[Influence of microaggregate transfusion filters on the rheological properties of blood]

Micro-aggregate transfusion filters have been suggested in order to prevent pulmonary complications in cases of shock after massive transfusions and cerebral complications after ECC. It is important to have prior knowledge of performance, in particular with regard to perfusion flow rate and the efficacy of filtration. Eight filters have been thoroughly studied: Bentley PF 127, Bentley PFF 100, Biotest, Fenwal 4C2417, Fenwal 4C 2423, Intersept, X Pall Ultipor SQ 40 S, Swank IL 40 S. For each of them, study included the following: perfusion flow rate, filtration pressure (Swank technique) of whole blood distal or proximal to the filter, viscosity and various haematological parameters (CBC, free haemoglobin, red cell ATP). Finally, the deposit retained by the filter must be studied morphologically by sweep electron microscopy. It would seem that good aggregate elimination power (decrease in filtration pressure of 75 to 95 per 100) often coincides with a poor flow rate and the need to rapidly change the filter. Efficacy is virtually the same for all filters with the exception of Pall filter where it seems to be less. The Bentley PF 100 and Fenwal 4C 2423 filters combine this efficacy with an adequate flow rate, resulting in easy use in practice. By contrast, the Pall filter with a very satisfactory flow rate is less effective than the other with regard to the retention of aggregates. Other parameters are only very slightly modified by filtration. The deposit collected on the filters consists of fibrinogen, deformed red cells (echniocytes), leucocytes and platelets.