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

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 13–45 years 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 2 minutes before insertion. Only the person administering the inhalation agent was aware of group assignment. The primary outcome was maximum pain assessed 2 minutes 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 ± 24.8 mm for the N2O/O2 group and 55.3 ± 20.9 mm 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