Absolute blood volume variations and vascular refilling in hemodialysis patients

The imbalance between ultrafiltration volume (UF) and vascular refilling is considered a major cause for intradialytic hypotension. Recent studies report a noninvasive method to estimate vascular refilling (V_REF ) by determining absolute blood volume (ABV). It was the aim of the study to analyze variations in ABV in a group of hemodialysis (HD) patients and examine V_REF . Thirty one stable chronic HD patients were studied, aged 71.07 ± 13.31 years. Dialysis duration and UF requirements were based on physician prescription. V_REF was calculated as: V_REF  = V_UF  - ΔV where ΔV is ABV variation during dialysis treatment. ABV at the beginning of the dialysis was 6.00 ± 2.39 L (92.82 ± 33.17 ml/kg) and at the end 5.38 ± 2.32 L (82.07 ± 31.41 ml/kg). Prescribed UF was 2.64 ± 0.83 L. Mean V_REF was 2.05 ± 0.80 L, with a refilling fraction of 75.75 ± 12.79%. V_REF was strongly correlated with UF volume (r² 0.877), and with pre-dialysis volume overload (r² 0.617). Patients under beta-blocker treatment showed significantly lower F_REF . ABV measurement is an easy and noninvasive method that allows us to study V_REF during HD. We found a strong correlation between V_REF and UF.