LAUSR

Background The validation of inferior vena cava (IVC) respiratory variation for predicting volume responsiveness is still under debate, especially in spontaneously breathing patients. The present study aims to verify the effectiveness and accuracy of IVC variability for volume assessment in the patients after abdominal surgery under artificially or spontaneously breathing. Methods A total of fifty-six patients after abdominal surgeries in the anesthesia intensive care unit ward were included. All patients received ultrasonographic examination before and after the fluid challenge of 5 ml/kg crystalloid within 15 min. The same measurements were performed when the patients were extubated. The IVC diameter, blood flow velocity–time integral of the left ventricular outflow tract, and cardiac output (CO) were recorded. Responders were defined as an increment in CO of 15% or more from baseline. Results There were 33 (58.9%) mechanically ventilated patients and 22 (39.3%) spontaneously breathing patients responding to fluid resuscitation, respectively. The area under the curve was 0.80 (95% CI: 0.68–0.90) for the IVC dimeter variation (cIVC1) in mechanically ventilated patients, 0.87 (95% CI: 0.75–0.94) for the collapsibility of IVC (cIVC2), and 0.85 (95% CI: 0.73–0.93) for the minimum IVC diameter (IVCmin) in spontaneously breathing patients. The optimal cutoff value was 15.32% for cIVC1, 30.25% for cIVC2, and 1.14 cm for IVCmin. Furthermore, the gray zone for cIVC2 was 30.72 to 38.32% and included 23.2% of spontaneously breathing patients, while 17.01 to 25.93% for cIVC1 comprising 44.6% of mechanically ventilated patients. Multivariable logistic regression analysis indicated that cIVC was an independent predictor of volume assessment for patients after surgery irrespective of breathing modes. Conclusion IVC respiratory variation is validated in predicting patients' volume responsiveness after abdominal surgery irrespective of the respiratory modes. However, cIVC or IVCmin in spontaneously breathing patients was superior to cIVC in mechanically ventilated patients in terms of clinical utility, with few subjects in the gray zone for the volume responsiveness appraisal. Trial registration ChiCTR-INR-17013093 . Initial registration date was 24/10/2017.