IS IT HIT OR HAT? M&M Conference 3/28/02

HAT Mild thrombocythopenia 100K- 130K Incidence: 25% 1-4 days after starting heparin Non immune-mediated (direct interaction between Heparin and platelet) Non thrombogenic Thrombocythopenia resolves after heparin discontinuation

HIT Un expected drop in platelet count Less than 100,000 And about 50% of base line Incidence: 1% to 3% on UFH On Heparin for at least 5 days OR Was on Heparin the last 3 months More with UFH than with LMWH Patient are at high risk of clothing NOT bleeding!

Pathophysiology Heparin has an affinity to PF4 which is found in platelet  granules Heparin-PF4 compleax induce IgG reaction IgG-heparin-PF4 complex attaches to platelet leading to aggregation (cloth)  more PF4 production and so on 80% cross reactivity with LMWH

Clinical manifestation HITTS in 25% VTE > ATE (4X) ATE Stroke. & Limb, bowel, splenic infarction VTE DVT & PE Acute HIT fever, N/V, chest pain Sub acute asymptomatic Delayed: accumulative risk of developing a cloth is 50% in one month

Diagnosis Clinical! Lab tests

Treatment All sources of heparin should be discontinued D/C H2 blockers, quinines and reassess the need for Abx HIT: Danaparoid Lepirudin or Bivalirudin DON’T use warfarin Or LMWH