A Simple and Feasible Method to Determine Absolute Blood Volume in Hemodialysis Patients in Clinical Practice

Abstract

Background: We developed a simple method to determine the absolute blood volume (V) during hemodialysis in everyday clinical practice and examined its relationship with volume overload, clinical relevance, and accuracy. Methods: The increase in relative blood volume (RBV_post - RBV_pre) measured before and after infusion of 240 ml of ultra-pure dialysate using the bolus function of a commercial online hemodiafiltration machine incorporating a relative blood volume monitor was applied to determine absolute blood volume. The specific blood volume (V_s, blood volume per kg body mass at dry weight, in ml/kg) was compared to volume status as assessed by bioimpedance analysis and clinical criteria. Results: The blood volume measured in 30 stable hemodialysis patients was 6.51 ± 1.70 l at the beginning, corresponding to a specific blood volume of 80.1 ± 12.8 ml/kg, and dropped to 5.84 ± 1.61 l or 72.0 ± 12.1 ml/kg at the end of the dialysis session, respectively. Specific blood volume correlated with volume status assessed both clinically and by bioimpedance analysis. Intradialytic morbid events occurred only in treatments where specific blood volume fell below 65 ml/kg. The reproducibility of the technique was better than 4% and the in vitro accuracy corresponds to a resolution in V_s of better than 1 ml/kg. Conclusion: Absolute blood volume can be easily measured at the beginning of the dialysis session using the current dialysis technology. Information about V and V_s could be a promising tool to avoid intradialytic morbid events. This technique could be completely automated without altering the hardware of currently available online dialysis devices. Therefore, it is recommended that this technique be integrated into all hemodiafiltration machines.

Vascular Refilling Is Not Reduced in Dialysis Sessions with Morbid Events

“…Current online hemodiafiltration machines equipped with a BVM and an online bolus function can be used to determine the absolute blood volume in clinical practice [10,11,13]. With a software modification, this technique can be automated without altering the hardware of the dialysis device.…”

“…Data of patients without IME were compared with those having normal blood volume (66-80 mL/kg) at the end of dialysis. These data were taken from a different study [11]. In this group, 6 patients were diabetics, 6 patients had heart diseases, and 1 patient received beta-blockers.…”

“…All patients gave written informed consent, and both studies [11,13] were approved by the Ethics Committee of the Berlin Medical Association.…”

“…Recently, we developed a simple and feasible method to determine absolute blood volume during routine hemodialysis sessions [10,11]. When the absolute blood volume is known, vascular refilling volume can be calculated from the absolute change in blood volume, and from the known UF volume [12].…”

Effects of Volume Overload and Current Techniques for the Assessment of Fluid Status in Patients with Renal Disease

“…However, there is definitely need for randomized controlled studies with large sample sizes to solve the conflict about the validity of RBV monitoring. The conflicts about the reliability and the results of RBV monitoring could be solved by new techniques that allow the estimation of absolute blood volumes [120][121][122]. Although there are a lot of unsolved disputes about RBV monitoring, it is definite that this area is an active area of research promoting scientists to take part in.…”