High incidence of antibodies to protamine and protamine/heparin complexes in patients undergoing cardiopulmonary bypass

Abstract

Key Points• A single exposure to protamine and heparin during CPB is highly sensitizing; 29% of patients develop Abs to PRT/H complexes by day 30 after CPB.• PRT/H Abs share several features with platelet factor 4/ heparin Abs, including high titer formation after CPB, heparin dependence, antigen specificity, and platelet activation.Protamine is routinely used to reverse heparin anticoagulation during cardiopulmonary bypass (CPB). Heparin interacts with protamine to form ultralarge complexes that are immunogenic in mice. We hypothesized that patients exposed to protamine and heparin during CPB will develop antibodies (Abs) to protamine/heparin (PRT/H) complexes that are capable of platelet activation. Specimens from a recently completed prospective clinical trial (HIT [for heparin-induced thrombocytopenia] 5801 study; n 5 500) of CPB patients were examined for PRT/H Abs at baseline, at time of hospital discharge (between days 3 through 7), and 30 days after CPB. PRT/H antibody features were characterized and correlated with adverse cardiovascular outcomes. We found a high incidence of PRT/H antibody formation (29%) in patients undergoing cardiac surgery. PRT/H Abs were of high titer (mean titer 1:14 744), showed heparin-dependent binding, and activated platelets in the presence of protamine. PRT/H Abs showed no cross-reactivity to platelet factor 4/heparin complexes, but were cross-reactive with protamine-containing insulin preparations.In the absence of circulating antigen at day 30, there were no complications of thrombocytopenia, thrombotic events, or long-term cardiovascular events. These studies show that Abs to PRT/H occur commonly after cardiac bypass surgery, share a number of serologic features with HIT Abs, including platelet activation, and may pose health risks to patients requiring drug reexposure. (Blood. 2013;121(15):2828-2835 IntroductionProtamine sulfate is currently the only therapeutic agent approved by the US Food and Drug Administration for reversal of heparin anticoagulation. It is the mainstay of therapy in cardiopulmonary bypass (CPB), where rapid reversal of heparin anticoagulation is essential for achieving surgical hemostasis. However, protamine use in CPB is associated with the development of a number of adverse effects, ranging from minor hemodynamic instability to life-threatening anaphylactic complications and fatal cardiovascular collapse. [1][2][3][4] Major adverse reactions related to protamine exposure have been reported to occur in 2.6% of cardiac surgical procedures, 3 and these complications of protamine therapy are highly associated with adverse postoperative outcome. 5,6 Protamine, a highly basic protein, binds heparin through charge interactions and sequesters heparin from its catalytic effects on antithrombin. Recently, we have shown that heparinbinding proteins such as protamine and lysozyme interact with heparin in a charge-dependent manner to form protamine/heparin (PRT/H) or lysozyme/H ultralarge complexes that are immunogenic in mice. 7 In this preliminary clinical...

Approach to the Diagnosis and Management of Drug-Induced Immune Thrombocytopenia

“…Antibodies bind to the PF4/heparin complex by their Fab portion and to the surface of platelets and monocytes by their Fc portion causing intense platelet activation and release of procoagulant microparticles [35,36]. A similar syndrome has recently been described following exposure to protamine used to reverse the effects of heparin after cardiac surgery [37][38][39]. Protamine binds heparin to form antigenic complexes that are immunogenic in mice and humans.…”

“…Protamine binds heparin to form antigenic complexes that are immunogenic in mice and humans. These complexes bind IgG antibodies which activate platelets via FcγRIIa leading to thrombocytopenia and potentially thrombosis [38,39]. The mechanism underlying HIT is distinct from other forms of DITP and the clinical presentation is characterized by thrombosis rather than bleeding [40] (Table 2).…”

Małopłytkowość indukowana protaminą — nowy problem czy inny typ małopłytkowości poheparynowej?

“…Taki schemat leczenia wiąże się z zagrażającymi życiu działaniami niepożądanymi, szczególnie powikłaniami immunologicznymi [3]. Infuzja protaminy może prowadzić do formowania się przeciwciał przeciwko protaminie (PRT abs) i kompleksowi protamina-heparyna (PIT abs), które aktywują płytki krwi poprzez receptor FcγIIa, prowadząc do trombocytopenii [4,5]. Zarówno heparyna, jak i protamina wykazują udowodniony potencjał immunogenny, a kontakt krwi z silikonowymi drenami podczas CPB dodatkowo prowadzi do uwalniania szeregu mediatorów ostrych i przewlekłych reakcji immunologicznych.…”

“…Wynika to z faktu, że odnotowano zmiany w liczbie płytek krwi po podaniu samej protaminy [6]. Połączenie protaminy i heparyny również indukuje trombocytopenię, co powoduje trudności z ustaleniem etiologii zjawiska [4,5]. Najnowsze wyniki badań wskazują, że odpowiedź przeciwciał ukierunkowanych na kompleksy protamina-heparyna różni się od wcześniej opisywanych reakcji na samą protaminę.…”

Rationale and design of a phase III safety trial of idarucizumab in children receiving dabigatran etexilate for venous thromboembolism

“…Current standards of care for reversal of anticoagulant effects are suboptimal and have shown undesired effects 6, 7, 8, 9, 10, 11…”