January 23, 2017

Nitrous oxide for labor analgesia is used widely in some European countries, Australia, New Zealand and Canada, but relatively rarely in the United States.  It was available in the U.S. at one time, but virtually disappeared in the 1970s with the development of neuraxial anesthesia.  This appears to be changing.  The inhalational agent has seen an upswing in interest among women and clinicians in recent years.

In 2011, only a small handful of U.S. hospitals were offering nitrous oxide as an option to laboring women, but today, more than 300 hospitals provide the service, according to a recent report on National Public Radio’s health blog.

Though 300 still represents a small minority of institutions, demand for the tasteless, odorless gas in labor and delivery suites is rising along with the growing desire among laboring women for more options.  Food and Drug Administration approval in 2011 of a portable nitrous oxide unit that delivers 50 percent nitrous oxide and 50 percent oxygen in a set concentration that cannot be altered has helped fuel the increased availability and renewed attention.

Despite the revival, debate regarding the pros and cons of nitrous oxide’s use for labor pain continues.  This eAlert looks at recent data and thinking to help those of you who deliver obstetric anesthesia weigh whether nitrous oxide would be a meaningful addition to your practices.

More Research Needed

Epidural and combined spinal-epidural anesthetics remain the “gold standard” in the management of labor pain, but some women want the control over their own analgesia that nitrous oxide affords.  The gas, which can be used alone or in conjunction with other pain management methods, including epidurals, is delivered through a handheld mask that the laboring woman can inhale through as often as she wants in anticipation of labor contractions.  It acts primarily by reducing anxiety and the perception of pain, and can be used during the first, second and third stages of labor, as well as for post-delivery procedures, such as laceration repairs.

The American College of Obstetricians and Gynecologists (ACOG) does not have a formal position on nitrous oxide.  However, Laura Goetzl, MD, MPH, of Temple University, who helped draft ACOG’s 2002 guidelines on labor analgesia, said in the NPR article she believes nitrous oxide to be “a safe and reasonable option,” noting that her hospital is working on adding a service. 

A 2014 systematic review in Anesthesia & Analgesia of 58 studies reveals a dearth of well-designed research on nitrous oxide for labor pain and the need for high-quality studies on effectiveness, patient satisfaction and adverse effects.  In a review prepared for the Agency for Healthcare Research and Quality on its website, the American Society of Anesthesiologists (ASA) notes the need for obtaining informed consent and the possibility of long-term effects on neurological development in children, while also acknowledging the “good safety outcomes for both mother and child” in the United Kingdom, where nitrous oxide has been used for labor analgesia for decades.  Clinicians from Vanderbilt University Medical Center and the University of California San Francisco contend in a 2012 review in Obstetrics & Gynecology that nitrous oxide’s long track record of safe use outside of the U.S. and in their own institutions demonstrates its viability as a labor pain management option that should be more readily available in the U.S.

Pros and Cons

The Society for Obstetric Anesthesia and Perinatology (SOAP) explored the rationale and scientific evidence both for and against using nitrous oxide for labor analgesia in recent issues of its newsletter.  For clinicians and hospital departments interested in developing a policy for not using nitrous oxide, Mark I. Zakowski, MD, of Cedars-Sinai Medical Center, offers the following:

• The Centers for Medicare and Medicaid Services (CMS) Conditions of Participation (42CFR 482.52 Anesthesia Services) directs the Department of Anesthesia at each hospital to be responsible for and to oversee the administration of all anesthesia at the hospital.  This gives anesthesia departments the authority to choose not to offer nitrous oxide for labor analgesia.  “While the efficacy of nitrous oxide for analgesia remains controversial, your ability to say ‘no’ remains,” Dr. Zakowski writes.
• Insignificant reduction of labor pain.  Nitrous oxide has not been shown to significantly reduce labor pain.  It “provides at best minimal relief, with nausea, vomiting, drowsiness and dizziness,” he argues, quoting the conclusion from the Anesthesia & Analgesia review cited above that “the strength of the evidence was insufficient for effectiveness in managing labor pain, low for satisfaction, and moderate for harms.”

[A study presented at ANESTHESIOLOGY 2016^® found that 60 percent of women at one institution who initially chose nitrous oxide for delivery ultimately decided to receive an epidural.  The average pain score of 8 before nitrous oxide was inhaled (0 to 10 scale) did not change following inhalation.  Epidural use was associated with labor induction and augmentation.  More studies are needed to know which patients are more likely to convert from nitrous oxide to an epidural, according to lead researcher Caitlin Sutton, MD, of Stanford University.  This data would help anesthesiologists offer more individualized counseling to labor patients.]

• Environmental risk to people in the room.  Chronic exposure to nitrous oxide has been associated with an increased risk of spontaneous abortions and decreased fertility in humans, among other harmful effects. 

[According to the ASA, “environmental pollution is frequent if adequate methods of scavenging of unbreathed and exhaled [nitrous oxide] gas are not employed.  This may pose health risks to exposed health care workers and other participants in the mother’s care, and may contribute significantly to global warming (nitrous oxide is a ‘greenhouse gas’).”]

• Risk to the baby.  Several studies have shown adverse effects in animal models during the utero/preterm/newborn periods when the brain is undergoing rapid growth.  “These studies and others have evoked great concern within the anesthesiology community on what the effects are and how to provide anesthesia safely to pregnant moms, newborns and children,” Dr. Zakowski writes.

In an article in another issue of the SOAP newsletter—for clinicians and departments interested in developing a policy that supports a nitrous oxide service at their institutions—clinicians from Brigham and Women’s Hospital, West Virginia University and other hospitals underscore nitrous oxide’s value as “an alternative technique, other than parenteral opioids, for women who may not wish to have regional analgesia, to those who are not candidates for medical reasons, and to women who have delivered and need analgesia for post-delivery repair.” 

Nitrous oxide’s track record of safety and usefulness as an alternative for laboring patients who respond poorly to opioids or have high opioid tolerance, chronic pain or anxiety, or certain coagulation disorders also make it a valuable addition to the options offered for obstetric anesthesia, the authors assert.  However, they also stress the importance of understanding that nitrous oxide does not deliver the pain relief of an epidural and will not affect an institution’s epidural rate.  “The key to a successful nitrous oxide program is appropriate recognition of proper patient selection and realistic expectations regarding the quality of analgesia offered by this agent,” they write.  “Compared to many other agents we have tried, it has less side effects, is economically feasible, readily available and rapidly reversible and without proven impact on neonatal outcomes.” 

A study of more than 6,500 women published in the December issue of Anesthesia & Analgesia suggests a connection between nitrous oxide and patient satisfaction.  The study found that “patients who received nitrous oxide alone were as likely to express satisfaction with anesthesia care as those who received neuraxial analgesia, even though they were less likely to report excellent analgesia.”  Among all women who reported poor analgesia, those who received nitrous oxide alone were more likely to report high satisfaction than women who received epidural analgesia alone.  The authors conclude that although pain relief contributes to satisfaction with labor analgesia care, “it is not the only contributor to maternal satisfaction.”

Starting a Service

If you’re interested in creating a nitrous oxide service in your hospital, Catherine McGovern, RN, MSN, CNM, of Brigham and Women’s Hospital, offers the following helpful hints in an article in OBG Management:

• Do your research to determine which type of equipment is right for the size and volume of your organization.  Network with other practitioners on other units currently using nitrous oxide.  Consider ease and access of use for staff in bringing this option to the bedside promptly and safely.
• Determine storage ability.  Speak with your environmental safety officer to determine location and regulations regarding safe storage and tank capacity.  You may be able to develop a protocol for your unit based on existing hospital environmental policy.
• Collaborate on a protocol.  After determining the best equipment for your unit, propose the idea to committees that can contribute to the development of pain and sedation management protocols.   Include potential medication interactions and contraindications for use in the protocol.  Collaborate with infection control in reviewing the equipment that will reduce infection risk, including filter options, disposal options and cleaning ability.
• Include all parties in training and final roll out.  Share your policy before you go live.  Include midwives, physicians, nurses, technicians and administrative staff in training.  Provide background to all trainees to ensure safe use and appropriate patient selection.  “The most important factor in a successful implementation is an inter-professional team that works together to develop a safe and patient-friendly program,” she says.

Though nitrous oxide’s popularity among obstetric patients is growing, the answers are still not clear cut.  If you are pondering the possibility of beginning a nitrous oxide service for labor analgesia at your institution, we hope the information provided here assists you in making an informed decision.  ABC clients:  Please contact your client manager if you’re considering using nitrous oxide for labor analgesia in your practice.

With best wishes,

Tony Mira
President and CEO