）中添加70%氧化亚氮后，CMRglu保持不变（54（4）μmol/100 g·min-1）。我们得出结论，70%氧化亚氮与0.5 MAC异氟烷合用时不会改变脑代谢率。由于在非常相似的条件下CBF会大幅增加，我们的数据表明，氧化亚氮与挥发性麻醉剂合用时对CBF的影响是直接的，且由脑代谢率变化以外的因素介导。
