Objective:To evaluate the effect of laryngopharyngeal reflux on sedation-related adverse events in the patients undergoing painless gastroscopy.Methods:Two hundred and eighty-nine American Society of Anesthesiologists physical status Ⅰ-Ⅲ patients of both sexes, aged 18-75 yr, with body mass index 18.5-28.0 kg/m 2, scheduled for elective painless gastrocopy, were selected.Specimens of glottic secretions before and after gastroscopy were collected, and the concentration of human pepsin was measured by enzyme-linked immunosorbent assay.The patients in whom the concentration of pepsin was positive before the examination were excluded (the concentration ≥ 31.34 pg/ml was considered as positive). The patients were divided into laryngopharyngeal reflux group (R group, the concentration of pepsin was positive after gastroscopy) and non-laryngopharyngeal reflux group (N group, the concentration of pepsin was negative after gastroscopy) according to the concentration of pepsin in the secretion samples before and after gastroscopy.The occurrence of hypoxemia, hypotension, bradycardia, bucking and body movement during operation was recorded.The patients were followed up by telephone on the 1st, 3rd and 7th days after operation.The sore throat, hoarseness, nausea and vomiting, cough and expectoration and use of antibiotics were recorded. Results:Compared with group N, the incidence of bucking and hypoxemia was significantly increased, the incidence of sore throat and hoarseness was increased on the 1st day after operation, and the incidence of cough and expectoration was increased on the 1st and 3rd days after gastroscopy in group R ( P<0.05). Conclusion:Laryngopharyngeal reflux can increase the development of intraoperative and postoperative sedation-related adverse events in the patients undergoing painless gastroscopy.