Tuesday, January 21, 2014

The Evidence Says: Nitrous Oxide for Labor & Birth

Each year, Childbirth Today Blog brings a series called “The Evidence Says”.  This series covers major topics discussed in maternity care.  The 2014 Series begins with the topic: Nitrous Oxide.

Nitrous Oxide, or N2O, has been a common pain reliever for labor and childbirth in Europe, Canada and Australia for several centuries.  First produced by an English chemist in 1772, it was the first anesthetic to be commonly used but was replaced by either and chloroform due to the potency.  Nitrous oxide depresses normal brain function, although exactly how has not been discovered.  It is thought to increase the release of endorphin, dopamine and other natural pain relievers in the brain.  Nitrous also has an anti-anxiety effect, which may help women with tocophobia.

When nitrous oxide is inhaled, it quickly mixes with the air in the lungs.  It then passes into the bloodstream and into general circulation.  The gas then changes to a solution and reaches the brain in approximately 20 seconds.  The amount of gas that reaches the brain depends on the concentration inhaled and how long it is inhaled.  Like other substances, nitrous oxide crosses the
placental barrier and enters the baby’s blood stream.  However, unlike other medications, nitrous oxide does not have to be broken down by the liver and is thus metabolized and excreted rapidly.  Because of this rapid metabolization, the medication does not become concentrated in either the maternal or fetal body. Nitrous oxide is considered safe for mothers, baby’s and care providers when the nitrous is delivered as a 50% blend with oxygen.

The odorless nitrous oxide is delivered via a machine (with mask) that mixes the gas with oxygen in certain percentages.  The gas is only delivered when the machine detects that someone is inhaling into the mask.  The mask reduces wastage and tries to prevent others in the room from experiencing the effects of the gas.  There are various types of machines on the market, however availability is limited in the U.S.   The University of California San Francisco birth center has had their own machines for years, even after some the nitrous oxide machine manufacturers in the U.S. ceased production of the machines, after the surge in popularity of the epidural and other medications used for labor/birth.  It is reported that other U.S. facilities use nitrous oxide including University of Washington Hospital in Seattle, St. Joseph Regional Medical Center in Idaho, Okanogan Douglas Hospital in Washington, and Vanderbilt in Tennessee.  This patient information page appears on the Dartmouth-Hitchcock Children’s Hospital at Dartmouth in New Hampshire – Click Here. The American College of Nurse-Midwives have a detailed position paper on the use of nitrous oxide.

The advantages of self-administering nitrous oxide include increase perception of control, can be used anytime during labor, does not appear to have adverse effects on the baby’s condition at the moment of birth, can be quickly administered and the effects are nearly immediate, effects reverse when inhalation stops, does not require the presence of an anesthesiologist.  While there are few reported complications using nitrous oxide as an anesthetic during labor and birth, nitrous does appear to have more side effects such as nausea, vomiting, dizziness and drowsiness.  Nitrous oxide administration does limit position changes and movement due to the mask being connected to the administration machine and may cause additional complications if used in conjunction with other pain relievers.

More research about the use of Nitrous Oxide for use during labor and birth.  However, at first glance, it does appear to be preferable to narcotics and epidural anesthesia.

References and Resources:

American College of Nurse-Midwives  (2011) Position Statement: Nitrous Oxide for Labor Analgesia. Last access 1/21/14. 

Agency for Healthcare Research and Quality. (2012). Executive Summary: Nitrous Oxide for Management of Labor Pain.  Last access 1/21/14.

Baysinger, C.  and the American Society of Anesthesiologists Research Statement (no date)

College of Midwives of Ontario (2012) Position Statement: The Use of Nitrous Oxide at Home Births.  Last access 1/21/14.

Jones, L. et al. (2012) Pain management for women in labor: an overview of systematic reviews.  Cochrane Database of Systematic Reviews. Mar 14;3.

Klomp, T. et al. (2012) Inhaled analgesia for pain management in labor.  Cochrane Database Systematic Review, September 12;9.

Rooks, J.P. (2011)  Safety and risks of nitrous oxide labor analgesia: a review.  Journal of Midwifery and Womens Health.  Nov/Dec. 56(6):557-65.

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