Relation of anesthesia to total hip replacement and control of operative blood loss.

Blood loss during total hip replacement has been reported as ranging from 500 to more than 4000 ml. To find reasons for this large variation, 167 case reports were studied. Blood loss was higher with nitrous oxide-oxygen-curare-morphine aneasthesia than with halothane-nitrous oxide-oxygen. Blood loss was also higher in patients with cups, prostheses, and neoplasms of the femoral head and neck than in patients with degenerative and rheumatoid arthritis. In patients undergoing bilateral total hip replacement, operative blood loss was significantly (p=0.05) higher during the second operation. However, the most striking correlation of blood loss was with intraoperative systolic blood pressure (r=0.84), a finding confirmed by a prospective study in 58 patients. Blood loss, operative time, the number of blood transfusions, and the hypotensive and hypoxic response to acrylic bone-cement application decreased when intraoperative systolic blood pressure was lowered by 20 to 30 percent of the preoperative value by the use of trimethaphan or sodium nitroprusside. This moderate reduction of blood pressure resulted in a saving of 2 to 3 units of blood in an average case and a considerably clearer surgical field. The authors consider moderate lowering of blood pressure to be a useful adjuvant in anesthesia for total hip replacement.