Summary
The clinical course of heparin-induced thrombocytopenia (HIT) may be separated into
five sequential phases: 1. suspected HIT, 2. acute HIT, 3. subacute HIT A, 4. subacute
HIT B, and 5. remote HIT. Each phase confronts the clinician with a unique set of
management questions. In this review, the phases of HIT are defined and key management
questions associated with each phase are discussed. Among patients with Suspected
HIT, I use the 4Ts score to determine which patients have a sufficiently high probability
of HIT to justify discontinuation of heparin and initiation of a non-heparin parenteral
anticoagulant. An algorithm for selecting an appropriate non-heparin anticoagulant
based on the patient’s clinical stability, renal and hepatic function, drug availability,
and physician comfort is provided. In patients with Acute HIT, I generally avoid prophylactic
platelet transfusion and inferior vena cava filter insertion because of a potential
increased risk of thrombosis. I perform 4-limb screening compression ultrasonography.
In patients with symptomatic thromboembolism or asymptomatic proximal deep-vein thrombosis,
I treat with anticoagulation for three months. In patients without thrombosis, I discontinue
anticoagulation upon platelet count recovery. I do not transition patients to an oral
anticoagulant until platelet count recovery (i. e. Subacute HIT A). I increasingly
choose direct oral anticoagulants over vitamin K antagonists in this setting because
of their greater convenience and safety. In Subacute HIT B and Remote HIT, I use heparin
for cardiovascular surgery, whereas I use bivalirudin in patients with Acute HIT and
Subacute HIT A in whom surgery cannot be delayed.
Keywords Heparin-induced thrombocytopenia - management - treatment
