Supervisors info:
Παρασκευή Ματσώτα, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Αργυρή Γιαλεράκη, Επίκουρη Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Στυλιανή Κοκκόρη, Επίκουρη Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Extracorporeal circulation ( or cardiopulmonary bypass - CPB) is a procedure during which the blood of the patient is drained from the right side of the heart, oxygenated through an artificial device and pumped back to the aorta. Conventional CPB is used for cardiac surgery, while another form, the extracorporeal membrane oxygenation (ECMO) is used for respiratory support (VV ECMO) or cardiac support (VA ECMO).
Heparin, a polysaccharide, potentiate thrombin inhibition by binding with antithrombin III (ATIII) and is the anticoagulant of choice for CPB, mostly because of its easy neutralization with protamine. Heparin exposure can induce the formation of pathogenic IgG antibodies that cause platelet activation by recognizing complexes of platelet factor 4 (PF4) and heparin on platelet surfaces and thus resulting in thrombocytopenia and thrombin generation with increased risk of thrombosis. The disorder is called heparin induced thrombocytopenia (HIT) and its initial clinical diagnosis is based on a scoring system (which includes multiple variables) and then confirmed by laboratory testing. Treatment of HIT includes the immediate stop of heparin and the use of alternative anticoagulants, such as direct thrombin inhibitors (argatroban, lepirudin, bivalirudin), the heparinoid (danaparoid) and fondaparinux.
Specific for the post-CPB patients, who had cardiac surgery, is a scoring system, which assesses, among others, the duration of CPB; this is necessary because of the thrombocytopenia caused as a side effect of CPB. A patient with an historic of HIT but with undetectable antibodies can be safely re-exposed to heparin for cardiac surgery with CPB. However, if an urgent cardiac surgical procedure with CPB must be performed while HIT antibodies remain detectable, alternative anticoagulant agents, such as the direct thrombin inhibitors, lepirudin, argatroban and bivalirudin, must be used, with the last being the drug of choice. Especially for ECMO, it is recommended the delivery of lower dose infusion of argatroban or bivalirudin, compared with conventional CPB.
Keywords:
Extracorporeal circulation, Heparin, Thrombocytopenia, Anticoagulant
