A Healthcare Risk Control (HRC) member recently asked for guidance and information on the use of nitrous oxide as an option for labor analgesia.
In our response, we noted that nitrous oxide is commonly used for labor analgesia in several countries; a review article from the American Society of Anesthesiologists' (ASA) Committee on Obstetrical Anesthesia noted that nitrous oxide “has been used for several decades in the United Kingdom with good safety outcomes for both mother and child." However, its use for this purpose is currently much less common in the United States.
For labor analgesia, nitrous oxide is delivered in a mix of 50% nitrous oxide and 50% oxygen. The laboring patient self-administers the gas by holding the mask to her face when she desires pain relief. According to the American College of Obstetricians and Gynecologists' (ACOG) list of frequently asked questions (FAQ) for patients regarding pain relief medications during labor, pain relief is most effective if the patient starts inhaling 30 seconds before a contraction begins.
A recently published practice bulletin from ACOG discusses anesthesia and analgesia during labor, including the use of nitrous oxide. According to the practice bulletin, nitrous oxide provides less effective pain relief than do epidurals, when measured using pain scores, but many women report being satisfied with the pain relief it provides. It allows patient mobility and does not necessitate further monitoring. The patient controls its use, and the effect ceases soon after the patient removes the mask.
When using nitrous oxide, the laboring patient may experience nausea, vomiting, dizziness, or drowsiness. The ASA review article notes that concomitant use of nitrous oxide and systemic opioids “would be expected to increase the risk of respiratory depression." This may suggest the need for additional caution in prescribing and patient monitoring, possibly including continuous monitoring (e.g., with pulse oximetry), when both are used simultaneously. The ACOG FAQ for patients states that “nitrous oxide is safe for the mother and the baby" and notes that dizziness or nausea goes away within a few minutes when use is discontinued.
The effects of maternal nitrous oxide use on the fetus are unknown. Although nitrous oxide passes through the placenta, the newborn quickly eliminates it on starting to breathe, according to the ACOG practice bulletin. Research has identified neurotoxic effects of anesthetics, including nitrous oxide, on young rodent and primate brains. The inhalation of high concentrations for long periods may be harmful; however, the intermittent use of moderate concentrations “would be expected to have negligible effects," states a review article from Reviews in Obstetrics & Gynecology. According to a separate review article from the Agency for Healthcare Research and Quality, newborns whose mothers used nitrous oxide during labor had Apgar scores similar to those of babies whose mothers used no or other pain management modalities during labor. A position statement from the American College of Nurse-Midwives discusses safety issues in more detail, as do some of the other resources already mentioned.
Organizations that wish to offer nitrous oxide for pain management during labor should address the issue in policies and procedures. The organization may begin by convening a team with representatives from several affected disciplines and departments (e.g., obstetrics, midwifery, anesthesiology, neonatology, labor and delivery nursing). The risks and benefits to the mother and fetus, including issues that are unknown, should be discussed with patients, and consent should be obtained. The article from Reviews in Obstetrics & Gynecology describes the experiences of two U.S.-based organizations that offer nitrous oxide for pain relief during labor.
Clinical issues to address in policies and procedures may include training of and competencies for those who will administer nitrous oxide and monitor laboring patients. For example, staff should know how to operate equipment and teach laboring patients about the use of nitrous oxide, and they should remain alert for patient drowsiness or dizziness and take steps to prevent falls.
Compressed gases, such as nitrous oxide, can pose patient and worker safety issues if proper procedures are not followed. The guidance article Compressed Gases discusses safety considerations in regard to compressed gases.
Concerns may also arise about the potential for exposure of healthcare workers and others to waste anesthetic gases, a category that includes nitrous oxide. Before the consistent use of appropriate engineering controls such as scavenging—which became widespread starting in the 1980s—some studies found that long-term exposure to waste anesthetic gases was associated with adverse health effects. Many early studies also involved toxic agents that are no longer in use in the United States. Thus, the effects of long-term exposure to low concentrations of waste anesthetic gases, such as those achievable with consistent use of engineering and work-practice controls, are not entirely clear. Despite this uncertainty, it is prudent to use controls to minimize exposure. Controls include proper ventilation, waste gas scavenging, hazard communication and training, device maintenance and checks, and work-practice controls. Specifically in regard to nitrous oxide use during labor, the ACOG practice bulletin stresses the importance of having a demand valve, which permits delivery of gas only when the patient inhales through the mask, and gas scavenging. See the guidance article Waste Anesthetic Gases for more information on controls to minimize exposure and medical surveillance for workers.
The recommendations contained in Ask HRC do not constitute legal advice. Facilities should consult legal counsel for specific guidance and develop clinical guidance in consultation with their clinical staff.