Be alert for HIT in presentation and patient history[30]

Clinical case history

HIT: Be Aware
A 60-year-old woman underwent repair of an aortic aneurysm with aortic valve replacement. Postoperatively the patient received LMWH followed by warfarin therapy.

HIT: Be Alert
She presented to the emergency department 33 days after initial heparin exposure with proximal-thigh deep vein thrombosis despite a prothrombin international normalized ratio (INR) of 4.2. Platelet count was 420,000/mcL.

HIT: Take Action
Immediately after receiving an intravenous heparin bolus, she developed dyspnea, tachycardia, and hypotension. Hours after bolus dose, platelet count dropped to 47,000/mcL. She needed therapy with a direct thrombin inhibitor immediately. The patient later tested positive on ELISA for heparin antibody.

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Questions to Ask

Has the patient been hospitalized recently? If so, was the patient likely to have received heparin?

Many patients seen in the ED have recently been hospitalized. Hospitalization generally includes exposure to heparin (e.g., catheter flushes, coated stents, infusions, LMWH. Patients may have antibodies from prior exposure.

Has the patient been using LMWH at home?

UFH carries the greatest risk of HIT but HIT also results from the use of LMWH.[33,34]

What is the platelet count?

Clinicians should suspect HIT any time the platelet count drops to less than 50% of baseline or is less than 150,000/mcL.[2]

Is there a new thrombosis present?

Formation of thrombi is a hallmark of HIT with or without thrombosis as HIT is a hypercoagable state.[30] The most common thromboembolic complications of HIT are DVT, PE, MI, and stroke. These manifestations may be clinically overt or may not be seen unless further diagnostic evaluation is performed.[9,18]