Estimating the rate of thrombin and fibrin generation in vivo during cardiopulmonary bypass

Abstract

Our objective was to estimate the in vivo rates of thrombin and fibrin generation to better understand how coagulation is regulated. Studied were 9 males undergoing cardiopulmonary bypass (CPB). The rates of thrombin, total fibrin, and soluble fibrin generation in vivo were based on measured levels of prothrombin activation peptide F1.2, thrombin-antithrombin complex, fibrinopeptide A, and soluble fibrin, combined with a computer model of the patient's vascular system that accounted for marker clearance, hemodilution, blood loss, and transfusion. Prior to surgery, the average thrombin generation rate was 0.24 ؎ 0.11 pmol/s. Each thrombin molecule in turn generated about 100 fibrin molecules, of which 1% was soluble fibrin. The thrombin generation rate did not change after sternotomy or administration of heparin, then rapidly increased 20-fold to 5.60 ؎ 6.65 pmol/s after 5 minutes of CPB (P ‫؍‬ .000 05). Early in CPB each new thrombin generated only 4 fibrin molecules, of which 35% was soluble fibrin. The thrombin generation rate was 2.14 ؎ 1.88 pmol/s during the remainder of CPB, increasing again to 5.47 ؎ 4.08 pmol/s after reperfusion of the ischemic heart (P ‫؍‬ .000 08). After heparin neutralization with protamine, thrombin generation remained high (5.34 ؎ 4.01 pmol/s, P ‫؍‬ .0002) and total fibrin generation increased, while soluble fibrin generation decreased. By 2 hours after surgery, thrombin and fibrin generation rates were returning to baseline levels. We conclude that cardiopulmonary bypass and reperfusion of the ischemic heart results in bursts of nonhemostatic thrombin generation and dysregulated fibrin formation, not just a steady increase in thrombin generation as suggested by previous studies.

Thrombin Generation in Vitreous and Subretinal Fluid of Patients with Retinal Detachment

“…In plasma, TAT is cleared about 10 times faster by the liver from the circulation than F1+2 (8 min vs. 90 min), which results in a difference in molar concentrations and a ratio of approximately 0.1 [7]. In the ocular fluids, the molar concentration ratio was closer to 1 (Fig.…”

Dynamics of Thrombin Generation and Flux from Clots during Whole Human Blood Flow over Collagen/Tissue Factor Surfaces

“…2D) was developed from 13 individual experiments with blood from 13 donors, representing the average dynamics of human thrombin generation from clots formed on collagen/ high TF surface (ϳ1 molecule TF/m 2 , 5 mM GPRP, 40 g/ml CTI): a slow increase in thrombin flux during the first 500 s to 0.5 ϫ 10 Ϫ12 nmol/m 2 -s followed by an accelerated increase (ϳ4ϫ higher than the rate of increase during the first 500 s), reaching a thrombin flux of ϳ1.5 ϫ 10 Ϫ12 nmol/m 2 -s by 800 s at the end point of the experiment. The standard error was attributed to interdonor variation in thrombin generation of about Ϯ50%, as has been previously observed with measurements of thrombin generation by the CAT assay (47). Given this observed variation, subsequent experiments were conducted with at least four donors under matched conditions.…”

“…Thrombin half-life is less than a minute in the presence of AT (46), a reaction accelerated by heparin. TAT complex measurement has been routinely used to estimate thrombin level in plasma samples (17,47,48). Here we measure thrombin flux from TF bearing collagen surface and aggregated platelets at a venous shear rate in a human whole blood microfluidic thrombosis assay by collecting effluent at the outlet of the microfluidic system and subsequently measuring TAT complex concentration with enzyme linked immunosorbent assay (ELISA).…”

The effect of acute normovolemic hemodilution on plasma fibrinogen level in coronary artery bypass grafting

“…[13] Due to an increased plasmin generation, most of this soluble fibrin is degraded, and is not available for coagulation following heparin reversal. [14] If this hyperfibrinolytic state is prevented with the use of anti-fibrinolytic drugs, hemodilution appears to be the main cause of reduced fibrinogen levels.…”