Residual sleepiness after N2O sedation: a randomized control trial [ISRCTN88442975]

Background

Nitrous oxide (N₂O) provides sedation for procedures that result in constant low-intensity pain. How long do individuals remain sleepy after receiving N₂O? We hypothesized that drug effects would be apparent for an hour or more.

Methods

This was a randomized, double blind controlled study. On three separate occasions, volunteers (N = 12) received 100% oxygen or 20% or 40% N₂O for 30 min. Dependent measures included the multiple sleep latency test (MSLT), a Drug Effects/Liking questionnaire, visual analogue scales, and five psychomotor tests. Repeated measures analysis of variance was performed with drug and time as factors.

Results

During inhalation, drug effects were apparent based on the questionnaire, visual analogue scales, and psychomotor tests. Three hours after inhaling 100% oxygen or 20% N₂O, subjects were sleepier than if they breathed 40% N₂O. No other drug effects were apparent 1 hour after inhalation ceased. Patients did not demonstrate increased sleepiness after N₂O inhalation.

Conclusion

We found no evidence for increased sleepiness greater than 1 hour after N₂O inhalation. Our study suggests that long-term effects of N₂O are not significant.