Platelet disorders Thrombocytopenia
Rarely symptomatic until the platelet count <50 x 109/l; spontaneous bleeding is more likely <20 x 109/l. Although bleeding is often minor, e.g. skin petechiae, oozing at intravascular catheter sites, it may be massive or life-threatening, e.g. haemoptysis, intracranial haemorrhage.
• Sepsis — in the ICU this is the commonest cause of a low platelet count; often provides a good barometer of recovery or deterioration
• Disseminated intravascular coagulation
• Related to antiplatelet antibody production, e.g. heparin (heparin-induced thrombocytopenia syndrome, 'HITS'), sulphonamides, quinine
• Resulting in bone marrow suppression, e.g. chemotherapy agents
• Others, e.g. aspirin, chlorpromazine, prochlorperazine, digoxin
• Following massive bleeding and multiple blood transfusions
• Bone marrow failure, e.g. tumour infiltration, drugs
• Thrombotic thrombocytopenic purpura (TTP), haemolytic uraemic syndrome (HUS)
• Idiopathic thrombocytopenic purpura (ITP)
• Specific infections, e.g. measles, infectious mononucleosis, typhus
• Collagen vascular diseases, e.g. SLE
1. Directed at the cause, e.g. antibiotics for sepsis, stopping offending drugs, plasma exchange for TTP, splenectomy and steroids for ITP.
2. Platelet support
• Given routinely (e.g. 6-10 units/day) when counts <10-20 x 109/l
• 6-10 units given if <50 x 109/l and either symptomatic or due to undergo surgery or another invasive procedure
3. Unless actively bleeding, avoid platelet transfusions in TTP or HUS.