The incidence of large venous emboli during total knee arthroplasty without pneumatic tourniquet use

Echogenic venous emboli accompany tourniquet deflation during total knee arthroplasty. Two types of echogenic emboli appear in the central circulation: small venous emboli (miliary emboli) and large venous emboli (masses of echogenic material superimposed on miliary emboli). Presumably, medullary cavity trespass releases small and large echogenic emboli. However, patients undergoing lower extremity procedures with a tourniquet have large echogenic emboli regardless of medullary cavity invasion. Avoiding tourniquet inflation may decrease the release of large venous emboli. Thirteen patients undergoing total knee arthroplasty without pneumatic tourniquet received intramedullary guides and 11 patients received tibial extramedullary guides. Recordings of hemodynamic variables, mixed venous oximetry, end-tidal CO,, and echocardiographic images were made after the induction of anesthesia and for 15 min after femoral prosthesis cementing. Mean arterial pressure did not change during the study, and mean pulmonary arterial pressure increased minimally. Large venous emboli appeared in eight patients, small Venous emboli appeared in 12 patients, and no emboli appeared in four patients. Compared with previous investigations of large venous emboli during total knee arthroplasty with a pneumatic tourniquet, multiple logistic regression analysis discloses a 5.33-fold greater risk of large venous embolism accompanied the use of a tourniquet during total knee arthroplasty. Implications: One third of knee replacements performed without a tourniquet demonstrated large emboli. Reducing marrow cavity invasion did not decrease the release of large emboli. Compared with knee replacement without tourniquet, tourniquet use places patients at a 5.33-fold greater risk of having a large emboli.