Manohar M, Parks C M
J Cardiovasc Pharmacol. 1984 Nov-Dec;6(6):1092-101.
Brain and myocardial blood flow (MBF) were examined in 10 previously instrumented swine during isocapnic conditions using 15 micron in diameter radionuclide-labeled microspheres that were injected into the left atrium. Minimum alveolar concentration (MAC) of enflurane required to prevent 50% of the pigs from responding by gross purposeful movement to a noxious stimulus was 1.66%. In pigs, 50% nitrous oxide decreased enflurane requirement for 1.0 MAC anesthesia by 0.82%. Each animal was studied during the following conditions: (a) unanesthetized (control); (b) 1.0 MAC enflurane anesthesia (1.66% end-tidal concentration); (c) 1.5 MAC (2.49%) enflurane anesthesia; (d) the equivalent of 1.0 and 1.5 MAC anesthesia produced by enflurane (0.84 and 1.67%) plus 50% nitrous oxide. Cerebral and total brain blood flow values were the same as control values during both levels of enflurane anesthesia. However, blood flow in the brainstem and cerebellum exhibited a dose-related increase; the increment of 28% for each of these regions at 1.5 MAC achieved statistical significance. Vascular resistance in all regions of the brain decreased with enflurane anesthesia. Substitution of 50% nitrous oxide for enflurane to maintain the same level of anesthesia markedly increased cerebral blood flow. At 1.0 and 1.5 MAC anesthesia produced using enflurane plus 50% nitrous oxide, cerebral blood flow was 151 and 183% of the control value, respectively. During enflurane plus nitrous oxide anesthesia equivalent to 1.5 MAC, cerebellar and brain stem blood flow were 135 and 180% of respective control values. MBF in all regions decreased in a dose-related manner with enflurane anesthesia. At 1.5 MAC enflurane, perfusion values in the walls of the left and the right ventricles were 52 and 59% of respective control values. During both levels of enflurane plus 50% nitrous oxide anesthesia, transmural MBF in all regions remained close to awake values. Subendocardial/subepicardial perfusion ration in both ventricles exceeded 1.00 during all steps of the protocol, thereby suggesting that subendocardial O2 delivery kept pace with O2 demand. These experiments have demonstrated that usage of 50% N2O with enflurane to produce equipotent anesthesia resulted in a dramatic increase in cerebral blood flow while MBF remained near awake value.
在10只先前已植入仪器的猪身上，在等碳酸血症条件下，通过将直径15微米的放射性核素标记微球注入左心房来检测脑血流量和心肌血流量（MBF）。预防50%的猪对有害刺激产生明显的自主运动反应所需的安氟醚最低肺泡浓度（MAC）为1.66%。在猪中，50%的氧化亚氮使1.0 MAC麻醉所需的安氟醚剂量降低了0.82%。在以下条件下对每只动物进行研究：（a）未麻醉（对照）；（b）1.0 MAC安氟醚麻醉（呼气末浓度1.66%）；（c）1.5 MAC（2.49%）安氟醚麻醉；（d）由安氟醚（0.84%和1.67%）加50%氧化亚氮产生的相当于1.0和1.5 MAC的麻醉。在两种安氟醚麻醉水平下，脑血流量和全脑血流量值与对照值相同。然而，脑干和小脑的血流量呈现剂量相关的增加；在1.5 MAC时，这些区域各自增加28%，达到统计学显著水平。安氟醚麻醉使脑的所有区域的血管阻力降低。用50%氧化亚氮替代安氟醚以维持相同麻醉水平可显著增加脑血流量。在使用安氟醚加50%氧化亚氮产生的1.0和1.5 MAC麻醉时，脑血流量分别为对照值的151%和183%。在相当于1.5 MAC的安氟醚加氧化亚氮麻醉期间，小脑和脑干血流量分别为各自对照值的135%和180%。安氟醚麻醉使所有区域的MBF呈剂量相关下降。在1.5 MAC安氟醚时，左心室和右心室壁的灌注值分别为各自对照值的52%和59%。在两种安氟醚加50%氧化亚氮麻醉水平下，所有区域的跨壁MBF均接近清醒时的值。在实验方案的所有步骤中，两个心室的心内膜下/心外膜下灌注比值均超过1.00，因此表明心内膜下氧输送与氧需求保持同步。这些实验表明，使用50% N2O与安氟醚产生等效麻醉会导致脑血流量显著增加，而MBF仍接近清醒时的值。
