Randomised Controlled Trial of sedation for colonoscopy: Entonox versus Midazolam/Fentanyl

INTERVENTION: Prospective randomised controlled study. Pilot study initially involving 100 patients to determine statistical power. Pts will be randomised using the sealed envelope method of block randomisation. Patients randomised to the entonox group will be taught methods of use. Patients will be shown the visual analogue score for pain and asked to mark them. Those randomised to conventional intravenous sedation will be informed of same and will undergo colonoscopy using standard intravenous sedation protocols. Entonox group encouraged to inhale the nitrous oxide for a full 60 seconds initially and then as and when required throughout procedure. Post colonoscopy both groups will be asked to indicate pain using visual analogue scale in the recovery. CONDITION: Surgery: Sedation ; Surgery PRIMARY OUTCOME: Pain score assessed by VAS SECONDARY OUTCOME: Not provided at time of registration INCLUSION CRITERIA: All patients undergoing elective colonoscopy would be prospective participants.