Equimolar nitrous oxide/oxygen is suitable for pain control with minor pediatric procedures

Article Outline

• Question
• Design
• Setting
• Participants
• Intervention
• Outcomes
• Main Results
• Conclusions
• Commentary
• Copyright

Reinoso-Barbero F, Pascual-Pascual SI, de Lucas R, García S, Billoët C, Dequenne V, et al. Equimolar Nitrous Oxide/Oxygen Versus Placebo for Procedural Pain in Children: A Randomized Trial. Pediatrics 2011;127:e1464-70.

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Question 

Among children undergoing procedures, how effective is a premixed equimolar mixture of 50% oxygen and nitrous oxide (EMONO), compared with placebo (premixed 50% nitrogen and oxygen), at controlling pain?

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Design 

Randomized, single-dose, double-blind study.

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Setting 

Single university hospital in Madrid, Spain.

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Participants 

100 children, aged 1 to 18 years, who were undergoing cutaneous, muscle, or bone/ joint procedures.

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Intervention 

Patients received EMONO (n = 52) or placebo (n = 48) delivered by inhalation through a facial mask 3 minutes before their procedures. Rescue analgesia (with propofol or sevoflurane) was administered if pain scores were ≥ 8.

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Outcomes 

Pain was evaluated (on a scale from 0 –10) using a self-reported Faces Pain Scale–Revised (FPS-R) or a Spanish observational pain scale (LLANTO).

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Main Results 

There were significant differences between the 2 groups (EMONO versus placebo) for both scales (mean values): LLANTO: 3.5 vs 6.7, respectively (P = .01) and FPS-R: 3.2 vs 6.6, respectively (P = .0003). Patients not receiving EMONO (P = .0208)—in particular those aged younger than 3 years (P < .0001)—required more rescue analgesia. There were also significant differences between the 2 groups (EMONO versus placebo) for adequate collaboration (80% vs 35%; P < .0001) and acceptance (73% vs 25%; P < .0001). Ease of use was not significantly different between groups (98.1% vs 95.8%; P > .05). Only 2 patients (in the EMONO group) presented with mild adverse events.

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Conclusions 

EMONO inhalation was well tolerated and had an estimated analgesic potency of 50%, and it is therefore suitable for minor pediatric procedures.

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Commentary 

This interesting study by Spanish investigators (the PI was a consultant for the manufacturer of the device) found that EMONO inhalation was well tolerated and mean scores on standardized pain scales were nearly 50% lower than in the placebo group. It is not surprising that giving analgesia is better than no analgesia for painful procedures. It will be interesting to see if EMONO will show equivalence or be superior compared with other invasive (IV/IM) and non invasive (PO/IN/PR) analgesic preparations. The investigators included children with different indications for pain, which may have “contaminated,” to some extent, the findings in this RCT. Yet, the procedures studied represent the mix of cases seen in any large hospital and the myriad indications to provide analgesia may have been similar in both groups. Finally, the use of self-reported pain is widespread in the pain-related literature. One must always ask if there is a difference in perception of pain (and expression of pain in self-reported scales) between children that had previous procedures (eg, circumcision, immunizations, diagnostic and therapeutic procedures) and those who experienced their first painful procedure during the trial. All in all, with a good methodology, the study helped clarify that EMONO is suitable for minor pediatric procedures, especially among older children that will tolerate inhaled therapy.