الفهرس 
Physiology of Coagulation SystemOnly 14 pages are availabe for public view
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Abstract
Today’s understanding of coagulation is time-based .At the site of injury, tissue factor is expressed and binds to FVIIa, which circulates in minute quantities in its activated form, activating small quantities of FXa, which produces small amounts of thrombin (FIIa). By several positive feedback-loops, the generation of thrombin is amplified and propagated. When thrombin generation is maximal, fibrin monomers are formed.
Indications and thromboprophylaxis regimens are reviewed, including the use of recently introduced drugs such as fondaparinux and (xi)melagatran. The impact of such treatment on patients undergoing regional anaesthesia are outlined.
Diagnostic procedures and treatment regimens for patients with pre-existing or intraoperative coagulation defects are increasingly challenging and these are discussed in detail.
The perioperative management of patients receiving anticoagulation agents can be problematic. It is important that the benefit of surgery is first weighed against the risk of altering the anticoagulation regimen. where doubt exists, there should be a discussion involving the physician managing the anticoagulation, the surgeon and the anaesthetist about the risks and benefits of continuing the anticoagulation agents.
It may also be wise to involve the patient in the decision-making process and to consider an individual plan for complex situations. A multidisciplinary approach helps to manage the perioperative anticoagulation therapy safely and effectively
In the patient requiring urgent surgery, the options to treat an elevated INR are fresh frozen plasma and prothrombin concentrate complex. Vitamin K takes 1-2 days to achieve the target INR and is considered an adjunct in this setting. In the case of semi-urgent surgery, vitamin K can reverse the INR in 1-3 days. Oral administration is preferred, and the dose is based on the INR at presentation.
In elective procedures, Coumadin can be discontinued 5 days prior to surgery to achieve a target INR of 1.3 or less. Bridging therapy with unfractionated heparin or low molecular weight heparin is indicated in patients with a high or intermediate risk of thromboembolism. In patients requiring surgery with a high risk of bleeding, there may be a role for a temporary IVC filter. In general, Coumadin can be restarted on the first post-operativeevening at the maintenance dose. Bridging therapy may be used in post-operatively until the INR is therapeutic.