Establishing reference ranges of cord blood: point-of-care hemostatic function assessment in preterm and term neonates.

BACKGROUND: Thrombelastometry, allowing timely assessment of global hemostatic function, is increasingly used to guide hemostatic interventions in bleeding patients. Reference values are available for adults and children, including infants but not neonates immediately after birth. METHODS: Neonates were grouped as preterm (30 + 0 to 36 + 6 weeks/days) and term (37 + 0 to 39 + 6 weeks/days). Blood samples were drawn from the umbilical cord immediately after cesarean section and analyzed by thrombelastometry. Reference ranges were determined for the extrinsic and intrinsic coagulation pathways, fibrin polymerization, and hyperfibrinolysis detection. RESULTS: All extrinsically activated test parameters, but maximum lysis (P = 0.139) differed significantly between both groups (P ≤ 0.001). Maximum clot firmness in the fibrin polymerization test was comparable (P = 0.141). All intrinsically activated test parameters other than coagulation time (P = 0.537) and maximum lysis (P = 0.888) differed significantly (P < 0.001), and so did all aprotinin-related test parameters (P ≤ 0.001) but maximum lysis (P = 0.851). CONCLUSIONS: This is the first study to identify reference ranges for thrombelastometry in preterm and term neonates immediately after birth. We also report differences in clot initiation and clot strength in neonates born <37 versus ≤40 weeks of gestation, mirroring developmental hemostasis. IMPACT: Impact: This prospective observational study is the first to present reference ranges in preterm and term infants for all types of commercially available tests of thrombelastometry, notably also including the fibrin polymerization test. IMPORTANCE: Viscoelastic coagulation assays such as thrombelastometry have become integral to the management of perioperative bleeding by present-day standards. Reference values are available for adults, children, and infants but not for neonates. Key message: Clot initiation and formation was faster and clot strength higher in the term than in the preterm group. Parameters of thrombelastometry obtained from cord blood do not apply interchangeably to preterm and term neonates.

Viscoelastic testing in liver transplantation.

Despite the lack of large randomized clinical studies, viscoelastic tests (VETs) have been a critical armamentarium for hemostatic control in liver transplantation (LT) since the 1960s. Many transplant institutions have adopted VETs in their clinical practice. Several small-size randomized clinical trials on LT patients have suggested that VET-guided hemostatic treatment algorithms have led to decreased indications for and amounts of transfused blood products, especially fresh-frozen plasma, compared to standard laboratory-based hemostatic management. VETs have also been reported to offer insight into the diagnosis and prediction of LT patients' development of hypercoagulability-related morbidity and mortality. There is still a need for VET device-specific hemostatic algorithms in LT, and clinicians must take into account the tendency to underestimate the coagulation capacity of VETs in patients with end-stage liver disease where hemostasis is rebalanced.

Assessment of Coagulation by Thromboelastography During Ongoing Postpartum Hemorrhage: A Retrospective Cohort Analysis.

BACKGROUND: Rapid assessment of hemostasis during postpartum hemorrhage (PPH) is essential to allow characterization of coagulopathy, to estimate bleeding severity, and to improve outcome. Point of care (POC) coagulation monitors could be of great interest for early diagnosis and treatment of coagulation disorders in PPH. METHODS: Women with ongoing PPH >500 mL who clinically required an assessment of coagulation with thromboelastography (TEG) were included. The primary aim of this retrospective observational cohort study was to assess the predictive accuracy of TEG parameters for the diagnosis of coagulation disorders (hypofibrinogenemia ≤2 g/L, thrombocytopenia ≤80,000/mm, prothrombin ratio ≤50%, or activated partial thromboplastin time ratio ≥1.5) during PPH. The analyzed TEG parameters were Kaolin-maximum amplitude (K-MA), Kaolin-maximum rate of thrombus generation using G (K-MRTGG), functional fibrinogen-maximum amplitude (FF-MA), and functional fibrinogen-maximum rate of thrombus generation using G (FF-MRTGG). Secondary aims of this study were (1) comparison of the time delay between classical parameters and velocity curve-derived parameters (K-MA versus K-MRTGG and FF-MA versus FF-MRTGG) and (2) evaluation of the accuracy of TEG parameters to predict severe hemorrhage estimated by calculated blood losses. RESULTS: Ninety-eight patients were included with 98 simultaneous TEG analyses and laboratory assays. All parameters had an excellent predictive performance. For the Kaolin assay, no significant difference was evidenced between K-MA and K-MRTGG for the predictive performance for hypofibrinogenemia ≤2 g/L and/or thrombocytopenia ≤80,000/mm (respective area under the curve [AUC], 0.970 vs 0.981). For the functional fibrinogen assay, no significant difference was evidenced between FF-MA and FF-MRTGG for the predictive performance for hypofibrinogenemia ≤2 g/L (respective AUC, 0.988 vs 0.974). For both assays, the time to obtain results was shorter for the velocity parameters (K-MRTGG: 7.7 minutes [2.4 minutes] versus K-MA: 24.7 minutes [4.2 minutes], P < .001; FF-MRTGG: 2.7 minutes [2.7 minutes] versus FF-MA: 14.0 minutes [4.3 minutes], P < .001). All TEG parameters derived from the Kaolin and functional fibrinogen assays and Clauss fibrinogen were significantly predictive of severe PPH >2500 mL. CONCLUSIONS: During PPH, when coagulation assessment is indicated, TEG provides a rapid and reliable detection of hypofibrinogenemia ≤2 g/L and/or thrombocytopenia ≤80,000/mm. No difference in performance was evidenced between the velocity-derived parameters (K-MRTGG and FF-MRTGG) and the classical parameters (K-MA and FF-MA). However, velocity-derived parameters offer the advantage of a shorter time to obtain results: FF-MRTGG parameter is available within ≤5 minutes. POC assessment of hemostasis during PPH management may help physicians to diagnose clotting disorders and to provide appropriate hemostatic support.

Thromboelastography testing in mice following blood collection from facial vein and cardiac puncture.

: Blood collection is critical for mouse research studies particularly in hemostatic testing. Cardiac puncture; a standard effective method requires anesthesia and is a terminal procedure while facial vein technique allows multiple collections. Thromboelastography (TEG) is a global hemostasis test, provides a dynamic real-time picture of coagulation. However, TEG experiments in mice require large number of animals and may not allow pre/postinterventions assessment. In this study, we aimed to investigate the feasibility of facial vein sampling for TEG analysis as an alternative to cardiac puncture and examined the impact on coagulation results. Blood samples were obtained from a total of 10 C57BL/6 and CD-1 mice via cardiac puncture and a total of another eight mice of similar strains via facial vein sampling. We compared TEG parameters in both methods using descriptive statistics and the Student t test. Results show no significant difference in any of the TEG parameters between cardiac and facial vein blood indicating the two methods are comparable. Facial vein sampling provides a less costly alternative to cardiac puncture. It is a suitable blood collection method for pre/postinterventions or follow-up studies and it better addresses reduction and refinement goals in mouse studies. A larger study to evaluate the sex or strain and genetic background differences will be valuable.

Assessment of agreement and interchangeability between the TEG5000 and TEG6S thromboelastography haemostasis analysers: a prospective validation study.

BACKGROUND: TEG6S® and TEG5000® (Haemonetics Corp, USA) are haemostasis analysers that measure viscoelasticity properties of whole blood. Both use different mechanisms to assess similar components of the coagulation process. The aim of this study was to assess agreement and interchangeability between the TEG6S and TEG5000 analysers. METHODS: 3.5 mL whole blood was collected from 25 adult patients in a tertiary intensive care unit (ICU). Analysis was performed using TEG6S and TEG5000 haemostatic platforms. Agreement between platforms was measured using Lin's concordance coefficient (Lin's CC), further validated using intraclass correlation coefficients and reduced major axis regression (RMAR). RESULTS: Sixteen (64%) patients were male; mean (range) age: 59yo (23-86). TEG6S and TEG5000 systems were broadly interchangeable. The majority of TEG variables demonstrated almost perfect or substantial agreement and minimal proportional bias (maximum amplitude demonstrated a fixed bias). LY30%, however, demonstrated poor agreement and a proportional bias. Lin's CC coefficients (95% CI, RMAR slope, intercept) between TEG6S and TEG5000 variables were: R time: 0.78 (0.64-0.92, 0.76, 0.92); K time: 0.82 (0.69-0.94, 1.30, - 0.93); alpha angle: 0.79 (0.64-0.95, 1.04, - 1.43); maximum amplitude (MA): 0.90 (0.83-0.96, 0.99, - 5.0); LY30%: 0.34 (0.1-0.58, 0.43, 0.04). CONCLUSIONS: Adult patients with critical illness demonstrate almost perfect agreement in the R time and MA, substantial agreement in K time and alpha angle, but poor agreement in LY30%, as measured by the TEG6S and TEG5000 analysers. With the exception of LY30%, the TEG6S and TEG5000 platforms appear interchangeable. This has important implications for use in clinical practice and multi-site research programs. TRIAL REGISTRATION: ANZCRT number: 12617000062325 , registered 12/Jan17. Retrospectively registered.

Prospective assessment of the diagnostic and prognostic utility of rotational thromboelastometry for canine disseminated intravascular coagulation.

This study compared the haematological, haemostatic and thromboelastometric (TEM) parameters between dogs with and without suspected disseminated intravascular coagulation (DIC). Seventy-six dogs with a medical condition known to predispose to DIC were prospectively included in the study. Thirty-eight dogs (50 per cent) presented with haemorrhagic diatheses. DIC was diagnosed in 32 dogs (42 per cent). Thirty-five dogs (46 per cent) had a normal TEM profile, 25 dogs (33 per cent) had a hypercoagulable profile and 16 dogs (21 per cent) had a hypocoagulable profile. Except for the lysis parameters, all TEM parameters were significantly correlated with the presence of DIC in univariate and multivariate analyses. Mortality rates were significantly higher in dogs with DIC (50 per cent) than in dogs without DIC (27 per cent, P=0.043; OR 2.667, 95 per cent CI 1.049 to 6.701), and mortality rates were significantly higher in dogs with a hypocoagulable profile (69 per cent) than in dogs with a hypercoagulable (24 per cent, P=0.017; OR 4.800, 95 per cent CI 1.241 to 16.220) or a normal profile (31 per cent, P=0.046; OR 3.429; 95 per cent CI 1.006 to 11.470). All TEM parameters were significantly associated with mortality in univariate and multivariate analyses. Thromboelastometry appears to be a valuable tool for the diagnosis and prognosis of dogs with suspected DIC, especially those with a hypocoagulable profile that was associated with increased risk of death and increased risk of haemorrhagic diatheses.

Laboratory assessment of anti-thrombotic therapy in heart failure, atrial fibrillation and coronary artery disease: insights using thrombelastography and a micro-titre plate assay of thrombogenesis and fibrinolysis.

As heart failure, coronary artery disease and atrial fibrillation all bring a risk of thrombosis, anti-thrombotic therapy is recommended. Despite such treatment, major cardiovascular events such as myocardial infarction and stroke still occur, implying inadequate suppression of thrombus formation. Accordingly, identification of patients whose haemostasis remains unimpaired by treatment is valuable. We compared indices for assessing thrombogenesis and fibrinolysis by two different techniques in patients on different anti-thrombotic agents, i.e. aspirin or warfarin. We determined fibrin clot formation and fibrinolysis by a microplate assay and thromboelastography, and platelet marker soluble P selectin in 181 patients with acute or chronic heart failure, coronary artery disease who were taking either aspirin or warfarin. Five thromboelastograph indices and four microplate assay indices were different on aspirin versus warfarin (p < 0.05). In multivariate regression analysis, only microplate assay indices rate of clot formation and rate of clot dissolution were independently related to aspirin or warfarin use (p ≤ 0.001). Five microplate assay indices, but no thrombelastograph index, were different (p < 0.001) in aspirin users. Three microplate assay indices were different (p ≤ 0.002) in warfarin users. The microplate assay indices of lag time and rate of clot formation were abnormal in chronic heart failure patients on aspirin, suggesting increased risk of thrombosis despite anti-platelet use. Soluble P selectin was lower in patients on aspirin (p = 0.0175) but failed to correlate with any other index of haemostasis. The microplate assay shows promise as a tool for dissecting thrombogenesis and fibrinolysis in cardiovascular disease, and the impact of antithrombotic therapy. Prospective studies are required to determine a role in predicting thrombotic risk.

Validity of Thromboelastometry for Rapid Assessment of Fibrinogen Levels in Heparinized Samples During Cardiac Surgery: A Retrospective, Single-center, Observational Study.

OBJECTIVE: To assess the validity of fibrinogen assay of rotational thromboelastometry (FIBTEM)-derived estimates of fibrinogen in samples collected during cardiopulmonary bypass in cardiac surgical patients by comparison to Clauss method fibrinogen concentration. DESIGN: Retrospective observational study. SETTING: Single university hospital center. PARTICIPANTS: Human participants. INTERVENTIONS: Retrospectively obtained laboratory assays including rotational thromboelastometry (ROTEM) and Clauss fibrinogen assay. MEASUREMENTS AND MAIN RESULTS: A retrospective review was performed of anesthesia records at a single university teaching hospital during a 1-year period. From paired samples taken near the end of cardiopulmonary bypass, fibrinogen concentrations (Clauss method) were compared with FIBTEM-derived measures of maximal clot firmness (MCF) and clot amplitude at 10 minutes (A10) using Spearman's rank correlation, linear regression, and receiver operating characteristic curve analysis. The study included 1,077 patients. Clauss fibrinogen was correlated strongly with FIBTEM amplitudes (r = 0.78 for MCF and A10; p<0.01). The correlation was related inversely to hemoglobin concentration (p<0.01). The area under the receiver operating characteristic curve was 0.95; the optimal FIBTEM A10 cutoff for diagnosis of a fibrinogen concentration of<1.5 g/L was ≤8 mm. CONCLUSIONS: The FIBTEM was a valid point-of-care method for estimating the fibrinogen concentration during cardiopulmonary bypass and may be used for prediction of hypofibrinogenemia before separation from the extracorporeal circuit.

Assessment of the resonance thromboelastograph CS-3 for differentiation of coagulation disorders: a pilot in vitro investigation of simulated post-cardiopulmonary bypass coagulopathies.

Resonance thromboelastography (RTG), a further development of the thromboelastogram (TEG), has been designed for improved differentiation of the effect of the plasmatic coagulation factors (increasing F-leg) and platelets (decreasing P-leg) on clot formation. It is based on the effect of clot elasticity on the resonance of a swinging wire. We assessed the RTG for its ability to differentiate coagulation disorders that frequently occur after cardiac surgery. The RTG was performed with a CS-3 Analyzer. Samples from 10 healthy volunteers were investigated after the following preparations: (1) baseline values, (2) dilution to a hematocrit of 30% and 20% with either hydroxyl ethyl starch (HES) 10% or plasma; (3) addition of 0.25, 0.5, and 1.0 IU/mL porcine heparin with and without heparinase; and (4) addition of 1.0, 3.0, 4.0, and 5.0 microg/mL of the antiplatelet agent abciximab (ReoPro). Increasing concentrations of abciximab led to a slower decrease or in the case of higher concentrations, to a persistent elevation of the platelet leg of the RTG. Dilution of the hematocrit with plasma had no effect on the fibrin and platelet leg; whereas, dilution with HES 10% led to an inhibition of the fibrin and platelet leg. Dilution of the plasmatic coagulation factors resulted in an inhibition of both the fibrin and the platelet leg. The addition of 0.25 and 0.5 IU/mL of heparin led to an increased coagulation time and inhibition of the fibrin and platelet legs. These effects were eliminated by the addition of heparinase. The RTG enables the evaluation of platelet function under the condition of a nonimpaired plasma coagulation system. Depletion of plasma coagulation factors and the administration of small amounts of heparin do not enable the distinction between residual effects of an anticoagulant, coagulation factor deficiency, or impaired platelet function. However, the heparin effects can be eliminated by the addition of heparinase. Further improvement may be achieved using a modified RTG by adding plasma coagulation factors in one channel for an improved evaluation of platelet function, even under the condition of a loss of procoagulants.

Usefulness of thrombelastography in assessment of trauma patient coagulation.

OBJECTIVE: Thrombelastography (TEG) is used to rapidly assess coagulation abnormalities in cardiac and transplant surgery. The purpose of this study was to investigate TEG in the initial assessment of trauma patient coagulation. METHODS: TEG was performed on 69 adult blunt trauma patients during their initial evaluation. Demographics, history of inherited coagulopathies, medications, TEG parameters, platelet count, prothrombin time/partial thromboplastin time, Revised Trauma Score (RTS), Injury Severity Score (ISS), use of blood products, and outcome were recorded. RESULTS: Mortality was 4.3%. Fifty-two patients demonstrated coagulation abnormalities by TEG; of these, 45 were hypercoagulable (mean ISS 13.1), and seven were hypocoagulable (mean ISS 28.6). Six of the seven hypocoagulable patients received blood transfusions within the first 24 hours. Mean ISS of the 17 patients with normal TEG parameters was 3.7. Logistic regression of ISS, Revised Trauma Score, prothrombin time/partial thromboplastin time, and TEG on use/nonuse of blood products within the first 24 hours demonstrates that only ISS (p < 0.001) and TEG (p < 0.05) are predictive of early transfusion. CONCLUSIONS: The majority of blunt trauma patients in this series were hypercoagulable. TEG is a rapid, simple test that can broadly determine coagulation abnormalities. TEG is an early predictor of transfusion in blunt injury patients.