From the Editor

Nitrous oxide for labor pain

OBG Manag. 2014 December;26(12):10-12,14

References

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4. Ullman R, Smith LA, Burns E, Mori R, Dowswell T. Parenteral opioids for maternal pain management in labor. Cochrane Database Syst Rev. 2010;(9):CD007396.

5. Rosen MA. Nitrous oxide for relief of labor pain: a systematic review. Am J Obstet Gynecol. 2002;186(5 suppl Nature):S110–S126.

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11. Likis FE, Andrews JC, Collins MR, et al. Nitrous oxide for the management of labor pain: a systematic review. Anesth Analg. 2014;118(1):153–167.

12. Eger EI 2nd, Saidman LJ. Hazards of nitrous oxide anesthesia in bowel obstruction and pneumothorax. Anesthesiology. 1965;26:61–66.

13. Agency for Healthcare Research and Quality. Nitrous oxide for the management of labor pain. Comparative Effectiveness Review Number 67. August 2012. http://www.effectivehealthcare.ahrq.gov/ehc/products/260/1175/CER67_NitrousOxideLaborPain_FinalReport_20120817.pdf. Accessed November 7, 2014.

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17. Rooks JP. Labor pain management other than neuraxial: what do we know and where do we go next? Birth. 2012;39(4):318–322.

18. American College of Nurse-Midwives. From the American College of Nurse-Midwives. Nitrous oxide for labor analgesia. J Midwifery Womens Health. 2010;55(3):292–296.

19. Bishop JT. Administration of nitrous oxide in labor: expanding the options for women. J Midwifery Womens Health. 2007;52(3):308–309.

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Nitrous oxide inactivates vitamin B₁₂ by oxidation; therefore, vitamin B₁₂ deficiency or related disorders may be considered a relative contraindication. However, compared with more extensive continuous use, such as during prolonged general anesthesia, intermittent use for a limited time during labor is associated with minimal to no hematologic effects.

If a laboring woman is using N₂O, parenteral opioids should be administered only with great caution by an experienced clinician.

What do the data indicate?
The Agency for Healthcare Research and Quality (AHRQ) recently invited the Vanderbilt Evidence-based Practice Center to review the world literature on nitrous oxide for labor pain and to provide a summary of the research. Fifty-eight publications were identified, with 46 rated as poor quality.^11,13 Given this overall poor quality of available research, many of the recommendations concerning the use of nitrous oxide for labor pain are based on clinical experience and expert opinion.

The experts concluded that, for the relief of labor pain, neuraxial anesthesia was more effective than nitrous oxide inhalation. In one randomized trial included in their systematic review, nulliparous laboring women were randomly assigned to neuraxial anesthesia or nitrous oxide plus meperidine.¹⁴ About 94% of nulliparous laboring women reported satisfaction with neuraxial anesthesia, compared with 54% treated with nitrous oxide and meperidine.¹⁴

Nitrous oxide is believed to be generally safe for mother and fetus. Its use does not impact the newborn Apgar score¹⁵ or alter uterine
contractility.¹⁶

Considering a nitrous oxide program for your birthing unit? Helpful hints to get started.

Catherine McGovern, RN, MSN, CNM

Do your research to determine which type of equipment is right for the size and volume of your organization.
You need to consider ease of access and use for staff to bring this option to the bedside in a prompt and safe manner. Initial research includes visiting or speaking with practitioners on units currently using nitrous oxide. Use of nitrous oxide is growing, and networking is helpful in terms of planning your program. Making sure you have the correct gas line connectors for oxygen as well as for suction when using a scavenger system is a preliminary necessity.
Determine storage ability.
Your environmental safety officer is a good resource to determine location and regulations regarding safe storage as well as tank capacity. He or she also can help you determine where else in your organization nitrous oxide is used so you may be able to develop your unit-specific protocol from hospital-wide policy that is already in place.
Collaborate on a protocol.
After determining which type of equipment is best for you, propose the idea to committees that can contribute to the development of pain and sedation management protocols. The anesthesia department, pain committee, and postoperative pain management teams are knowledgeable resources and can help you write a safe protocol. Keep as the main focus the safe application and use of nitrous oxide for various patient populations. Potential medication interactions and contraindications for use should be discussed and included in a protocol.
One more department you want to include in your planning is infection control. For our unit, reviewing various types of equipment to determine the best infection control revealed some interesting design benefits to reduce infection risk. Because the nitrous oxide equipment would be mobile, the types of filter options, disposal options, and cleaning ability are important components for final equipment choice.
Include all parties in training and final roll out.
Once you develop your policy with input from all stakeholders, make sure you share it early and often before you go live. Include midwives, physicians, nurses, technicians, and administrative staff in training, which will help to dispel myths and increase awareness of availability within your unit. Provide background information to all trainees to ensure safe use and appropriate patient selection.
The most important determinant of success is the formation of an interprofessional team that works well together to develop a safe clinician- and patient-friendly program for the use of nitrous oxide.

Nitrous oxide, a bridge to an epidural or a natural childbirth
Many women start labor unsure about whether they want to use an epidural. For these women, nitrous oxide may be an option for reducing labor pain, thereby giving the woman more time to make a decision about whether to have an epidural anesthetic. In our practice, a significant percentage of women who use nitrous oxide early in labor subsequently request a neuraxial anesthetic. However, many women planning natural childbirth use nitrous oxide to reduce labor pain and successfully achieve their goal.

Postpartum pain reliever
Some women deliver without the use of any pain medicine. Sometimes birth is complicated by perineal lacerations requiring significant surgical repair. If a woman does not have adequate analgesia after injection of a local anesthetic, nitrous oxide may help reduce her pain during the perineal repair and facilitate quick completion of the procedure by allowing her to remain still. N₂O also has been used to facilitate analgesia during manual removal of the placenta.