Coagulation abnormalities in critically ill patients

Table 1 Differential diagnosis of thrombocytopenia in the intensive care unit

Differential diagnosis	Approximate relative incidence	Additional diagnostic clues
Sepsis	52%	Positive (blood) cultures, positive sepsis criteria, hematophagocytosis in bone marrow aspirate
DIC^a	25%	Prolonged aPTT and PT, increased fibrin split products, low levels of physiological anticoagulant factors (antithrombin, protein C)
Massive blood loss	8%	Major bleeding, low hemoglobin, prolonged aPTT and PT
Thrombotic microangiopathy	1%	Schistocytes in blood smear, Coombs-negative hemolysis, fever, neurological symptoms, renal insufficiency
Heparin-induced thrombocytopenia	1%	Use of heparin, venous or arterial thrombosis, positive HIT test (usually ELISA for heparin-platelet factor IV antibodies), rebound of platelets after cessation of heparin
Immune thrombocytopenia	3%	Anti-platelet antibodies, normal or increased number of megakaryocytes in bone marrow aspirate, thrombopoeitin decreased
Drug-induced thrombocytopenia	10%	Decreased number of megakaryocytes in bone marrow aspirate or detection of drug-induced anti-platelet antibodies, rebound of platelet count after cessation of drug

Seven major causes of thrombocytopenia (platelet count <150 × 10⁹/l) are listed. Relative incidences are based on two studies in consecutive intensive care unit patients [1,6] but may vary depending on the population studied. Patients with hematological malignancies were excluded.
^aPatients with sepsis and disseminated intravascular coagulation (DIC) are classified as DIC. aPTT, activated partial thromboplastin time; ELISA, enzyme-linked immunosorbent assay; HIT, heparin-induced thrombocytopenia; PT, prothrombin time.

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