How do we approach thrombocytopenia in critically ill patients?

A low platelet count is a frequently encountered haematological abnormality in patients treated in intensive treatment units (ITUs). Although severe thrombocytopenia (platelet count <20 × 10⁹ /l) can be associated with bleeding, even moderate-degree thrombocytopenia is associated with organ failure and adverse prognosis. The aetiology for thrombocytopenia in ITU is often multifactorial and correcting one aetiology may not normalise the low platelet count. The classical view for thrombocytopenia in this setting is consumption associated with thrombin-mediated platelet activation, but other concepts, including platelet adhesion to endothelial cells and leucocytes, platelet aggregation by increased von Willebrand factor release, red cell damage and histone release, and platelet destruction by the complement system, have recently been described. The management of severe thrombocytopenia is platelet transfusion in the presence of active bleeding or invasive procedure, but the risk-benefit of prophylactic platelet transfusions in this setting is uncertain. In this review, the incidence and mechanisms of thrombocytopenia in patients with ITU, its prognostic significance and the impact on organ function is discussed. A practical approach based on the authors' experience is described to guide management of a critically ill patient who develops thrombocytopenia.