The influence of HES on the filtration properties of capillary membrane plasmaseparation

Plasmaseparation is a treatment under discussion for critically ill patients, especially in sepsis and multiorgan failure. These patients receive a variety of different fluid substitutes, including hydroxyethylstarch (HES). HES is known to influence rheological properties, but nothing is known about the possible interactions between HES and the plamaseparation procedure. We used an in vitro plasmaseparation circuit with heparinized porcine blood. Before priming the system, 2 liters of blood were supplemented by adding 100 ml of either NaCl 0.9% or HES (n=6 in each group). We monitored the transmembrane (TMP) and the filtration pressure (PF) and measured free plasma hemoglobin (free Hb) and platelet counts before and after the two hours plasmaseparation procedure. The final transmembrane pressure was significantly higher with HES substitution. In the HES group we found negative filtration pressures from the very beginning with a significant further decrease toward the end of the experiments. A significant increase in free Hb and decrease in platelet counts were noted only in the HES group. Volume substitution with HES leads to impaired filtration properties and deteriorated hemocompatibility in in vitro plasmaseparation. Further studies have yet to evaluate whether or not the effects described also occur under clinical conditions.