Koren G, Sloan I
Res Commun Chem Pathol Pharmacol. 1985 Jul;49(1):95-108.
A new approach is described for the calculation of elimination half-life of inhaled N2O. We generated the elimination rate constant (Ke) by measuring the cumulative fraction of exhaled N2O versus time during induction of anaesthesia with oxygen and nitrous oxide. The amount of N2O which remained in the body at 90% steady-state (X1 90%) was estimated by subtracting the cumulative exhaled N2O from the cumulative inhaled N2O. In young children (age range 4-36 mo, mean 19 mo) the elimination rate constant was significantly higher than in adolescents and young adults (age range 14-20 yr, mean 16.8 yr) (0.14 +/- 0.055/sec and 0.0646 +/- 0.019/sec, respectively) (P = 0.025). Elimination T1/2 was therefore shorter in the young children (6.1 +/- 3.3 vs 11.1 +/- 3 sec) (P less than 0.025). T1/2 was longer (14 +/- 2.6 sec) in children with left to right shunt despite being younger than the adolescents and young adults (age range 3.25-15 yr, mean 9.9). X1 90% was significantly larger in the young children (30 +/- 3% of the administered dose) than in the older children (26.7 +/- 2%) (P less than 0.05). Elimination T1/2 positively correlated with the amount of N2O which remained in the body at 90% steady-state (X1 90%) (r = 0.85, P less than 0.01), suggesting that the distribution of N2O and not its clearance is the main determinant of its elimination T1/2 in normal children.
本文描述了一种计算吸入氧化亚氮消除半衰期的新方法。我们通过测量在氧气和氧化亚氮诱导麻醉期间呼出氧化亚氮的累积分数随时间的变化来生成消除速率常数（Ke）。通过从累积吸入的氧化亚氮中减去累积呼出的氧化亚氮来估计在90%稳态时体内残留的氧化亚氮量（X1 90%）。在幼儿（年龄范围4 - 36个月，平均19个月）中，消除速率常数显著高于青少年和年轻成年人（年龄范围14 - 20岁，平均16.8岁）（分别为0.14±0.055/秒和0.0646±0.019/秒）（P = 0.025）。因此，幼儿的消除半衰期较短（6.1±3.3秒对11.1±3秒）（P < 0.025）。尽管年龄小于青少年和年轻成年人（年龄范围3.25 - 15岁，平均9.9岁），但左向右分流的儿童的半衰期更长（14±2.6秒）。幼儿的X1 90%（给药剂量的30±3%）显著大于大龄儿童（26.7±2%）（P < 0.05）。消除半衰期与在90%稳态时体内残留的氧化亚氮量（X1 90%）呈正相关（r = 0.85，P < 0.01），这表明在正常儿童中，氧化亚氮的分布而非其清除率是其消除半衰期的主要决定因素。
