In performing noncardiac surgery on patients on anticoagulation, the major concern is when it is safe to perform surgery without increasing the risk of hemorrhage or increasing the risk of thromboembolism (venous, arterial) after discontinuing coumadin. In treating patients on long-term coumadin perioperatively, consider the risks of hemorrhage versus thromboembolism. Patients with prosthetic heart valves pose a particular problem. Arterial thromboembolism from the heart often results in death (40% of events) or major disability (20% of events). When considering noncardiac surgery, these factors and the need to weigh the risk of hemorrhage against that of thromboembolism must be taken into account. The other problem encountered is that no consensus exists regarding the optimal perioperative management of anticoagulation for patients who have been receiving long-term warfarin therapy.

INDICATIONS FOR PERIOPERATIVE MANAGEMENT

Any patient who is on long-term anticoagulation and is to undergo a major surgery needs proactive management. Some authors believe that patients can be maintained on oral anticoagulation for minor procedures, such as dental extractions, biopsies, and ophthalmic operations, as long as the therapeutic range of the prothrombin time (PT) value is not greater than 2.5.

In general, antithrombotic therapy is indicated for venous thromboembolic disease (ie, deep venous thrombosis [DVT]; pulmonary embolism (PE); primary prophylaxis of DVT or PE; antithrombin III [ATIII], protein C, and protein S deficiency); arterial thromboembolic disease (ie, prosthetic heart valves, atrial fibrillation, congestive cardiomyopathies, mural cardiac thrombus, acute myocardial infarction, mitral valve disease); disseminated intravascular coagulation; and maintaining patency of vascular grafts, shunts, and bypasses.

Usually, unless accompanied by significant cardiomyopathy or recent arterial embolus, patients with atrial fibrillation can have their coumadin stopped 4 days prior to surgery, then resumed at the usual dose the night of surgery.

Patients with prosthetic heart valves usually are treated with perioperative Lovenox, although randomized controlled trials validating this method are lacking. Coumadin can be stopped 4-5 days preoperatively, with Lovenox started the next day at a dose of 1 mg/kg twice a day. The last dose should be 12 hours preoperatively. The Lovenox and coumadin can be retitrated the evening of the operative day. The Lovenox is stopped when the coumadin reaches the target range. For patients at higher risk of valve thrombosis (ie, patients with 2 prosthetic valves or with caged-ball type of valves), whether Lovenox provides adequate anticoagulant protection is unclear. For these patients, consider use of perioperative unfractionated heparin instead of Lovenox. Preoperatively, the heparin should be stopped 6 hours before the procedure. Postoperatively, the heparin can be restarted when the surgeon agrees that it is safe, usually 6-12 hours postoperatively.

Contraindications to antithrombotic therapy are relative, and the risks and benefits need to be weighed. Relative contraindications are bleeding abnormality (eg, thrombocytopenia, platelet defect, peptic ulcer disease), CNS lesion (eg, stroke, surgery, trauma), spinal anesthesia or lumbar puncture, malignant hypertension, and advanced retinopathy. Contraindications specific to warfarin are early or late pregnancy, poor patient cooperation, and occupational risk.

PREOPERATIVE TREATMENT

Warfarin should be withheld for only 4 doses if the most recent episode of VTE was between 1 and 3 months before surgery. If the patient has been anticoagulated for 3 or more months, 5 doses of warfarin can be withheld before surgery. Preoperatively, subcutaneous unfractionated heparin or low molecular weight heparin (LMWH) is needed only for immobilized inpatients with an INR of less than 1.8.

POSTOPERATIVE MANAGEMENT

Arterial thromboembolism

If surgery is performed within a month after an episode of arterial thromboembolism, intravenous heparin is warranted until the INR reaches 2.0 if the risk of bleeding is not very high. Administer intravenous unfractionated heparin without a leading dose 12 hours after surgery at a rate of no more than 18 U/kg/h. Defer the first activated partial thromboplastin time (aPTT) for 12 hours to attain a stable anticoagulant response. Postoperative intravenous heparin is not recommended for patients who undergo major surgery and who are at high risk for anticoagulant-induced bleeding, even if an episode of arterial embolism has occurred within 1 month before surgery. Instead, administer subcutaneous unfractionated heparin or LMWH (3000 U bid) until the INR reaches 1.8.

Venous thromboembolism

If the patient had an episode of VTE within 3 months before surgery, intravenous unfractionated heparin is recommended until the INR is 2.0 or greater. Patients who have a vena caval filter are protected from pulmonary embolism, and intravenous heparin can be avoided in their early postoperative period. If no previous episodes of VTE occurred within 3 months, postoperative intravenous heparin is not indicated. Subcutaneous heparin is recommended.

Madura et al (1994) recommend discontinuing coumadin 5 days before surgery and beginning intravenous heparin at 1000 U/h, while adjusting to maintain the aPTT at therapeutic levels. Heparin is discontinued 6-12 hours before surgery and restarted at 200-400 U/h at 4-6 hours after surgery. Coumadin is restarted as soon as the patient can tolerate it.

Stop oral anticoagulants at least 5 days preoperatively, and do not perform the procedure until the PT is in the reference range. Substitute intravenous heparin infusion for oral anticoagulant therapy preoperatively to prevent thromboembolic complications in the perioperative period. Stop the intravenous heparin infusion 6-12 hours preoperatively to allow the aPTT to return to normal for adequate intraoperative hemostasis. Restart the intravenous heparin infusion within 6 hours of completion of the surgical procedure to prevent postoperative thromboembolism. Resume oral coumadin therapy as soon as the patient is able to tolerate oral liquids. Do not release the patient until PT is once again therapeutic.

AMERICAN COLLEGE OF CHEST PHYSICIANS CONSENSUS CONFERENCE ON ANTITHROMBOTIC THER

Perioperative management of anticoagulation entails an understanding of all thromboembolic events, indications for treatment, and duration of treatment. The American College of Chest Physicians (ACCP) for Prevention of Thromboembolism has published the following guidelines. A full listing is available at American College of Chest Physicians.

• Low-risk general surgery patients - Early ambulation

   

• Moderate-risk general surgery patients - Low-dose unfractionated heparin (LDUH), LMWH, intermittent pneumatic compression (IPC), or elastic stockings (ES)

   

• Higher-risk general surgery patients - LDUH or higher-dosage LMWH

   

• Higher-risk general surgery patients prone to wound complications (eg, hematomas, infection) - IPC is an alternative.

   

• Very high-risk general surgery patients with multiple risk factors - LDUH or LMWH combined with IPC

   

• Selected very high-risk general surgery patients - Perioperative warfarin (goal INR 2.5, range 2.0-3.0)

   

• Patients undergoing total hip replacement surgery - LMWH started 12-24 hours after surgery or warfarin started before or immediately after surgery (goal INR 2.5, range 2.0-3.0) if adjusted-dose heparin is started preoperatively; possible adjuvant use of ES or IPC

   

• Patients undergoing total knee replacement surgery - LMWH, warfarin, or IPC

   

• Patients undergoing hip fracture surgery - LMWH or warfarin (goal INR 2.5, range 2.0-3.0) started preoperatively or immediately after surgery

   

• High-risk patients undergoing orthopedic surgery - Inferior vena cava (IVC) filter placement only if other forms of anticoagulant-based prophylaxis are not feasible because of active bleeding (should rarely be necessary)

   

• Patients undergoing intracranial neurosurgery - IPC with or without ES; LMWH and LDUH may be acceptable alternatives; consider IPC or ES, with LMWH or LDUH, for high-risk patients

   

• Patients with acute spinal cord injury - LMWH; although ES and IPC appear ineffective when used alone, ES and IPC may have benefit when used with LMWH or if anticoagulants are contraindicated; during rehabilitation, consider continuation of LMWH or conversion to full-dose oral anticoagulation

   

• Trauma patients with an identifiable risk factor for thromboembolism - LMWH, as soon as considered safe; consider initial prophylaxis with IPC if administration of LMWH is delayed or is contraindicated; in high-risk patients with suboptimal prophylaxis, consider screening with duplex ultrasonography or filter placement in the IVC

   

• Patients with myocardial infarction - LDUH or full-dose anticoagulation; IPC and possibly ES may be useful when heparin is contraindicated

   

• Patients with ischemic stroke and lower extremity paralysis - LDUH or LMWH; IPC with ES also probably is effective

   

• General medical patients with clinical risk factors for VTE, particularly those with congestive heart failure (CHF) or chest infections - LDUH or LMWH

   

• Patients with long-term indwelling central vein catheters - Warfarin (1 mg/d) or daily LMWH to prevent axillary-subclavian venous thrombosis

   

• Patients having spinal puncture or epidural catheters placed for regional anesthesia or analgesia - LMWH should be used with caution (additional data are now reported on timing of catheter removal), ES, LDUH

BIBLIOGRAPHY

• American College of Chest Physicians: Proceedings of the American College of Chest Physicians 5th Consensus on Antithrombotic Therapy. 1998. Chest 1998 Nov; 114(5 Suppl): 439S-769S

• Kearon C: Perioperative management of long-term anticoagulation. Semin Thromb Hemost 1998; 24 Suppl 1: 77-83

• Lanzat M, Danna AT, Jacobson DS: New protocols for perioperative management of podiatric patients taking oral anticoagulants. J Foot Ankle Surg 1994 Jan-Feb; 33(1): 16-20[

• Madura JA, Rookstool M, Wease G: The management of patients on chronic Coumadin therapy undergoing subsequent surgical procedures. Am Surg 1994 Jul; 60(7): 542-6; discussion 546-7

• Rutherford R: Fundamental therapeutic and technical consideration. In: Vascular Surgery. Philadelphia, Pa: W.B. Saunders Company; 1995.