A 65-year-old man comes to the emergency department due to severe right leg pain and is found to have an acute thrombotic occlusion of the right popliteal artery. He has a history of hypertension, type 2 diabetes mellitus, and hyperlipidemia. The patient is admitted to the surgical floor and initiated on intravenous unfractionated heparin. The following morning, he undergoes surgical revascularization of the right leg. The patient's hospital course progresses well, but 5 days postoperatively his platelet count decreases from 240,000/mm³ on admission to 65,000/mm³. His vital signs are stable. The surgical wound is healing well. There are no rashes or pitting edema. Which of the following is the most appropriate next step in management of this patient?

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11ec25c8_d886_4dcf_bc81_ffecc7755a01_MD0003_00 Type 2 heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin therapy. A drop in the platelet count by >50% or a new thrombus within 5-10 days of initiating heparin should raise suspicion for HIT (HIT may manifest sooner in patients previously exposed to heparin). HIT is antibody mediated and causes a mild to moderate thrombocytopenia (rarely <20,000/mm³) with minimal bleeding risk. However, venous and arterial thrombotic risk is significant, as high as 50% in untreated HIT. If HIT is suspected, all heparin products (including heparin flushes) should be discontinued immediately, and anticoagulation should be initiated with a nonheparin medication (eg, argatroban, fondaparinux). (Choices A, B, and C) Although the diagnosis of HIT is confirmed with a high titer immunoassay or a functional assay of the blood (eg, serotonin release assay), discontinuing heparin and initiating nonheparin anticoagulation should not be delayed for laboratory results due to the high risk of thrombus. Platelet counts typically normalize 2-7 days after stopping heparin; transfusions are not required unless the patient is overtly bleeding (which is uncommon in HIT). (Choice E) Warfarin is used for anticoagulation maintenance in patients with HIT but only after the patient has received another anticoagulant and the platelet count is >150,000/mm³. Initial treatment with warfarin is contraindicated in patients with HIT as it rapidly lowers protein C levels, which may transiently increase the risk of thrombus. (Choice F) All heparin products, including low molecular weight heparin, should be avoided in patients with HIT. Educational objective: Suspected heparin-induced thrombocytopenia requires immediate cessation of all forms of heparin and initiation of anticoagulation with an alternate agent (eg, argatroban, fondaparinux). Once the platelet count is >150,000/mm³, most patients can be switched safely to warfarin. References: Heparin-induced thrombocytopenia: an update. (http://www.ncbi.nlm.nih.gov/pubmed/22399304)

A 65-Year-Old Man Comes to the Emergency Department Due to Severe