The respiratory variation in inferior vena cava diameter as a guide to fluid therapy

Objective To investigate whether the respiratory variation in inferior vena cava diameter (D_IVC) could be related to fluid responsiveness in mechanically ventilated patients.Design Prospective clinical study.Setting Medical ICU of a non-university hospital.Patients Mechanically ventilated patients with septic shock (n=39).Interventions Volume loading with 8 mL/kg of 6% hydroxyethylstarch over 20 min.Measurements and results Cardiac output and D_IVC were assessed by echography before and immediately after the standardized volume load. Volume loading induced an increase in cardiac output from 5.7±2.0 to 6.4±1.9 L/min (P<0.001) and a decrease in D_IVC from 13.8±13.6 vs 5.2±5.8% (P<0.001). Sixteen patients responded to volume loading by an increase in cardiac output 15% (responders). Before volume loading, the D_IVC was greater in responders than in non-responders (25±15 vs 6±4%, P<0.001), closely correlated with the increase in cardiac output (r=0.82, P<0.001), and a 12% D_IVC cut-off value allowed identification of responders with positive and negative predictive values of 93% and 92%, respectively.Conclusion Analysis of D_IVC is a simple and non-invasive method to detect fluid responsiveness in mechanically ventilated patients with septic shock.