Managing anticoagulation in patients undergoing surgery

In patients who are already anti-coagulated and contemplating surgery, it is important to balance the risk of haemorrhage if the INR is not reduced against the risk of thromboembolism if it is reduced too low for too long. The patient should be referred to the anti-coagulant clinic well in advance of any planned surgery to advise patients about their anti-coagulant therapy modification.

Minor surgery. For most minor procedures, e.g., dental work, it is sufficient to simply omit warfarin for 2 days prior to the procedure and restart with the usual maintenance dose immediately afterwards (the same day). Alternatively, warfarin could be stopped for 3 days before the procedure and recommenced the day immediately before the procedure (it takes time for warfarin effect to be established). If any problems are anticipated or there have been problems in the past, then the INR should be checked beforehand. If INR < 2.5 then it is safe to proceed (Fig. 12).183

Extreme caution should be exercised with patients who have prosthetic heart valves. The INR should not be allowed to drop too low. If several extractions are required or there is any doubt, then follow the guidelines for major procedures.

Intermediate and major surgery (Fig. 13)

(I) Low risk patients

E.g., Mitral valve disease, atrial fibrillation, cardiomyopathy183 Stop warfarin 3 days prior to surgery.

Start heparin 5000 iu s/c 3 times daily or equivalent LMWH dose when INR < 2.5.

Avoid giving heparin < 2 hours before surgery. Chech INR < 2 and APTT < 45 seconds before surgery. Restart warfarin postoperatively and overlap with heparin until INR > 2.5 for at least 2 consecutive days.

(II) High risk patients

E.g., Mechanical valve replacement, recurrent or acute thromboem-bolism, known thrombophilia183

The management of these patients requires considerable effort and attention. Coordination and communication between the surgeons and the anti-coagulant clinic team is paramount. Stop warfarin > 3 days before surgery.

When INR < 2.5 start iv heparin at 20,000 iu per 24 hours and adjust to give APTT 1.5-2.5 times control if patient is hospitalised. Alternatively give LMWH therapeutic dose as an outpatient.

ANTI-COAGULATION AND SURGERY

Minor procedures e.g. Dental work

•Omit warfarin for 2 days prior to procedure •Restart warfarin with the usual maintenance dose immediately afterwards (same day)

Fig. 12 Flow chart summarising the management of oral anti-coagulation in minor surgical procedures.

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