Perioperative Management of Oral Anticoagulation

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Perioperative Management of Oral 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

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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 gt45 minutes)
• Low include non-major operations and procedures
  (lasting lt45 minutes)
• Perioperative anticoagulants
• 2-day period 2 to 4 for major surgery
• 0 to 2 for non-major
  surgery.

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Thromboembolic risk when discontinuing OAC
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Procedural Bleeding Risks
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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.

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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.

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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.

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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.

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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.

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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.

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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)

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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)

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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 1224
  hours after
• surgery once hemostasis is achieved
• 4. Discontinue LMWH when INR in therapeutic range
  (1.9)

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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

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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).

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Thanks for your attentions !