[Prevention of deep venous thrombosis]

The positive and negative clinical symptoms and signs of deep venous thrombosis are both insensitive and non-specific. Venography is the reference investigation: Duplex ultrasonography is the usual diagnostic procedure for distal deep venous thrombosis but it is less reliable in proximal lesions. The sensitivity of plethysmography in proximal deep venous thrombosis is high but the diagnosis of isolated calf vein thrombosis and non-obstructive proximal thrombosis escape diagnosis in this technique. Most cases of deep venous thrombosis occur after major surgery, during pregnancy, in the post-partum period, after prolonged immobilisation and in obese patients or those with varicose veins. Congenital and acquired causes should also be investigated when spontaneous deep venous thrombosis occurs or when the condition complicates minor surgical trauma in a young patient. The incidence of deep venous thrombosis varies with the type of surgical procedure: 25% in general surgery, 50% after hip or knee arthroplasty, 43% after fracture of femur, 24% after neurosurgery. Graduated pressure stockings should be used for the prevention of deep venous thrombosis. Other measures include aspirin, dextran, oral and subcutaneous anticoagulants, non-fractionated and low molecular weight heparins. The relative efficacy of these different measures is discussed with respect to each type of surgical procedure.