1998 Volume 31 Issue 1 Pages 57-62
Hemodiafiltration (HDF) therapy develops less intradialytic symptoms than hemodialysis (HD). By continuously monitoring the hematocrit in extracorporeal circulation, we assessed changes in circulating blood volume during HD and HDF in nine patients on regular dialysis. The total decrease in blood volume was significantly more in HDF than in HD therapy (-18.2±0.9 vs. -15.0±1.2%) although the fluid volume removed during the therapy was comparable. In HDF, the blood volume reduced sharply in the early half of the therapy and the reduction at the mid point was 49.5±2.5% of the total. In HD, the reduction was 41.1±3.0% at the mid point and was sharp in the latter half. Serum concentrations of urea nitrogen, creatinine and human atrial natriuretic polypeptide were not different between HD and HDF. At the mid point of the therapy, however, hematocrit and serum protein concentration were higher, and osmolarity and sodium concentration were lower in HDF than in HD. These results indicate that, during the first half of HDF therapy, circulating blood is more concentrated than during HD probably because of less plasma refilling from the extravascular space into vessels. Higher plasma oncotic pressure due to hemoconcentration may maintain high plasma refilling rates in the latter half of the therapy and thus be of benefit to the hemodynamic stability in patients. During HD, a larger part of the reduction in blood volume was observed in the latter half, which may be one of the reasons why intradialytic symptoms or hypotension tends to occur in this phase of the therapy.
