Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Risk of stroke
On the basis of the experience cited above, antithrombotic therapy can be recommended for patients undergoing the following types of infrainguinal arterial bypass: (1) all bypasses in which prosthetic material is used; (2) long bypasses to small arteries (infrapopliteal); (3) complex reconstructions involving composite grafts or adjunctive endarterectomy; and (4) “compromised” operations (marginally adequate vein grafts, poor distal runoff, etc). For optimal protection, antithrombotic therapy should be started preoperatively and should consist of aspirin, 325 mg/d. Although it is not clear that preoperative dipyridamole is effective antithrombotic therapy, it has been used successfully in patients undergoing saphenous vein aortocoronary bypass and does not appear to increase intraoperative bleeding. For patients at high risk for graft failure, the combination of warfarin (INR 2 to 3) and aspirin (80 to 325 mg) can be recommended.
Long-term therapy is aimed at reducing the risk of stroke and MI in addition to possibly improving bypass patency. For long-term antithrombotic therapy, aspirin, 325 mg/d, with or without dipyridamole, 75 mg three times daily, is recommended. It is not clear that dipyridamole is necessary, and further trials will be needed to settle this question. However, because of animal studies demonstrating that dipyridamole dramatically augments aspirin’s antithrombotic effect on artificial surfaces, it may be prudent to use dipyridamole in conjunction with aspirin in patients with vascular prostheses. For patients with complex, tenuous reconstructions, or for those who have thrombosed a primary reconstruction and thrombectomy has been successful in restoring secondary patency, warfarin therapy might be an appropriate choice in selected patients. Because of conflicting data and the risk of hemorrhage, warfarin, with or without aspirin, cannot be recommended for routine treatment in patients with lower-extremity bypasses. ventolin inhaler
Intraoperative anticoagulation with heparin also deserves comment. Practices vary widely among vascular surgeons and there is no consensus with regard to heparin dosage, method of administration (regional vs systemic), and timing. The problem is compounded by the lack of controlled studies. Because of the experience with antiplatelet agents demonstrating that early antithrombotic therapy is important in determining postoperative patency, it is probable that intraoperative thrombus formation along suture lines, on prosthetic surfaces, and at areas of stasis proximal or distal to vascular clamps is detrimental. Therefore, maximal anticoagulation at the time of application of cross clamps seems desirable. Also, the stimulus for thrombus formation and clotting is particularly intense with vessel trauma from manipulation, dissection, endarterectomy, and other forms of surgical injury that release large amounts of tissue thromboplastin and other clot-promoting substances as well as expose collagen and prosthetic surfaces to nonflowing, pooling blood.