Hypoxemia During Moderate Sedation for Gastrointestinal Endoscopy: Causes and Associations

Background/aims: Although prolonged hypoxemia (henceforth referred to as hypoxemia) is not uncommon during moderate sedation for endoscopy, there are only sparse data regarding its relationship with medications, endoscopic intubations and ventilation patterns. We aimed to study these relationships.

Methods: 123 patients enrolled in the control arm of a randomized trial of ventilation monitoring during endoscopy were analyzed. Hypoxemia was defined as oxygen saturation of <90% for ≥15 s, and apnea as lack of respiratory activity for ≥15 s.

Results: There were 132 hypoxemic events; 46 (35%) and 112 (85%) events occurred within 1 and 5 min of medication administration/endoscopic intubations, and conversely, 46/638 (7%) and 112/638 (18%) of all medication administration/endoscopic intubations led to hypoxemia in 1 and 5 min, respectively. Apnea, abnormal ventilation and normal ventilation were associated with 36, 30 and 34% of all hypoxemia events, respectively. However, only 101/268 (38%) apnea/abnormal ventilation events led to hypoxemia. Significant predictors of apnea were total dose of meperidine/fentanyl 1.3 (1.02-1.6) and total dose of midazolam 0.84 (0.71-0.99).

Conclusions: Hypoxemia occurs typically within 5 min of medication administration or endoscope intubation and only one third of all apnea/abnormal ventilation events eventually lead to hypoxemia.