title: Nitrous oxide for colonoscopy: a randomized controlled study.
abstract: BACKGROUND
  Intravenous sedation/analgesia for colonoscopy is accompanied with certain risks and postprocedure drowsiness. We sought to determine whether inhaled nitrous oxide (Entonox: 50% nitrous oxide, 50% oxygen) provides adequate analgesia for colonoscopy and the impact of this agent on recovery.
  
  
  METHODS
  All patients undergoing outpatient colonoscopy were considered for the study (n = 248) except those with previous colonic resection. Data for patients unsuitable for randomization (n = 58) and those who declined to participate (n = 88) were also analyzed.
  
  
  RESULTS
  One hundred two patients were randomized to receive inhaled Entonox alone (n = 56) or intravenous midazolam and meperidine (n = 46). Forty-nine (88%) patients randomized to Entonox underwent complete colonoscopy without conversion to intravenous medications. Entonox patients reported more pain (p < 0.0001), tolerated colonoscopy less well (p < 0.0001), were less satisfied (p = 0.01), and less willing to undergo colonoscopy again under the same circumstances (p = 0.04). Of patients receiving intravenous medication, 91% found colonoscopy less unpleasant and 9% as unpleasant as anticipated; this compares with 52% and 21% Entonox patients, respectively, and an additional 27% Entonox patients who found colonoscopy more unpleasant than anticipated. Recovery was faster among Entonox patients (median 30 versus 60 minutes, p < 0.0001).
  
  
  CONCLUSIONS
  Entonox is less effective than midazolam with meperidine for colonoscopy but is acceptable in many patients and allows faster recovery.
authors.affiliation: Department of Gastroenterology, Royal Perth Hospital, Perth, Western Australia.
authors.forename: G M
authors.initials: GM
authors.lastname: Forbes
authors.forename: B J
authors.initials: BJ
authors.lastname: Collins
mesh_terms: D000280:Administration, Inhalation; D000553:Ambulatory Care; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage; D000701:Analgesics, Opioid / Q000008:administration & dosage; D000762:Anesthesia Recovery Period; D001291:Attitude of Health Personnel; D003113:Colonoscopy / Q000009:adverse effects / Q000523:psychology; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage; D007275:Injections, Intravenous; D008297:Male; D008614:Meperidine / Q000008:administration & dosage; D008874:Midazolam / Q000008:administration & dosage; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage; D017060:Patient Satisfaction
chemical_list: D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D006993:Hypnotics and Sedatives; D008614:Meperidine; D009609:Nitrous Oxide; D008874:Midazolam