Nishina K, Mikawa K, Shiga M, Maekawa N, Obara H
Department of Anesthesiology, Kobe University School of Medicine, Japan.
Anesthesiology. 1997 Dec;87(6):1324-7. doi: 10.1097/00000542-199712000-00010.
Sevoflurane is a useful anesthetic for inhalational induction in children because of its low solubility in blood and relatively nonpungent odor. Clonidine has sedative and anxiolytic properties and reduces the requirement for inhalation agents. Nitrous oxide (N2O) also decreases the requirement of inhaled anesthetics, but the effect is variable. The minimum alveolar concentration for tracheal intubation (MAC(TI)) of sevoflurane was assessed with and without N2O and clonidine premedication.
Seventy-two patients, aged 3-11 yr, were assigned to one of six groups (n = 12 each). They received one of three preanesthetic medications (two groups for each premedication): placebo (control), 2 microg/kg oral clonidine or 4 microg/kg oral clonidine. In one group of each premedication, anesthesia was induced with sevoflurane in oxygen; in the other group, anesthesia was induced with sevoflurane in the presence of 60% N2O. Each concentration of sevoflurane at which tracheal intubation was attempted was predetermined according to Dixon's up-and-down method and held constant for at least 20 min before the trial
The MAC(TI) of sevoflurane in the absence of N2O (mean +/- SEM) was 3.2 +/- 0.2%, 2.5 +/- 0.1%, and 1.9 +/- 0.2% in the control, 2-microg/kg clonidine, and 4-microg/kg clonidine groups, respectively. Nitrous oxide (60%) decreased the MAC(TI) of sevoflurane by 26%, 24%, and 27% in the control, 2-microg/kg clonidine, and 4-microg/kg clonidine groups.
Oral clonidine premedication decreased the MAC(TI) of sevoflurane. Nitrous oxide also decreased the MAC(TI). The combination of clonidine and N2O lessened the MAC(TI) of sevoflurane more than did either drug alone.
七氟醚因其在血液中溶解度低且气味相对不刺鼻，是儿童吸入诱导麻醉的常用药物。可乐定具有镇静和抗焦虑特性，可降低吸入麻醉药的需求量。氧化亚氮（N2O）也可降低吸入麻醉药的需求量，但效果不一。评估了在使用和不使用N2O及可乐定预处理的情况下七氟醚的气管插管最低肺泡浓度（MAC(TI)）。
72例3至11岁患者被分为六组（每组n = 12）。他们接受三种麻醉前用药之一（每种预处理两组）：安慰剂（对照组）、2μg/kg口服可乐定或4μg/kg口服可乐定。每种预处理的一组中，用七氟醚在氧气中诱导麻醉；另一组中，在60% N2O存在下用七氟醚诱导麻醉。根据狄克逊上下法预先确定每次尝试气管插管时七氟醚的每种浓度，并在试验前保持至少20分钟不变。
在不使用N2O时，对照组、2μg/kg可乐定组和4μg/kg可乐定组七氟醚的MAC(TI)（均值±标准误）分别为3.2±0.2%、2.5±0.1%和1.9±0.2%。氧化亚氮（60%）使对照组、2μg/kg可乐定组和4μg/kg可乐定组七氟醚的MAC(TI)分别降低26%、24%和27%。
口服可乐定预处理降低了七氟醚的MAC(TI)。氧化亚氮也降低了MAC(TI)。可乐定与N2O联合使用比单独使用任何一种药物更能降低七氟醚的MAC(TI)。
