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: Demographic changes and aggressive platelet inhibition have resulted in a marked increase in blood- and coagulation product expenditure and costs in cardiac surgery. We analyzed "bedside" coagulation test (ROTEM) in order to verify clot forming quality for the purpose of finding a cost-effective treatment path. Annual treatment costs of all cardiosurgical patients were analyzed before (729 patients) and after (693 patients) implementation of "bedside" ROTEM. Cumulative numbers and costs of platelet concentrates (PltC), fresh frozen plasma (FFP), red blood cell units (RBC), and coagulation factors: pooled coagulation concentrates (PCC), recombinant factor VIIa (rFVIIa), factor XIII (FXIII), and fibrinogen were assessed. Average monthly numbers and costs were compared. Number of resternotomies and early mortality was assessed and compared in both periods. After ROTEM implementation cumulative RBC expenditure showed 25% decrease while PltC exhibited 50% decrease. FFP expenditure remained unchanged. PCC, FXIII were markedly reduced (-80%) while rFVIIa were entirely omitted. Fibrinogen, however, increased two-fold. Cumulative average monthly costs of all blood products decreased from 66,000 euro to 45,000 euro (-32%). Coagulation factor average monthly costs decreased from 60,000 euro to 30,000 euro (-50%) yielding combined savings of 44%. In contrast, average monthly costs for ROTEM were 1.580 euro. Total number of resternotomies decreased from 6.6% to 5.5% while early mortality (5.9%; 6.0%) remained stable. Cumulative costs for treatment of perioperative coagulation disorders can be reduced by "bedside" ROTEM analysis to achieve a selective substitution management. Saved costs for blood- and coagulation products clearly outweighed the expenses of ROTEM. Adequate differential coagulation management can therefore be cost-effective.European Journal of Cardio-Thoracic Surgery 06/2007; 31(6):1052-7. · 2.67 Impact Factor
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ABSTRACT: The objective of this study was to determine the relationship of the kaolin-activated Thrombelastograph (TEG) with postoperative bleeding and laboratory tests of coagulation in the setting of cardiac surgery with the routine use of -aminocaproic acid. Prospective observational study. An adult heart center at a tertiary referral, university hospital. Thirty adult cardiac surgical patients. The kaolin-activated TEG, platelet counts, prothrombin times, activated partial thromboplastin times, and fibrinogen levels were measured before induction of anesthesia, during cardiopulmonary bypass, and on arrival in the intensive care unit. Mediastinal and thoracostomy drainage were measured every hour for 4 hours after arrival in the intensive care unit. Correlation and multivariate linear regression modeling were used to describe relationships among coagulation tests, TEG parameters, and early postoperative bleeding. The TEG maximum amplitude (MA) parameter correlated well with postoperative bleeding (r = -0.6, p = 0.0018), more so than platelet count (r = -0.45, p = 0.02), fibrinogen level (r = -0.40, p = 0.06), or prothrombin time (r = 0.43, p = 0.02). The receiver operating characteristic curve c-index describing MA as a predictor for postoperative bleeding is 0.78. Abnormalities in all the laboratory test results were associated with an abnormal MA. In conclusion, the kaolin-activated TEG is associated with early coagulopathic bleeding. It may reflect the severity of a global coagulopathy affecting both platelets and coagulation factors and be a guide to incremental prohemostatic therapy in this setting.Journal of Cardiothoracic and Vascular Anesthesia 09/2006; 20(4):531-5. · 1.45 Impact Factor
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ABSTRACT: The Thromboelastogram (TEG; Haemoscope Corporation, Niles, IL) and the ROTEM thromboelastometry analyzer (Pentapharm GmbH, Munich, Germany) are coagulation monitors that measure the viscoelastic changes accompanying whole-blood coagulation generation and lysis. It is not clear whether TEG and ROTEM transfusion algorithms suggest similar blood component intervention. This study aims to report the extent to which administration of platelets, fresh frozen plasma, and cryoprecipitate would be indicated using protocol-dictated interventions by the Rotem, TEG, and conventional coagulation screens during orthotopic liver transplantation (OLT). Prospective observational study. University hospital. Twenty patients undergoing orthotopic liver transplantation. Coagulation was managed with native TEG protocols. Additional samples for kaolin TEG, kaolin heparinase TEG, Rotem in-TEM, Rotem hep-TEM, Rotem fib-TEM, full blood count, prothrombin time, and Clauss fibrinogen assays were taken at 5 fixed operative stages. Results were reviewed and protocol-indicated interventions recorded. There was moderate agreement between Clauss fibrinogen and Rotem fib-TEM assays about fulfilling fibrinogen transfusion criteria (kappa = 0.42, p < or = 0.05). Agreement between TEG and Rotem to transfuse platelets was fair (Rotem in-TEM/native heparinase TEG, kappa = 0.33, Rotem in-TEM/kaolin heparinase TEG, kappa = 0.28). There was moderate agreement between Rotem in-TEM and prothrombin time (kappa = 0.42), and poor agreement between other tests about the point to administer fresh frozen plasma. Transfusion practice is likely to differ according to the method of coagulation monitoring used. A prospective case-matched study using the viscoelastic tests used in this study would be beneficial in determining the optimal therapy. Rotem fib-TEM monitoring may improve hemostasis management.Journal of Cardiothoracic and Vascular Anesthesia 08/2006; 20(4):548-53. · 1.45 Impact Factor