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Keywords:

  • INR;
  • warfarin;
  • thromboembolism

INTRODUCTION

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

Warfarin has been increasingly used to treat or prevent thromboembolic events, and it is estimated that more than a million people in North America are taking this drug [1]. The most common indications for warfarin therapy are atrial fibrillation, prophylaxis against recurrent venous thrombosis, or the presence of a mechanical heart valve [2]. Patients on oral anticoagulants can present management problems when attending for urological surgery. Their risk of haemorrhage is higher, given their anticoagulated state, and to interrupt their warfarin therapy may place the patient at increased risk of a thromboembolic event. There is no consensus of opinion on the appropriate management of these patients before and after surgery. Despite this, there remains a wide array of ‘recommendations’ as to how best to manage their anticoagulation. Depending on the indication for anticoagulation, this ranges from stopping warfarin several days before surgery and recommencing it immediately afterward, to admitting the patient several days before surgery to start intravenous unfractionated heparin to ensure that the patient remains anticoagulated. In addition to this, there is increasing usage of low molecular weight unfractionated heparins (LMWH) as an alternative method of perioperative anticoagulation in certain groups of chronically anticoagulated patients [3].

In this article we review existing publications on the management of anticoagulated patients who are scheduled for elective surgery, these having been identified by a Medline search using the criteria of ‘surgery’ and ‘anticoagulation’. Based on these reports we make recommendations for managing anticoagulated patients, considering the indications for warfarin therapy and the procedure the patient is scheduled to undergo.

INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

The international normalized ratio (INR) is the recommended method for reporting prothrombin time results to control oral anticoagulation [4]. The dose of warfarin is adjusted to maintain the INR within a given therapeutic range, which for warfarin depends on its indication for usage. Clinicians regulate the dosage of warfarin according to the INR, aiming for a target INR, conventionally regarded as the midpoint of the range. A study by Rose [5] revealed that only half of INRs in a population of patients taking warfarin are usually within the target range at any given time. Given this it was felt that rather than adopting a range, a target INR should be assigned to each indication for warfarin therapy, as this would enable a tighter anticoagulation control. The guidelines on the indications for oral anticoagulation with warfarin, and their target INRs (rather than therapeutic ranges) have recently been revised [6] and are outlined in Table 1.

Table 1.  Indications for oral anticoagulation and target INR
IndicationTarget INR
Pulmonary embolus2.5
Proximal DVT2.5
Calf vein thrombosis2.5
Recurrence of venous thromboembolism:
 when no longer on warfarin therapy2.5
 whilst on warfarin therapy3.5
Symptomatic inherited thrombophilia2.5
Antiphospholipid syndrome3.5
Non-rheumatic atrial fibrillation2.5
Atrial fibrillation caused by:
 rheumatic heart disease2.5
 congenital heart disease2.5
 thyrotoxicosis2.5
Cardioversion2.5
Mural thrombus2.5
Cardiomyopathy2.5
Mechanical prosthetic heart valve3.5

WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

After stopping warfarin therapy it takes ≈ 4 days for the INR to reach 1.5 in almost all patients [8], an INR of ≤ 1.5 being deemed a ratio at which most surgical procedures are safe [9]. After the surgical procedure, if warfarin is restarted, it takes ≈ 3 days for the INR to reach 2.0 [10]. This temporary discontinuation of warfarin places the patient at some increased risk of thromboembolism. In addition to the risks of stopping patients’ anticoagulation, there is good evidence that surgery itself can increase the risk of venous thromboembolism [11]. There is additional biochemical evidence that discontinuing warfarin may cause a physiological ‘rebound’ increase in clotting factors [12], thus leading to a rebound hypercoagulable state. However, there is no evidence that surgery itself increases the risk of arterial embolism in those with atrial fibrillation or mechanical heart valves.

Spandorfer [1] categorized anticoagulated preoperative patients as being either at high or low risk of a thromboembolic complication, after stopping warfarin. This depended on the reason for their initial anticoagulation (Table 2).

Table 2.  Thrombosis risk after stopping warfarin therapy [1]
High riskLow risk
Mitral mechanical valves:
Older (first-generation) (Ball, Bjork-Shiley, Lillehei-Kaster)Newer (second-generation)
Atrial fibrillation:
+ history of stroke or multiple risk factors for strokeNo risk factors for stroke
DVT diagnosed withinthe last monthDVT treated for > 1 month
Hypercoagulable state plus recent thrombosis or history of life-threatening thrombosis 

WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

The estimated risk of the previously warfarinized patient having a thromboembolic complication depends on their initial indication for warfarin therapy. In patients with non-valvular atrial fibrillation, their mean (range) annual risk of stroke with no anticoagulation is 4.5 (1–20)%, depending on the number of risk factors for atrial fibrillation-associated stroke [13]. Oral anticoagulation reduces the risk of embolism by 66% [13,14]. For a patient whose warfarin has been discontinued for an operative procedure, Spandorfer [1] reported a risk of stroke of 0.012–0.3%, assuming the INR is subtherapeutic for a total of 4–6 days.

WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

This depends upon the length of time for which the patient has been anticoagulated with warfarin. If oral anticoagulation is stopped after a recent venous thromboembolism the patient is at high risk of developing a recurrence. This is ≈ 40% in a 1-month interval (over the period of the first month after the initial thromboembolism), reducing to 10% in a 2-month interval during the second or third month of oral anticoagulation [1,9]. It is advisable that whenever possible surgery is postponed for 3 months after an acute venous thromboembolism, as at this stage preoperative anticoagulation is no longer warranted after a single venous thromboembolism [9], because the risks of therapy are liable to outweigh any potential benefits.

WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

As mentioned in Table 2, patients with older first-generation aortic mechanical valves (Ball, Bjork-Shirley, Lillehei-Kaster) and mitral valve replacements are at higher risk than those patients with newer valves, and valves in the aortic position. Regardless of the type of valve, long-term anticoagulation is recommended [15]. The approximate risk of stroke for those patients with a mechanical valve whose warfarin has been stopped for a procedure, where the INR is subtherapeutic for 4–6 days, has been estimated at 0.08–0.36% per day [1].

THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

Preoperative intravenous unfractionated heparin may be commenced after warfarin has been stopped, and the patient's INR has become subtherapeutic. The use of intravenous unfractionated heparin is usually considered in those patients deemed to be at very high risk of thromboembolism after stopping warfarin therapy. Very high-risk patients include those with mechanical mitral valves, those who have had a venous thromboembolism within the last month, and those with older (first-generation) aortic mechanical valves (Ball, Bjork-Shiley, Lillehei-Kaster). In patients such as these who require surgery that is a high risk for bleeding (e.g. TURP), anticoagulation should be continued until ≈ 6 h before the procedure and started 12 h afterward, to help minimize any thrombotic complications. We suggest that restarting unfractionated heparin should be delayed further if the surgeon is not satisfied with the degree of haemostasis. Intravenous unfractionated heparin after surgery should be restarted with no loading bolus at 800–1200 units/h. The activated partial thromboplastin time (APTT) should be re-measured after 6–12 h and the infusion rate adjusted to give an APTT ratio of 1.5–2.5.

Patients receiving unfractionated heparin therapy are at risk of heparin-induced thrombocytopenia (HIT), which occurs in up to 6% of patients receiving unfractionated heparin therapy for any reason [16]. There are two types of HIT that occur clinically. Type I, which is more common, appears early after starting therapy and is mild, with the platelet count decreasing to 80–100. The patients tend to be asymptomatic, and type I HIT is rarely associated with thromboembolic events. Type II HIT is typically delayed in onset and the thrombocytopenia is more severe. Limb and/or life-threatening thromboembolic complications can occur. The diagnosis is essentially clinical and, although confirmatory tests are available (e.g. serotonin release assay), haematological advice should be sought. The management of this condition involves discontinuing all unfractionated heparin, including unfractionated heparin flushes and unfractionated heparin-coated catheters, and the institution of a synthetic heparinoid, e.g. danaparoid sodium. Risk factors for HIT include previous exposure to unfractionated heparin and cardiopulmonary bypass [17].

LMWH

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

Since the beginning of the 1990s there has been a progressive movement towards the use of LMWH for managing venous thromboembolism. These agents confer significant advantages over standard unfractionated heparin, as shown in Table 3.

Table 3.  Comparison of treatment with unfractionated heparin and LMWH
Unfractionated heparinLMWH
Administration:
Intravenous or subcutaneousSubcutaneous
Dose
VariableFixed, weight-based
Laboratory monitoring
Yes – APTTNot generally required anti Xa Assayanti

LMWHs given subcutaneously, e.g. enoxaparin (clexane), nadroparin (fraxiparine), and dalteparin (fragmin), are being used increasingly before and after surgery instead of conventional intravenous unfractionated heparin. Recent randomized trials [18,19] in acute venous thromboembolism have shown that using standard unfractionated heparin or the LMWH enoxaparin resulted in equivalent rates of recurrent thromboembolic events and bleeding. If, for example, enoxaparin is used, it is advised that it should be stopped 12 h before surgery and should not be used afterward until the surgeon considers that the risk of bleeding is acceptable [3].

Should LMWHs be used then caution is advised in those with renal impairment. LMWHs are eliminated principally via the kidney; with renal impairment their elimination is delayed and peak antifactor Xa levels are higher. At present there are only few data available to determine the safety of their use in those with renal failure, and therefore cautious usage is advised, with monitoring of peak antifactor Xa levels (3–4 h after dosing).

VENA CAVAL FILTERS

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

The insertion of a vena caval filter to prevent pulmonary embolism should be considered if the risk of venous thromboembolism is very high. This situation could occur in an individual who has had a recent venous thromboembolism, who is due to undergo pelvic surgery, which itself is associated with a significant risk of bleeding. Given the risks of bleeding, full and effective anticoagulation becomes difficult and dangerous. In situations such as this the opinion of an interventional radiologist should be sought, as there are now short-term removable filters available, which could cover the anticoagulation requirements of the patient during the operative period [20].

RECOMMENDATIONS

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES

The urologist and anaesthetist responsible for the patient's care must be aware that the patient is anticoagulated and should agree to an individual management plan, which should also be discussed with the patient. In each case, the plan will be based on a balance of risks. Although it is difficult to produce didactic guidelines that can be applied to all patients who are anticoagulated with warfarin, we make the following recommendations:

FOR PATIENTS UNDERGOING A UROLOGICAL PROCEDURE WITH A LOW BLEEDING RISK

This would include urological procedures such as vasectomy. Patients can undergo these procedures with an ‘INR at the lower end of the range’, e.g. for a target INR of 2.5 an INR of 2.0 would be suitable. This would mean stopping anticoagulation for 1–2 days. The INR should be checked on the day of admission. Restarting warfarin can be delayed if bleeding complications occur during the procedure. This would apply to patients at low risk of thromboembolism. In the case of a patient at high risk, e.g. with a high-risk valve, the involvement of a haematologist is recommended.

FOR THOSE AT LOW RISK OF THROMBOSIS UNDERGOING UROLOGICAL SURGERY WITH A HIGH BLEEDING RISK (E.G. TURP)

This group of patients would include those with atrial fibrillation but no additional risk factors for a stroke, and patients with a deep vein thrombosis (DVT) who have been anticoagulated for at least 3 months after the acute event, with no additional risk factors such as hospitalization or cancer, in which case preoperative LMWH prophylaxis would be appropriate. Those with no additional risk factors should have their warfarin stopped 3–4 days before the procedure, and have their INR checked immediately before surgery to ensure that it is < 1.5. If the INR remains > 1.5 then the procedure should be deferred. Intravenous vitamin K, at doses of 0.5–1.0 mg, can be used to reverse the warfarin effect in this setting, but will take an additional 6–12 h to have effect.

After the procedure warfarin should be restarted as soon as the patient is able to take medications orally. Postoperative LMWH, e.g. enoxaparin 40 mg, should be started in those who were anticoagulated for DVT or have atrial fibrillation. This should be continued until oral anticoagulation is re-established (INR > 2.0). A loading dose of warfarin is generally not recommended; patients can recommence their previous ‘steady- state’ warfarin dose. The restarting of anticoagulation should be delayed in the event of bleeding complications of the procedure.

FOR THOSE WITH A MODERATELY HIGH RISK OF THROMBOSIS UNDERGOING UROLOGICAL SURGERY WITH A HIGH BLEEDING RISK (E.G. TURP)

This group would include those patients who have had a DVT ≥ 1 month but < 3 months earlier, those with aortic valves, and those on lifelong warfarin with continued risk factors. In this group we would recommend stopping warfarin (usually 3 days before surgery) and using a LMWH before the procedure when the INR decreases to < 2.5. The INR should be checked on the day of the surgery, and the last dose of LMWH given 12 h before surgery. The LMWH should then be continued afterward until the patient resumes warfarin.

FOR THOSE AT VERY HIGH RISK OF THROMBOSIS UNDERGOING UROLOGICAL SURGERY WITH A HIGH BLEEDING RISK (E.G. TURP)

This group includes those with a mechanical valve, particularly with a mitral valve replacement, those with atrial fibrillation with multiple risk factors for a stroke, and those who have had a DVT within the last month. In this group of patients anticoagulation should be continued as close as possible to the procedure and restarted as soon as possible afterward. We recommend that warfarin is stopped 3–4 days before surgery and once the INR is subtherapeutic (i.e. < 2.5) the patient should be started on a treatment dose of intravenous unfractionated heparin (to obtain an APTT ratio of 2.5). The unfractionated heparin should be discontinued 6 h before surgery and recommenced 12 h afterward or later if inadequate haemostasis is present (see earlier section). An alternative to full-dose intravenous unfractionated heparin would be a treatment dose of LMWH (1.5 mg/kg) with the last dose being given 12 h before surgery. As before, oral anticoagulation can be recommenced once the patient can take medications by mouth, and postoperative haemostasis is secured.

For all of these groups of patients it is advisable to encourage early mobilization and encourage the use of compression stockings.

REFERENCES

  1. Top of page
  2. INTRODUCTION
  3. INDICATIONS FOR ORAL ANTICOAGULATION WITH WARFARIN
  4. WHY STOP WARFARIN?
  5. WHAT ARE THE RISKS OF STOPPING WARFARIN FOR SURGERY?
  6. WHAT IS THE RISK OF THROMBOEMBOLISM IN THE PATIENT WITH ATRIAL FIBRILLATION WHOSE WARFARIN HAS BEEN STOPPED?
  7. WHAT IS THE RISK OF THROMOEMBOLISM IN THE PATIENT WITH VENOUS THROMBOEMBOLIC DISEASE WHOSE WARFARIN HAS BEEN STOPPED?
  8. WHAT IS THE RISK OF STROKE IN THE PATIENT WITH A PROSTHETIC HEART VALVE WHOSE WARFARIN HAS BEEN STOPPED?
  9. THE USE OF INTRAVENOUS UNFRACTIONATED HEPARIN ONCE WARFARIN THERAPY HAS BEEN STOPPED
  10. LMWH
  11. VENA CAVAL FILTERS
  12. RECOMMENDATIONS
  13. SUMMARY
  14. REFERENCES
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Abbreviations
LMWH

low molecular weight unfractionated heparins

INR

international normalized ratio

APTT

activated partial thromboplastin time

HIT

heparin-induced thrombocytopenia

DVT

deep vein thrombosis.