NEW YORK (Reuters Health) – Pediatric patients undergoing minor but painful procedures experience significantly less pain when given inhaled nitrous oxide, according to the results of a randomized controlled trial conducted in Spain.

Inhalation of an equimolar mixture of 50% oxygen and nitrous oxide (EMONO) “was well tolerated and had an estimated analgesic potency of 50%,” Dr. Francisco Reinoso-Barbero, with the University Hospital La Paz in Madrid, and colleagues report in the June issue of Pediatrics.

To evaluate the potency of nitrous oxide analgesia in pediatric patients, the team randomized 100 patients 1 to 18 years of age to receive EMONO or 50% nitrogen and oxygen (placebo) 3 minutes before and during minor cutaneous, muscle, or bone/joint procedures.

Considering the ethics of a placebo-controlled trial in this setting, the researchers included only medical procedures that were usually conducted without any kind of analgesia or sedation in their hospital. For some larger cutaneous procedures, local anesthetics were also used, and rescue analgesia with propofol or sevoflurane was administered if apparent pain levels were high.

Pain was evaluated on a 0 – 10 scale using a self-reported Faces Pain Scale–Revised (FPS-R) for children older than 6 years, or a Spanish observational pain scale (LLANTO) for younger patients, the authors explain.

Pain scores immediately after the procedure were significantly different between the EMONO and placebo groups on both scales: 3.2 vs 6.6, respectively (p=0.0003) on the FPS-R, and 3.5 vs 6.7 (p=0.01) on the LLANTO scale, the researchers report.

Children younger than 3 years were more likely than older children to require rescue analgesia, the team found.

Nurse-assessed cooperativeness was significantly better in the EMONO group, the data indicate.

No cardiac or respiratory adverse effects were observed during the procedures in either group, and no patients experienced nausea or vomiting, Dr. Reinoso-Barbero and colleagues report.

In concluding, they point out that while the results demonstrate the effectiveness of EMONO for minor procedures, “Future studies will be needed to determine if the intensity of the manipulation influences the efficacy of EMONO analgesia and whether this analgesic technique can be helpful in more painful procedures such as thoracic tube removal.”

Equimolar Nitrous Oxide/Oxygen vs. Placebo for Procedural Pain in Children: A Randomized Trial
Pediatrics 2011;127:e1464–e1470.