A randomized controlled trial of nitrous oxide for intrauterine device insertion in nulliparous women

Abstract

Objective: To evaluate the effectiveness of inhaled nitrous oxide for pain management among nulliparous women undergoing intrauterine device (IUD) insertion.

Methods: A double-blind, randomized controlled trial was conducted among nulliparous women aged 13-45years who underwent IUD insertion at a US center between October 1, 2013, and August 31, 2014. Using a computer-generated randomization sequence, participants were randomly assigned to inhale either oxygen (O₂) or a mixture of 50% nitrous oxide and 50% oxygen (N₂O/O₂) through a nasal mask for 2minutes before insertion. Only the person administering the inhalation agent was aware of group assignment. The primary outcome was maximum pain assessed 2minutes after insertion via a 100-mm visual analog scale. Analyses were by intention to treat.

Results: Forty women were assigned to each group. Mean maximum pain score at the time of insertion was 54.3±24.8mm for the N₂O/O₂ group and 55.3±20.9mm for the O₂ group (P=0.86). Adverse effects were reported for 6 (15%) women in the N₂O/O₂ group and 7 (18%) in the O₂ group (P=0.32).

Conclusion: N₂O/O₂ did not reduce the pain of IUD insertion among nulliparous women. ClinicalTrials.gov: NCT02391714.

Keywords: Insertion; Intrauterine device; Nitrous oxide; Pain.