Impact of fibrinogen concentration in severely ill patients on mechanical properties of whole blood clots.
ABSTRACT Fibrinogen concentration influences mechanical and functional properties of the clot. The purpose of the present study was to identify threshold concentrations of fibrinogen resulting in relevant changes in whole blood clot elastic modulus and platelet contractile force, as well as plasma prothrombin time and activated partial thromboplastin time. We measured clot elastic modulus, platelet contractile force, and other hemostasis parameters in whole blood samples from 552 patients admitted to a surgical intensive care unit. Platelet contractile force and clot elastic modulus were measured using the Hemodyne apparatus. Fibrinogen levels were between less than 0.10 and 9.44 g/l, with a mean of 2.41 g/l. Mean platelet count was 203 x 10(9) l(-1), with a range of 16 x 10(9) l(-1) to 682 x 10(9) l(-1). High levels of fibrinogen result in improved mechanical stability and improved interaction of platelets with the fibrin network. Clot elastic modulus and platelet contractile force are correlated positively with plasma fibrinogen concentration. However, there was no threshold concentration or ceiling effect concerning the mechanical properties of the clots. In contrast, clotting time assays such as prothrombin time, thrombin time, or activated partial thromboplastin time are influenced by the fibrinogen concentration only at levels below 1 g/l. In linear regression analysis, clot elastic modulus was mainly influenced by fibrinogen concentration (F = 185.4, P < 0.0001), whereas platelet contractile force was influenced by fibrinogen (F = 197.0, P < 0.0001) and platelet count (F = 104.7, P < 0.0001). The present data show that 1 g/l is a threshold fibrinogen concentration for an effect on coagulation assays such as prothrombin time, thrombin time, or activated partial thromboplastin time, but increasing fibrinogen concentrations above this level results in further continuous improvement of mechanical properties of the whole blood clot.
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ABSTRACT: We have developed and investigated a novel optical approach, Laser Speckle Rheology (LSR), to evaluate a patient's coagulation status by measuring the viscoelastic properties of blood during coagulation. In LSR, a blood sample is illuminated with laser light and temporal speckle intensity fluctuations are measured using a high-speed CMOS camera. During blood coagulation, changes in the viscoelastic properties of the clot restrict Brownian displacements of light scattering centers within the sample, altering the rate of speckle intensity fluctuations. As a result, blood coagulation status can be measured by relating the time scale of speckle intensity fluctuations with clinically relevant coagulation metrics including clotting time and fibrinogen content. Our results report a close correlation between coagulation metrics measured using LSR and conventional coagulation results of activated partial thromboplastin time, prothrombin time and functional fibrinogen levels, creating the unique opportunity to evaluate a patient's coagulation status in real-time at the point of care.Biomedical Optics Express 03/2014; 5(3):817-31. · 3.50 Impact Factor
Article: In reply.Transfusion 05/2014; 54(5):1443-4. · 3.57 Impact Factor
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ABSTRACT: We aimed to create a theoretical tool to model the effect of three haemostatic agents containing fibrinogen (therapeutic plasma, cryoprecipitate, and fibrinogen concentrate) on the patient's plasma fibrinogen level.BJA British Journal of Anaesthesia 07/2014; · 4.24 Impact Factor