In Doppler group decided to provide VE ( @-@ m@/kg of Hydroxyethyl starches HES ) when the index stroke volume decreased by @ % from the baseline value , in clinical group , hemodynamic variables triggering colloid administration mean arterial blood pressure ( MAP ) less than @ % below baseline or central venous pressure ( CVP ) < @ cmH@O in both groups : Ringer 's acetate was infused at constant rate ( @ m @/kg/h ) .