Nitrous Oxide Use for Pain in Labor, Conversion to Neuraxial Analgesia, and Birth Outcome

Introduction

A variety of labor pain management options is essential to patients and their care providers. Inhaled, patient controlled nitrous oxide (N₂O) is a valuable addition to these options. The purpose of this study was to examine laboring patient, newborn, and provider characteristics associated with N₂O use for pain relief in labor and to examine the association between N₂O, conversion to neuraxial analgesia, and cesarean birth.

Methods

This was a retrospective observational cohort study of the first year of N₂O use in one large academic medical center. Patients at least 37 weeks’ gestation who were admitted for labor with intended vaginal birth from August 1, 2018, to June 30, 2019, were included (N = 2605). Laboring patient and newborn factors and their relationship to N₂O use were calculated as unadjusted and adjusted relative risks (RRs). Poisson regression was used to model the association between N₂O use and subsequent use of neuraxial analgesia and type of birth for both nulliparous and multiparous patients.

Results

Overall, 20.2% of patients used N₂O during labor. Multiparous patients were 24% less likely to use N₂O than nulliparous patients (RR, 0.76; 95% CI, 0.69-0.84). Use of N₂O did not differ significantly between patients cared for by midwives compared with patients cared for by physicians (RR, 0.95; 95% CI, 0.90-1.00). In multivariable modeling, N₂O use in multiparous patients was associated with a 17% decrease in use of neuraxial analgesia (RR, 0.83; 95% CI, 0.73-0.94). There was no association between N₂O use and use of neuraxial analgesia in nulliparous patients (RR, 0.99; 95% CI, 0.93-1.06). N₂O use was not associated with cesarean birth in either group.

Discussion

N₂O is an important pain management option for laboring patients and those who care for them. Study results may assist midwives, physicians, and nurses in counseling patients about analgesia options.