Abstract: Objective To explore the predictive value of carotid corrected flow time (FTc) and velocity time integral (VTI) for post-induction hypotension (PIH) in patients undergoing gastrointestinal tumor surgery. Methods Patients scheduled for elective gastrointestinal tumor surgery with an American Society of Anesthesiol- ogists (ASA) anesthesia classification ofⅠ-Ⅲ were selected as the study subjects. Before anesthesia induction, carotid VTI and FTc were measured using ultrasound in all patients. According to whether hypotension occurred after anesthesia induction, the patients were divided into a hypotension group and a non-hypotension group. The receiver operating characteristic (ROC) curve was used to evaluate the predictive efficacy of VTI, FTc, and their combination for PIH. Multivariate logistic regression analysis was conducted to screen the influencing factors of PIH. Results A total of 115 patients were included in this study. After excluding 2 patients with unclear carotid spectra, 2 patients with canceled surgeries, and 3 patients with multiple systolic blood pressure measurements ex- ceeding 180 mmHg after entering the operating room, 108 patients were finally included. Among them, 43 patients (39. 8%) developed hypotension after anesthesia induction (hypotension group), and 65 patients (60. 2%) did not develop hypotension (non-hypotension group). The proportions of patients with higher systolic blood pressure (SBP), mean arterial pressure (MAP), ASA classification of Ⅲ, and concurrent hypertension in the hypotension group were all higher than those in the non-hypotension group. The FTc in the hypotension group was shorter, and the VTI was lower than those in the non-hypotension group, with statistically significant differences (all P<0. 05). The area under the ROC curve for FTc in predicting PIH was 0. 899 (95% CI:0. 766-0. 920, P<0. 05), with a sensitivity of 86. 0% and a specificity of 81. 5%. The area under the ROC curve for VTI in predicting PIH was 0. 807 (95% CI:0. 721-0. 892, P<0. 05), with a sensitivity of 79. 1% and a specificity of 75. 4%. The area under the ROC curve for the combined prediction of FTc and VTI for PIH was 0. 909 (95% CI:0. 853-0. 965, P<0. 05), with a sensitivity of 95. 3% and a specificity of 75. 4%. The predictive efficacy of the combined FTc and VTI for PIH was higher than that of FTc or VTI alone. Both FTc and VTI were negatively correlated with the decrease percentage of systolic blood pressure (SBP%) and the decrease percentage of mean arterial pressure (MAP%), and the correlation between FTc and SBP% was stronger than that between VTI and SBP%. FTc showed a moderate negative correlation with SBP% (r=-0. 430, P<0. 001), and VTI showed a weak negative correlation with SBP% (r=-0. 240, P=0. 012). The results of multivariate logistic regression analysis showed that there were no statistically significant differences in body mass index, age, ASA classification (Ⅲ grad- ing), VTI, SBP, and MAP (all P>0. 05), while FTc showed a statistically significant difference (P<0. 05). Conclusions Both carotid FTc and VTI can predict the occurrence of PIH in elderly patients un- dergoing gastrointestinal tumor surgery, but the predictive efficacy of FTc is higher than that of VTI. The com- bined application of FTc and VTI has a higher predictive efficacy for the occurrence of PIH in elderly patients undergoing gastrointestinal tumor surgery than FTc or VTI alone.