Zhou H H, Norman P, DeLima L G, Mehta M, Bass D
Department of Anesthesiology, New York University Medical Center, New York 10016, USA.
Anesthesiology. 1995 Jun;82(6):1364-8. doi: 10.1097/00000542-199506000-00007.
The minimum alveolar concentration (MAC) of volatile anesthetics is decreased during pregnancy, but MAC in the early postpartum period has not been reported. The aim of this study was to determine the MAC of isoflurane and to evaluate the relation between MAC and serum progesterone and beta-endorphin in patients after delivery.
Eight patients undergoing elective bilateral tubal ligation during general anesthesia in the early postpartum period (< 12 h postpartum) and eight patients undergoing this procedure in the late postpartum period (12-25 h postpartum) were studied. Eight patients undergoing bilateral tubal ligation more than 6 weeks after delivery served as control subjects. Anesthesia was induced with propofol and maintained with isoflurane in oxygen to a steady end-tidal concentration of 0.8-1.0 vol% for 10 min. Reaction to a standardized electric stimulation applied to the forearm was graded as positive (gross or delayed movement) or negative. By using the bracketing technique, the concentration of isoflurane was increased or decreased by 0.1 vol%, depending on the positive or negative responses.
The MAC (mean +/- SD) in patients in the early postpartum period was significantly less (0.75 +/- 0.17 vol%) than that in control subjects (1.04 +/- 0.12 vol%; P < 0.01) and that in patients in the late postpartum period (0.95 +/- 0.2 vol%; P < 0.05). The difference in MAC values between late postpartum and control was not significant (P > 0.05). There was an inverse correlation between progesterone concentration postpartum and time after delivery (r = -0.527; P = 0.036), but P = 0.744). There was no correlation between plasma progesterone or beta-endorphin and MAC by multiple regression (r = 0.166; P = 0.950).
Isoflurane MAC remains 28% less than normal within the 1st 12 h postpartum and then returns to normal 12-25 h after delivery.
挥发性麻醉剂的最低肺泡浓度（MAC）在孕期会降低，但产后早期的MAC尚未见报道。本研究的目的是确定异氟烷的MAC，并评估产后患者MAC与血清孕酮及β-内啡肽之间的关系。
对8例产后早期（产后<12小时）全身麻醉下行择期双侧输卵管结扎术的患者和8例产后晚期（产后12 - 25小时）行此手术的患者进行研究。8例产后6周以上行双侧输卵管结扎术的患者作为对照。用丙泊酚诱导麻醉，并用异氟烷维持麻醉，在氧气中使呼气末浓度稳定在0.8 - 1.0 vol%，持续10分钟。对应用于前臂的标准化电刺激的反应分为阳性（明显或延迟运动）或阴性。采用括值法，根据阳性或阴性反应将异氟烷浓度提高或降低0.1 vol%。
产后早期患者的MAC（均值±标准差）显著低于对照组（1.04±0.12 vol%；P<0.01）和产后晚期患者（0.95±0.2 vol%；P<0.05）。产后晚期与对照组MAC值的差异无统计学意义（P>0.05）。产后孕酮浓度与产后时间呈负相关（r = -0.527；P = 0.036），但P = 0.744）。多元回归分析显示血浆孕酮或β-内啡肽与MAC之间无相关性（r = 0.166；P = 0.950）。
产后12小时内异氟烷MAC比正常水平低28%，然后在产后12 - 25小时恢复正常。
