title: Arterial oxygen desaturation during endoscopic ultrasonography combined with gastroscopy: a safety evaluation in out-patients.
abstract: OBJECTIVE
  Data concerning potential clinically relevant arterial oxygen desaturation (SaO2 <90.0 %) during endoscopic ultrasonography (EUS) combined with a prior conventional gastroscopy are not available, but are nevertheless important in view of the increasing numbers of examinations and relevant safety standards. We therefore continuously measured SaO2 before and during the periods of gastroscopy and subsequent EUS in order to answer the question of whether EUS has additional effects on arterial oxygen desaturation. A secondary aim of the study was to define patients with particular risks for decreased SaO2.
  
  
  METHODS
  SaO2 was continuously monitored in 96 outpatients before and during the endoscopic procedures. After sedation with midazolam, an exploratory gastroscopy was performed, followed by endoscopic ultrasonography.
  
  
  RESULTS
  In all patients undergoing gastroscopy followed by EUS (n = 96), SaO2 values significantly decreased from 96.5 +/- 2.6 % to 92.4 +/- 4.7 % (P < 0.0001). Analysis of the time-related SaO2 courses showed that the minimal SaO2 was reached after 7.5 minutes. The SaO2 curves in patients with desaturation (n = 29) were similar to those in patients who had no desaturation, except for a significantly lower nadir (88.6 +/- 5.3 %, P< 0.0001). The SaO2 time courses in all patients showed no further decrease or a second minimum during the EUS period, as might have been expected with the insertion of a second instrument. Baseline (pre-procedure) and minimal SaO2 were significantly correlated (T(s): 0.604, P<0.038). Quantitative analysis yielded the lowest significant percentage of desaturation, with baseline SaO2 equal to or above 97.5 % (6.3 %, P< 0.038).
  
  
  CONCLUSIONS
  EUS following an exploratory gastroscopy under mild sedation causes no additional reduction in SaO2. Patients with an initial arterial oxygen saturation equal to or above 97.5 % may have a low probability of desaturation during the combined procedure after sedation with one single midazolam dose, and are therefore unlikely to need further monitoring after an initial assessment. Patients below this limit, however, should be continuously monitored, due to the increasing probability of desaturation below this limit.
authors.affiliation: Medical Clinic I, Klinikum Karlsruhe, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Allgayer
authors.forename: C
authors.initials: C
authors.lastname: Pohl
authors.forename: W
authors.initials: W
authors.lastname: Kruis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004067:Digestive System Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging / Q000473:pathology; D019160:Endosonography / Q000009:adverse effects*; D005260:Female; D005773:Gastroscopy / Q000009:adverse effects*; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D010100:Oxygen / Q000097:blood*; D012449:Safety; D013997:Time Factors
chemical_list: D010100:Oxygen