The causes of hypoxemia in elderly patients during endoscopy.

Changes in arterial gas tensions were determined in 114 patients undergoing elective gastrointestinal endoscopic examinations with standard or pediatric gastroscopes or colonoscopes. All patients were premedicated intravenously with 0.5 mg of atropine and 10 mg of diazepam. In addition, two thirds received a narcotic, either 50 mg of meperidine or 0.05 mg of the short acting drug fentanyl. The choice of instrument or premedication was usually sequential. There was significant depression of the arterial oxygen tension (Pao2), of 17.4%, immediately following premedication that included a narcotic but not with diazepam alone. Significant reduction of the Pao2 persisted during upper endoscopy if a standard gastroscope was used and meperidine or fentanyl was included in the premedication. If a narrow diameter gastroscope was employed, only meperidine was associated with persistent depression of the Pao2. To minimize hypoxia in elderly patients during upper endoscopy, no narcotic or only a short acting one should be included in their premedication, and a narrow diameter instrument should be used for the examination.