ECHOGENIC EMBOLI UPON TOURNIQUET RELEASE DURING TOTAL KNEE ARTHROPLASTY - PULMONARY HEMODYNAMIC-CHANGES AND EMBOLIC COMPOSITION

Echogenic venous emboli accompany tourniquet deflation during total kn ee arthroplasty. The associated pulmonary hemodynamic alterations and determined embolic composition were measured in 34 patients, undergoin g 35 procedures. Ten patients received a femoral venous catheter on th e operative side. Hemodynamic variables, heart rate and mixed venous o ximetry, end-tidal CO2 and nitrogen tensions, and transesophageal echo cardiograms were recorded after induction of anesthesia (baseline), af ter tourniquet inflation, after cementing, and for 15 min after tourni quet deflation. Echocardiograms revealed either showers of miliary ech ogenic material (Group S, 9 patients), or large echogenic masses super imposed on the showers (Group MS, 26 patients). In Group MS only, pulm onary vascular resistance index increased above baseline (205 +/- 16 [ SEM] dyne.s.cm(-2)) beginning 5 min after tourniquet deflation (maximu m 328 +/- 29, P < 0.05). Mean pulmonary arterial pressure increased ab ove baseline (20 +/- 1.0 mm Hg) for both Groups S and MS beginning 3 m in after tourniquet deflation (27 +/- 1.0, P < 0.05). Cardiac index di d not change. Five of 10 patients demonstrated fresh thrombus from the catheter in the operative limb. Echogenic emboli occurred in all pati ents upon tourniquet deflation during knee arthroplasty. Pulmonary vas cular resistance index increased only in patients with large echogenic material. Our data suggest that these emboli represent fresh thrombus formation during tourniquet inflation. Heparin administration prior t o tourniquet inflation may diminish embolic showers.