The intrathoracic blood volume index as an indicator of fluid responsiveness in critically ill patients with acute circulatory failure: a comparison with central venous pressure.

BACKGROUND: The intrathoracic blood volume index (ITBVI) and central venous pressure (CVP) are routinely used to predict fluid responsiveness in critically ill patients with acute circulatory failure (systolic blood pressure < 90 mm Hg or vasopressor requirement). However, they have never been compared.

METHODS: In this prospective interventional study, we included 35 (21 men) mechanically ventilated and sedated patients with acute cardiovascular failure requiring cardiac output measurement (transpulmonary thermodilution technique). Fluid responsiveness was defined as an increase in stroke index (cardiac output/heart rate/body surface area) > or =15%. Receiver operating characteristic curves were generated for ITBVI and CVP.

RESULTS: Fluid challenge induced a stroke index increase > or =15% in 18 (51%) patients (responders). At baseline, no studied hemodynamic variables were different between responders and nonresponders. The areas under the receiver operating characteristic curves were 0.64 [95% CI: 0.46-0.80] for ITBVI and 0.68 [95% CI: 0.50-0.83] for CVP, without any statistical difference (P = 0.73). The best cut-off values for CVP and ITBVI were 9 mm Hg (sensitivity = 61%; specificity = 82%) and 928 mL . m(-2) (sensitivity = 78%; specificity = 53%).

CONCLUSION: ITBVI is similar to CVP in its ability to predict fluid responsiveness in critically ill patients with acute circulatory failure.