Inhaled nitrous oxide is effective pain control for patients undergoing in-office hysteroscopic sterilisation, according to results of a double-blind trial presented at the 2016 Annual Clinical Meeting of the American College of Obstetricians and Gynecologists (ACOG).
“We were not only able to reduce pain, but also operative time, with statistically significant differences, as well as increase patient satisfaction for the procedure in the office,” stated lead author Emily Schneider, MD, MS, now at Health One Rose Medical Center, Denver, Colorado, speaking here at a poster presentation on May 16.
Dr. Schneider conducted this study when she was at University of New Mexico, Albuquerque, New Mexico. She and her colleagues there evaluated 64 women who had had successful bilateral coil placement. The intervention group (n = 34) received nitrous oxide titrated to a maximum 70%:30% mixture and placebo pills, while the control group (n = 30) received inhaled oxygen during the procedure and 5/325 mg hydrocodone/acetaminophen and 1 mg lorazepam prior to it.
All women received an intramuscular dose of ketorolac and study medications 30 minutes prior to the procedure, as well as a standardised paracervical block.
The primary outcome was maximum procedural pain on a 100-mm visual analogue scale (VAS) assessed 3 to 5 minutes following the procedure. Nitrous oxide was clearly superior (22.8 ±27.6 mm vs 54.5 ±32.7 mm; P = .001).
The post-procedure survey found that 85% and 77% of the respective groups were satisfied or very satisfied with their pain control. Virtually all participants (97%) felt that nitrous oxide should be offered as an option for gynaecologic office procedures, and 86% said they would pay for it out of pocket if it were not a covered benefit.
Patient characteristics were similar in both groups. There was a statistically significant difference in total procedure time that favoured nitrous oxide use (14.4 ±6.5 minutes vs 18.9 ±10.4 minutes; P = .04).
“The benefit of the nitrous oxide is that there is rapid onset and rapid reversal, [with] very minimal contraindications, so it is safe and easy to administer,” Dr. Schneider concluded. In addition, it reduces the need for a clinic escort after the procedure.
One impediment to wider use of nitrous oxide in the clinic has been the up-front cost, generally $5,000 to $10,000, primarily for a scavenging system to safely administer the gas. “But, at the end of the day, it is probably going to be cheaper than [intravenous] sedation,” said Dr. Schneider.
Regulatory issues of who can administer the gas vary from state to state, and can provide an additional burden.
[Presentation title: Nitrous Oxide for Pain Management During In-Office Hysteroscopic Sterilization: A Randomized Controlled Trial. Abstract 21O]