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Product Profile : Platelets

Platelet transfusions are required for the treatment or prevention of bleeding due to reduced platelet numbers or function. In general, the risk of bleeding increases only when the platelet count falls to below 50x109/l and spontaneous bleeding seldom occurs at platelet counts above 20x109/l.

Good transfusion practice

  • Platelets should be transfused in accordance not only with clinical guidelines but also with reference to the individual patient's clinical status.
  • Do not give prophylactic transfusions without verification of the platelet count on the peripheral smear.
  • Ensure that the patient is not on drugs which might potentiate bleeding e.g. Aspirin.
  • Consider the appropriate use of other measures such as antifibrinolytics, fibrin glue etc.
1. Indications for platelet transfusions

Transfusion of platelet concentrates is standard treatment for bleeding associated with thrombocytopenia and /or defective platelet function in conditions such as:
  • Bone marrow failure e.g. aplastic anaemia, acute leukaemia.
  • Massive transfusion with dilutional thrombocytopenia.
  • Acute disseminated intravascular coagulation.
  • Congenital disorders of platelet function.
The role and clinical efficacy of prophylactic platelet transfusions is less well defined. Spontaneous bleeding is unusual at counts higher than 5x109/l.

The following transfusion triggers are widely accepted:
  • Threshold of 10x109 /l for adult stable patients.
  • Threshold of 20x109 /l for patients at increased bleeding risk:
    • Anatomic lesions e.g. peptic ulcer.
    • Fever/sepsis.
    • Recent severe haemorrhage or bleeding from mucous membranes.
    • Anticoagulant therapy.
    • On drugs affecting platelet function.
    • Severe anaemia.
  • For patients with chronic stable thrombocytopenia e.g. aplastic anaemia, prophylactic transfusions are generally not indicated.
  • Platelet transfusion is not required for bone marrow aspirate or biopsy. Application of local pressure is sufficient.
  • Threshold of 50 x109 /l for most surgical procedures e.g. laparotomy, liver biopsy.
  • Threshold of 100 x109 /l for CNS surgery, ocular surgery.
  • For massive transfusion maintain platelet count at >50x 109 /l.
  • In situations of multiple trauma and head injury, maintain platelet count at > 100x109 /l.
  • Cardiopulmonary bypass - transfuse only in the presence of microvascular bleeding and platelet count < 100 x109 /l.
 2. Contraindications to platelet transfusions

Platelet transfusions are generally contraindicated in patients with immune causes of thrombocytopenia unless there is severe life threatening haemorrhage.
  • Immune Thrombocytopenic Purpura(ITP): Transfused platelets will be destroyed by the autoantibodies.
  • Thrombotic Thrombocytopenic Purpura(TTP): Platelet transfusion may potentiate thrombotic tendency.
  • Heparin Induced Thrombocytopenia(HIT): May potentiate thrombosis.
 3. Platelet products

a. Random donor pooled platelets
  • Prepared from the buffy layers of whole blood donations within 8 hours of collection.
  • Stored with continuous agitation for up to 5 days at 22 oC.
  • Adult dose consists of platelets from 5 individual donations pooled together to produce 1 platelet concentrate.
  • Each unit contains a minimum of >2.4 x 1011 platelets with a volume of 200-300mls.
  • Random donor platelets are indicated for patients with acute causes of thrombocytopenia e.g. DIC and who are unlikely to require long term platelet transfusion therapy.
b. Single donor apheresis platelet concentrates.
  • Complete dose derived from 1 donor with minimum yield of 2,4 x 1011 platelets and volume of 200 - 300ml.
  • Leucocyte reduction occurs during apheresis procedure; therefore recommended for patients who experience febrile reactions as a result of sensitisation to leucocyte antigens.
  • Reduced donor exposure and therefore reduced risk of alloimmunisation to HLA antigens.
  • Recommended for patients who are on long term therapy e.g. leukaemia.
4. Compatibility
  • It is recommended that, as far as possible, group specific platelet concentrates be administered. However, not infrequently, clinical demands and stock availability dictates that patients receive platelet transfusion that are not ABO matched. A good clinical outcome is usually attained as ABO antigens are weakly expressed on platelets.
  • Platelet concentrates may contain a small number of red cells. Therefore Rh-D negative platelets should be given to Rh-D negative women with child bearing potential. If this is not possible, administration of anti-D immunoglobulin should be considered, once the platelet count is corrected.
5. Administration
  • Platelets should be transfused through a platelet giving set over a period of 15-30 minutes. Transfusion through a standard red cell giving set will reduce the number of platelets received.
  • Dose: In South Africa the services provide buffy coat derived platelets (5 donors per pool) suspended in plasma. This is equivalent to one adult dose. Apheresis (single donor) platelets are given as a single adult dose. Platelets for paediatric use are subdivided into aliquots from a single apheresis unit and a recommended dose for neonates and infants is 5-10 ml/kg.
6. Expected increments

Tne platelet count should increase by 20-40 x 109 /l per standard adult dose. The increment will vary, however, and be lower in patients with:
  • Splenomegaly
  • DIC
  • Septicaemia
7. Platelet refractoriness

An increment of less than 10x109 /l on more than one occasion may be due to development of antibodies to HLA and/or platelet antigens. Consult with the transfusion service regarding provision of matched platelets.

8. Adverse effects of platelet transfusion

As with other blood products adverse reactions may occur. Febrile reactions are the most common and may be treated symptomatically. For subsequent transfusions leukocyte depleted preparations are indicated. In addition, the risk of bacterial contamination is greater with platelet transfusions because of room temperature storage.
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9. Irradiation

Platelets may be irradiated as indicated with no loss of function.
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