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 (VREF ) 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 VREF . Thirty one stable chronic HD patients were studied, aged 71.07 ± 13.31 years. Dialysis duration and UF requirements were based on physician prescription. VREF was calculated as: VREF  = VUF  - 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 VREF was 2.05 ± 0.80 L, with a refilling fraction of 75.75 ± 12.79%. VREF 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 FREF . ABV measurement is an easy and noninvasive method that allows us to study VREF during HD. We found a strong correlation between VREF and UF.