Antognini J F, Kien N D
Department of Anesthesiology, University of California, Davis 95616-8634, USA.
Anesth Analg. 1995 Jul;81(1):69-72. doi: 10.1097/00000539-199507000-00014.
The spinal cord is an important site where inhaled anesthetics suppress movement in response to noxious stimuli. Inhaled anesthetics also act in peripheral tissues, although it is unclear whether these actions influence anesthetic requirements. In six isoflurane-anesthetized mongrel dogs, we placed Y cannulas in the lower aorta and vena cava, allowing us to divert blood to, and infuse blood from, a bubble oxygenator/roller pump system or to maintain normal blood flow. This technique permits a greatly diminished isoflurane concentration at the site of the noxious stimulus (tail), while maintaining isoflurane in the remainder of the body. After baseline minimum alveolar anesthetic concentration (MAC1) was determined, venous blood from the lower body was diverted to the bubble oxygenator and reinfused into the lower body via the aortic cannula; MAC2 was determined with isoflurane in the lower body at approximately 0.2%, and MAC3 was determined with isoflurane in the lower body matched to the end-tidal isoflurane. Bypass was terminated, the native circulation established, and MAC4 determined. MAC1, 2, 3, and 4 were (mean +/- SD) 1.3 +/- 0.3%, 1.2 +/- 0.1%, 1.2 +/- 0.2%, and 1.1 +/- 0.2%, respectively (P > 0.05). We conclude that the peripheral effects of isoflurane do not influence the response to a noxious stimulus.
脊髓是吸入麻醉药抑制对伤害性刺激做出反应的运动的重要部位。吸入麻醉药也作用于外周组织，尽管尚不清楚这些作用是否会影响麻醉需求。在六只异氟烷麻醉的杂种犬中，我们在下主动脉和腔静脉中放置了Y形插管，使我们能够将血液分流至气泡氧合器/滚压泵系统并从该系统输注血液，或维持正常血流。该技术可在伤害性刺激部位（尾巴）大大降低异氟烷浓度，同时在身体其余部位维持异氟烷浓度。在确定基线最低肺泡麻醉浓度（MAC1）后，将来自下半身的静脉血分流至气泡氧合器，并通过主动脉插管重新输注到下半身；在异氟烷在下半身浓度约为0.2% 时测定MAC2，在异氟烷在下半身浓度与呼气末异氟烷相匹配时测定MAC3。停止体外循环，恢复正常循环，并测定MAC4。MAC1、2、3和4分别为（平均值±标准差）1.3±0.3%、1.2±0.1%、1.2±0.2% 和1.1±0.2%（P>0.05）。我们得出结论，异氟烷的外周作用不影响对伤害性刺激的反应。
