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WASHINGTON — The use of nitrous oxide to manage pain and anxiety for endometrial sampling was associated with a reduction in operating room (OR) procedures, according to research presented at the American College of Obstetricians and Gynecologists (ACOG) 2026 Annual Meeting.

The umbrella term of endometrial sampling refers to endometrial biopsy, dilation and curettage (D&C), hysteroscopy, and fibroidectomy, Sriha Srinivasan, medical student at the GW School of Medicine and Health Sciences in Washington, DC, told attendees. Reducing how many of these procedures are done in the OR comes with multiple advantages, she said.

“Optimizing office-based sampling improves access to care,” she said. “It is so much easier for our patients to come in for an office-based procedure than it is to have to schedule time in the [OR].”

One of the considerations for patients and healthcare providers when deciding whether to undergo a procedure in the office or the OR is pain and anxiety. Clinicians currently use nonsteroidal anti-inflammatory drugs, oral opiates, benzodiazepines, and/or paracervical or intrauterine lidocaine block to manage pain and anxiety for these procedures.

However, nitrous oxide, long used in dental settings, is a noninvasive analgesic and anxiolytic that can also be considered for various ob/gyn procedures, such as intrauterine device insertion or removal, hysteroscopies, and D&C.

This study looked at whether offering in-office nitrous oxide as an option for managing pain and anxiety during endometrial sampling procedures affected the proportion of procedures done in the OR vs in the office.

The researchers looked at trends over three time periods at a single center. The period before implementation of nitrous oxide use, from March to November 2023, included 872 patients. Clinicians were trained in the use of nitrous oxide from January to February 2024, and then 743 patients were tracked when it was implemented, from March to November 2024. Then, from November 2024 to January 2025, implementation was temporarily halted for additional training, providing an opportunity to track 188 patients during that time. (Its use resumed after this pause.)

The proportion of endometrial sampling done in the office increased from 72% pre-implementation to 84% during nitrous oxide use and then fell again to 76% during the pause in nitrous oxide use (P < .01). Accordingly, the proportion of endometrial sampling procedures done in the OR fell from 28% pre-implementation to 16% during implementation and then rose to 25% during the pause (P < .01).

When looking specifically at hysteroscopies, the proportion done in the office rose from 11% pre-implementation to 31% during implementation and then fell again to 20% during the pause (P < .001).

The researchers also looked at whether the office-based procedure samples were sufficient because a return for an insufficient sample would require an OR procedure. Srinivasan reported that the insufficiency rate actually dropped from 0.108 during pre-implementation to 0.093 during nitrous oxide use, though the drop was not statistically significant.

The insufficiency rate also fell in OR-based procedures, from 0.102 to 0.092. While the simultaneous drop in OR-based procedures suggests the decrease in insufficient samples was not related to nitrous oxide use, “it means that our insufficiency rate wasn’t a problem when procedures were converted to office-based,” Srinivasan said.

In addition to the cost-effectiveness of in-office procedures and the reduction in OR burden, another advantage to using nitrous oxide, she said, is that patients do not need a driver to take them home, so it’s not necessary for a friend or family member to take off work. “When the nitrous oxide is removed, within minutes they’re ready to go home,” Srinivasan said.

Ryan C. McDonald, MD, a clinical professor of obstetrics and gynecology at the University of Wisconsin School of Medicine and Public Health in Madison, Wisconsin, told Medscape Medical News that he was impressed with Srinivasan’s study.

“This was a really fantastic talk looking at using a style of analgesia that we’ve had for a long time in a new way because we’re increasingly doing in-office procedures, and everybody is committed to reducing pain for our patients,” McDonald said.

McDonald had asked during the presentation about the environmental impact of nitrous oxide, and Srinivasan noted that a single OR procedure “comes with a huge amount of single-use plastic,” which suggests that the net environmental impact is likely lower with nitrous oxide use, though further research would be necessary to determine that.

“I loved that somebody came up with an idea of using older, cheaper, less expensive technology in a better way, rather than depending on the age-old system of looking for something newer and more expensive [that we assume] must be better,” Kurt T. Barnhart, MD, director of the Women’s Health Clinical Research Center at the University of Pennsylvania in Philadelphia, said. “This was a really nice way of saying, in an evidence-based way, that we can do better with the resources we have. We don’t always need new technology.”

No external funding for the study was noted. Srinivasan, McDonald, and Barnhart reported having no disclosures.

Tara Haelle is a science/health journalist based in Dallas.