Heparin-induced thrombocytopenia
Description
- An antibody-mediated PROTHROMBOTIC drug reaction that happens to lower the platelet count
- *The thrombocytopenia is the clue; thrombosis is the disease*
- Thrombosis in up to 50% if heparin is simply stopped without alternative anticoagulation
- Venous > arterial (~4:1) - DVT/PE, but also limb ischaemia, stroke, MI, adrenal haemorrhagic infarction, skin necrosis at injection sites
| Type I (non-immune) | Type II (immune) = "HIT" | |
|---|---|---|
| Mechanism | Direct platelet aggregation | Anti-PF4/heparin IgG |
| Onset | 1-4 days | 5-10 days |
| Platelet nadir | >100, mild | ~50-70, or a 50% fall |
| Thrombosis | No | Yes, high risk |
| Action | Continue heparin | Stop all heparin, anticoagulate with a non-heparin agent |
- Bleeding is distinctly unusual - a bleeding patient with thrombocytopenia on heparin usually has something else
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