During CPB , COP was reduced by 22 % in the HES-group [ ( 16.7 3.9 ) vs ( 21.5 2.2 ) mmHg , P < 0.05 ] while it was reduced by more than 50 % of the pre-CPB value [ 10.7 2.0 vs ( 22.7 1.9 ) mmHg , P < 0.05 ] in the crystalloid group ( P < 0.05 HES-group vs. crystalloid group ) .