Prevention of venous thrombosis

Current recommendations in prevention of thrombosis in surgery

Fatal pulmonary embolism is a major cause of postoperative death. When no prophylaxis is given in general surgery, it has a frequency of about 1%. Apart from the immediate risk to life, one must also consider the late sequelae of extensive deep vein thrombosis--swelling of the legs, varicose veins, ulceration and other trophic changes which represent an equally distressing situation. Recently, three large-scale surveys have been published, where the data of over 100 randomized controlled clinical trials of prophylaxis against venous thromboembolism has been analysed. The purpose of this talk is to provide an overview of the currently available prophylactic methods analysed in these surveys, with an aim to define a policy for preventing venous thromboembolism, with particular emphasis on the surgical patients. There is evidence suggesting that the frequency of fatal pulmonary embolism can be reduced by such prophylactic remedies as low-dose heparin, dextran, the combination of dihydroergotamine plus heparin, and low molecular weight heparin.

[Prophylaxis and therapy of shunt thrombosis in terminal renal insufficiency (author's transl)]

In terminal renal insufficiency thrombosis occurs almost exclusively in the arteriovenous shunt. The management of this acute, life threatening thrombosis is hardly contested. On the other hand, few results are available concerning effective thrombosis prophylaxis. In addition to the effectiveness, the pharmacokinetics of a substance and also possible bleeding complications must be taken into account. The parenteral administration of heparin and its short half life restrict it to use in thehospital. Oral anticoagulants, because they are difficult to dose, should be avoided when possible. Dextrans (Rheomacrodex) and acetylsalicylic acid (Colfarit) appear to be best suited for thrombosis prophylaxis in renal insufficiency. Dextran has the disadvantage of volume overload, and acetylsalicylic acid that of stomach intolerance. Sulfinpyrazone (Anturano) also appears to be effective, although its pharmacokinetic behaviour in renal insufficiency is still not known. Dipyridamole (Persantin), whose effectiveness for this purpose has not yet been demonstrate, should be administered even more cautiously.

Thrombosis following hip arthroplasty. A study using phlebography and 125I-fibrinogen test

Venous thrombosis after hip arthroplasty was studied using the 125I-fibrinogen test and phlebography. Eight out of ten dextran-treated and six out of ten control patients developed thrombosis. The thrombi were small and most frequently dorsal and dorso-lateral veins were involved. There were no thigh thrombi without concurrent calf thrombi. Half of the thrombi were found within the first postoperative week whereas the remainder occurred later. Preoperative venous pathology predisposed to postoperative thrombosis.

The incidence of venous thrombosis in the lower limbs following elective gallbladder surgery

The frequency of postoperative venous thrombosis and the prophylactic effect of dextran 40 and 70 were studied in 90 otherwise healthy patients undergoing cholecystectomy. The 125-I-fibrinogen test was employed as the diagnostic method. The frequency of thrombosis was very low (1.1%) compared with other investigations on patients undergoing elective general surgery. Thus nothing can be concluded about the prophylactic effect of dextran from this series, but it can be presumed that this type of patient does not need routine prophylaxis against deep venous thrombosis.