Dynamic and Quantitative Assessment of Blood Coagulation Status with an Oscillatory Rheometer

Abstract

During open heart surgery, the haemostasis status of a patient has to be monitored permanently in order to quickly and reliably detect bleeding or coagulation-based disorders. Currently, no single medical device is available to provide a comprehensive solution for monitoring the coagulation status (coagulation, platelets and fibrinolysis). We intend to approach this problem with a rheological method. Here, we compared the performance of an oscillatory rheometer with a medical reference device, a ball coagulometer. Measuring the extrinsic coagulation (prothrombin time; PT), various heparin concentrations (0.5–2.0 IU/mL) could be differentiated and also discriminated from the intrinsic coagulation (activated partial thromboplastin time; aPTT) providing comparable clotting times between rheometer and ball coagulometer. In addition, the oscillatory rheometer was capable to detect the antagonising of heparin with the equimolar concentration of protamine and also the titration of various protamine concentrations (0.5–3.0 IU/mL) to a fixed heparin concentration (2 IU/mL). The addition of increasing concentrations of heparin to citrated blood prolonged the clotting time (CT), changed the slope calculated by linear regression of the elastic and viscous shear moduli (i.e., information of the coagulation process) and changed the value of the shear moduli at the end of the measurement (300 s). These results indicate that the oscillatory rheometer is capable to dynamically measure the haemostasis status with different activators and various inhibitor concentrations.

Keywords

• oscillatory rheometry
• blood coagulation
• haemorheology
• viscoelastic
• point-of-care