The Influence of Hypoalbuminemia on Maximal Flow Rates and Transmembrane Pressure during Plasmapheresis – An in vitro Study

Abstract

Background: Plasmapheresis has been used for the treatment of acute liver failure (ALF). In these patients, hypoalbuminemia is often observed. Since albumin improves the disaggregability of erythrocytes, hypoalbuminemia might deteriorate rheology and thus influence the overall performance of plasmapheresis. Methods: Hypoalbuminemia was mimicked by using porcine blood because of its physiologically low albumin/globulin ratio (AGR). Filters (n = 16) were integrated in a closed extracorporeal in vitro system. In the control group (n = 8), native porcine blood (AGR 0.8) was used. In the study group (n = 8), we used porcine blood supplemented with human albumin to obtain the human AGR value of 1.2. Two different heparinization protocols were compared in each group (2.5 IU/ml: n = 4 with albumin and n = 4 without albumin versus 5 IU/ml: n = 4 with and n = 4 without albumin). Results: In both heparinization protocols the higher AGR led to lower transmembrane pressure (TMP) levels compared to the lower AGR. The reduced TMPs enabled higher blood flow and filtration rates. Conclusion: Maintenance of a physiological AGR in ALF patients might improve the performance of plasmapheresis and – as opposed to raised heparinization – contribute to a safer application.

Hydroxyethyl Starch 130 KD/0.4 and Albumin Improve CVVH Biocompatibility Whereas Gelatin and Hydroxyethyl Starch 200 KD/0.5 Lead to Adverse Side Effects of CVVH in Anesthetized Pigs

“…In particular, unfavorable hemorheological conditions are given because of a low ALB/globulin ratio and a very low hematocrit level. Both aspects are highly supportive for increased blood cell aggregability and hemofilter blockage (19,24,25). A low stress resistance of the right ventricular function in pigs is given as a partly neglected side effect of breeding programs exclusively focused on special preferences in food consumption.…”

“…However, we have shown that cell aggregation in convection-based membrane processes is a main problem (18,19). Increased blood cell aggregation may lead to a reduced blood flow velocity and cessation of blood flow within the hollow fibers, which in turn automatically accelerates hemostasis and increases the overall activation of the coagulation system.…”

First Level Prevention Instead of Third Level Intervention—Review of Research to Improve Biocompatibility and Performance of Capillary Membrane Apheresis in Critically Ill Patients

“…HES 130/0.4 is known to reduce RBC aggregability. These findings are paralleled by the observation that substitution of both—ALB and HES 130 kD/0.4—increases blood sedimentation rates .…”

“…We questioned whether or not the impaired hemorheology in critically ill patients (hyperaggregability due to changes in blood cell counts, impaired RBC features after transfusion, or decreases in the AGR) may be a dominant reason for unfavorable flow dynamics in the filters' hollow fibers and, in turn, the main reason for filter “clotting” . Histopathological examinations of the capillary membranes of plasmafilters, which were operated in our in vitro system, revealed extensive RBC aggregates as the main reason for blocked hollow fibers (Fig.…”

Maximal flow rates and sieving coefficients in different plasmafilters: Effects of increased membrane surfaces and effective length under standardized in vitro conditions

“…For in vivo it is also described that crystalloids and colloids aect rheological properties in a dierent manner [13]. Using a specially established in vitro system, we found that the solutions, which are chosen for volume replacement, in¯uence pressure pro®les and hemocompatibility of the plasmaseparation procedure based on capillary membrane ®lters [14,15].…”