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Effect of epidural analgesia on venous blood flow after hip arthroplasty.

The effects of postoperative epidural infusions using local anesthetic and narcotic were assessed in reference to lower extremity blood flow. Nineteen patients who underwent unilateral total hip arthroplasty were randomly assigned to receive a postoperative epidural infusion of either 5 microg/ml fentanyl or 5 microg/ml fentanyl plus 0.125% bupivacaine at a rate of 10 ml per hour. The infusions were started after complete resolution of the operative epidural blockade. Femoral venous blood flow volume and velocity were measured above and below the saphenous vein bifurcation using an Acuson #128XP/10 computed sonography system (duplex ultrasound) and proprietary software. Femoral venous blood flow was not affected by the type of infusion and did not increase during the study period. However, femoral venous blood flow volume increased 50% after active flexion and extension of the foot, 10 times in quick succession. The addition of bupivacaine (a local anesthetic that blocks sympathetic afferent nerves) to a postoperative epidural infusion does not augment blood flow from the deep veins of the leg after total hip arthroplasty. Alternatively, lower extremity skeletal muscle activity significantly enhances femoral venous blood flow and may be a useful adjunct in deep venous thrombosis prevention.