Cardiorespiratory and vascular dysfunction related to major reconstructive orthopedic surgery.

Major orthopedic reconstructive surgery is highly traumatic and may be associated with serious peri-operative cardiorespiratory and vascular complications which occasionally may be fatal. These complications are commonest in patients receiving cemented hip prostheses following femoral neck fractures. The etiology is multifactorial. Bone traumatization induces activation of the hemostatic system, i.e., thrombin generation, in venous blood draining the operation area. When this activated blood passes the lung, more thrombin is generated and the blood becomes hypercoagulable and causes fibrin-formation in the lung vessels, with trapping of cellular debris. Thrombin has many hormone-like effects beyond its function in the coagulation cascade system. It may increase vein wall permeability and cause constriction of vessels, which increases blood pressure in the lung. In addition, impaction of bone cement to fill bone cavities or to fix prostheses causes additional mechanical trauma and further release of procoagulant substances into venous blood. Further, release of the cytotoxic chemical methyl-methacrylate monomer into venous blood is superimposed on the thrombin-primed hemostatic disturbances in the lung microvasculature. All these effects may finally induce hemodynamic insufficiency, which occasionally may be fatal. To prevent these adverse reactions, thrombin activity should be reduced and impaction of bone cement minimized.