Multicenter Study Evaluating Nitrous Oxide Use for Labor Analgesia at High- and Low-Altitude Institutions

Area of Science:

• Obstetrics and Gynecology
• Anesthesiology
• Altitude Medicine

Background:

• Nitrous oxide (N2O) is increasingly used for labor analgesia in the US.
• Reduced partial pressure of gases at high altitudes may impact N2O's analgesic efficacy.
• Limited research exists on altitude's effect on N2O labor analgesia.

Purpose of the Study:

• To evaluate the impact of altitude on the use of 50% nitrous oxide for labor analgesia.
• To compare conversion rates to alternative analgesics and side effect profiles between high and low altitude settings.
• To identify predictors of conversion from N2O during labor.

Main Methods:

• Multicenter retrospective data analysis of a N2O registry from four institutions over three years.
• Comparison of labor analgesia outcomes (conversion rates, side effects) between high and low altitude institutions.
• Multivariable regression models adjusted for demographic factors (race, ethnicity, education, age).

Main Results:

• No significant difference in conversion rates from 50% N2O to other analgesics between high and low altitudes.
• Parturients at low altitudes were more likely to convert to neuraxial analgesia and experienced more side effects.
• High-altitude parturients who converted were more likely to do so due to inadequate pain relief.

Conclusions:

• This study is the first to assess 50% N2O for labor analgesia at high altitude.
• Lower side effects were observed at high altitude, likely due to reduced N2O partial pressure.
• No significant increase in N2O conversion rates or adverse neonatal outcomes were found at high altitude.