Stroke volume variation obtained with Vigileo/FloTrac™ system during bleeding and fluid overload in dogs

Stroke volume variation (SVV) is a parameter for estimating fluid responsiveness. Recently, the Vigileo™ and the Flo-Trac™ sensor (Edwards Lifesciences, Irvine, CA, USA) were made available for clinical use to estimate SVV. The aim of this study was to investigate the relationship between the circulating blood volume and SVV, measured by the Vigileo-FloTrac™ system (SVV-FloTrac) or by central venous pressure (CVP), during a dynamic change in circulating blood transfusion volume, using a continuous constant bleeding and fluid-overload model in dogs.

Ten anesthetized and mechanically ventilated beagles were used. SVV-FloTrac and CVP were measured during a bleeding period (2 ml/kg/min, 15 min), a stabilization period (15 min), a blood transfusion period (2 ml/kg/min, 15 min), and a 6% hydroxyethyl starch solution overload period (2 ml/kg/min, 15 min).

SVV-FloTrac changed significantly when more than 8 ml/kg blood was withdrawn or when more than 8 ml/kg blood was transfused. The change in SVV-FloTrac directly reflected the circulating blood volume change during continuous bleeding and blood transfusion. CVP decreased significantly when more than 4 ml/kg blood was withdrawn or when more than 10 ml/kg was infused, and this indicated that the CVP change did not directly reflect the level of the circulating blood volume change. During the stable circulating blood volume period after blood withdrawal, SVV-FloTrac changed significantly but CVP remained constant. During the fluid overload period, CVP, but not SVV-FloTrac, changed significantly.

SVV-FloTrac is a sensitive indicator of the dynamic circulating blood volume change during both bleeding and transfusion, but not during either the stable circulating blood volume period after blood withdrawal or the fluid-overload period, in mechanically ventilated dogs.