Heparin Induced Thrombocytopenia
Incidence- 1% to 3% of postoperative patients
Only 50% of anti-PF4/heparin + patients have “true” HIT ( platelet-activating IgG antibodies)
Risk factors – Females, postoperative>medical, prophylactic doses > therapeutic
Types-
•Delayed HIT- thrombocytopenia occurs several days after a brief exposure to heparin or worsens despite stopping heparin
•Spontaneous HIT syndrome- knee replacement surgery (perhaps because of release of heparin-like glycosaminoglycans from knee cartilage) and infection.
•Rapid-onset HIT - count fall occurs abruptly after restarting UFH or LMWH- due to pre-existing Abs
Clinical spectrum –
•The platelet count fall usually begins 5–10 days after the initiation
•Highly prothrombotic condition may involve the following scenarios-
•Venous- deep vein thrombosis and/or pulmonary embolism
•Arterial- aortic and iliofemoral arterial thrombosis, stroke, or myocardial infarction
•Necrotizing skin lesions at the sites of injection
•Unexplained hypotension or abdominal pain in a patient with HIT suggests bilateral adrenal hemorrhagic infarction, 2ₒ to adrenal vein thrombosis – characteristic feature
Differential diagnosis- Post op case with Low Plt + Thrombotic spectrum
•Sepsis- Fever + , Cultures +
•DIC – FDP / D Dimer +
•HIT- CL/F 5-10 days after heparin dosing
Treatment –
•Stop all heparin
•Alternative Anticoagulants-
•Indirect Factor Xa Inhibitors – preferred but off label use- due to direct Xa monitoring
•DTIs- widely used and approved. Disadv -affects APTT and risk of underdosing due to HIT induced DIC independently elevating APTT, also at risk rebound hypercoagulability
•Overlap Anticoagulant with warfarin after platelet count >150
•Platelet transfusions indicated only if bleeding/ <20,000 (DIC)