Comparison of some effects of dipyridamole and adenosine on thrombus formation, platelet adhesiveness and blood pressure in rabbits and rats

Prophylaxis of venous thromboembolism

The objective of prophylaxis in venous thromboembolism is, first, to prevent fatal pulmonary embolism and, second, to reduce the morbidity associated with deep vein thrombosis (DVT) and the postphlebitic limb. This should now be standard practice for most patients over 40 years of age undergoing major surgery and for younger patients with a history of venous thromboembolism. Particularly high-risk groups include patients over 60 years of age undergoing major surgery, those with malignancy, and those requiring hip operations. Low-dose subcutaneous heparin 5,000 IU commencing 2 hours preoperatively and continuing 12 hourly until the patient is fully mobile is unequivocally effective in preventing DVT in medical and surgical patients and, most importantly, significantly reduces the incidence of fatal postoperative pulmonary embolism and total mortality. Such prophylaxis, in the presence of established DVT, also limits proximal clot propagation, which is the precursor of major pulmonary embolism. Low-dose heparin prophylaxis is associated with a small risk of bleeding complications, evidenced mostly by an increased frequency of wound hematoma rather than major clinical hemorrhage. Low molecular weight heparin fragments (e.g., Fragmin, Choay, Enoxaparine) are emerging as useful alternative agents, having the advantage of once daily administration and yet providing similar efficacy in the prevention of DVT. Mechanical methods of prevention which counteract venous stasis, such as graduated elastic compression stockings, are also useful in protecting against DVT but have not been shown to prevent fatal postoperative pulmonary embolism. They are recommended particularly for patients in whom heparin prophylaxis is best avoided (e.g., neurosurgery) and possibly in combination with heparin in very high-risk patients.

Prevention of venous thrombosis and pulmonary embolism

Deep vein thrombosis (DVT) leads to hospitalization for up to 600,000 persons each year in the United States. Venous thrombosis in itself may be benign, but the condition can lead to dangerous complications and has a high recurrence rate. Strategies to prevent DVT involve prevention of stasis and reversal of changes in blood coagulability that allow thrombi to form. Pharmacologic agents have been effective in reducing the incidence of DVT and pulmonary embolism. Low-dose subcutaneous heparin is considered a nearly ideal DVT preventative for surgically treated patients. The risk of hemorrhage is the main limitation to routine use of subcutaneous anticoagulants for DVT, but careful patient selection can minimize that risk. After anticoagulant therapy with heparin, generally for 7 to 10 days, oral warfarin is the drug of choice for maintenance anticoagulation to prevent DVT recurrence. Therapy for pulmonary embolism is the same as for DVT--immediate anticoagulation with heparin followed by maintenance with warfarin.

Effect of dipyridamole on microaggregate formation in the pump oxygenator

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The effect of dipyridamole on tissue perfusion following freezing injury in the rat

A drug with known platelet disaggregating properties, dipyridamole, has been used for the treatment of experimental frost-bite in the rat. A standardized cold injury applied to the rat tail was treated by a variety of régimes. Tissue survival was then assessed by several methods and correlated with the therapeutic régimes. The results suggested that dipyridamole had a beneficial effect on the maintenance of tissue perfusion and subsequent viability of the injured tail.

Altered platelet function in patients with prosthetic mitral valves. Effects of sulfinpyrazone therapy

Platelet survival time and platelet adhesiveness and aggregation were examined in 16 patients with prosthetic mitral valves. Subsequently, nine patients were treated with sulfinpyrazone in doses of 400 mg and 800 mg/day, and the studies were repeated after a treatment period of 5 to 8 weeks. 51 Chromium survival time was shortened in 15 of 16 patients, and the mean value for the entire group was 5.49 ± 0.23 days (normal, 6.73 ± 0.21 days; P < 0.001). Mean platelet adhesiveness in glass bead columns was 53 ± 5% (normal, 30 to 60%). Platelet aggregation (turbidometric technic of Born) was normal. Treatment with 400 mg of sulfinpyrazone daily reduced platelet adhesiveness to 40 ± 5% ( P < 0.05), but effected no change in platelet survival time or platelet aggregation. Therapy with 800 mg of sulfinpyrazone daily corrected platelet survival time to normal, 6.68 ± 0.57 days ( P < 0.01), but it produced no further decrease in adhesiveness and no change in aggregation. It is concluded that platelet abnormalities regularly occur in patients with prosthetic mitral valves and may contribute to thromboembolism in this group. Platelet survival time is a more sensitive measure of altered platelet kinetics than platelet adhesiveness or platelet aggregation. Therapy with 800 mg of sulfinpyrazone per day corrects demonstrated abnormalities and may be useful for prevention of thromboembolism in patients with prosthetic mitral valves.