Influence of regional anesthesia, local anesthetics, and sympathicomimetics on the pathophysiology of deep vein thrombosis.

Studies have shown that lumbar epidural and spinal anesthesia seem to offer two distinct clinical advantages over general anesthesia, particularly in total hip replacement patients. These major regional blocks reduce the frequency of deep vein thrombosis and pulmonary embolism and reduce intraoperative and postoperative blood losses. The beneficial effects on thromboembolism are probably explained by several factors, such as hyperkinetic blood flow in the lower legs, reduced tendency to coagulation, and improved fibrinolytic function. The effects of local anesthetics on leukocytes, platelets, erythrocytes, and plasma proteins and on the interactions among various blood cells and endothelial cells are other factors in the protection against thromboembolism. Sympathicomimetic agents (i.e., epinephrine in the local anesthetic solution together with ephedrine given prophylactically to maintain a stable blood pressure) probably also play a significant role, notably on fibrinolytic function. The reduction in blood loss and thus in transfusion requirements may also be important.