Faster spatial fibrin clot formation in neonates than in adults.
A. Schlagenhauf, S. Pohl, E. Zoehrer, B. Leschnik, H. Haidl, S. Gallistl, W. Muntean (Graz, Austria)
Time: 08:00 - 09:15
Objective: Neonates have lower levels of clotting factors but also inhibitors resulting in a hemostatic balance that is more fragile than that of adults. Most conventional clotting assays show apparent hypocoagulation, because added tissue factor concentrations are too high. We have shown that neonatal and adult hemostasis is almost comparable when low levels of tissue factor are used. We assumed a well functioning tissue factor independent propagation phase in clot formation as underlying cause for our findings. The Thrombodynamics assay is the first assay that takes local separation of initiation and propagation phase into account, thus allowing isolated evaluation of fibrin clot formation in spatial distance from immobilized tissue factor. We aimed to test neonatal and adult samples with this assay and to compare results with those obtained with Calibrated Automated Thrombography (CAT).
Methods: Plasma from cord blood (N=26), respective maternal venous blood (N=10), as well as from venous blood of healthy neonates (N=8) and adults (N=10) was measured with the Thrombodynamics assay. All samples except venous blood from neonates were also measured with CAT using 1 pM and 5 pM tissue factor.
Results: In the Thrombodynamics assay initial (Vi) and stationary rates (Vs) of clot formation were significantly higher in neonatal than in adult samples (Vi: 72.41±7.32 µm/min vs. 58.53±5.04 µm/min P<0.001; Vs: 54.67±16.18 µm/min vs. 29.18±4.95 µm/min, P<0.001). No differences were observed between cord blood and neonatal venous blood. Maternal samples exhibited higher stationary rates than samples from healthy adults (Vs: 55.74±5.272 µm/min vs. 29.40±4.945 µm/min, P<0.001). CAT parameters showed higher correlations with Thrombodynamics parameters when small amounts of tissue factor were used. The highest correlation was observed between Vi and the endogenous thrombin potential (R=0,667, P<0,001).
Conclusion: The Thrombodynamics assay depicts the neonatal hemostatic phenotype better than conventional clotting assays showing that clot propagation occurs faster than in adults when tissue factor is immobilized on a surface mimicking a damaged vessel wall.