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Pediatrics. 2011 Jun;127(6):e1464-70. doi: 10.1542/peds.2010-1142. Epub 2011 May 23.

Equimolar nitrous oxide/oxygen versus placebo for procedural pain in children: a randomized trial.

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Department of Anaesthesiology, University Hospital La Paz, Madrid, Spain.



This randomized, single-dose, double-blind, Phase III study was designed to compare the level of procedural pain after use of premixed equimolar mixture of 50% oxygen and nitrous oxide (EMONO) or placebo (premixed 50% nitrogen and oxygen).


Patients aged 1 to 18 years were randomly assigned to receive EMONO (n = 52) or placebo (n = 48) delivered by inhalation through a facial mask 3 minutes before cutaneous, muscle, or bone/joint procedures. 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). Rescue analgesia (with propofol or sevoflurane) was administered if pain scores were greater than or equal to 8. Collaboration, acceptance, ease of use and safety were evaluated by the attending nurse.


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.


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

[Indexed for MEDLINE]

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