Preparation and administration

Platelets for transfusion can be harvested from whole blood as platelet-rich plasma or buffy coat, or by platelet-pheresis techniques ( Fig 1).

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Fig. 1 Donor blood collection protocols indicating processing pathways for the manufacture of blood products: SAGM, saline adenine glucose mannitol; FFP, fresh frozen plasma.

The decision on when to transfuse platelets will depend on the clinical condition of the patient, the platelet count, and the procedure that the patient is to undergo. The usual threshold for transfusion in bone marrow failure syndromes is a platelet count of 5 * 10 9/l to 15 * 109/l (higher if septic or bleeding), but the threshold level may be higher in other conditions.

An adult dose of platelets is 2 * 1011 to 4 * 1011 which is contained in either a single apheresis pack or a 'pool' of four to six random donor units. Recovery of platelets 1 h after transfusion is 50 to 80 per cent, and the effective half-life in the circulation is about 4 days. Ideally, platelets should be of the same ABO and Rh group as the patient, but in an emergency incompatible groups can be given although this may result in mild immune hemolysis or the development of anti-D.

The normal shelf-life of platelet concentrates is 5 days and they should be kept at room temperature (22 ± 2 °C), ideally on an agitator. They should be infused through a blood- or platelet-giving set and, if indicated, they can be filtered at the transfusion center or at the bedside and/or gamma-irradiated. Indications for filtration include the prevention of HLA alloimmunization or non-hemolytic transfusion reactions in multiply transfused patients and newly diagnosed patients with aplastic anemia, and also to reduce the chance of cytomegalovirus transmission when cytomegalovirus-negative blood products are not available.

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