Objective Nitrous oxide 70% (N₂O 70%) is an excellent medication for procedural analgosedation (PAS), yet the limit of its analgesic power remains uncertain; therefore, a combination with intranasal fentanyl (INF) was suggested. However, this combination seems to result in a higher rate of vomiting and deeper sedation. This study aimed at assessing the analgesic efficacy, sedation depth and rate of adverse events of PAS with N₂O 70% with and without INF.

Methods Patients aged 2–16 years who qualified for PAS with N₂O 70% were randomly assigned to receive either INF or placebo prior to N₂O inhalation in this randomised, double-blind study, which was performed in a tertiary children’s hospital ED between September 2015 and October 2017. Behaviour during the procedure was evaluated using the Face, Leg, Activity, Cry and Consolability (FLACC) scale and the Modified Behavioural Pain Scale (MBPS); analgesic efficacy was assessed with a self-reported pain scale. Sedation depth using the validated University of Michigan Sedation Scale and adverse events in the ED and during the following 12 hours were documented.

Results A total of 402 patients were included; 3 did not tolerate N₂O and therefore had to be excluded. Overall, 399 patients were analysed, of whom 201 (50.4%) received INF. No significant group differences with regard to FLACC scale score, self-reported pain, MBPS score and sedation depth were found. In addition, the two groups did not differ with regard to all types of adverse events.

Conclusion Combining N₂O 70% with INF resulted in no differences with regard to FLACC scale score, self-reported pain, MBPS score, patient and parental satisfaction rate, sedation depth, and adverse events.

Trial registration number NCT02533908