Arterial oxygen tension changes in elderly patients undergoing upper gastrointestinal endoscopy. II. Influence of the narcotic premedication and endoscope diameter.

Changes in arterial oxygen and carbon dioxide tensions were determined in 56 patients, mean age 67 years, during elective upper gastrointestinal endoscopy with standard or pediatric instruments. All the patients received intravenous atropine, diazepam, and either meperidine or fentanyl premedication. There was an immediate and significant fall in PaO2 levels (20.3%-16.5%) after both narcotic injections. The oxygen tension remained significantly depressed during the endoscopic examinations except in the group receiving fentanyl premedication and examined with the narrow pediatric instrument. To minimize hypoxemia in elderly patients during endoscopy, a short-acting narcotic or, preferably, no narcotic at all should be used in the premedication, and a narrow, pediatric instrument be used.