Westling F, Milsom I, Zetterström H, Ekström-Jodal B
Department of Anesthesiology, University of Göteborg, East Hospital, Sweden.
Acta Anaesthesiol Scand. 1992 Feb;36(2):175-81. doi: 10.1111/j.1399-6576.1992.tb03447.x.
The hemodynamic changes occurring during the first stage of labor were studied in 24 healthy pregnant women during inhalation of different nitrous oxide/oxygen (N2O/O2) gas mixtures (intermittent 70/30, 40/60, 0/100 and continuous 40/60). Cardiac output increased (P less than 0.01) from 6.6 +/- 0.2 l/min between uterine contractions to 8.5 +/- 0.3 l/min during contractions. Heart rate, stroke volume, systolic, diastolic and mean arterial pressures were increased (P less than 0.01) and total peripheral vascular resistance was reduced (P less than 0.01) during contractions compared to measurements performed between contractions. The maternal circulation was influenced by the use of N2O/O2. During intermittent inhalation, higher concentrations of N2O were associated with a decrease (P less than 0.01) in heart rate, cardiac output and arterial pressure as well as an increase (P less than 0.01) in stroke volume. The degree of pain relief also increased (P less than 0.01) with increasing concentrations of inhaled nitrous oxide. The circulatory influence of intermittent inhalation given during uterine contractions was also apparent during the interval between contractions when N2O/O2 was not administered. The most obvious effects on both circulation and pain were demonstrated during continuous inhalation of N2O/O2. There was a close association between analgetic and cardiovascular effects indicating that the latter, at least partly, were due to pain relief. However, it was not possible to exclude or confirm possible direct pharmacological effects of N2O/O2 on maternal circulation.
对24名健康孕妇在吸入不同的一氧化二氮/氧气（N2O/O2）混合气体（间歇性70/30、40/60、0/100以及持续性40/60）时第一产程中发生的血流动力学变化进行了研究。心输出量从子宫收缩间期的6.6±0.2升/分钟增加（P<0.01）至宫缩时的8.5±0.3升/分钟。与宫缩间期的测量值相比，宫缩时心率、每搏输出量、收缩压、舒张压及平均动脉压均升高（P<0.01），总外周血管阻力降低（P<0.01）。产妇循环受到N2O/O2使用的影响。在间歇性吸入期间，较高浓度的N2O与心率、心输出量及动脉压的降低（P<0.01）以及每搏输出量的增加（P<0.01）相关。随着吸入一氧化二氮浓度的增加，疼痛缓解程度也增加（P<0.01）。在未给予N2O/O2的宫缩间期，宫缩时给予的间歇性吸入对循环的影响也很明显。在持续吸入N2O/O2期间，对循环和疼痛的影响最为明显。镇痛作用和心血管作用之间存在密切关联，表明后者至少部分是由于疼痛缓解所致。然而，无法排除或证实N2O/O2对产妇循环可能存在的直接药理作用。
