Comparison of carotid corrected blood flow time and inferior vena cava respiratory variation in predicting fluid responsiveness in patients after surgery

Objective To explore the reliability of ultrasonographic measurement of carotid corrected blood flow time (FTc) and inferior vena cava respiratory variability (dIVC) in predicting fluid responsiveness of mechanically ventilated patients after abdominal surgery. Methods A total of 65 mechanically ventilated patients after elective abdominal surgery, aged 25—75 years, ASA physical status Ⅱ—Ⅲ, with BMI 20—26 kg/m², and admitted in the anesthesia ICU (AICU) were enrolled in this study. According to the increase of cardiac output (CO) by≥15% after infusion with 5 ml/kg of compound sodium chloride within 15 min, the patients were divided into two groups: a responder group (group R, CO≥15%) and a non-responder group (group NR, CO<15%). The end-inspiratory maximum diameter of IVC (IVCmax), the end-expiratory minimum diameter of IVC (IVCmin), FTc and CO were measured by ultrasonography, and the immediate hemodynamic parameters were recorded before and after the volume expansion test. The receiver operating characteristic (ROC) curve was plotted to assess the value of related indicators in predicting fluid responsiveness. Results There were 29 patients (44.6%) who responded to fluid challenge, and 36 non-responders (55.4%). There was no statistical difference in general information and intraoperative characteristics between the two groups (P>0.05). Under baseline condition, group R presented decreases in IVCmax and IVCmin, and increases in dIVC, compared with group NR (P<0.05). The areas under the ROC curve (AUC) of dIVC, IVCmin and FTc were 0.781 (0.661—0.874, P<0.001), 0.746 (0.62—0.846, P<0.001), and 0.542 (0.413-0.666, P>0.05), respectively. AUC_FTc significantly decreased, compared with AUC_dIVC and AUC_IVCmin (P<0.05). The optimal cutoff was 17.36% for dIVC and 1.24 cm for IVCmin. The gray zone for dIVC included 41.5% of patients (10.10% to 23.71%), and the gray zone for IVCmin included 47.7% of patients (1.01 to 1.68 cm). Conclusions The accuracy of dIVC in predicting fluid responsiveness of mechanically ventilated patients after abdominal surgery is superior to FTc, and can be used to evaluate when combined with IVCmin.