A 54-year-old man comes to the emergency department with pain and swelling of his right leg. He injured his leg 2 days ago while playing soccer and noticed the swelling the next day. His medical history is significant for hypertension and chronic kidney disease. His medications include amlodipine, lisinopril, and clonidine. He has not been hospitalized previously.
Laboratory results are as follows:

Ultrasound examination shows deep venous thrombosis of the right lower extremity extending to the superficial femoral vein. The patient is hospitalized and started on heparin infusion and oral warfarin.
On the second day of hospitalization, his platelet count is 130,000/mm³ and International Normalized Ratio is 1.1. He reports no additional symptoms and the remainder of his laboratory workup is unremarkable. Leg pain and swelling are decreased.
Which of the following is the best next step in management of this patient?

Question

A 54-year-old man comes to the emergency department with pain and swelling of his right leg. He injured his leg 2 days ago while playing soccer and noticed the swelling the next day. His medical history is significant for hypertension and chronic kidney disease. His medications include amlodipine, lisinopril, and clonidine. He has not been hospitalized previously.
Laboratory results are as follows:

Ultrasound examination shows deep venous thrombosis of the right lower extremity extending to the superficial femoral vein. The patient is hospitalized and started on heparin infusion and oral warfarin.
On the second day of hospitalization, his platelet count is 130,000/mm³ and International Normalized Ratio is 1.1. He reports no additional symptoms and the remainder of his laboratory workup is unremarkable. Leg pain and swelling are decreased.
Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec193a_96e1_2dc4_853d_1b464ac8c804_MD0002_00 This patient's presentation suggests non-immune heparin-induced thrombocytopenia (HIT), also known as type 1 HIT. Non-immune HIT occurs as an immediate (usually within 48 hours), mild, and transient effect of heparin on platelets. The platelet count rarely drops to <100,000/mm³ and recovers spontaneously regardless of heparin continuation or discontinuation. The pathophysiology of type 1 HIT is unknown. However, it is not associated with an increased thrombosis risk and is not clinically significant. Thus, heparin therapy should not be discontinued in these patients. ³ Type 2 HIT is an immune-mediated disorder that results in thrombocytopenia 5-10 days (or ≤1 day with prior heparin exposure) after heparin therapy initiation. Diagnosis is confirmed with serotonin release assays (preferred), heparin-induced platelet aggregation assays, or solid phase immunoassays with ELISA for heparin-PF4 complexes. The 4Ts, a pretest clinical score, has been developed to predict the probability of HIT. Based on this system, this patient's score is only 2 and suggests a low probability. Observation and continuation of heparin therapy are therefore recommended. 4Ts, a pretest clinical score (Choices A, C, and D) This patient has no prior exposure to heparin products, and the timing of the drop in platelet counts is not suggestive of immune-mediated HIT. Thus, checking for heparin-PF4 antibodies is not recommended. Similarly, argatroban (direct thrombin inhibitor) is indicated only in patients with intermediate to high pre-test probability of type 2 HIT. Educational objective: Type 1 heparin-induced thrombocytopenia is a non-immune-mediated thrombocytopenia due to an immediate (within 48 hours) reaction to heparin therapy. Platelet counts rarely drop to <100,000/mm³ and usually recover spontaneously regardless of heparin continuation or discontinuation. ³ __________ References: How I treat heparin-induced thrombocytopenia. (http://www.ncbi.nlm.nih.gov/pubmed/22246036)

A 54-Year-Old Man Comes to the Emergency Department with Pain