Systematic review: the use of nitrous oxide gas for lower gastrointestinal endoscopy.

BACKGROUND Nitrous oxide gas (N(2)O) has been proposed as an alternative to intravenous (i.v.) analgesia in patients undergoing lower gastrointestinal endoscopy. AIM To perform a systematic review of randomized studies where N(2)O was compared against control in patients undergoing either flexible sigmoidoscopy or colonoscopy. METHODS Electronic databases were searched; reference lists were checked and letters were sent to authors requesting data. Methodological quality was assessed. Data were tabulated on the duration and difficulty of the procedure, quality of sedation and speed of patient recovery. RESULTS A total of 11 studies were identified containing 623 patients. No differences were seen between groups for duration, difficulty of procedure or complications. Patient-reported pain was similar for N(2)O when undergoing flexible sigmoidoscopy vs. no sedation and when undergoing colonoscopy vs. i.v. sedation. Differences in delivery of N(2)O were identified. In all studies, N(2)O was associated with a more rapid recovery than i.v. sedation. CONCLUSION For patients undergoing colonoscopy, N(2)O provides comparable analgesia to i.v. sedation. The rapid psychomotor recovery with N(2)O enables quicker patient discharge and removes the need for a patient to be chaperoned. Benefit was not seen from N(2)O in patients undergoing flexible sigmoidoscopy possibly because it was delivered on demand rather than continuously.