Although the equimolecular mixture of oxygen and nitrous oxide (EMONO) seems a good choice to relieve procedure-related pain in children, it has not been accepted everywhere. In France, the rapid spread of its use has elicited suspicion and doubts regarding its safety. To assess the use and the safety of this gas mixture in the pediatric settings in France, we conducted a national survey.


Centers that had accepted a nation- wide invitation to participate in the survey filled out a questionnaire after each EMONO administration during a 2-month study. Procedure and inhalation characteristics, as well as pain evaluations and side effects, were reported.


One thousand nineteen EMONO inhalations from 31 centers that agreed to participate in this 2-month survey were analyzed. Median (range) age was 6.4 (0–18) years. Four percent (46) of children were 12 months old or younger, 29% (295) were 5 years old or younger, 45% (459) were 6 to 10 years old, and 26% (265) were older than 10 years of age.

The procedures performed with EMONO inhalation were: lumbar punctures (286), bone marrow aspirations (BMA; 231), laceration repairs (215), minor procedures (75), minor surgery (53), punctures (49), fractures (45), dental care (43), and pulmonary endoscopy (22). Nine percent of procedures were undertaken without the presence of a physician; the child being observed only by the attending nurse. A drug association was noted in 182 (17.9%) of procedures: midazolam (63%), acetaminophen (18%), nalbuphine (8.5%), hydroxyzine (5%), flunitrazepam (2%), chlorazepate (2%), morphine (1%), and lorazepam (.5%). EMLA cream (Astra) was applied in 98.6% of lumbar punctures, 93.7% of BMA, and 54.2% of punctures including lymph nodes, hematoma, or renal biopsies. Lidocaine infiltration was performed in 51% of minor surgery procedures, 40% of laceration repairs, and 28% of BMA.

The inhalation system included a whistle, a scented mask, and a nonrebreathing respiratory valve in 48.9%, 71.2%, and 78.3% of the patients, respectively. Initial physical restraint was needed in 18.2% of all the patients. Inhalation refusal was noted in 129 (12.7%) children; of these, 53 had an alternative method of analgesia (EMLA or lidocaine infiltration), 15 had no other analgesia, and in the remaining 61, EMONO inhalation was maintained against the child's will.

Median (interquartile) inhalation length was 4 (3–5) minutes before starting the procedure and 6 (6–15) minutes for the total inhalation.

Median (interquartile) procedural pain evaluations were 9 (0–30) for children on a 0 to 100 visual analog scale, 1 (0–3) for both nurses and parents on a 0 to 10 numerical scale. Median (interquartile) procedural pain as evaluated by nurses for the 3 most frequent procedures were 0 (0–2) for lumbar punctures, 2 (0–4) for bone marrow aspiration, and 2 (0–4) for laceration repair. Comparison of pain assessed by nurses in children 3 years old or younger and those older than 3 years of age showed a median (range) score of 2 (0–10) versus 1 (0–10), respectively. Pain self-assessment was completed in 647 children 6 years of age or older. Median (interquartile) children pain assessments were as follows: lumbar puncture (5; 0–20), bone marrow aspiration (12.5; 0–40), laceration repair (12; 0–40), minor procedures (18; 0–32), minor surgery (10; 0–35), punctures (0; 0–18), fracture (15; 0–30), dental care (20; 0–40), and pulmonary endoscopy (15; 0–30). Ninety-three percent of the 647 children who were able to answer the question said they would accept EMONO analgesia if a new procedure were to be performed. Behavioral reactions during procedures varied with age of the child; cry was observed in 44.1%, 24.4%, 12.9%, and 11.2% of children 3 years or younger, 4 to 6 years, 7 to 10 years, and 11 years or older, respectively. Physical restraint was necessary in 34.2%, 22%, 13.5%, and 8.4% of children aged 3 years or younger, 4 to 6 years, 7 to 10 years, and 11 years or older, respectively.

Staff satisfaction regarding EMONO efficacy was as follows: very satisfied (56.7%), satisfied (31.3%), not satisfied (8.6%), and very unsatisfied (3.3%). Minor side effects were observed during 381 (37%) inhalations. These side effects were euphoria (20.1%), change in visual or auditory perception (7.0%), dreams (5.7%), nausea and vomiting (3.7%), deep sedation (2.1%), paresthesia (1.7%), dizziness (1.6%), restlessness (1.5%), nightmares and hallucinations (1.2%), and miscellaneous (1.9%). All side effects were transient and vanished within 5 minutes after removing the inhalation device. No serious side effects were noted.


This survey shows that EMONO is used to provide analgesia in a great variety of procedures. Although analgesia obtained during procedures is good, this gas mixture is not efficacious in all patients. Therefore, physicians should quickly detect failures to switch to another analgesic approach. The best results are obtained in children 3 years of age or older. Although minor effects are frequent during EMONO inhalation, its use seems very safe because no single serious side effect was noted during this study. This helpful method is still underused, and it should be readily available in each emergency and pediatric department.

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