Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 143

Platelets prepared by either method can be stored in either plasma or PAS. Platelets stored at 20–24°C maintain functional effectiveness for several days [13, 77–80]. Many variables affect the quality of platelets during storage. In addition to temperature, these other variables include the anticoagulant–preservative solution, storage container, type of agitation, anticoagulant, and volume of plasma [72, 81–83]. Gentle horizontal agitation is preferable to end‐over‐end agitation [83]. If continuous agitation is interrupted, platelets stored for up to 5 days maintain appropriate in vitro characteristics for up to 24 hours of interruption of agitation [84]. The composition, surface area, and size of the storage container influence the ability for carbon dioxide to diffuse out and oxygen to enter the platelet concentrate, and storage containers specifically designed to optimize platelet quality are now used routinely [85, 86].

Maintenance of the pH greater than 6.0 is the crucial factor indicating satisfactory platelet preservation. This combination of storage container, agitation, preservative solution, temperature, and the use of about 50 mL of plasma provides satisfactory preservation of platelets for up to 7 days [85, 87]. However, several instances of bacterial contamination of platelet concentrates stored for this period were reported [87, 88], and the storage time was reduced to the 5 days currently used [24]. The problem of bacterial contamination still exists (see Chapter 16), although recently with additional point of care testing for bacterial detection, the FDA approved storage of apheresis platelets up to 7 days [89] (see Chapter 7). The storage container needs to be FDA approved for apheresis platelet storage up to 7 days. In addition, large‐volume delayed sampling and secondary cultures can be used to extend platelet storage to 7 days [89].

Several platelet concentrates are usually pooled to provide an adequate dose for most patients (see Chapter 10). For some patients, the volume of plasma in the final pooled component is too large, and plasma must be removed prior to transfusion. This involves another centrifugation step after the platelets have been pooled that causes a loss of 15% to as much as 55% of the platelets [90, 91].