Anticoagulation

ANTICOAGULATION

Patients with mechanical prosthetic heart valves require anticoagulation, which is currently accom-plished with warfarin. Aspirin is also indicated in this population, as well as in patients with bio-prosthetic valves, to prevent thrombus formation. Warfarin is sometimes also used initially for mitral bioprosthetic valves ( Table 21–16).

Patients with prosthetic valves often present for noncardiac surgery that will require temporary discontinuation of anticoagulation. The ACC/AHA guidelines indicate that patients at low risk of throm-bosis, such as those with bileaflet mechanical valves

in the aortic position with no additional problems (eg, no AF or no hypercoaguable state) can discon-tinue warfarin 48–72 hours preoperatively so that the INR falls below 1.5. In patients at greater risk of thrombosis, warfarin should be discontinued and heparin, either unfractionated or low molecular weight, started when the INR falls below 2.0. Heparin can be discontinued 4–6 hours prior to surgery and then restarted as soon as surgical bleeding permits, until the patient can be restarted on warfarin therapy. Fresh frozen plasma may be given, if needed, in an emergency situation to interrupt warfarin therapy. Vitamin K should not be administered, as it could potentially lead to a hypercoaguable state. Anesthesia staff should always consult with the patient’s surgeon and the physician responsible for prescribing the anticoagulation before adjusting anticoagulation or antiplatelet regimens perioperatively.