Is heparin (unfractionated heparin) safe to use in patients with thrombocytopenia (low platelet count)?

From the Guidelines

Heparin is not safe for patients with low platelets, especially if they have heparin-induced thrombocytopenia (HIT), and alternative anticoagulants should be considered. According to the most recent and highest quality study available, which is from 2018 1, for patients with lower-risk events, a dose-modification strategy using 50% or prophylactic-dose low molecular weight heparin (LMWH) may be considered, but anticoagulation is generally withheld for patients with platelet counts of < 25,000/μL.

Key Considerations

• HIT is a serious immune-mediated reaction where heparin causes antibody formation against platelet factor 4, leading to platelet activation, consumption, and potentially life-threatening thrombosis despite low platelet counts 1.
• If a patient develops HIT or is suspected to have it, all heparin products should be immediately discontinued, and alternative anticoagulants such as direct thrombin inhibitors (argatroban, bivalirudin) or fondaparinux should be used instead 1.
• For patients with low platelets from other causes, the decision to use heparin requires careful risk-benefit assessment, and generally, platelet counts below 50,000/μL increase bleeding risk with anticoagulation, and counts below 20,000/μL present significant danger 1.
• The underlying cause of thrombocytopenia should always be investigated and addressed while managing anticoagulation needs.

Management Strategies

• Alternative anticoagulants such as fondaparinux may be used, which has been shown to have a lower risk of HIT and does not require platelet count monitoring 1.
• Dose-modified anticoagulation may be considered for patients with proximal VTE in whom maintenance of a transfused platelet target is difficult or impractical 1.
• Reduced doses with close monitoring may be considered, or alternative strategies might be employed for patients with low platelets from other causes 1.

From the FDA Drug Label

If the platelet count falls below 100,000/mm3 or if recurrent thrombosis develops, promptly discontinue heparin, evaluate for HIT and HITT, and, if necessary, administer an alternative anticoagulant. Thrombocytopenia in patients receiving heparin has been reported at frequencies up to 30%. Obtain platelet counts before and periodically during heparin therapy. Monitor thrombocytopenia of any degree closely

Heparin is not safe with low platelets. The FDA recommends discontinuing heparin if the platelet count falls below 100,000/mm3 due to the risk of heparin-induced thrombocytopenia (HIT) and thrombosis (HITT) 2.

• Key considerations:
  • Monitor platelet counts before and during heparin therapy
  • Discontinue heparin if platelet count falls below 100,000/mm3
  • Evaluate for HIT and HITT if thrombocytopenia or thrombosis occurs
  • Consider alternative anticoagulants if necessary 2

From the Research

Heparin Safety with Low Platelets

• Heparin-induced thrombocytopenia (HIT) is an immune-mediated disorder that can occur in patients receiving heparin, characterized by a low platelet count and an increased risk of thromboembolic complications 3.
• The use of heparin in patients with low platelets is not recommended, as it can exacerbate the condition and increase the risk of thrombosis 4, 5.
• Alternative anticoagulants, such as argatroban, bivalirudin, and fondaparinux, can be used in patients with HIT or low platelets 3, 4, 6.
• The management of HIT requires a stepwise approach, including the use of risk-stratification tools and laboratory assays to diagnose the condition, and the selection of non-heparin anticoagulation to manage the patient's increased thrombotic risk and possible concurrent increased bleeding risk due to thrombocytopenia 5, 6.
• The evidence for the use of direct oral anticoagulants (DOACs) in patients with HIT is limited, and their use should be reserved for clinically stable patients without severe thrombotic complications 4, 6.

Key Considerations

• Heparin and all heparin-containing products should be discontinued in patients with suspected or confirmed HIT 3, 5.
• Warfarin therapy should not be initiated until the platelet count has recovered and the patient is systemically anticoagulated 3.
• Vitamin K should be administered to patients receiving warfarin at the time of diagnosis of HIT 3.
• The use of inferior vena cava filters or platelet transfusion may result in greater harm than not using these approaches 6.