How satisfied are women with N2O for labor analgesia?

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Results from a recent presentation at the ANESTHESIOLOGY 2019 annual meeting indicate that women who use inhaled nitrous oxide (N₂O) for pain management during labor are satisfied with the option, though epidural remains the preferred option. Although inhaled N₂O has been a popular pain management option in Europe for labor, it has only recently gained popularity in the United States.

The objective of the multi-institutional N₂O study was to gather prospective maternal and newborn outcome data from several US institutions with the hope of motivating more institutions nationwide to offer this analgesic option.

Methods
The University of Colorado started the process of incorporating N₂O into their labor and delivery unit in November 2014. Following implementation, the university created the Intrapartum Nitrous Oxide Workgroup (I-NOW), which includes six labor and delivery units across the country. I-NOW then created a data collection tool that included relevant information about the institution, patient, and delivery. The authors performed a prospective chart review of all women using N₂O during labor at all six centers between March 2016 and March 2018.

Results
The study included 1885 patients from the participating institutions. Mean maternal age at admission was 29. N_2­­O users were racially diverse with 61.5% non-Hispanic patients (different subgroups included 45.8% white, 13.7% African American, 4.7% Asian, 0.4% Native Hawaiian, and 0.3% American Indian). Mean parity of participants was 1.64 and mean gestational age was 39.09.

The authors noted that only 850 patients included in the study had available information about maternal satisfaction. However, the mean satisfaction rate for N₂O use was 7.37 (based on a scale of 0 to 10 to evaluate satisfaction). The rate of conversion to another analgesic modality documented in 1644 patients was 64.7%, with conversion to a neuraxial technique in 92.9% of these patients. The authors also noted that newborn Apgar scores averaged 8 and 9 at 1 and 5 minutes, respectively, which indicated safety of use of N₂O for the fetuses.

Conclusion
Overall, the authors believe their findings indicate that women who chose nitrous oxide for labor analgesia were satisfied. However, more than half of the participants ultimately chose an epidural for their pain management technique. The authors were also able to show fetal/neonatal safety of nitrous oxide.