# Dynamic and Quantitative Assessment of Blood Coagulation Status with an Oscillatory Rheometer
## 3 Results
### Antagonising Heparin with Equimolar Concentrations of Proamine  
During extracorporeal circulation, human whole blood is usually anticoagulated with heparin. After weaning from ECC, protamine is used as heparin antagonist to restore the initial coagulation state. The following experiments were performed to visualise the ability of the oscillatory rheometer to determine the effect of protamine neutralising heparin. Therefore, citrated whole blood was additionally anticoagulated with 1.0, 2.0 and 3.0 IU/mL heparin and simultaneously neutralised with the equivalent amount of protamine before activation with Thromb (Figure 3). As reference measurements, citrated blood without heparin (orange curves) and with 1 IU/mL heparin (black curves) were activated with Thromb. Once a ratio of 1:1 of heparin and protamine was given, the effect of heparin was almost completely abolished and the curves were more or less congruent to the reference measurement of citrated blood with Thromb. In contrast, the heparin solution with 1 IU/mL showed a prolonged clotting time and a lower slope compared to the reversed heparin measurements. The following table (Table 3) summarises the clotting times, linear slopes and the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Test** & **Kinexus Pro** & **KC 1A** & \multicolumn{3}{c}{**Kinexus Pro**} \\ \hline  & **CT/s** & **CT/s** & **G\({}^{\prime}\) (Pa) at 300 s** & **G\({}^{\prime\prime}\) (Pa) at 300 s** & **m (G\({}^{\prime}\)/Pa s\({}^{-1}\))** & **m (G\({}^{\prime\prime}\)/Pa s\({}^{-1}\))** \\ \hline aPTT & 43.7 \(\pm\) 3.9 & 44.1 \(\pm\) 4.3 & 6.2 \(\times\) 10\({}^{-1}\) \(\pm\) 0.4 \(\times\) 10\({}^{-1}\) & 7.4 \(\times\) 10\({}^{-2}\)\(\pm\) 1.9 \(\times\) 10\({}^{-2}\) & 2.6 \(\times\) 10\({}^{-2}\)\(\pm\) 0.4 \(\times\) 10\({}^{-2}\) & 6.4 \(\times\) 10\({}^{-3}\)\(\pm\) 1.4 \(\times\) 10\({}^{-3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Citrated blood activated by Pathromit and CaCl\({}_{2}\) (_n_ = 10). Summary of the clotting time (CT), elastic (G\({}^{\prime}\)) and viscous (G\({}^{\prime\prime}\)) shear moduli at 300 s and linear slopes (m (G\({}^{\prime}\)) and m (G\({}^{\prime\prime}\))). Figure 2: The activated partial thromboplastin time (aPTT) is performed as a further coagulation assay with the oscillatory rheometer. Citrated blood was activated by Pathromit and CaCl\({}_{2}\). (**a**) The mean of \(n\) = 10 measurements with respective standard deviations are shown. The measurement was performed at a shear stress of 0.04 Pa with 0.1 Hz and a 1\({}^{\circ}\)/40 mm stainless steel cone geometry; (**b**) Enlarged part from diagram (**a**). The dashed red line at 0.02 Pa visualises the elastic shear modulus and the dotted blue line at 0.05 Pa the viscous shear modulus of uncoagulated citrated blood with no coagulation activator. After the addition of the activator Pathromitin and CaCl\({}_{2}\) an increase of G\({}^{\prime}\) and G\({}^{\prime\prime}\) was observed. The clotting time (CT) is about 43.7 s (black solid line). The values of G\({}^{\prime}\) and G\({}^{\prime\prime}\) at 300 s are smaller in comparison to the PT control measurements. viscous and elastic shear moduli at 300 s. As before, there was no significant difference between clotting times measured by the oscillatory rheometer and KC 1A, neither at measurements with or without additional heparin or at the various combinations of heparin and protamine (Appendix A Figure A7). Furthermore, the clotting times (CTs) of the protamine antagonised heparin concentrations were not significantly different from the control measurement without heparin, but significantly different from the heparinised (1 IU/mL) control samples, providing evidence of the functionality of equimolar protamine as antagonist. An exception was the CT of the ball coagulometer at a concentration 2 IU/mL heparin/protamine that was significantly different from the mean control.