Abstract
BackgroundRelative blood volume (RBV) changes during hemodialysis (HD) are typically estimated based on online measurements of hematocrit, hemoglobin or total blood protein. The aim of this study was to assess changes in the above parameters during HD in order to compare the potential differences in the RBV changes estimated by individual methods.Methods25 anuric maintenance HD patients were monitored during a 1-week conventional HD treatment. Blood samples were collected from the arterial dialysis blood line at the beginning and at the end of each HD session. The analysis of blood samples was performed using the hematology analyzer Advia 2120 and clinical chemistry analyzer Advia 1800 (Siemens Healthcare).ResultsDuring the analyzed 30 HD sessions with ultrafiltration in the range 0.7–4.0 L (2.5 ± 0.8 L) hematocrit (HCT) increased by 9.1 ± 7.0% (mean ± SD), hemoglobin (HGB) increased by 10.6 ± 6.3%, total plasma protein (TPP) increased by 15.6 ± 9.5%, total blood protein (TBP) increased by 10.4 ± 5.8%, red blood cell count (RBC) increased by 10.8 ± 7.1%, while mean corpuscular red cell volume (MCV) decreased by 1.5 ± 1.1% (all changes statistically significant, p < 0.001). HGB increased on average by 1.5% more than HCT (p < 0.001). The difference between HGB and TBP increase was insignificant (p = 0.16).ConclusionsTracking HGB or TBP can be treated as equivalent for the purpose of estimating RBV changes during HD. Due to the reduction of MCV, the HCT-based estimate of RBV changes may underestimate the actual blood volume changes.
Highlights
Relative blood volume (RBV) changes during hemodialysis (HD) are typically estimated from continuous non-invasive measurements of optical, electrical, acoustic or viscous properties of blood flowing through the dialyzer lines [1, 2] The three most common methods of estimating RBV changes during HD are based on measurements of: 1) hematocrit, 2) hemoglobin concentration in the whole blood, or 3) total blood protein concentration [2, 3]
During the analyzed 30 HD sessions with ultrafiltration in the range 0.7–4.0 L (2.5 ± 0.8 L) hematocrit (HCT) increased by 9.1 ± 7.0%, hemoglobin (HGB) increased by 10.6 ± 6.3%, total plasma protein (TPP) increased by 15.6 ± 9.5%, total blood protein (TBP) increased by 10.4 ± 5.8%, red blood cell count (RBC) increased by 10.8 ± 7.1%, while mean corpuscular red cell volume (MCV) decreased by 1.5 ± 1.1%
The method assumes that the total volume of red blood cells (RBCs) in the circulatory system remains constant throughout dialysis, which requires a constant number of RBCs available in the circulation, and the lack of osmotic water shifts between plasma and RBCs
Summary
Relative blood volume (RBV) changes during hemodialysis (HD) are typically estimated from continuous (or quasi-continuous) non-invasive measurements of optical, electrical, acoustic or viscous properties of blood flowing through the dialyzer lines [1, 2] The three most common methods of estimating RBV changes during HD are based on measurements of: 1) hematocrit, 2) hemoglobin concentration in the whole blood, or 3) total blood protein concentration [2, 3] (see Table 1). The method assumes that the total volume of red blood cells (RBCs) in the circulatory system (including the extracorporeal circuit) remains constant throughout dialysis, which requires a constant number of RBCs available in the circulation (i.e. no sequestration or release of RBCs in the spleen and a negligible or balanced erythropoiesis and erythrocyte lysis), and the lack of osmotic water shifts between plasma and RBCs (note that there are other possible cases satisfying the assumption of a constant total volume of RBCs, such as a lower number of larger erythrocytes or a higher number of smaller erythrocytes) It assumes that the ratio of whole-body HCT to central HCT (known as the F-cells ratio [4]) remains constant, so that any changes in HCT measured at the dialyzer blood line are consistent with the global HCT changes on the whole-body level. The aim of this study was to assess changes in the above parameters during HD in order to compare the potential differences in the RBV changes estimated by individual methods
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