Which laboratory information will the nurse monitor to detect heparin-induced thrombocytopenia (HIT) in a patient who is receiving a continuous heparin infusion?

A. Erythrocyte count: The red blood cell count reflects oxygen-carrying capacity and anemia but does not indicate platelet destruction or immune-mediated reactions. HIT specifically affects platelets, so monitoring erythrocytes would not detect this complication. B. Fibrinogen degradation products: Fibrinogen degradation products (FDPs) are elevated in disseminated intravascular coagulation or significant clot breakdown. While they reflect fibrinolytic activity, they are not specific or sensitive for heparin-induced thrombocytopenia. C. Activated partial thromboplastin time (aPTT): Although aPTT is used to monitor therapeutic anticoagulation during heparin infusion, frequent platelet counts are the most direct laboratory marker for HIT. Monitoring aPTT ensures the patient is within the therapeutic range, but detection of a sudden drop in platelet count is crucial for early recognition of HIT. D. Prothrombin time (PT): PT evaluates the extrinsic coagulation pathway and is primarily used to monitor warfarin therapy. It is not sensitive to heparin therapy or the development of HIT, which involves immune-mediated platelet activation and thrombocytopenia rather than changes in PT.