Tissue factor is rapidly elevated in plasma collected from the pericardialcavity during cardiopulmonary bypass

There is growing evidence that the tissue factor/factor VIIa pathway of coa gulation is enhanced during cardiopulmonary bypass. Hitherto, available evi dence has suggested that upregulated monocyte bound tissue factor is made a vailable, either in the blood collected from the site of surgery or on circ ulating cells. However, cellular upregulation is slow, while generation of factor VIIa in blood collected from the pericardial cavity is rapid. We hav e therefore investigated the possibility of in alternative sourer of tissue factor, plasma las opposed to cellular) tissue factor In blood samples tak en from the central vein catheter (systemic circulation) and collected from the pericardial cavity during cardiopulmonary bypass. Six patients undergo ing first time cardiopulmonary bypass grafting were studied. Tissue factor antigen was found to be rapidly elevated (by 15 min) in the pericardial pla sma, similar to 5-fold above systemic levels (p <0.004). Similar elevations were found in markers of coagulation activation, factor VIIa antigen (p = 0.066), prothrombin fragment F1+2 (P <0.003) and thrombin-antithrombin comp lex (p <0.03). To explore whether plasma tissue factor was (or had been) fu nctionally active, factor VIIa was measured also with the soluble tissue fa ctor functional assay after removal of heparin. Functional factor VIIa acti vity fell significantly in the systemic circulation, probably due to the he parin-induced increase (similar to 15-fold) in tissue factor pathway inhibi tor (TFPI), but was elevated in pericardial blood compared ed with that tak en from the central line catheter (p <0.006). These results demonstrate tha t both components of the activation complex for the extrinsic pathway of co agulation are rapidly generated in pericardial blood during bypass.