Oral anticoagulants in arterial disease

Drugs used for disorders of coagulation

Bleeding and thrombosis are altered states of hemostasis. Inhibition of normal hemostatic mechanisms results in spontaneous hemorrhage, whereas excessive hemostasis results in thrombus formation. The drugs used to prevent and treat thrombosis and those used to arrest bleeding are the subjects of this article.

Anticoagulants and cerebral venous thrombosis

Three patients with cerebral venous thrombosis are described. The management of this rare condition is discussed and a case is made for using anticoagulant therapy provided the diagnosis is established before cerebral infarction or hemorrhage have occurred.

Epidural analgesia and anticoagulant therapy. Experience with one thousand cases of continuous epidurals

One thousand lumbar epidural blocks in 950 patients undergoing vascular surgery are reported. All patients were receiving oral anticoagulants pre-operatively. Mean thrombotest (TT) was 19.3% (normal range 70-130%). During surgery intravascular heparin was administered. At the end of surgery, the kaolin cephalin clotting time (KCCT) was 68 (+/- 0.8) seconds (normal range 35-60 seconds), and partial thromboplastin time (PTT) was 536 (77.9%, normal control of 100%). Despite the anticoagulant therapy, no side effects were observed in any patient which could be related to haemorrhage or haematoma formation in the epidural space. It is concluded that, provided adequate precautions are taken, epidural analgesia can be safely used in patients receiving anticoagulant therapy.

Can drugs help patients with lower limb ischaemia?

The prevalence of symptomatic arterial disease of the lower limbs is 2 per cent of the population aged 45-60, but it has a relatively benign course, with 70 per cent of patients requiring no therapy. Of the numerous drugs used in the treatment of the disease, there is no evidence to suggest that antilipaemic drugs, anticoagulants, vasodilators or rheological agents confer any benefit to the patient. The initial use of antiplatelet drugs and prostaglandins has been disappointing despite the undoubted importance of the platelet/endothelial interaction in the aetiology of atherosclerosis. As it is unlikely that we can reverse advanced disease, this is hardly surprising. Long term use of these drugs may prevent deterioration in those patients with progressive disease, and controlled trials on this aspect of treatment are now required. Symptomatic relief in the claudicant may perhaps be obtained with naftidrofuryl and suloctodil and with the former in more severe ischaemia, but their use should not replace the beneficial effects of exercise and cessation of smoking.

The effect of Coumadin upon thrombus forming on foreign surfaces

Experience with the Stagnation Point Flow Experiment has revealed the earliest microscopic events surrounding thrombus inception and growth on foreign surfaces in a perfectly defined flow field. Using 40 and 80 X magnification, the effects of Coumadin upon these events was studied. These events include leukocyte adherence, fibrin deposition and platelet aggregation, deviation of flow streamlines around these aggregates, and subsequent downstream thrombus growth. Surface density of leukocytes was measured as a function of time and shear, and served as an index of the quantity of thrombus on the surface, which in turn, allowed direct comparisons of thrombus growth rate between experiments. Coumadin decreases the adhesive force between leukocytes or thrombi and the foreign surface. Emboli are more frequent with Coumadin, but are smaller. Thrombus inception is not altered. These results suggest that clinical benefit obtained from use of Coumadin derives from reduction in size of emboli.