ObjectiveTo evaluate left lateral position I-scope tracheal intubation for optimizing anesthesia time during the patient's general anesthesia before endoscopic submucosal dissection. MethodsA total of 150 patients with early upper gastrointestinal cancer were enrolled in the study for endoscopic submucosal dissection in Beijing Friendship Hospital, Capital Medical University from March to December 2018. Patients were randomly divided into three groups with 50 patients in each group. The SL group underwent I-scope tracheal intubation in the left lateral position, SS group underwent I-scope tracheal intubation in the supine position, and MS group underwent Macintosh laryngoscope tracheal intubation in the supine position. Preoperative non-essential anesthesia time (the time between successful intubation and operation), attempts for tracheal intubation and complications related to intubation were analyzed. ResultsThe preoperative non-essential anesthesia time was 8.55±2.16 min in SL group, 10.44±2.43 min in SS group, and 10.56±3.20 min in MS group, with significant difference among three groups (F=9.08, P＜0.001), and the time in SL group was shorter than that in SS group (P<0.001) and MS group (P<0.001). However, there was no statistical difference in non-essential anesthesia time between the SS group and MS group (P=0.819). The success rate of first attempt intubation was 96.0% (48/50) in SL group, 90.0% (45/50) in SS group, and 92.0% (46/50) in MS group, with no significant differences among three groups (χ2=2.601, P=0.627). The incidences of cough and expectoration, dry mouth and mucosal injury showed no statistical differences among three groups during transference to the ward after tracheal catheter removal (all P>0.05). The incidence of sore throat in MS group (38.0%, 19/50) was higher than that in SL group (18.0%, 9/50, P<0.05) and SS group (18.0%, 9/50, P<0.05), while the difference was not statistically significant between SL group and SS group (P>0.05). ConclusionI-scope tracheal intubation in the left lateral position may shorten the preoperative anesthesia time in patients undergoing general anesthesia for the operation in the left lateral position, and optimize overall anesthesia time.