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CARDIOVASCULAR ANESTHESIA

Qualitative Thrombelastographic Detection of Tissue Factor in Human Plasma

Vance G. Nielsen, MD^*, Paul Audu, MD, Lana Cankovic, MD^*, Ralph T. Lyerly, III, MD^*, Brad L. Steenwyk, MD^*, Valerie Armstead, MD, and Garry Powell, BS

From the Department of *Anesthesiology, The University of Alabama at Birmingham, Birmingham, Alabama and Department of Anesthesiology, Thomas Jefferson University, Philadelphia, Pennsylvania.

BACKGROUND: Tissue factor (TF) is the principal in vivo initiator of coagulation, with normal circulating TF concentrations reported to be approximately 23–158 pg/mL. However, patients with atherosclerosis or cancer have been reported to have TF concentrations ranging between 800 and 9000 pg/mL. Of interest, thrombelastographic (TEG®)-based measures of clot initiation and propagation have demonstrated hypercoagulability in such patients at risk for thromboembolic events. Thus, our goal in the present investigation was to establish a concentration-response relationship of the effect of TF on TEG® variables, and determine specificity of TF-mediated events with a monoclonal TF antibody.

METHODS: Thrombelastography was performed on normal human plasma exposed to 0, 500, 1000, or 2000 pg/mL TF. Additional experiments with plasma exposed to 0 or 750 pg/mL TF in the presence or absence of a monoclonal TF antibody (1:360 dilution, 10 min incubation) were also performed. Clot initiation time (R) and the speed of clot propagation (MRTG, maximum rate of thrombus generation) were determined.

RESULTS: The addition of TF to normal plasma resulted in a significant, concentration-dependent decrease in R and increase MRTG values. The addition of TF antibody to samples with TF significantly increased R and decreased MRTG values compared to samples with TF addition.

CONCLUSIONS: In conclusion, changes in TEG® variables in conjunction with use of a TF antibody can detect pathological concentrations of TF in human plasma in vitro. Further investigation is warranted to determine if TEG®-based monitoring could assist in the detection and prevention of TF-initiated thromboembolic events.