Laird Harrison

May 08, 2015

SAN FRANCISCO — The inhalation of nitrous oxide during the insertion of an intrauterine device (IUD) increases satisfaction with the procedure, a new study shows.

"We do a lot of procedures that are painful, and we know they are painful," said Lauren Thaxton, MD, from the University of New Mexico in Albuquerque. "Women deserve more options."

Dr Thaxton presented the study findings here at the American Congress of Obstetricians and Gynecologists Annual Clinical Meeting 2015, where it was named Second Prize Paper.

The average woman feels moderate pain when an IUD is inserted, she told Medscape Medical News. Fear of this pain could deter some women from using IUDs.

In the study, Dr Thaxton and her colleagues assessed whether the gas could make IUD insertion less traumatic.

The research team randomly assigned 40 women to inhale a mixture of half nitrous oxide and half oxygen through a scented mask during IUD insertion. Another 40 other women were randomly assigned to inhale 100% oxygen.

Nitrous oxide has advantages over some other approaches because it has analgesic, anesthetic, and amnestic effects. It sets in rapidly, causes few adverse effects, and is inexpensive, noninvasive, and easily reversible, Dr Thaxton explained.

Women deserve more options.

All the women were nulliparous and premenopausal. There were no significant differences between the two groups in terms of ethnicity, marital status, education, employment status, or type of IUD.

Women were then asked to rate the pain they experienced during the procedure on a 100-point scale, where 0 indicated no pain and 100 indicated "pain as bad as it could be." The pain score was slightly lower in the nitrous oxide group than in the oxygen group, but the difference was not significant (54.3 vs 55.3; P = .85).

However, significantly more women in the nitrous oxide group than in the than the oxygen group reported being satisfied or very satisfied with the procedure (67.5% vs 42.5%; P = .04).

"I think part of it is that nitrous works in so many different pathways," said Dr Thaxton, explaining why women expressed satisfaction with nitrous oxide when it didn't reduce their pain. For example, it could have soothed a woman's anxiety or blunted the memory of pain, she pointed out.

The research team is planning a study in which they will titrate the level of nitrous oxide. "We think really being able to gear the dosage to the patient might show more of a result in pain scores," she said.

More than 95% of the study participants said they would choose an IUD again and would want nitrous oxide during the insertion.

And 87.5% of the participants reported that they were not less likely to choose an IUD in the future because of the pain they experienced.

Overall, 63% of the participants said they were willing to pay in an extra $20 to $50 to cover the cost of nitrous oxide.

None of the women experienced any adverse events.

A lively discussion ensued after the presentation.

One audience member speculated that because the pain experienced during IUD insertion is so brief, it is hard to study. Another expressed concern about the adverse effects of nitrous oxide.

However, a third audience member argued that pain is a serious problem for many women contemplating IUD placement. "What you're doing is great," he said. "Keep looking. There is something out there."

The pain of IUD insertion probably does not deter very many women from the procedure, said session moderator J.K. Williams, MD, from the University of South Florida in Tampa.

However, nitrous oxide might be useful for the small number of women who are most anxious about the procedure, Dr Williams told Medscape Medical News. "If we had something like this, we could offer it to those patients."

Dr Thaxton and Dr Williams have disclosed no relevant financial relationships.

American Congress of Obstetricians and Gynecologists (ACOG) Annual Clinical Meeting 2015: Abstract 22. Presented May 4, 2015.


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