Perioperative Management of Oral Anticoagulation

Ri Ri 陳信宏陳信宏

ReferencesReferences

Perioperative Management of Oral Anticoagulation

Clinics Geriatric Medicine 22 (2006) 199– 213 Perioperative bridging therapy for the at-risk patient on chroni

c anticoagulation

Disease-A-Month 01-FEB-2005; 51(2-3): 183-93Disease-A-Month 01-FEB-2005; 51(2-3): 183-93

Introduction(1)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)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 perioperative bridging 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 acut

e 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 episod

e 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 anticoagulat

ion － not use bridging therapy.

Arterial thromboembolism

Nonvalvular atrial fibrillation (NVAF): Average risk of systemic embolism － 4.5%/y

ear in the absence of OAC. The CHADS2 Score(estimate expected stroke r

ate 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 p

rostheses 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 procedur

es or trauma Use of concomitant antiplatelet and nonsteroidal antiinflamma

tory medications.Procedure: High :include major operations and procedures (lasting >45 mi

nutes) 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.

Thromboembolic risk when discontinuing OAC

Procedural Bleeding Risks

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 app

roximately 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 appro

ximately 60 hours after the last dose of

warfarin.

Unfractionated heparin (UFH)

Advantage: A short half-life(60 minutes) easily reversed (by protamine sulfate)

Disadvantage:Disadvantage: Intravenous administration necessitates hospita

lization 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 risk

s 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)

SummarySummary OAC should be discontinued at least 4 days prior to t

he surgical intervention or procedure Heparin (either UFH or LMWH) initiated at least 2 da

ys 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

SummarySummary

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).

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