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Surgery in patients on anticoagulants |
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Elective surgery in patients on warfarin:
Minor surgical procedures can be performed if INR < 2
Major surgical procedures require lowering of the INR to < 1.5. The need for continuing anticoagulation depends on their risk of thrombo-embolism.
High risk for thromboembolism: Such patients will need bridging anti-coagulation therapy
Ø Protein C deficiency
Ø Protein S deficiency
Ø Antithrombin III deficiency
Ø Homozygous factor V Leiden mutation
Ø Antiphospholipid-antibody syndrome (1,2)
Intermediate risk for thromboembolism: bridging anticoagulation therapy may be required
Low risk for thromboembolism: bridging anticoagulation therapy not advised
Bridging anticoagulation therapy: Anticoagulation can be maintained either by heparin infusion or Low molecular weight heparin.
Bridging by using heparin: Discontinue warfarin 4-5 days before the day of surgery. Heparin should be started when the INR is < 2.5 in high risk patients (for example, in patients with mitral mechanical valves) and < 2.0 in patients with aortic mechanical valves. The activated partial thromboplastin time (aPTT) should be checked and prolonged to 1.5–2.0 of the control value. Heparin should be continued until six hours before surgery and resumed 6–12 hours after surgery, when surgically feasible. Oral anticoagulation can be resumed 1–2 days after surgery and once INR is > 2, heparin can be discontinued. (1,2,3)
Bridging by using low molecular weight heparin: Discontinue warfarin 4-5 days before the day of surgery. If INR< 2.5 in high risk patients (for example, in patients with mitral mechanical valves) and < 2.0 in patients with aortic mechanical valves, start low molecular weight heparin in therapeutic doses. (Enoxaparin 1.5 mg/kg subcutaneously every 24 hours. Continue low molecular weight heparin until 24hrs before procedure. Restart low molecular weight heparin 12-24 hours after procedure and when haemostasis is established and restart warfarin night of or day after procedure. (1,2,3)
Emergency Surgery in patients on warfarin:
Urgent reversal of anticoagulation is required in patients with raised INR who need emergency surgery. Immediate reversal can be achieved by FFP transfusion, however for semi-urgent procedure (that can wait >12hrs) IV Vitamin K can be tried in first instance.
Fresh-frozen plasma(FFP) if given at the dose of 15 mls/kg body weight can reverse anticoagulation immediately without causing any resistance to warfarin. However, it is associated with the risks of transfusion, and its effects are short-lived.
After transfusion ensure that INR < 1.5 before starting surgery. If necessary more FPPs will be required. (1,2)
Vitamin K: smaller doses of IV vit K (1.25 – 2.5 mg) should be used to avoid postoperative resistance to warfarin. One study found that the median time to reversal of anticoagulation after a 1-mg IV vitamin K was approximately 27 hours (range 0.7–147 hours). (1,2)
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