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Perioperative Management of Oral Anticoagulation. Ri 陳信宏. References. Perioperative Management of Oral Anticoagulation Clinics Geriatric Medicine 22 (2006) 199 – 213 Perioperative bridging therapy for the at-risk patient on chronic anticoagulation
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References • Perioperative Management of Oral Anticoagulation Clinics Geriatric Medicine 22 (2006) 199– 213 • Perioperative bridging therapy for the at-risk patient on chronic anticoagulation Disease-A-Month 01-FEB-2005; 51(2-3): 183-93
Introduction(1) • OAC therapy during surgery is associated with increased excessive operative bleeding. • Patients receiving long-term oral anticoagulant (OAC) therapy that requires temporary discontinuation for an elective surgical or invasive procedure. • Anticoagulation cessation, -increased risk of thromboembolism, especially in the postoperative period.
Introduction(2) • A management strategy for the at-risk patient on chronic OAC requiring temporary discontinuation for an elective surgical or invasive procedure. • Emphasis on the indications for use of perioperativebridging therapy. • The use of parenteral, short-acting anticoagulants such as unfractionated heparin (UFH) or low-molecular-weight-heparin (LMWH) in the perioperative period.
Thromboembolic and Bleeding Risks in the Perioperative Period • Thromboembolic risks: (1)Disease specific thromboembolic risks when discontinuing warfarin (2)Hypercoagulability associated with surgery. • Bleeding risks: (1) the patient (2) the use of anticoagulant therapy (3) the surgery or procedure
Thromboembolic Risk When Discontinuing Warfarin Venous thromboembolism (VTE): • The absence of OAC during the first month of an acute VTE event-Recurrence 40%/month • During the second and third month- Recurrence 10%/2month • After the 3 month treatment-15%/year • Surgery should be deferred following an acute episode of venous thromboembolism until patients have received at least 1 month, and preferably 3 months,of anticoagulation.
Venous thromboembolism • Surgery is performed within 1 month of an acute event, bridging therapy should be used while the INR is less than 2. • Within 1 and 3 months previously, patients are immobilized-bridging therapy • Treated with 3 or more months of anticoagulation-not use bridging therapy.
Arterial thromboembolism Nonvalvular atrial fibrillation (NVAF): • Average risk of systemic embolism -4.5%/year in the absence of OAC. • The CHADS2 Score(estimate expected stroke rate per 100 patient-years): • Moderate-risk patients have an adjusted stroke rate of up to 5.9% • High-risk patients have adjusted stroke rates of 8.5 to 18.2%.
Arterial thromboembolism Mechanical prosthetic cardiac valves (MHV) • In the absence of OAC, mitral position valve prostheses have an annualized thrombosis risk of 22% compared with an annualized risk of approximately 10 to 12% for aortic position valves. • The average rate of major thromboembolism in non-anticoagulated patients with mechanical heart valves is estimated to be 8%.
Previous thromboembolism • The single most important risk factor for ischemic stroke in patients with atrial fibrillation • Also an important risk factor in patients with prosthetic heart valve.
Hypercoagulability associated with surgery • Prothrombotic effect of major surgery and laparoscopic procedures-theoretically increase the postoperative VTE risk 100-fold. • A recent systematic review revealed a 10-fold greater risk of stroke than expected in patients not receiving perioperative anticoagulation.
Bleeding Risks Patient: • Previous history of bleeding, especially with invasive procedures or trauma • Use of concomitant antiplatelet and nonsteroidal antiinflammatory medications. Procedure: • High :include major operations and procedures (lasting >45 minutes) • Low : include non-major operations and procedures (lasting <45 minutes) Perioperative anticoagulants: • 2-day period : 2 to 4% for major surgery 0 to 2% for non-major surgery.
Clinical consequences • MHV thrombosis is fatal in 15% of patients • ATE: mortality -about 40% of events major disability -about 20% of events • VTE : mortality -approximately 6% major disability -approximately 5% or less in treated patients. • Postoperative major bleeding has a fatality rate of approximately 3%.
Perioperative Management Recommendations The Seventh American College of Chest Physician Consensus Conference: • Intermediate risk of thromboembolism-prophylactic (or higher) dose UFH or LMWH as perioperative bridging therapy • High risk of thromboembolism- full-dose UFH or LMWH • Low risk of bleeding- Continue warfarin therapy at a lower dose to maintain an INR of 1.3 to 1.5.
Perioperative bridging algorithm • Low risk of ATE or VTE: No heparin bridging preoperatively and only prophylactic doses of LMWH or UFH postoperatively in conjunction with resumption of warfarin.
Warfarin • INR starts to fall at approximately 29 hours after the last dose of warfarin • A half-life of approximately 22 hours • It is reasonable to start bridging therapy approximately 60 hours after the last dose of warfarin.
Unfractionated heparin (UFH) Advantage: • A short half-life(60 minutes) • easily reversed (by protamine sulfate) Disadvantage: • Intravenous administration necessitates hospitalization before surgery, • Inconvenient and expensive.
Low-molecular-weight-heparin (LMWH) • Allowed bridging therapy to be administered to outpatients. • Doses of LMWH that are recommended for treatment of venous thromboembolism are administered once or twice daily, generally for 3 days before surgery. • Required to determine whether the benefit of bridging therapy outweighs the associated risks of bleeding.
Perioperative bridging protocol Instructions regarding warfarin use: • 1. Stop warfarin at least 4 days prior to surgery • 2. Check INR 1 day prior to surgery If 1.5, proceed with surgery If 1.5 to 1.8, consider low-level reversal with Vitamin K If 1.8, recommend reversal with Vitamin K (either 1 mg SC or 2.5 mg PO) • 3. Recheck INR day of surgery • 4. Restart maintenance dose of warfarin the evening of surgery • 5. Daily INR until in therapeutic range (1.9)
Perioperative bridging protocol Instructions regarding IV UFH use • 1. Should start at least 2 days prior to surgery at therapeutic dose using a validated, aPTT-adjusted, weight-based nomogram (ie, 80 U/kg bolus dose IV followed by a maintenance dose of 18 U/kg/h IV) • 2. Discontinue 6 hours prior to surgery • 3. Restart no less than 12 hours postoperatively at the previous maintenance dose once hemostasis is achieved • 4. Discontinue IV UFH when INR is in therapeutic range (1.9)
Perioperative bridging protocol Instructions regarding LMWH use: • 1. Should start at least 2 days prior to surgery at BID therapeutic dose (ie, enoxaparin 1 mg/kg SC BID or dalteparin 100 IU/kg SQ BID) • 2. Discontinue at least 12 hours prior to surgery (if surgery is in early A.M. consider holding previous evening dose) • 3. Restart usual therapeutic dose within 12–24 hours after surgery once hemostasis is achieved • 4. Discontinue LMWH when INR in therapeutic range (1.9)
Summary • OAC should be discontinued at least 4 days prior to the surgical intervention or procedure • Heparin (either UFH or LMWH) initiated at least 2 days prior to the intervention. • Many experts-advocate preoperative therapeutic-dose UFH or LMWH for intermediate- to high-risk patients • Considerable disagreement -prophylactic dose, treatment dose, or no heparin bridging therapy should be initiated postoperatively in conjunction with resumption of OAC
Summary • OAC should be resumed at the usual maintenance dose within 24 hours of the procedure, preferably the same evening. • Heparin should be reinitiated within 24 hours of the procedure, provided that adequate hemostasis is achieved, and discontinued once the INR is in therapeutic range (1.9).