Evidence for induction of cardiorespiratory and vascular complications by methylmethacrylate monomer in hip replacement surgery. Laboratory and animal investigations

Hip replacement surgery (HRS) using acrylic cement for prosthetic fixation is associated with perioperative cardiorespiratory dysfunction. Large amounts of thrombin are generated locally and systemically in the pulmonary microcirculation during traumatization of bone. Hypercoagulation is rapidly followed by maximal central venous blood concentrations of methylmethacrylate monomer (MMA) released during impaction of bone cement into the femoral shaft. In vitro and in vivo studies have shown that MMA in different ways contribute to activation of coagulation. In addition, MMA per se is cytotoxic and may in clinically relevant concentrations cause disintegration of vascular and blood cells with potential release of proteolytic enzymes and exposure of subendothelial constituents. The present experimental studies showed that implantation of cement and prosthesis into the femoral shaft or injection of MMA into a femoral vein caused a marked increase in mean pulmonary arterial blood pressure (MPAP) and a transient fall in mean arterial blood pressure (MAP) followed by a compensatory increase. To avoid admixed reactions by other elements than MMA alone, MMA in different concentrations was injected directly into a pulmonary artery. MPAP increased and MAP decreased in a clear dose response relationship. Analyses of blood MMA concentrations following injection of 5 ml MMA (200 mg/ml) into a femoral vein, revealed a ten to hundred fold reduced MMA concentration at the moment blood entered the pulmonary capillaries and additionally ten times reduction when the blood had passed the lungs. This may indicate that the MMA concentrations recorded in central venous and mixed venous blood of earlier reports only reflect a small fraction of the actual concentrations in vein blood close to cemented areas. This rapid decrease of MMA concentrations by passage of blood from the femoral vein to the pulmonary artery is mainly due to dilution but also underlines the highly lipophilic character of MMA. In areas of high concentrations MMA rapidly penetrates and destroys cell membranes and may potentially contribute to development of local deep vein thrombosis. In addition, systemic effects of MMA may superimpose on existing disturbances of the thrombohaemorrhagic balance during hip replacement surgery and cause haemodynamic alterations which occasionally may be fatal. (Hip International 1997; 7: 158-68)