Inhaled Analgesics Take the Edge Off Labor Pain

Although inhaled analgesic pain relief during labor is generally not an option in the United States and most other countries, except the United Kingdom and Canada, researchers have found that inhaled nitrous oxide and flurane derivatives are an effective means of reducing the intensity of labor pain.¹

Lack of availability aside, researchers identified 26 studies involving 2959 women that either directly compared 2 types of inhaled analgesics or compared inhaled analgesia with placebo or no treatment.¹ In the analysis comparing flurane derivatives with nitrous oxide, researchers found that flurane derivatives provided better pain relief than nitrous oxide. Using a visual analog score from 0 to 100, with 100 representing the most pain relief, the average pain relief score for flurane derivatives was 14.39 points higher than that for nitrous oxide. Pain intensity was also measured using a visual analog scale from 0 to 100, with 100 representing the most intense pain; the average pain intensity score was 16.32 points lower for flurane derivatives than that for nitrous oxide. Drowsiness was more common in women who received flurane derivatives, and nausea was more common in those who received nitrous oxide.

In the analysis comparing nitrous oxide with no treatment or with placebo, nitrous oxide offered more pain relief than placebo or no treatment. However, nitrous oxide caused more adverse effects, including nausea, vomiting, dizziness, and drowsiness, when compared with placebo or no treatment than when compared with flurane derivatives.

There were no significant differences noted for the varying strengths of inhaled analgesia or for different delivery systems. There also was no difference in risk of cesarean delivery or risk of an assisted vaginal delivery regardless of whether a patient received inhaled analgesia or what type was given.

The safe administration of inhaled analgesics ideally requires a room that has special ventilation. For flurane derivatives, which can only be administered by certified anesthesia technicians, dosing precision is important because a woman can become unconsciousness if too much substance is inhaled. The safety for medical professionals is also unknown; additional research is needed to determine whether these gases cause any long-term adverse effects with regular, long-term exposure.

Although this type of pain relief is not widely available in the United States, Trudy Klomp, lead researcher of the review, has advocated that women should have more choices for noninvasive pain relief.² Inhaled analgesics can “take the edge off” labor pain without hindering the normal processes of birth, Klomp explained.

Pertinent Points:
- Inhaled analgesia effectively manages pain during labor, with flurane derivatives being slightly more effective than nitrous oxide.
- Nausea is more common with nitrous oxide, and drowsiness is more common with flurane derivatives.

References:

1. Klomp T, van Poppel M, Jones L, et al. Inhaled analgesia for pain management in labour. Cochrane Database System Rev. 2012;9:DOI: 10.1002/14651858.CD009351.pub2.
2. Pittman G. Inhaled pain relief safe during labor: review. Available at: http://www.reuters.com/article/2012/09/12/us-inhaled-pain-idUSBRE88B0ZP20120912. Accessed October 18, 2012.