Intramedullary pressure and pulmonary function during total knee arthroplasty

Twenty-eight patients who underwent unilateral total knee arthroplasty and 20 patients who underwent simultaneous bilateral total knee arthroplasties participated in. this study and mere randomized to have either a fluted or round IO-mm diameter femoral intramedullary alignment rod used during surge ry, The intramedullary rods were cannulated and connected with pressure tub ing to a monitor which provided measurements of pressure at the tip of each rod. Arterial blood gas measurements on room air were obtained before and on the morning after surgery. An arterial line was placed and an arterial b lood gas measurement was obtained at the time of skin incision and again af ter tourniquet release. Pulmonary shunt was calculated from the arterial bl ood gas measurements. Intramedullary pressure during rod insertion was sign ificantly higher for the groups of patients having the round compared with the fluted rod. The change in pulmonary shunt during surgery was lowest for the patients in the unilateral group having the fluted rod and highest for the patients in the bilateral group having the round rod. A fluted rather than a round intramedullary alignment rod should be used to minimize intram edullary pressure and pulmonary shunting during unilateral and bilateral to tal knee arthroplasties.