Thrombocytopenia in the intensive care unit: diagnosis and management

This narrative review aims to describe the epidemiology and aetiologies of thrombocytopenia in critically ill patients, the bleeding risk assessment in thrombocytopenic patients, and provide an update on platelet transfusion indications.

Thrombocytopenia is a common disorder in critically ill patients. The classic definition relies on an absolute platelet count below 150 × 10⁹/L. Alternatively, the definition has extended to a relative decrease in platelet count (typically within a range of >30->50% decrease) from baseline, yet remaining above 150 × 10⁹/L. Thrombocytopenia may result from multiple mechanisms depending upon the underlying conditions and the current clinical setting. Regardless of the causes, thrombocytopenia accounts as an independent determinant of poor outcomes in critically ill patients, albeit often of unclear interpretation. Nevertheless, it is well established that thrombocytopenia is associated with an increased incidence of bleeding complications. However, alternative factors also contribute to the risk of bleeding, making it difficult to establish definite links between nadir platelet counts at the expense of potential adverse events. Platelet transfusion represents the primary supportive treatment of thrombocytopenia to prevent or treat bleeding. As randomised controlled trials comparing different platelet count thresholds for prophylactic platelet transfusion in the ICU are lacking, the prophylactic transfusion strategy is largely derived from studies performed in stable haematology patients. Similarly, the platelet count transfusion threshold to secure invasive procedures remains based on a low level of evidence. Indications of platelet transfusions for the treatment of severe bleeding in thrombocytopenic patients remain largely empirical, with platelet count thresholds ranging from 50 to 100 × 10⁹/L. In addition, early and aggressive platelet transfusion is part of massive transfusion protocols in the setting of severe trauma-related haemorrhage.

Thrombocytopenia in critically ill patients is very frequent with various etiologies, and is associated with worsened prognosis, with or without bleeding complications. Interventional trials focused on critically ill patients are eagerly needed to better delineate the benefits and harms of platelet transfusions.