Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 133

The blood filters used for routine transfusions have a pore size of 170–260 mm. They filter out clots and fibrin strands but do not effectively remove leukocytes. During the 1960s and 1970s, it was recognized that leukocytes were important in the pathogenesis of febrile nonhemolytic transfusion reactions and could cause alloimmunization, which would later interfere with organ transplantation or platelet transfusion (see Chapter 16). Thus, considerable interest developed in removing leukocytes before transfusion. Early methods involved centrifuging the red cells (either upright or inverted); sedimenting red cells with dextran or hydroxyethyl starch; filtration with nylon or cotton wool, which removed only granulocytes [51]; or washing, freezing, and deglycerolizing [50]. These methods removed from 65% to 99% of the original leukocytes and from 5% to 20% of the original red cells. A huge body of literature developed describing the advantages and disadvantages of the different methods and some of the clinical effects of their use. Although they are of historical interest, these studies are not described extensively in this chapter because the methods are not used today. Leukodepletion continues to be a major issue in transfusion medicine because even more adverse effects of leukocytes contained in blood components have been identified (Table 5.8). The consequences of these effects are described in more detail in Chapter 16. As these adverse effects of leukocytes have been more extensively described, the technology for producing leukodepleted red cells has evolved to provide more extensive leukocyte depletion than was possible using earlier methods [52].

Clinical and animal studies suggested that red cells intended to prevent febrile nonhemolytic transfusion reactions must contain fewer than 5 × 10⁸ leukocytes, and those intended to prevent alloimmunization contain fewer than 5 × 10⁶ leukocytes [24]. The latter requires removal of about 99.9% of the leukocytes. Sophisticated filters have been developed to accomplish this.