Relative Blood Volume Changes Underestimate Total Blood Volume Changes during Hemodialysis

Abstract

Background: Measurements of relative blood volume changes (⌬RBV) during hemodialysis (HD) are based on hemoconcentration and assume uniform mixing of erythrocytes and plasma throughout the circulation. However, whole-body hematocrit (Ht) is lower than systemic Ht. During HD, a change in the ratio between whole-body to systemic Ht (F cell ratio) is likely to occur as a result of a net shift of low Ht blood from the microcirculation to the macrocirculation. Hence, ⌬RBV may differ significantly from total blood volume changes (⌬TBV). Therefore, this study compared ⌬RBV and ⌬TBV during HD.Design, setting, participants, and measurements: Plasma and erythrocyte volumes were measured using 125 I-and 123 Iradioiodinated albumin and 51 Cr-labeled erythrocytes, respectively. After validation of the standardized method in two patients on a nondialysis day, seven patients completed the protocol during HD.125 I-albumin and 51 Cr-labeled erythrocytes were administered 20 min before the start of HD.123 I-albumin was administered at 160 min into the HD session to quantify and correct for 125 I-albumin leakage. ⌬RBV was measured continuously throughout HD. The F cell ratio was derived from whole-body and systemic Ht.Results: Total ultrafiltration volume was 2450 ؎ 770 ml. TBV declined from 5905 ؎ 824 to 4877 ؎ 722 ml during HD. Thus, TBV declined 17.3 ؎ 4.4%, whereas the RBV decline was only 8.2 ؎ 3.7% (P ‫؍‬ 0.001). The F cell ratio increased from 0.896 ؎ 0.036 to 0.993 ؎ 0.049 during HD (P ‫؍‬ 0.002).Conclusions: ⌬RBV significantly underestimates ⌬TBV during HD. The rise in F cell ratio strongly suggests that during HD, blood translocates from the microcirculation to the macrocirculation, probably as a cardiovascular compensatory mechanism in response to hypovolemia.

Neutrophil Activation and Resistance to Recombinant Human Erythropoietin Therapy in Hemodialysis Patients

“…After hemodialysis, a higher hemoglobin level was found, and has been attributed to a translocation of erythrocytes from the splanchnic circulation (and possibly from the spleen) in order to compensate for the hypovolemic stress during dialysis ultrafiltration [17, 18]. After hemodialysis we also found a statistically significant increase in both elastase and lactoferrin concentrations (and in their ratios per neutrophil), suggesting a neutrophilic activation process with degranulation during the hemodialysis procedure.…”

Changes in Red Blood Cells Membrane Protein Composition during Hemodialysis Procedure

“…Higher Hb levels and RBC counts were found after HD. This increase in circulating RBCs has been described [14,15] to be associated with a translocation of RBCs from the splanchnic circulation (and possibly from the splenic circulation) in order to compensate the hypovolemic stress during dialysis ultrafiltration.…”

Critical Evaluation of Blood Volume Measurements during Hemodialysis

“…Recently, we showed by direct measurement of absolute plasma volume ( 125 I and 123 I radio-ionated albumin) and erythrocyte volume ( 51 Cr-labeled erythrocytes) that the fall in RBV significantly underestimated the decrease in total blood volume (fig. 2) [15]. …”