Use of inhaled nitrous oxide for minor eyelid surgery: a placebo-controlled study

Abstract

Background: Pain from local anaesthetic injection for minor eyelid surgery can often be severe enough to be the most unpleasant part of the procedure. This study was aimed at assessing the efficacy of 50 : 50 N(2)O/O( 2) (Entonox) in relieving such pain.

Methods: In this randomised placebo-controlled double blind trial, 100 patients were randomised to receive either Entonox or air. Questions regarding pain during the administration of local anaesthetic, discomfort during the procedure and side effects experienced were asked by an investigator who was blinded to the type of gas inhaled.

Results: The difference in pain score between the Entonox and control groups was not statistically significant (p = 0.474). The difference in discomfort score between the two groups was also not statistically significant (p = 0.948). More side effects were noted with Entonox than with air (p = 0.003, statistically significant). However, this was not clinically significant.

Conclusion: Entonox has been used effectively in different specialties for pain relief. However, our study was unable to show this beneficial effect in relieving pain from local anaesthetic injections for minor eyelid surgery.