Filterability of autotransfusion blood cells and plasma after total knee arthroplasty

Postoperatively filtered drain blood can be used for autotransfusion, but quality has been questioned. The blood contains activated or destroyed blood cells, debris, and chemicals from the wound. The ConstaVac autotransfusion system was used in 18 patients operated with a total knee prosthesis. Samples were taken from drain blood and compared with venous blood at different sampling times (to 24 h) and different incubation conditions. Micro‐rheology was measured as pore filterability (5 \mu m) in whole blood, erythrocyte resuspension, and plasma. The filtration flow resistance was significantly lower in drain whole blood, but was unchanged in erythrocyte resuspension compared to venous blood. However, the rate of filter clogging was unchanged in drain whole blood, but was increased in the erythrocyte resuspension at 2 h. Drain plasma filterability indicated particle contamination. In total, the filterability of resuspended drain erythrocytes and cell‐free plasma is affected, but this is not significant enough to have effects on drain whole blood filterability which is increased, possibly due to the leukocyte reduction. From these perspectives, we consider drain blood acceptable for autotransfusion.