Abstract BACKGROUND: Recent evidence suggests that ultrasound measurements of carotid and brachial artery corrected flow time (FTc) and respirophasic variation in blood flow peak velocity (ΔVpeak) are valuable for predicting fluid responsiveness in mechanical ventilated patients. We performed the study to reveal the performance of ultrasonic measurements of radial artery FTc, and ΔVpeak for predicting fluid responsiveness in mechanical ventilated patients undergoing gynecological surgery.METHODS: A total of eighty mechanical ventilated patients were enrolled. Radial artery FTc and ΔVpeak, and non-invasive PPV were measured before and after fluid challenge. Fluid responsiveness was defined as an increase in stroke volume index (SVI) of 15% or more after the fluid challenge. RESULTS: Forty-four (55%) patients were fluid responders. Multivariate logistic regression analysis showed that radial artery FTc and ΔVpeak were the independent predictors of fluid responsiveness, with odds ratios of 1.152 [95% confidence interval (CI) 1.045 to 1.270] and 0.581 (95% CI 0.403 to 0.839). The area under the ROC curve of fluid responsiveness predicted by FTc was 0.802 (95% CI, 0.706-0.898), and ΔVpeak was 0.812 (95% CI, 0.714-0.909). The optimal cut-off values of FTc for fluid responsiveness was 336.6 ms (sensitivity of 75.3%; specificity of 75.9%), ΔVpeak was 14.2% (sensitivity of 88.2%; specificity of 67.9%). The grey zone for FTc was 313.5-336.6 ms, ΔVpeak was 12.2-16.5%.CONCLUSIONS: Ultrasound measurement of radial artery FTc and ΔVpeak are the feasible and reliable methods for predicting fluid responsiveness in mechanically ventilated patients.The trial was registered at the Chinese Clinical Trial Registry (ChiCTR)(www.chictr.org), registration number ChiCTR-ICR-2000040941.This study was approved by the Research Ethics Committee of Women’s Hospital, Zhejiang University School of Medicine (20200197).