课件：使用抗凝剂患者实施椎管内麻醉处理原则.ppt

* * * * * 人们早就认识到内源性和外源性凝血系统并非是独立的两个系统。如：十二因子缺乏、前激肽释放酶和高分子量激肽原缺乏并不会引起出血，而八因子和九因子缺乏所引起的出血并不能为外源性凝血系统所代偿。同样，七因子缺乏所引起的出血也不能为内源性凝血系统所代偿。研究还进一步证实TF/VIIa复合物同时能够激活IX因子和X因子。这些现象都提示两个凝血系统是相互有关联的。 * Normally secreted from Mast and other cells Injectable is heparin agonist Both result in prevention of conversion of fibrinogen to fibrin Description: Protamine sulfate, a protein derived from fish sperm, is a chemical antagonist of heparin. Clinically, protamine is indicated for heparin overdose and is commonly used to neutralize heparin during extracorporeal circulation following dialysis, and arterial or cardiac surgery. Protamine was approved by the FDA in December 1948. Mechanism of Action: Protamine possesses weak anticoagulant effects when administered alone; however, upon contact with heparin, it forms a salt, neutralizing the anticoagulant effect of both drugs. Protamine, a strongly basic compound, forms complexes with heparin sodium or heparin calcium, which are acidic compounds. Formation of this complex can result in disruption of the heparin-antithrombin III complex responsible for the anticoagulant activity of heparin. The protamine-heparin complex does not possess anticoagulant properties. Protamines anticoagulant effect usually is clinically insignificant and is likely the result of thromboplastin inhibition, which diminishes thrombin activity. Pharmacokinetics: Protamine is administered via intravenous infusion. The onset of action is rapid, with neutralization of heparin evident within 5 minutes. The duration of action can persist up to 2 hours, depending on body temperature. The fate of the heparin-protein complex is unknown, but it appears to be partially degraded, with the release of heparin. * * Type II (immune) heparin-induced thrombocytopenia occurred in 2.7% of 332 hip surgery patients treated prophylactically with unfractionated SQ heparin for 5 or more days * * This has implications for in vitro clotting tests, as low molecular wt do not interfere with