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HEPARIN INDUCED THROMBOCYTOPENIA (HIT)

Haematology

HEPARIN INDUCED THROMBOCYTOPENIA (HIT)

1. HIT Type I develops within 1-2 days of initiation of heparins. HIT-1 is common and of no clinical consequence.

2. HIT Type II is an immune response where anti-H-PF4 antibodies develop against the complex of heparin and platelet factor 4 resulting in arterial and venous thromboemboli.

3. HIT-II starts 4-10 days after initiation of treatment in 1-3% of patients receiving UFH and 0.5% of patients receiving LMWH.

4. Always monitor the platelet count in patients on heparin.

5. If plt drop > 50% and/or thromboembolic symptoms develop, stop using heparin (even heparin flushes) and commence direct thrombin inhibitor, such as dextran, lepirudin or argatroban.

6. Start warfarin when the platelet count recovers to > 100,000 (and continue the thrombin inhibitor) because there is a long-term risk of clots as long as the antibodies are present.


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REFERENCES

1. Wilkinson, I. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press.
2. Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
3. Image: no reference available.

Ⓒ A. Manickam 2018

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