Respiratory changes in inferior vena cava diameter are helpful in predicting fluid responsiveness in ventilated septic patients.

OBJECTIVE

To evaluate the extent to which respiratory changes in inferior vena cava (IVC) diameter can be used to predict fluid responsiveness.

DESIGN

Prospective clinical study.

SETTING

Hospital intensive care unit.

PATIENTS

Twenty-three patients with acute circulatory failure related to sepsis and mechanically ventilated because of an acute lung injury.

MEASUREMENTS

Inferior vena cava diameter (D) at end-expiration (Dmin) and at end-inspiration (Dmax) was measured by echocardiography using a subcostal approach. The distensibility index of the IVC (dIVC) was calculated as the ratio of Dmax - Dmin / Dmin, and expressed as a percentage. The Doppler technique was applied in the pulmonary artery trunk to determine cardiac index (CI). Measurements were performed at baseline and after a 7 ml/kg volume expansion using a plasma expander. Patients were separated into responders (increase in CI > or =15%) and non-responders (increase in CI <15%).

RESULTS

Using a threshold dIVC of 18%, responders and non-responders were discriminated with 90% sensitivity and 90% specificity. A strong relation (r = 0.9) was observed between dIVC at baseline and the CI increase following blood volume expansion. Baseline central venous pressure did not accurately predict fluid responsiveness.

CONCLUSION

Our study suggests that respiratory change in IVC diameter is an accurate predictor of fluid responsiveness in septic patients.