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Effects of nitrous oxide/oxygen inhalation on the maternal circulation during vaginal delivery
Author(s) -
Westling F.,
Milsom I.,
Zetterström H.,
EkströmJodal B.
Publication year - 1992
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1992.tb03447.x
Subject(s) - medicine , inhalation , anesthesia , nitrous oxide , cardiac output , stroke volume , heart rate , hemodynamics , blood pressure
The hemodynamic changes occurring during the first stage of labor were studied in 24 healthy pregnant women during inhalation of different nitrous oxide/oxygen (N 2 O/O 2 ) gas mixtures (intermittent 70/30, 40/60, 0/100 and continuous 40/60). Cardiac output increased ( P <0.01) from 6.6 ± 0.2 1/min between uterine contractions to 8.5 ± 0.3 1/min during contractions. Heart rate, stroke volume, systolic, diastolic and mean arterial pressures were increased ( P <0.01) and total peripheral vascular resistance was reduced ( P <0.01) during contractions compared to measurements performed between contractions. The maternal circulation was influenced by the use of N 2 O/O 2 . During intermittent inhalation, higher concentrations of N 2 O were associated with a decrease ( P <0.01) in heart rate, cardiac output and arterial pressure as well as an increase ( P <0.01) in stroke volume. The degree of pain relief also increased ( P <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 N 2 O/O 2 was not administered. The most obvious effects on both circulation and pain were demonstrated during continuous inhalation of N 2 O/O 2 . 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 N 2 O/O 2 on maternal circulation.