Background and study aims
Entonox is a 50 : 50 combination of nitrous oxide and oxygen, which may be used to manage pain during colonoscopy. The optimal mode of Entonox administration is unknown. The aim of this study was therefore to compare continuous and as-required Entonox use.
Patients and methods
Patients attending for screening colonoscopy at a single centre were randomized to continuous or as-required Entonox use. The primary outcome measure was the patient’s overall pain rating at the time of discharge (verbally administered numerical ratings scale, 0=no pain and 10=extreme pain). Secondary outcome measures included the patients’ experience of pain during the colonoscopy (rated every 2 min), side effects and the need for rescue intravenous medications.
A total of 108 patients were randomized, and 100 completed the study (46 continuous, 54 as required). The overall pain scores at discharge did not differ between those who used Entonox continuously and as required (mean=2.4 vs. 3.2, P=0.08). There were also no differences in the experience of pain during colonoscopy (mean=1.8 vs. 2.2, P=0.28; peak=4.2 vs. 4.8, P=0.26; and area under curve=23 vs. 30, P=0.24). Patients with high anxiety had greater overall pain scores (mean=3.7 vs. 2.4, P=0.03). Light headedness occurred more often with continuous Entonox use (48 vs. 21%, P=0.009).
Among patients attending for screening colonoscopy, comfort ratings were similar in those using Entonox continuously and as required, but light headedness was more common with continuous use (NCT identifier: 01865721).