PREDICTING THE RISK OF FAT EMBOLISM SYNDROME AFTER THE FIRST OF BILATERAL SINGLE-STAGE TOTAL KNEE ARTHROPLASTIES: INTRAOPERATIVE MONITORING OF ONE HUNDRED AND SIXTY-THREE PATIENTS.

Abstract

To reduce the reported 1% mortality rate in the first month because of embolism and cardiopulmonary complications, intraoperative Swan Ganz catheter monitoring has become routine at our institution for patients undergoing bilateral total knee arthroplasties. By calculating the pulmonary vascular resistance, patients at risk for fat embolism syndrome can be identified after the first of single-stage, sequential bilateral total knee arthroplasties prior to proceeding to the second arthroplasty. This study evaluates the reliability of quantitative parameters for canceling the second side.

The purpose of this study was to evaluate the reliability of quantitative criteria for proceeding with the second side of single-stage, sequential bilateral total knee arthroplasties.

Our experience did enable this procedure to be performed in a consistently safe manner. Bilateral total knee replacements have a reported 1% mortality rate in the first month largely because of embolism and cardiopulmonary complications. Adhering to a monitoring protocol that allows this risk to be minimized enables surgeons to offer this treatment to the many patients with bilateral gonarthrosis.

One hundred and sixty-three consecutive patients who had one-stage, sequential, bilateral total knee arthroplasties were monitored prospectively with a pulmonary artery Swan Ganz catheter. The pulmonary vascular resistance was calculated before skin incision, ten minutes after deflation of the tourniquet following completion of the first arthroplasty, and again after the second knee replacement. The second knee replacement was cancelled in seventeen patients because the pulmonary vascular resistance after the first arthroplasty had either doubled from baseline, or was above 200 dyne/second/cm⁵. Of those who had their bilateral arthroplasties performed, 2% developed signs of fat embolism syndrome, while in the group in whom the second side was cancelled, a 6% incidence was observed. The mortality rate for the entire cohort was 0%. Intraoperative monitoring with a pulmonary artery catheter reliably indicates which patients are at increased risk for pulmonary vascular compromise after one total knee replacement and therefore are not eligible for a second total knee replacement at the same operation.