Pathogenesis and prophylaxis of circulatory reactions during total hip replacement.

Circulatory reactions such as a drop in blood pressure, bradycardia, cardiac arrest, and even intraoperative death after insertion of the stem are well known events during total hip replacement. The present paper reports bone marrow intravasation after rise of intramedullary pressure in the femoral cavity during insertion of hip prostheses, demonstrated by intraoperative transesophageal echocardiography. In an animal study, the ultrasound echoes were identified as "mixed emboli" consisting of a core of bone marrow surrounded by thrombus. These results suggested the use of an intramedullary plug to restrict the intravasation of bone marrow. A trial was undertaken in 60 total hip replacement operations. The first 30 were performed using the conventional technique without an intramedullary plug. In a second series of 30 operations, an intramedullary plug made of cancellous bone taken from the resected femoral head was placed 2 cm below the expected location of the tip of the stem. The cement was applied from distal to proximal by syringe. After implantation of the prosthesis using the conventional technique, a significant drop in blood pressure was observed. In the second series, the drop in blood pressure did not occur. In conclusion, it was demonstrated that effective venting of the bone marrow cavity by a bore hole, and avoidance of compression of the bone-marrow-filled distal femoral cavity by using a plug, results in effective prevention of circulatory reactions: no drop in blood pressure occurred. The use of an intramedullary plug is discussed and recommended.