Autotransfusion of filtered knee drain blood (FKDB) is frequently practised in orthopaedic surgery, but questioned because it contains inflammatory cytokines, contaminants from lysed blood cells, debris and chemicals from the wound. We have studied the microrheology (5
\mu
m pore filtration) of FKDB (
n={}
23) with versus without the addition of a leukocyte reducing filter (LRF) in line with the drain. As expected the whole blood clogging was reduced (
p<{}
0.01) due to the lowered leukocyte number by the LRF. FKDB plasma contains clogging particles of unknown origin. With the LRF the increased plasma clogging was reduced (
p \approx{}
0.05). With resuspended erythrocytes there was an increase in clogging rate in FKDB at 24 hours. This increase was abolished with the addition of the LRF, which may indicate that the erythrocyte trauma results from the incubation together with leukocytes in the drain container. There is a potential for further improvement of the filters in autotransfusion drains.
