The role of lumbar epidural anaesthesia as antithrombotic prophylaxis in total hip replacement.

A review of a series of clinical and experimental investigations established that the incidence of deep venous thrombosis and of pulmonary embolism after total hip replacement surgery was lower in patients given continuous lumbar epidural anaesthesia than in others with general anaesthesia. The thromboprophylactic effect of continuous lumbar epidural anaesthesia is explained by its beneficial influence on all factors of the triad proposed by Virchow, viz. blood flow, factors within the blood itself, and the vascular endothelium. Continuous lumbar epidural anaesthesia is associated with hyperkinetic blood flow in the major vessels of the lower limbs, lessened tendency to coagulation of the blood and better preservation of fibrinolysis function. Other characteristics include an inhibitory action on platelet aggregation and stabilizing effect on leukocytes and endothelial cells--effects exerted by the local anaesthetics per se. The smaller blood loss and thus the lower transfusion requirements during continuous lumbar epidural anaesthesia may also play a beneficial role as a thromboprophylactic factor.