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

To investigate whether the respiratory variation in inferior vena cava diameter (ΔDIVC) could be related to fluid responsiveness in mechanically ventilated patients. Prospective clinical study. Medical ICU of a non-university hospital. Mechanically ventilated patients with septic shock (n=39). Volume loading with 8 mL/kg of 6% hydroxyethylstarch over 20 min. Cardiac output and ΔDIVC 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 ΔDIVC 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 ΔDIVC 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% ΔDIVC cut-off value allowed identification of responders with positive and negative predictive values of 93% and 92%, respectively. Analysis of ΔDIVC is a simple and non-invasive method to detect fluid responsiveness in mechanically ventilated patients with septic shock.