Katoh T, Suguro Y, Kimura T, Ikeda K
Department of Anesthesiology and Intensive Care Medicine, Hamamatsu University School of Medicine, Japan.
Anesth Analg. 1993 Nov;77(5):1012-7. doi: 10.1213/00000539-199311000-00024.
We studied 49 patients of ASA physical status I to determine cerebral anesthetic concentration on awakening calculated with end-tidal anesthetic concentration, when the end-tidal concentration decreased spontaneously. We also attempted to explain the difference in the average of the bracketing alveolar anesthetic concentration that allows and prevents the response to verbal command during recovery from anesthesia (MAC-Awake) between slow and fast alveolar washout by comparing the cerebral anesthetic concentrations with MAC-Awake determined by fast and slow washout. Slow washout was obtained by decreasing anesthetic concentrations in predetermined steps of 15 min, assuming equilibration between brain and alveolar partial pressures. Fast alveolar washout was obtained by discontinuation of the inhaled anesthetic, which had been maintained at 0.5 minimum alveolar anesthetic concentration (MAC) for at least 15 min. MAC-Awake values for sevoflurane and isoflurane obtained by slow washout were 0.34 +/- 0.05 and 0.31 +/- 0.05 (mean +/- SD), respectively, when MAC-Awake was expressed as a ratio to age-adjusted MAC. MAC-Awake values obtained by fast washout (0.22 +/- 0.07 MAC for sevoflurane, 0.22 +/- 0.05 MAC for isoflurane) were significantly smaller than those obtained by slow washout. Anesthetic concentrations in the brain at first eye opening calculated with end-tidal concentrations during fast alveolar washout (0.34 +/- 0.08 MAC for sevoflurane, 0.30 +/- 0.08 MAC for isoflurane) were nearly equal to MAC-Awake obtained by slow alveolar washout. The difference in MAC-Awake between fast and slow alveolar washout could be explained by arterial-to-cerebral and end-tidal-to-arterial anesthetic differences.
我们研究了49例美国麻醉医师协会（ASA）身体状况为I级的患者，以确定在呼气末麻醉浓度自发下降时，苏醒时的脑麻醉浓度，该浓度通过呼气末麻醉浓度计算得出。我们还试图通过比较快速和慢速肺泡清除时的脑麻醉浓度与通过快速和慢速清除确定的苏醒期最低肺泡有效浓度（MAC-Awake），来解释在麻醉恢复过程中允许和阻止对语言指令做出反应的括弧内肺泡麻醉浓度平均值（MAC-Awake）在快速和慢速肺泡清除之间的差异。通过以15分钟的预定步长降低麻醉浓度来实现慢速清除，假定脑与肺泡分压之间达到平衡。通过停止吸入麻醉药来实现快速肺泡清除，吸入麻醉药已维持在0.5最低肺泡有效浓度（MAC）至少15分钟。当MAC-Awake表示为与年龄调整后的MAC的比值时，通过慢速清除获得的七氟烷和异氟烷的MAC-Awake值分别为0.34±0.05和0.31±0.05（平均值±标准差）。通过快速清除获得的MAC-Awake值（七氟烷为0.22±0.07 MAC，异氟烷为0.22±0.05 MAC）明显低于通过慢速清除获得的值。在快速肺泡清除期间，根据呼气末浓度计算的首次睁眼时脑内的麻醉浓度（七氟烷为0.34±0.08 MAC，异氟烷为0.30±0.08 MAC）几乎等于通过慢速肺泡清除获得的MAC-Awake。快速和慢速肺泡清除之间MAC-Awake的差异可以通过动脉至脑和呼气末至动脉的麻醉差异来解释。
