Heparin rebound

Heparin rebound may occur several hours after heparin has been neutralized (usually 8-9 hr after protamine administration). Heparin rebound occurs most often after arterial or cardiac surgery. 

Di Nisio M, Bijsterveld NR, Meijers JC, Levi M, Buller HR, Peters RJ. Effects of clopidogrel on the rebound hypercoagula-ble state after heparin discontinuation in patients with acute coronary syndromes. J Am Coll Cardiol 2005 46 I 582-1583,... 

Two types of thrombocytopenia associated with heparin use have been described. " As many as of 25% of patients receiving heparin therapy develop a benign, mild reduction in platelet counts referred to as non-immune-mediated heparin-associated thrombocytopenia (HAT) or previously called HIT type 1. HAT produces a transient fall in platelet count that occurs early, typically between days 2 and 4, during the course of therapy. The degree of thrombocytopenia is usually mild, with platelet counts rarely going below 100,000/mm . It is not necessary to discontinue heparin therapy in these patients because platelet counts generally rebound to baseline values despite continued use. The exact mechanism of HAT is unknown, but it may be the result of platelet aggregation, a dilutional effect, or diminished platelet... 

B. A rebound effect caused by heparin may occur within 8 hours of protamine administration. 

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