Serial measurements of total blood volume in patients on maintenance hemodialysis.

In 10 patients on maintenance dialysis red cell and plasma volumes (PV) were measured before and after dialysis and several times during the next 3 days in order to establish the usual pattern of intravascular variation associated with this treatment and to determine whether there was a correlation with dialysis induced untoward effects. PV decreased from 23.7 +/- 1.5 before to 20.7 +/- 1.5 ml/cm body height immediately after dialysis. Unexpectedly it was even significantly lower 16 h after (20.1 +/- 1.4 ml/cm). Nevertheless, undesired dialysis symptoms had disappeared by that time indicating that they had not been caused by a reduction in PV or that the patients had adapted to it. Changes in PV correlated better with changes in hematocrit (r = 0.89) than with changes in body weight (r = 0.60). Therefore careful determination of the large vessel hematocrit offers a reliable estimation of blood volume variations over short periods.