Oral Anticoagulants, Dextran Or Low-Dose Subcutaneous Heparin : Which Is It To Be In The Prophylaxis Of Deep Vein Thrombosis Of Operated Patients ?

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Abstract
The standard low-dose of heparin for the prevention of deep-vein thrombosis in operated patients is 5,000 units subcutaneously 2 hours before operation and at 8 or 12 hourly intervals for the next seven days. Low-dose heparin can at present be recommended as an effective agent in the prevention of deep-vein thrombosis in patients over the age of 40 years who are undergoing a major abdominothoracic or gynaecological operation. There is reasonable evidence that low-dose heparin also offers satisfactory protection against fatal embolism for patients at high risk after general abdominothoracic operations. The evidence on the effectiveness of low-dose heparin in the prevention of deep-vein thrombosis is less well established in other groups and particularly in high risk patients e.g. after urologic operations (suprapubic prostatectomy) and hip operations. This important distinction must be made in terms of the population at risk and the efficacy of low-dose heparin. Considering the evidence so far available, it appears that the post-operative state in which dextran has been shown to reduce the incidence of less phlebographically confirmed less deep-venous thrombi most convincingly is orthopaedic surgery. Major orthopaedic surgery is precisely the type of surgery in which the superiority of low-dose heparin is controversial. Unless proven otherwise, dextran 70 (infusion of 500 to 100 ml of a 6% solution started before operation, and 500 ml the following and next 3 alternate days) may be the agent of choice in preventing deep-venous thrombosis in major orthopaedic surgery. Using this scheme the prophylaxis of post-operative deep-vein thrombosis appears as effective with dextran 70 as with oral anticoagulants. Whether the protection offered by dextran 70 will also prevent fatal and non-fatal pulmonary embolism is still an open question. Low-dose heparin and dextran do not expose patients to serious risks of bleeding after operation, and with the recommended doses of the latter drug, other untoward effects are rare. At the doses recommended here neither of these two drugs requires laboratory monitoring.