A Cochrane review shows that inhaled pain relief is more effective than no pain relief at all in reducing pain intensity during the first stage of labor, say researchers.
Trudy Klomp (Midwifery Academy of Amsterdam, the Netherlands) and team also report that inhaling a combination of flurane derivative plus oxygen may provide more effective pain relief than nitrous oxide plus oxygen and produce fewer side effects.
"We need to apply some caution to these findings as there was a lot of variation in the analyses of pain intensity and of pain relief between the studies and some of the trials involved small numbers of women," said Klomp in a press statement.
"But despite these limitations, inhaled analgesia's ability to significantly reduce pain intensity and increase pain relief indicates that it can help women in labor, particularly those who want pain relief but do not want more intensive forms such as epidurals."
The Cochrane review of 26 randomized controlled trials involving 2959 women revealed that placebo or no treatment was found to offer significantly less pain relief compared with nitrous oxide, at a risk ratio of 0.06.
However, nitrous oxide was associated with significantly more side effects than placebo or no treatment in five of the trials reviewed, including nausea at a risk ratio of 43.10, vomiting at a risk ratio of 9.05, dizziness at a risk ratio of 113.98, and drowsiness at a risk ratio of 77.59.
The analysis also revealed that in three studies, flurane derivatives provided better pain relief than nitrous oxide in the first stage of labor, as demonstrated by lower pain intensity (defined as a lower score on a visual analog scale from 0-100 mm). Indeed, women who inhaled flurane derivatives had a VAS score for pain intensity that was, on average, 14.39 points lower than that of women who inhaled nitrous oxide.
Women who inhaled flurane derivatives had a pain relief score that was 16.32 points lower on a VAS than those who inhaled nitrous oxide, as shown in two studies. Women who inhaled nitrous oxide more often reported nausea than those who inhaled flurane derivatives, at a risk ratio of 6.60.
The researchers explain that nitrous oxide can be administered by midwives, whereas fluranes can only be administered to women under supervision of an educated analgesia professional.
"This is probably the main reason why flurane use is not widespread and also why little research is done on this form of inhaled analgesia for the management of labor pain," remarked Klomp.
They say that more trials must be conducted that involve larger numbers of women and look specifically at which forms of anesthetic give women a greater sense of control in labor, satisfaction with the childbirth experience, and ease in moving on to breastfeeding.
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