You’re asked to consult on a post-operative cardiothoracic patient with low platelets.
You consider the diagnosis of heparin-induced thrombocytopaenia (HITs).
HITs is caused by autoantibodies to heparin complexed with:
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You consider the diagnosis of heparin-induced thrombocytopaenia (HITs).
HITs is caused by autoantibodies to heparin complexed with:
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Platelet factor 4 (PF4)
Exposure to heparins -> PF4-heparin complexes form -> autoantibodies form immune complexes -> complexes bind to platelets -> platelet destruction and activation
Exposure to heparins -> PF4-heparin complexes form -> autoantibodies form immune complexes -> complexes bind to platelets -> platelet destruction and activation
It occurs more commonly with heparin than enoxaparin.
The antibody-platelet complexes are thought to form more effectively with unfractionated heparins.
HITs typically occurs how many days after initiation of heparin?
The antibody-platelet complexes are thought to form more effectively with unfractionated heparins.
HITs typically occurs how many days after initiation of heparin?
5-10 days
This is reflected in 4 Ts score which is used to make a presumptive diagnosis and to expedite treatment.
Confirmation is by testing for the PF4-heparin antibody followed by functional assays.
This is reflected in 4 Ts score which is used to make a presumptive diagnosis and to expedite treatment.
Confirmation is by testing for the PF4-heparin antibody followed by functional assays.
The PF4-heparin immune-complexes bind to platelets leading to their activation.
What is the most common complication of HITs?
What is the most common complication of HITs?
Thromboses, both venous and arterial, which can be life-threatening.
The consequences include:
- skin necrosis at injection sites
- organ ischaemia
- limb gangrene
PE is the most common cause of death.
The consequences include:
- skin necrosis at injection sites
- organ ischaemia
- limb gangrene
PE is the most common cause of death.
Management is by ceasing all heparin and prescribing non-heparin anticoagulation to prevent clotting.
Which of the following anticoagulants is most appropriate in the initial phase?
Which of the following anticoagulants is most appropriate in the initial phase?
Use a non-heparin anticoagulant
- Direct thrombin inhibitors
- Xa inhibitors
Avoid warfarin which depletes protein C contributing to the prothrombotic state.
Patients should be labelled as allergic to heparins. Use non-heparin anticoagulants for future VTE prophylaxis.
- Direct thrombin inhibitors
- Xa inhibitors
Avoid warfarin which depletes protein C contributing to the prothrombotic state.
Patients should be labelled as allergic to heparins. Use non-heparin anticoagulants for future VTE prophylaxis.
Summary:
- HITs is caused by antibodies to PF4-heparin complexes
- Leads to platelet destruction and thrombosis
- Platelets drop within 5-10 days of starting heparin
- Cease heparin and use non-heparin anticoagulants to prevents thrombosis
- Lifelong avoidance of heparins
- HITs is caused by antibodies to PF4-heparin complexes
- Leads to platelet destruction and thrombosis
- Platelets drop within 5-10 days of starting heparin
- Cease heparin and use non-heparin anticoagulants to prevents thrombosis
- Lifelong avoidance of heparins
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