++
KEY POINTS
The most common reasons for hematologic consultation in critically ill patients include thrombocytopenia, anemia, and less commonly, evaluation of leukocytosis and thrombocytosis.
Coagulopathies including severe bleeding and thrombotic disorders are very prevalent in intensive care unit (ICU) patients due to their underlying conditions including liver dysfunction and acquired vitamin K deficiency. Bleeding can occur due to renal insufficiency and the use of antiplatelet agents and anticoagulant therapy.
Inflammation occurs in sepsis, systemic inflammatory response syndrome, and other critical illnesses, and causes alterations in both hemostasis and fibrinolysis.
Disseminated intravascular coagulation (DIC) is observed in approximately 50% of patients with sepsis, and is an independent predictor of morbidity and mortality.
Thrombocytopenia (platelet count < 150,000/L) occurs in 15% to 58% of ICU patients and may be due to medications, infections, DIC, thrombotic microangiopathies (thrombotic thrombocytopenic purpura [TTP] and atypical hemolytic uremic syndrome), heparin-induced thrombocytopenia (HIT), catastrophic antiphospholipid syndrome, and immune thrombocytopenic purpura.
HIT is a clinicopathologic diagnosis that occurs in 1% to 4% of patients on unfractionated heparin (UFH), and less than 1% of patients on low-molecular-weight heparin (LMWH). It is more common in postsurgical patients than medical inpatients and in females.
Prompt interaction between the intensivist and the hematologist is key to optimize the care of critically ill patients with hematologic dysfunction.
++
Patients admitted to the ICU have frequent hematologic dysfunction as a result of critical illness leading to multiorgan dysfunction and failure. A hematology consultation is often requested for evaluation of hematologic complications in these critically ill patients. The most common reasons for hematologic consultation include evaluation of cytopenias mainly thrombocytopenia, anemia, and less commonly, evaluation of leukocytosis and thrombocytosis. Coagulopathies including severe bleeding and thrombotic disorders are very prevalent in the ICU patients due to their underlying conditions. These patients frequently develop DIC or severe coagulopathy secondary to liver dysfunction or acquired vitamin K deficiency. Bleeding can also be seen as a consequence of renal insufficiency, and the use of antiplatelet agents causing an acquired thrombocytopathy. The administration of anticoagulants in these patients is challenging as the bleeding risk is increased. Hemostasis is frequently disrupted, as these patients often require invasive and/or surgical procedures. Thrombotic complications either venous, arterial, or microvascular are commonly seen as a result of indwelling catheter placement or other invasive procedures, prolonged immobilization, underlying malignancy, autoimmune disorder, or medication related. Frequent exposure to blood products, increases the risk of transfusion reactions including transfusion-related acute lung injury (TRALI) and hemolytic, febrile, and allergic transfusion reactions. In addition dilution coagulopathies are seen in patients who are massively transfused. Prompt interaction between the intensivist and the hematologist is key to optimize the care of these challenging patients.
++
Overview of Hemostasis
++
Hemostasis maintains a closed system of vascular integrity and prevents blood loss from injury.1 The hemostatic response is initiated by injury to endothelial cell surfaces that leads to exposure of tissue factor (TF), collagen, von Willebrand factor (vWF), and fibronectin on the subendothelial matrix. Primary hemostasis consists of platelet adhesion by binding to collagen and vWF on the exposed endothelial surface. Platelets then aggregate via glycoprotein IIb-IIIa receptors, which ...