Russell G B, Graybeal J M
Department of Anesthesia, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Can J Anaesth. 1998 May;45(5 Pt 1):466-70. doi: 10.1007/BF03012583.
To test the hypothesis that the MAC values of nitrous oxide (N2O) and isoflurane were not linearly additive, as theorized by the postulated mode of action based on lipid solubility, in a rat model.
Eight Long Evans rats were randomly assigned to order of measurement of MAC for isoflurane and N2O alone and in combination using standard 45 sec supramaximal electrical stimulation (50 volts x 10 msec duration pulses at 50.sec-1 applied for 45 sec s.c. to the lower abdominal groin area). The MAC of N2O was measured at hyperbaric compression to 2.25 atmospheres absolute, 1710 mmHg.
The MAC values found were: isoflurane -0.98 +/- 0.12 and N2O - 159 +/- 12 volume (vol)%, or 1.59 +/- 0.12 atmospheres absolute (ATA) (All values are mean +/- standard deviation). The linear additivity theory suggests % MAC agent A + % MAC agent B = 1.0. However, % MAC isoflurane + % MAC N2O = 1.37 +/- 0.15 (P < .001).
Nonlinear additivity was demonstrated with direct MAC measurement for both isoflurane and N2O in rats. This suggests an agonist-antagonist relationship.
在大鼠模型中，验证如下假设：根据基于脂溶性的假定作用模式理论，氧化亚氮（N2O）和异氟烷的最低肺泡有效浓度（MAC）并非呈线性相加。
八只Long Evans大鼠被随机分配，按照标准的45秒超强电刺激（50伏×10毫秒持续时间脉冲，频率50秒-1，在下腹部腹股沟区皮下施加45秒），单独及联合测量异氟烷和N2O的MAC。在高压压缩至2.25绝对大气压（1710毫米汞柱）下测量N2O的MAC。
测得的MAC值为：异氟烷-0.98±0.12，N2O-159±12体积（vol）%，或1.59±0.12绝对大气压（ATA）（所有值均为平均值±标准差）。线性相加理论表明%MAC药物A+%MAC药物B = 1.0。然而，%MAC异氟烷+%MAC N2O = 1.37±0.15（P<.001）。
在大鼠中，通过直接测量MAC证明了异氟烷和N2O均存在非线性相加。这表明存在激动剂-拮抗剂关系。
