- Heparin Induced Thrombocytopenia
Link:inc.sagepub.com/content/11/1/20.full.pdf
- Immune reaction to the administration of heparin
- Leads to arterial and venous thrombosis
- Formation of complexes with platelet factor 4 (PF4), triggers a antibody-mediated reaction
- HIT
- Type 1
- Non-immune type
- Occurs in the first few days of treatment
- Platelets usually don't fall below 100
- Recovers spontaneously even if heparin continued
- Type 2
- Immune type
- Typically begins after 5/7
- 10x commoner if recieving UFH vs LMWH
- Classically present with platelets <100 or drop of 50%
- Severe thrombocytopenia <15 is rare
- Platelet count recovers on days 2-3 on cessation of heparin treatment
- Diagnosis
- Clinical suspicion
- HIT antibodies screen (PF4)
- Platelet activation assay
- Treatments
- Stop heparin
- Start alternative anticoagulant (Danaparoid)
- Continue alternative until platelet count has recovered
- Start warfarin after this period
- Stop alternative anticoagulant after 5/7 once INR therapeutic
- Do not re-challenge with heparin within 100 days
- Prophylactic transfusions of plts relatively contraindicated
- 4T scoring system
- Category Observed
- Thrombocytopenia
- >50% fall or 20-100
- 30-50% fall or 10-19
- Less than 30% fall or <10
- Timing of fall in platelets
- Day 5-10 (or day 1 if heparin exposure in past 1/12
- Beyond 10/7 or 1 day if heparin in past 30-100/7
- Thrombosis or other sequale
- Proven thrombosis or skin necrosis
- Recurrent or silent thrombosis
- Other cause