A double-blind, randomized controlled trial of the use of a 50:50 mixture of nitrous oxide/oxygen in legal abortions

Background: The study was conducted to evaluate the effectiveness of oxygen/nitrous oxide (O-2/N2O) in elective abortions by vacuum aspiration with paracervical block and intravenous paracetamol. Design: This single-center double-blinded randomized study tested O-2/N2O (n=36) and placebo (air, n=36) for additional analgesia in elective abortions with paracervical block and intravenous paracetamol. We assessed intra- and postoperative pain according to both a visual analogic scale rated from 0 to 10 and postoperative analgesic requirements. Results: Mean (+/- SD) intraoperative, immediate postoperative and late postoperative pain did not differ significantly for patients with O-2/N2O and with air [3.4 +/- 2.6 vs. 3.7 +/- 3.05 (p=.75), 1.89 +/- 2.4 vs. 1.56 +/- 2.03 (p=.78), 0.5 +/- 0.8 vs. 0.75 +/- 1.2 (p=.45)]. The number of patients with scores for low (0-4), moderate (4-7) and severe (7-10) intraoperative, immediate postoperative and late postoperative pain did not differ significantly between the groups. Total adverse effects were significantly higher in the O-2/N2O group [35/180 (19.4%) vs. 18/180 (10%), p=.01]. Conclusion: O-2/N2O did not reduce intraoperative or postoperative pain in elective abortions by vacuum aspiration with paracervical analgesia and intravenous paracetamol, and its adverse effect rate was substantial. (C) 2012 Elsevier Inc. All rights reserved.