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HIT (Heparin-Induced Thrombocytopenia)

 

 

Background 

 

  • Severe immune-mediated disease from exposure to heparin causing thrombosis (venous & arterial) & thrombocytopenia

    • d/t formation of IgG antibodies against heparin-platelet factor 4 complexes resulting in plt activation & consumption, & activation of multiple prothrombotic pathways

  • Typically see ↓ plts by >30%, 5-10 days after heparin started

  • Plts rarely drop <20

  • Risk UFH > LMWH

  • 4 Ts scoring system (pre-test probability):

    • Thrombocytopenia/↓ plts (Nadir ≥20, 50% drop)

    • Timing of plts ↓ (5-10 days)

    • Thrombosis

    • OTher causes ruled out (periop: sepsis, shock +/- mechanical circulatory support, DIC)

  • Dx based on detection of PF4 antibodies & functional HIT assay

    • Note: can take several days to get assay results; if strong suspicion, tx as HIT until proven otherwise

  • Mortality ~10-20%

 

 

Considerations 

 

  • Acute HIT:

    • Intraop anticoagulation during CVS surgery in patients w/ active HIT

      • Bivalirudin - requires modification of perfusion technique during CPB

        • May have excess bleeding (esp if impaired renal fxn/complex cardiac surgery)

      • Heparin + reversible antiplatelet

      • Periop plasmapheresis to reduce HIT antibody burden

      • High-dose IVIG + ultra short acting plt inhibitor (ex cangrelor) during CPB to facilitate heparin use

  • Prior HIT:

    • Delay non-urgent surgery >1 month after dx where possible

    • May require bridging anticoagulation (ex argatroban) if on warfarin/DOAC

    • Short term heparin tx may be possible if remote hx of HIT

  • Neuraxial techniques contraindicated w/ argatroban, bivalirudin

 

 

Prevention

 

  • Avoid heparin where possible

  • Use LMWH instead of UFH where possible

  • Monitor plt counts daily in high risk patients

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Management

 

  • Stop all heparin exposure

  • Treated w/ direct thrombin inhibitor (DTI) (ex argatroban, bivalirudin)

    • Fondaparinux another option

    • May transition to warfarin or DOAC for several months d/t ↑ risk of thrombosis

    • If refractory to DTIs, can consider IVIG or plasmapheresis​​

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References

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  • Andreas Koster, Michael Nagler, Gabor Erdoes, Jerrold H. Levy; Heparin-induced Thrombocytopenia: Perioperative Diagnosis and Management. Anesthesiology 2022; 136:336–344 doi: https://doi.org/10.1097/ALN.0000000000004090

  • Gruel Y, De Maistre E, Pouplard C, Mullier F, Susen S, Roullet S, Blais N, Le Gal G, Vincentelli A, Lasne D, Lecompte T, Albaladejo P, Godier A; Members of the French Working Group on Perioperative Haemostasis Groupe d’intérêt en hémostase périopératoire GIHP. Diagnosis and management of heparin-induced thrombocytopenia. Anaesth Crit Care Pain Med. 2020 Apr;39(2):291-310. doi: 10.1016/j.accpm.2020.03.012. Epub 2020 Apr 13. PMID: 32299756.

 

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