Effect of hemodialysis on blood volume distribution and cardiac output

Effects of hemodialysis on extracellular fluid volume distribution, left ventricular volumes, and cardiac output were determined in patients with end-stage renal disease (n = 19). Distribution of extracellular fluid loss from hemodialysis differed widely among patients, so that weight change correlated weakly with contraction of total blood volume (index of determination 29%, p less than 0.05). End-diastolic volume (EDV) decreased from 150 +/- 49 ml (mean +/- SD) to 118 +/- 42 ml, p less than 0.001; stroke volume (SV) decreased from 108 +/- 36 to 86 +/- 33 ml (p less than 0.001) without change in ejection fraction (from 0.73 +/- 0.09 to 0.74 +/- 0.11). A significant correlation was found between total blood volume (TBV) and EDV before (r = 0.66, p less than 0.005) and after dialysis (r = 0.61, p less than 0.001). The correlation between TBV and SV was highly significant before (r = 0.78, p less than 0.001) and after dialysis (r = 0.66, p less than 0.005), but there was no correlation between change in TBV and change in EDV or in SV. The ratio of EDV to TBV (EDV/TBV x 100) was reduced significantly from 3.49 +/- 0.92 to 3.06 +/- 0.97, p less than 0.001). There results suggest that, although intravascular volume was the major determinant of cardiac output in dialyzed patients, the postdialysis reduction in cardiac output might be related more to the relocation of blood volume than to the absolute degree of blood volume contraction.