Cardiac output remained more stable in extended sessions ( change during HD4 , -1.41.5 L/min ; during HDF4 , -1.61.0 L/min ; during HD8 , -0.40.9 L/min [ P = 0.02 vs. HDF4 ] ; and during HDF8 , -0.50.8 L/min [ P = 0.06 vs. HD4 ; P = 0.03 vs. HDF4 ) , in line with the decreased relative blood volume slope in long dialysis .