Inhaled analgesia for pain management in labour

Abstract

Many women would like to have a choice between different types of pain relief during labour, avoiding invasive methods of pain management if they can. One of the options might be inhaled analgesia, which involves the self-administered inhalation of sub-anaesthetic concentrations of agents while the mother remains awake. Most of the agents are easy to administer, can be started in less than a minute and become effective within a similar amount of time. This review makes an important contribution to the evidence base because it's important that women have access to relatively effective and safe analgesia during labour, and that this be available when they need some form of pharmacological pain relief. The review brings together the relevant research to support this option, remembering that even in hospitals with full-time obstetric anaesthesia coverage, no one may be available to place an epidural, offer other effective methods of labour analgesia, or provide a labour-intensive non-pharmacological method to help the woman in pain.[1] Alongside these issues of availability, the more invasive options, such as epidural analgesia, are associated with significant side effects. Our goal was to examine the effects of all modalities of inhaled analgesia on the mother and the baby, for mothers who planned to have a vaginal delivery. We searched widely for randomised trials comparing inhaled analgesia with other inhaled analgesia, placebo or no treatment, or other methods of non-pharmacological pain management in labour; and were able to include 26 studies with nearly 3000 women. We were able to analyse outcomes such as pain intensity, pain relief and side effects like nausea, but, because of a lack of data, we could not analyse other important outcomes, including sense of control, satisfaction with the childbirth experience, mother and baby interaction, breastfeeding, admission to special care baby unit, poor infant outcomes at long-term follow-up and costs. In the comparisons of different types of inhaled analgesia, Flurane derivatives offer slightly better pain relief than nitrous oxide in first stage of labour, leading to a lower pain intensity score and a higher pain relief score. More nausea was also found in the nitrous oxide group, compared with the flurane derivatives group. However, there were major differences between the trials and the findings should also be considered with caution because of the use of a cross-over design for the trials. When nitrous oxide was compared against placebo or no treatment, it was found to offer better pain relief but it also produced more side effects for women such as nausea, vomiting, dizziness and drowsiness. There were no significant differences for any of the outcomes in studies comparing different strengths of inhaled analgesia, different delivery systems or, in one study, comparing inhaled analgesia with Transcutaneous Electrical Nerve Stimulation (TENS). Our conclusion is that inhaled analgesia appears to be effective in reducing pain intensity and in giving pain relief in labour, but that nitrous oxide appears to result in more nausea compared with flurane derivatives and that when compared with no treatment or placebo, nitrous oxide appears to result in even more side effects such as nausea, vomiting, dizziness and drowsiness.