The effect of hemodialysis ultrafiltration on changes in whole blood viscosity

Abstract

Increased whole blood viscosity (WBV) can be injurious to the vascular endothelium and increase the risk of atherothrombotic events. This study examined the effect of hemodialysis ultrafiltration (UF) on WBV, with a focus on high vs. low-volume UF patients. In stable hemodialysis patients, blood was drawn for hematocrit (Hct) and WBV at the start, midpoint, and at the end of dialysis. For analysis, patients were divided into high UF (≥2700 mL) or low UF (<2700 mL) groups. A total of 59 patients completed the study. Mean Hct increased during dialysis in both groups. The intradialytic increase in Hct was significantly greater in the high vs. the low UF group (3.2% vs. 1.28%, P = 0.01), with a significantly higher end-dialysis Hct in the high UF group (40.5% vs. 38%, P = 0.02). At the end of dialysis, both high shear rate WBV (P < 0.01) and low shear rate WBV (P < 0.01) were significantly higher in the high UF compared with the low UF group. There was an approximately two-fold greater increase in high shear rate (P < 0.01) and low shear rate (P = 0.01) WBV during dialysis in high vs. low UF groups. The increase in high shear rate WBV during dialysis was significantly correlated with an increase in Hct (R(2) = 0.63, P < 0.01). We found that hemodialysis UF causes a surge in WBV. The surge was of greater magnitude in high than in low UF patients.

The passage of a hemodialysis filter affects hemorheology, red cell shape, and platelet aggregation

“…The (ultra-) filtration-dependent increase in blood viscosity, which we have measured after a single passage of the hemodialysis filter, was much less pronounced at the end of dialysis compared with the value at 60 min behind the filter, but still higher than at 60 min ahead of the filter in our study ( Table 3). The latter effect depends on the (ultra-)filtration rate, meanwhile the effect behind the filter at 60 min and a blood filter rate of 350 ml/min depends on the filtration rate, which is attenuated again by the postdilution substitute These results are in agreement with many other studies [8,11,20,26,35,41].…”

Doppler Ultrasound in Vascular Access care: the pearls and pitfalls of flow volume measurement

“…Also, under -gain will reduce the Doppler signal and cause a significant underestimation of the mean velocity 39 . The presence of plaques and calcifications may lead to a posterior acoustic window or decrease in the Doppler signal, underestimating the velocity measurement 40 .…”

Effects of high-volume online mixed-hemodiafiltration on anemia management in dialysis patients

“…However, this substitution mode may be challenging in certain patient groups, especially in patients with high predialysis hematocrit levels or low vascular access blood flow. Very high hematocrit may be achieved within the dialyzer capillaries in the attempt to force ultrafiltration and to obtain high convective volumes [20, 21]. The resulting hemoconcentration and hyper-viscosity coupled with increased shear stress and high pressure regimen inside the dialyzer is a known risk factor for red cell damage and hemolysis [21].…”

“…Very high hematocrit may be achieved within the dialyzer capillaries in the attempt to force ultrafiltration and to obtain high convective volumes [20, 21]. The resulting hemoconcentration and hyper-viscosity coupled with increased shear stress and high pressure regimen inside the dialyzer is a known risk factor for red cell damage and hemolysis [21]. In Mixed-HDF, the pre- and post-dilution substitution rates are adjusted by means of a feedback control system to obtain the maximal filtration fraction within safe pressure and hydraulic conditions, thus preventing progressive hemoconcentration [22, 23].…”