Cardiopulmonary and haemodynamic changes during total hip arthroplasty.

We report a prospective study of 30 patients who underwent total hip arthroplasty for osteoarthrosis in order to investigate the haemodynamic and respiratory changes which occur during operation. Cement was used in 17 cases and the implants were not cemented in 13. Pulmonary and cardiac function, blood levels of methylmethacrylate monomer, intramedullary pressure and transoesophageal echocardiography were recorded. Two well differentiated echogenic patterns appeared consistently during the operation. The intramedullary pressure became raised as the cement was inserted. The following changes occurred within seconds and continued for some minutes: elevation of mean arterial pressure and mean pulmonary artery pressure; decrease of arterial oxygen tension and of mixed venous PO2, and greater tissue consumption of oxygen. Although we recorded raised concentration of methylmethacrylate monomer in venous blood after the cement was inserted, there is no evidence that the monomer is responsible for the haemodynamic changes which take place.