[Leukocyte removal in a closed system of human red-cell concentrates: a technic coupled with the automated extraction of the buffy coat using a sterile connector from a filtration kit]

Separation of buffy coat using the top and bottom drainage system: reduction of red blood cell loss

We studied the effect of automated separation of the buffy coat in a top and bottom "drainage system" using a standard and a modified backplate. The use of the modified method results in reduction of the volume (36 +/-3 mL vs 49 +/-2 mL, P less than 0.001) and the red blood cell content (8 +/- 1% vs 15 +/- 2%, P less than 0.001) of the buffy coat, but also increases the leukocyte content (27 +/- 11% vs 17 +/- 11%, P less than 0.001) of the red cell concentrate. The leukocyte content of the red cell concentrate obtained with the modified method compares well with the reported results of manual buffy coat removal. Therefore the same advantages can be expected.

[Filtration technology]

The leukocyte removal technology of platelet and red blood cell concentrates is now based on the only method: the filtration. In order to perfectly control this technology, it is necessary to know the different parameters that interfere in the quality of the leukocyte removal. These different parameters are studied here. They are classified in two types: the parameters that are related to the concentrate to filtrate: method used for the preparation, age, state (temperature, aggregates), concentration of red blood cells, platelets and leukocytes; the parameters that are related to the leukocyte removal technology and to the different steps of its carrying out: filter type (composition, size, geometry), prefilter, priming of the filter, flow rate during the filtration, rinsing and centrifugation after the filtration, elimination of the air inside the filter and the filtered concentrate, sterile connections, and finally good behavior in front of the difficulties and hitchs that could occur during the filtration procedure.

[Technical constraints in rapid vascular fluid replacement]

Rapid fluid infusion remains the cornerstone for therapy of hypovolaemic shock. The principal limitations of flow rate are governed by the four variables of Poiseuille's law: tube internal diameter and length, viscosity of the fluid passing through the tube, and the pressure gradient between the two ends of the tube. Conventional transfusion systems, with wide bore tubing (up to 5.0 mm internal diameter), large bore cannulas (8.5 French introducer catheters), high pressure (up to 300 mmHg) and diluted blood, can result in a maximum flow rate of about 1,000 ml.min-1 (for crystalloid solutions). Specific apparatus for rapid infusion can increase this to 1,500 ml.min-1 (Rapid Infusion System, Haemonetics). Dry-heat warming devices and microfiltration, to remove microaggregates and prevent non haemolytic febrile transfusion reactions, seem necessary when carrying out rapid transfusions. However, the use of microaggregate filters could be avoided by the routine production of leukocyte-poor red blood cell concentrates.