The aim of this study was to evaluate the use of the caudal vena cava collapsibility index (CVCCI) and the inspiratory/minimum and expiratory/maximum diameters of the vena cava to predict fluid responsiveness in hospitalized, critically ill cats with hemodynamic and tissue perfusion abnormalities.

Twenty-four hospitalized cats with spontaneous breathing and compromised hemodynamics and tissue hypoperfusion were prospectively included. Ultrasonographic examination before and after fluid expansion with 10 ml/kg of lactated Ringer's solution. Fluid responsiveness was evaluated using the velocity-time integral (VTI) of the subaortic blood flow, by measuring it before and after a fluid load of 10 ml/kg of lactated Ringer's solution. The CVCCI was calculated using the following formula: (maximum diameter - minimum diameter / maximum diameter) × 100.