FIBTEM PLUS provides an improved thromboelastometry test for measurement of fibrin-based clot quality in cardiac surgery patients

Point-of-Care Viscoelastic Hemostatic Assays in Cardiac Surgery Patients: Comparison of Thromboelastography 6S, Thromboelastometry Sigma, and Quantra

OBJECTIVES

Viscoelastic tests allow a reduction in blood product transfusion. Three modern devices are currently available (rotational thromboelastometry [ROTEM] sigma, thromboelastography [TEG] 6S, and Quantra). No study has compared the performances of these 3 devices simultaneously.

DESIGN

An observational, nonrandomized cohort study.

SETTING

A single-center of cardiac surgery in a university hospital.

PARTICIPANTS

A total of 30 consecutive measurements from at least 10 adult patients presenting significant bleeding in the intensive care unit after cardiac surgery INTERVENTION: Viscoelastic tests using ROTEM sigma, TEG 6S, and Quantra were performed concomitantly with conventional coagulation measurements MEASUREMENTS AND MAIN RESULTS: The authors included 16 patients with 31 blood samples. After the exclusion of missing values, 27 samples were analyzed. Correlation with platelet count was as follows: ROTEM, r = 0.84 [0.66-0.93], p < 0.0001; Quantra, r = 0.83 [0.64-0.92], p < 0.0001; TEG 6S, r = 0.64 [0.29-0.83], p = 0.001. Correlation with fibrinogen (Clauss assay) was as follows: ROTEM, r = 0.85 [0.68-0.93], p < 0.0001; Quantra, r = 0.88 [0.74-0.95], p < 0.0001; TEG 6S, r = 0.79 [0.55-0.91], p < 0.0001. No difference was observed for the detection of residual circulating heparin (anti-Xa activity >0.1), with 87% of correct identification for Quantra and 80% for both ROTEM and TEG 6S (p = 0.3). Time to first results after the beginning of the test was shorter for Quantra than ROTEM and TEG 6S (136 [126-152] seconds v 205 [176-221] seconds, p = 0.003 and v 450 [372-516] seconds, p < 0.0001 respectively).

CONCLUSION

ROTEM sigma, TEG 6S, and Quantra performed similarly for exploring platelet count or residual circulating heparin. Thromboelastography 6S presented a weaker correlation with fibrinogen Clauss.

A comparison of the ClotPro system with rotational thromboelastometry in cardiac surgery: a prospective observational study

Viscoelastic coagulation tests have been increasingly used for hemostasis management in cardiac surgery. The ClotPro system is a novel viscoelastic device based on principles of rotational thromboelastometry. We aimed to compare ClotPro with ROTEM and plasma coagulation assays in cardiopulmonary bypass (CPB) patients. Blood samples were collected from 25 CPB patients at (1) baseline, (2) start of CPB, (3) end of CPB, and (4) end of surgery. The EX-test, IN-test, HI-test, FIB-test parameters on ClotPro were compared with corresponding ROTEM assay (EXTEM, INTEM, HEPTEM, and FIBTEM). Standard plasma coagulation assays and endogenous thrombin generation (TG) were simultaneously evaluated. Pearson correlation analyses showed moderate correlations between clotting times (CTs) (r = 0.63-0.67; p < 0.001, respectively), and strong correlations with maximal clot firmness (MCF) (r = 0.93-0.98; p < 0.001, respectively) between ClotPro and ROTEM. EX-test and IN-test MCF parameters were interchangeable with acceptable percentage errors (EX-test MCF: 7.3%, IN-test MCF: 8.3%), but FIB-test MCF (27.0%) and CT results were not (EX-test CT: 44.7%, IN-test CT: 31.4%). The correlations of PT/INR or peak TG with EX-test CTs were higher than with EXTEM CTs (PT/INR: r = 0.80 and 0.41, peak TG: 0.43 and 0.18, respectively). FIB-test MCF has strong correlation with plasma fibrinogen and factor XIII level (r = 0.84 and 0.66, respectively). ROC analyses showed that ClotPro was capable of emulating well-established ROTEM thresholds (area under curves: 0.83-1.00). ClotPro demonstrated strong correlations in MCF parameters of ROTEM in CPB patients. It may be reasonable to modify ROTEM-based transfusion algorithm pertaining to MCF parameters to establish cut-off values for ClotPro device.

Fibrinogen and Bleeding in Adult Cardiac Surgery: A Review of the Literature

Background: Fibrinogen is a substrate for blood clots formation. In cardiac surgery, a number of different mechanisms lead to a decrease in fibrinogen levels and consequent impaired haemostasis. Patients undergoing cardiac surgery are therefore frequently exposed to blood loss and allogeneic blood transfusion, which are risk factors associated with morbidity and mortality. Thus, particular efforts in fibrinogen management should be made to decrease bleeding and the need for blood transfusion. Therefore, fibrinogen remains an active focus of investigations from basic science to clinical practice. This review aims to summarise the latest evidence regarding the role of fibrinogen and current practices in fibrinogen management in adult cardiac surgery. Methods: The PubMed database was systematically searched for literature investigating the role and disorders of fibrinogen in cardiac surgery and diagnostic and therapeutic procedures related to fibrinogen deficiency aimed at reducing blood loss and transfusion requirements. Clinical trials and reviews from the last 10 years were included. Results: In total, 146 articles were analysed. Conclusion: The early diagnosis and treatment of fibrinogen deficiency is crucial in maintaining haemostasis in bleeding patients. Further studies are needed to better understand the association between fibrinogen levels, bleeding, and fibrinogen supplementation and their impacts on patient outcomes in different clinical settings.

The strengths and weaknesses of viscoelastic testing compared to traditional coagulation testing

Optimized acute bleeding management requires timely and reliable laboratory testing to detect and diagnose coagulopathies and guide transfusion therapy. Conventional coagulation tests (CCT) are inexpensive with minimal labor requirements, but CCTs may have delayed turnaround times. In addition, abnormal CCT values may not reflect in vivo coagulopathies that require treatment and may lead to overtransfusion. The use of viscoelastic testing (VET) has been rapidly expanding and is recommended by several recent bleeding guidelines. This review is intended to compare CCT to VET, review the strengths and weaknesses of both approaches, and evaluate and summarize the clinical studies that compared CCT-based and VET-based transfusion algorithms. Most studies of CCT vs VET transfusion algorithms favor the use of VET in the management of massively bleeding patients due to reductions in blood product utilization, bleeding, costs, and lengths of stay.

Viscoelastometric Testing to Assess Hemostasis of COVID-19: A Systematic Review

Infection by SARS-CoV-2 is associated with a high risk of thrombosis. The laboratory documentation of hypercoagulability and impaired fibrinolysis remains a challenge. Our aim was to assess the potential usefulness of viscoelastometric testing (VET) to predict thrombotic events in COVID-19 patients according to the literature. We also (i) analyzed the impact of anticoagulation and the methods used to neutralize heparin, (ii) analyzed whether maximal clot mechanical strength brings more information than Clauss fibrinogen, and (iii) critically scrutinized the diagnosis of hypofibrinolysis. We performed a systematic search in PubMed and Scopus databases until 31st December 2020. VET methods and parameters, and patients' features and outcomes were extracted. VET was performed for 1063 patients (893 intensive care unit (ICU) and 170 non-ICU, 44 studies). There was extensive heterogeneity concerning study design, VET device used (ROTEM, TEG, Quantra and ClotPro) and reagents (with non-systematic use of heparin neutralization), timing of assay, and definition of hypercoagulable state. Notably, only 4 out of 25 studies using ROTEM reported data with heparinase (HEPTEM). The common findings were increased clot mechanical strength mainly due to excessive fibrinogen component and impaired to absent fibrinolysis, more conspicuous in the presence of an added plasminogen activator. Only 4 studies out of the 16 that addressed the point found an association of VETs with thrombotic events. So-called functional fibrinogen assessed by VETs showed a variable correlation with Clauss fibrinogen. Abnormal VET pattern, often evidenced despite standard prophylactic anticoagulation, tended to normalize after increased dosing. VET studies reported heterogeneity, and small sample sizes do not support an association between the poorly defined prothrombotic phenotype of COVID-19 and thrombotic events.

A hybrid scaffold of gelatin glycosaminoglycan matrix and fibrin as a carrier of human corneal fibroblast cells

A hybrid scaffold of gelatin-glycosaminoglycan matrix and fibrin (FGG) has been synthesized to improve the mechanical properties, degradation time and cell response of fibrin-like scaffolds. The FGG scaffold was fabricated by optimizing some properties of fibrin-only gel and gelatin-glycosaminoglycan (GG) scaffolds. Mechanical analysis of optimized fibrin-only gel showed the Young module and tensile strength of up to 72 and 121 KPa, respectively. Significantly, the nine-fold increase in the Young modulus and a seven-fold increase in tensile strength was observed when fibrin reinforced with GG scaffold. Additionally, the results demonstrated that the degradation time of fibrin was enhanced successfully up to 7 days which was much longer time compared to fibrin-only gel with 38 h of degradation time. More than 45% of FGG initial mass was preserved on day 7 in the presence of aprotinin. Human corneal fibroblast cells (HCFCs) were seeded on the FGG, fibrin-only gel and GG scaffolds for 5 days. The FGG scaffold showed excellent cell viability over 5 days, and the proliferation of HCFCs also increased significantly in comparison with fibrin-only gel and GG scaffolds. The FGG scaffold illustrates the great potential to use in which appropriate stability and mechanical properties are essential to tissue functionality.

Diagnostic accuracy of viscoelastic point-of-care identification of hypofibrinogenaemia in cardiac surgical patients: A systematic review

Hypofibrinogenaemia during cardiac surgery may increase blood loss and bleeding complications. Viscoelastic point-of-care tests provide more rapid diagnosis than laboratory measurement, allowing earlier treatment. However, their diagnostic test accuracy for hypofibrinogenaemia has never been reviewed systematically. We aimed to systematically review their diagnostic test accuracy for the identification of hypofibrinogenaemia during cardiac surgery. Two reviewers assessed relevant articles from seven electronic databases, extracted data from eligible articles and assessed quality. The primary outcomes were sensitivity, specificity and positive and negative predictive values. A total of 576 articles were screened and 81 full texts were assessed, most of which were clinical agreement or outcome studies. Only 10 diagnostic test accuracy studies were identified and only nine were eligible (ROTEM delta 7; TEG5000 1; TEG6S 1, n = 1820 patients) (ROTEM, TEM International GmbH, Munich, Germany; TEG, Haemonetics, Braintree, MA, USA). None had a low risk of bias. Four ROTEM studies with a fibrinogen threshold less than 1.5–1.6 g/l and FIBTEM threshold A10 less than 7.5–8 mm had point estimates for sensitivity of 0.61–0.88; specificity 0.54–0.94; positive predictive value 0.42–0.70; and negative predictive value 0.74–0.98 (i.e. false positive rate 30%–58%; false negative rate 2%–26%). Two ROTEM studies with higher thresholds for both fibrinogen (<2 g/l) and FIBTEM A10 (<9.5 mm) had similar false positive rates (25%–46%), as did the two TEG studies (15%–48%). This review demonstrates that there have been few diagnostic test accuracy studies of viscoelastic point-of-care identification of hypofibrinogenaemia in cardiac surgical patients. The studies performed so far report false positive rates of up to 58%, but low false negative rates. Further diagnostic test accuracy studies of viscoelastic point-of-care identification of hypofibrinogenaemia are required to guide their better use during cardiac surgery.

Comparison between the new fully automated viscoelastic coagulation analysers TEG 6s and ROTEM Sigma in trauma patients: A prospective observational study

BACKGROUND

Viscoelastic coagulation testing is increasingly used to diagnose trauma-induced coagulopathy. Two fully automated analysers, TEG 6s and ROTEM Sigma, were launched recently. No previous studies have compared these devices in trauma paients.

OBJECTIVE

The aim of this study was to evaluate whether both fully automatic devices deliver comparable results.

DESIGN

Prospective observational study.

SETTING

Level one trauma centre from August 2017 to September 2018.

PATIENTS

A total of 105 blood samples from 67 trauma patients were analysed simultaneously on TEG 6s and ROTEM Sigma.

MAIN OUTCOME MEASURES

TEG 6s assays kaolin (CK), RapidTEG (CRT), kaolin with heparinase (CKH) and functional fibrinogen were compared with ROTEM Sigma assays INTEM, EXTEM, HEPTEM and FIBTEM. TEG 6s functional fibrinogen level was compared with plasma fibrinogen concentration, measured using the Clauss method. Correlations were classified as weak (Spearman correlation coefficient 0.20 to 0.39), moderate (0.40 to 0.59), strong (0.60 to 0.79) or very strong (≥0.80).

RESULTS

The TEG 6s parameters reaction time, kinetic time and α-angle (CK, CRT and CKH assays) mostly showed strong correlations with the corresponding ROTEM parameters clotting time, clot formation time and α-angle (INTEM, EXTEM and HEPTEM assays). The exceptions were CRT reaction time vs. EXTEM clotting time, and CK α-angle vs. INTEM α-angle, which correlated moderately. Absolute values for many of these parameters showed significant differences between the two devices. Very strong correlations and similar absolute values were observed between TEG 6s maximum amplitude (CRT, CK and CKH assays) and ROTEM maximum clot firmness (EXTEM, INTEM and HEPTEM assays). Correlations were also very strong for functional fibrinogen maximum amplitude vs. FIBTEM maximum clot firmness and functional fibrinogen level vs. Clauss fibrinogen concentration, but absolute values were significantly different.

CONCLUSION

Strong to very strong correlations were observed between corresponding TEG 6s and ROTEM Sigma parameters. However, absolute values showed significant differences for most of the measurements.

The Influence of Inflammation on Fibrinogen Turnover and Redistribution of the Hemostatic Balance to a Prothrombotic State in High On-Treatment Platelet Reactivity-Dual Poor Responder (HTPR-DPR) Patients

Knowledge about the influence of inflammation on platelet function and relocation of hemostatic balance to hypercoagulable state is still unclear. We compared two groups of patients who suffer from acute vs. chronic inflammatory process and additionally present high on-treatment platelet reactivity-dual platelet resistance. We did not found any differences in platelet aggregation between both investigated groups, but patients who suffer from chronic inflammation presented stronger relocation of the hemostatic balance to the hypercoagulability. A high concentration of prothrombin fragment F1+2 together with higher activity of von Willebrand factor in critical limb ischemia shows more exaggerated fibrinogen turnover although the blood concentration of this factor was in normal range. We concluded that high on-treatment platelet reactivity-dual platelet resistance and intensified inflammation are linked with elevated platelet and fibrinogen turnover to counteract proper hemostatic balance in favor of a prothrombotic state.

Thromboelastography and Thromboelastometry in Assessment of Fibrinogen Deficiency and Prediction for Transfusion Requirement: A Descriptive Review

Fibrinogen is crucial for the formation of blood clot and clinical outcomes in major bleeding. Both Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM) have been increasingly used to diagnose fibrinogen deficiency and guide fibrinogen transfusion in trauma and surgical bleeding patients. We conducted a comprehensive and comparative review on the technologies and clinical applications of two typical functional fibrinogen assays using TEG (FF TEG) and ROTEM (FIBTEM) for assessment of fibrinogen level and deficiency, and prediction of transfusion requirement. Clot strength and firmness of FF TEG and ROTEM FIBTEM were the most used parameters, and their associations with fibrinogen levels as measured by Clauss method ranged from 0 to 0.9 for FF TEG and 0.27 to 0.94 for FIBTEM. A comparison of the interchangeability and clinical performance of the functional fibrinogen assays using the two systems showed that the results were correlated, but are not interchangeable between the two systems. It appears that ROTEM FIBTEM showed better associations with the Clauss method and more clinical use for monitoring fibrinogen deficiency and predicting transfusion requirements including fibrinogen replacement than FF TEG. TEG and ROTEM functional fibrinogen tests play important roles in the diagnosis of fibrinogen-related coagulopathy and guidance of transfusion requirements. Despite the fact that high-quality evidence is still needed, the two systems are likely to remain popular for the hemostatic management of bleeding patients.

The contribution of the individual blood elements to the variability of thromboelastographic measures

BACKGROUND

Thromboelastography (TEG) is widely advocated as a rapid method for obtaining critical blood coagulation data to guide resuscitation, but the method suffers well-known limits in sensitivity, repeatability, and interpretability.

STUDY DESIGN AND METHODS

Mixtures of fresh human blood components were prepared that represent the range of blood element concentrations seen in health and disease and after injury. These mixtures were tested in a TEG device after kaolin, tissue factor and phospholipid, or tissue factor and phospholipid with abciximab activation. The results were measured as reproducibility and nonlinear effects in regression analysis and evaluated for interpretability.

RESULTS

Clot strength was associated with increased platelet (PLT) content and plasma fibrinogen concentration and content. Increasing hematocrit (Hct) reduced while increasing PLT or plasma concentration increased TEG clot strength. The abciximab dose used to block PLT activity did not fully inhibit the PLT contribution to clot strength. Clot strength is logarithmically correlated in the absence and linearly correlated to PLT concentration in the presence of abciximab. TEG clot strength with or without abciximab is dependent on Hct, PLT, and plasma (fibrinogen) concentrations in complex patterns.

CONCLUSION

Interpretation of TEG variables is limited without knowledge of the concentration of the blood components present. When "normal" TEG values are known for a certain PLT-plasma-red blood cell concentration, the assay can be used to assess PLT and plasma function in coagulation. The TEG "functional fibrinogen" assay should be used only as a gross estimate of the fibrinogen concentration in whole blood.

Fibrinogen measurement in cardiac surgery with cardiopulmonary bypass: Analysis of repeatability and agreement of Clauss method within and between six different laboratories

Plasma fibrinogen concentration is important for coagulopathy assessment, and is most commonly measured using the Clauss method. Several factors, including device type and reagent, have been shown to affect results. The study objective was to evaluate performance and repeatability of the Clauss method and to assess differences between measurements performed during and after cardiopulmonary bypass (CPB), by testing plasma samples from patients undergoing cardiac surgery with CPB. Samples were collected from 30 patients before surgery, approximately 20 minutes before weaning from CPB, and 5 minutes after CPB and protamine. Fibrinogen concentration was determined using the Clauss method at six quality-controlled specialised laboratories, according to accredited standard operating procedures. Regarding within-centre agreement for Clauss measurement, mean differences between duplicate measurements were between 0.00 g/l and 0.15 g/l, with intervals for 95% limits of agreement for mean Bland-Altman differences up to 1.3 g/l. Regarding between-centre agreement, some mean differences between pairs of centres were above 0.5 g/l. Differences of up to ∼2 g/l were observed with individual samples. Increased variability was observed between centres, with inter-class correlation values below 0.5 suggesting only fair agreement. There were no significant differences in fibrinogen concentration before weaning from CPB and after CPB for most centres and methods. In conclusion, considerable differences exist between Clauss-based plasma fibrinogen measured using different detection methods. Nevertheless, the similarity between measurements shortly before weaning from CPB and after CPB within centres suggests that on-pump measurements could provide an early estimation of fibrinogen deficit after CPB and thus guidance for haemostatic therapy.

Comparison of Thrombelastography-Derived Fibrinogen Values at Rewarming and Following Cardiopulmonary Bypass in Cardiac Surgery Patients

BACKGROUND

The inflated costs and documented deleterious effects of excess perioperative transfusion have led to the investigation of targeted coagulation factor replacement strategies. One particular coagulation factor of interest is factor I (fibrinogen). Hypofibrinogenemia is typically tested for using time-consuming standard laboratory assays. The thrombelastography (TEG)-based functional fibrinogen level (FLEV) provides an assessment of whole blood clot under platelet inhibition to report calculated fibrinogen levels in significantly less time. If FLEV values obtained on cardiopulmonary bypass (CPB) during rewarming are similar to values obtained immediately after the discontinuation of CPB, then rewarming values could be used for preemptive ordering of appropriate blood product therapy.

METHODS

Fifty-one cardiac surgery patients were enrolled into this prospective nonrandomized study to compare rewarming fibrinogen values with postbypass values using TEG FLEV assays. Baseline, rewarming, and postbypass fibrinogen values were recorded for all patients using both standard laboratory assay (Clauss method) and FLEV. Mixed-effects regression models were used to examine the change in TEG FLEV values over time. Bland-Altman analysis was used to examine bias and the limits of agreement (LOA) between the standard laboratory assay and FLEVs.

RESULTS

Forty-nine patients were included in the analysis. The mean FLEV value during rewarming was 333.9 mg/dL compared with 332.8 mg/dL after protamine, corresponding to an estimated difference of -1.1 mg/dL (95% confidence interval [CI], -25.8 to 23.6; P = 0.917). Rewarming values were available on average 47 minutes before postprotamine values. Bland-Altman analysis showed poor agreement between FLEV and standard assays: mean difference at baseline was 92.5 mg/dL (95% CI, 71.1 to 114.9), with a lower LOA of -56.5 mg/dL (95% CI, -94.4 to -18.6) and upper LOA of 242.4 mg/dL (95% CI, 204.5 to 280.3). The difference between assays increased after CPB and persisted after protamine administration.

CONCLUSIONS

Our results revealed negligible change in FLEV values from the rewarming to postbypass periods, with a CI that does not include clinically meaningful differences. These findings suggest that rewarming samples could be utilized for ordering fibrinogen-specific therapies before discontinuation of CPB. Mean FLEV values were consistently higher than the reference standard at each time point. Moreover, bias was highly heterogeneous among samples, implying a large range of potential differences between assays for any 1 patient.

Platelet reactivity in thromboelastometry. Revision of the FIBTEM test: a basic study

This study aimed to investigate modifications to the FIBTEM test to better assess fibrinogen levels and the quality of fibrin polymerization in citrated blood using Multiplate impedance aggregometry to verify platelet inhibition. Blood samples from 26 healthy volunteers were subjected to thromboelastometry studies (EXTEM/FIBTEM tests) in accordance with the standard study protocol (cytochalasin D) and according to a modified protocol (synthetic IIbIIIa receptor antagonist vs. acetylsalicylic acid [ASA] + synthetic IIbIIIa receptor antagonist instead of cytochalasin D). Independent of thromboelastometry, Multiplate impedance aggregometry was used to assess the degree of restriction by the platelet blocked with the following treatments: (1) cytochalasin D, (2) synthetic IIbIIIa antagonist or (3) ASA + synthetic IIbIIIa antagonist to assess the aggregation response to activation with an agonist (ADP, collagen, thrombin receptor activating peptide-6 [TRAP-6], and arachidonic acid). Via aggregometry, cytochalasin D more weakly inhibited platelet aggregation than simultaneous administration of the -IIbIIIa receptor antagonist with ASA. However, total platelet aggregation inhibition was observed after simultaneous administration of cytochalasin D combined with a synthetic IIbIIIa receptor antagonist. In the thromboelastometry, a significant decrease of the A10, A20 and MCF parameters were observed in the EXTEM/FIBTEM tests after they were modified by the addition of a synthetic IIbIIIa receptor antagonist alone or in combination with ASA. In conclusion, in this Multiplate- and ROTEM-based laboratory approach, a two-way blockade (IIbIIIa-antagonist + cytochalasine D) was sufficient to completely inhibit procoagulant platelet function as observed by aggregometry and thromboelastometry.

Can the Viscoelastic Parameter α-Angle Distinguish Fibrinogen from Platelet Deficiency and Guide Fibrinogen Supplementation?

Viscoelastic tests such as thrombelastography (TEG, Haemoscope Inc., Niles, IL) and thromboelastometry (ROTEM, Tem International GmbH, Munich, Germany), performed in whole blood, are increasingly used at the point-of-care to characterize coagulopathic states and guide hemostatic therapy. An algorithm, based on a mono-analysis (kaolin-activated assay) approach, was proposed in the TEG patent (issued in 2004) where the α-angle and the maximum amplitude parameters are used to guide fibrinogen supplementation and platelet administration, respectively. Although multiple assays for both the TEG and ROTEM devices are now available, algorithms based on TEG mono-analysis are still used in many institutions. In light of more recent findings, we discuss here the limitations and inaccuracies of the mono-analysis approach. Research shows that both α-angle and maximum amplitude parameters reflect the combined contribution of fibrinogen and platelets to clot strength. Therefore, although TEG mono-analysis is useful for identifying a coagulopathic state, it cannot be used to discriminate between fibrin/fibrinogen and/or platelet deficits, respectively. Conversely, the use of viscoelastic methods where 2 assays can be run simultaneously, one with platelet inhibitors and one without, can effectively allow for the identification of specific coagulopathic states, such as insufficient fibrin formation or an insufficient contribution of platelets to clot strength. Such information is critical for making the appropriate choice of hemostatic therapy.

Mechanisms of early trauma-induced coagulopathy: The clot thickens or not?

Traumatic-induced coagulopathy (TIC) is a hemostatic disorder that is associated with significant bleeding, transfusion requirements, morbidity and mortality. A disorder similar or analogous to TIC was reported around 70 years ago in patients with shock, hemorrhage, burns, cardiac arrest or undergoing major surgery, and the condition was referred to as a "severe bleeding tendency," "defibrination syndrome," "consumptive disorder," and later by surgeons treating US Vietnam combat casualties as a "diffuse oozing coagulopathy." In 1982, Moore's group termed it the "bloody vicious cycle," others "the lethal triad," and in 2003 Brohi and colleagues introduced "acute traumatic coagulopathy" (ATC). Since that time, early TIC has been cloaked in many names and acronyms, including a "fibrinolytic form of disseminated intravascular coagulopathy (DIC)." A global consensus on naming is urgently required to avoid confusion. In our view, TIC is a dynamic entity that evolves over time and no single hypothesis adequately explains the different manifestations of the coagulopathy. However, early TIC is not DIC because an increased thrombin-generating potential in vitro does not imply a clinically relevant thrombotic state in vivo as early TIC is characterized by excessive bleeding, not thrombosis. DIC with its diffuse anatomopathologic fibrin deposition appears to be a latter phase progression of TIC associated with unchecked inflammation and multiple organ dysfunction.

Assessing the Methodology for Calculating Platelet Contribution to Clot Strength (Platelet Component) in Thromboelastometry and Thrombelastography

The viscoelastic properties of blood clot have been studied most commonly using thrombelastography (TEG) and thromboelastometry (ROTEM). ROTEM-based bleeding treatment algorithms recommend administering platelets to patients with low EXTEM clot strength (e.g., clot amplitude at 10 minutes [A10] <40 mm) once clot strength of the ROTEM® fibrin-based test (FIBTEM) is corrected. Algorithms based on TEG typically use a low value of maximum amplitude (e.g., <50 mm) as a trigger for administering platelets. However, this parameter reflects the contributions of various blood components to the clot, including platelets and fibrin/fibrinogen. The platelet component of clot strength may provide a more sensitive indication of platelet deficiency than clot amplitude from a whole blood TEG or ROTEM® assay. The platelet component of the formed clot is derived from the results of TEG/ROTEM® tests performed with and without platelet inhibition. In this article, we review the basis for why this calculation should be based on clot elasticity (e.g., the E parameter with TEG and the CE parameter with ROTEM®) as opposed to clot amplitude (e.g., the A parameter with TEG or ROTEM®). This is because clot elasticity, unlike clot amplitude, reflects the force with which the blood clot resists rotation within the device, and the relationship between clot amplitude (variable X) and clot elasticity (variable Y) is nonlinear. A specific increment of X (ΔX) will be associated with different increments of Y (ΔY), depending on the initial value of X. When calculated correctly, using clot elasticity data, the platelet component of the clot can provide a valuable insight into platelet deficiency in emergency bleeding.

Validation of viscoelastic coagulation tests during cardiopulmonary bypass

BACKGROUND

Viscoelastic point-of-care tests such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are increasingly used to guide hemostatic therapy after cardiac surgery. The aim of this study was to assess their clinical utility during cardiopulmonary bypass to predict postbypass coagulation status and to guide therapy.

METHODS

In this prospective study, TEG and ROTEM tests were performed in 52 adult patients undergoing elective cardiac surgery at two time points: near the end of cardiopulmonary bypass and after heparin reversal with protamine. The 95% confidence intervals of the mean difference were compared with a prespecified clinically relevant limit of ± 20% of the value after protamine.

RESULTS

Both viscoelastic fibrinogen assays were well within the prespecified clinically relevant limit (≥ 79% of patients). The laboratory Clauss fibrinogen was much lower during cardiopulmonary bypass than after protamine (mean difference 1.2 g L(-1) , 95% CI 1.03-1.4, which was outside a clinically acceptable difference. For intrinsically activated tests, clotting times (CT) were different and outside the prespecified limit on TEG (mean difference -1.2 min, 95% CI -1.8 to -0.6) but not on ROTEM (mean difference 2.3 sec, 95% CI -8.6 to 13.2), while clot strength was well within the clinical limit on both devices (≥ 94% of patients). For extrinsically activated tests, clot strength on both TEG and ROTEM was within the pre-specified limit in 98% of patients.

CONCLUSIONS

Results from TEG and ROTEM tests performed toward the end of cardiopulmonary bypass are similar to results after reversal of heparin. Amplitudes indicating clot strength were the most stable parameters across all tests, whereas CT showed more variability. In contrast, laboratory testing of fibrinogen using the Clauss assay was essentially invalid during cardiopulmonary bypass.

Rapid measurement of fibrinogen concentration in whole blood using a steel ball coagulometer

Supplemental digital content is available in the text.

BACKGROUND

Fibrinogen plays a key role in hemostasis and is the first coagulation factor to reach critical levels in bleeding patients. Current European guidelines on the management of traumatic or perioperative bleeding recommend fibrinogen supplementation at specific threshold levels. Whole blood viscoelastic tests provide fast evaluation of fibrin deficits. Fast measurement of plasma fibrinogen concentration is not yet available. We investigated a method to rapidly determine whole blood fibrinogen concentration using standard Clauss assays and a steel ball coagulometer and provide an estimate of the “plasma-equivalent” fibrinogen concentration within minutes by adjustment of the measured whole blood fibrinogen concentration with a quickly measureable hemoglobin-derived hematocrit.

METHODS

The feasibility of this approach was tested with a Clauss assay using multiple porcine fresh blood samples obtained during in vivo bleeding, hemodilution, and after treatment with hemostatic therapy. Two different Clauss assays were then tested using multiple human volunteers’ blood samples diluted in vitro and supplemented with fibrinogen concentrate. Comparative measurements with fibrin-based thromboelastometry tests were performed.

RESULTS

Regression and Bland-Altman analyses of derived “plasma-equivalent” fibrinogen and measured plasma fibrinogen concentration was excellent in porcine and human blood samples, especially in the ranges relevant to traumatic or perioperative bleeding.

CONCLUSION

Fast whole blood fibrinogen measurements could be considered as an alternative to plasma fibrinogen measurement for acute bleeding management in trauma and perioperative care settings. Further studies are needed to prove this concept and determine the turnaround times for its clinical application in emergency departments and operating theaters.

The effectiveness of different functional fibrinogen polymerization assays in eliminating platelet contribution to clot strength in thromboelastometry

BACKGROUND

Viscoelastic tests such as functional fibrinogen polymerization assays (FFPAs) in thrombelastography (TEG®) or thromboelastometry (ROTEM®) measure clot elasticity under platelet inhibition. Incomplete platelet inhibition influences maximum clot firmness (MCF) of FFPAs. We compared the ability of existing and newly developed FFPAs to eliminate the platelet contribution to clot strength.

METHODS

MCF of whole blood (WB), platelet-rich plasma (PRP), and platelet-poor plasma samples was recorded using a ROTEM device with different FFPAs, including the TEG functional fibrinogen test (FFTEG) and different ROTEM-based assays: the standard fib-tem reagent (FIBTEM), a lyophilized single-portion reagent fib-tem S (FIBTEM-S), a newly developed reagent FIBTEM PLUS, as well as FIBTEM or the standard extrinsic activation reagent ex-tem® (EXTEM) combined with 10-μg abciximab (FIBTEM-ABC/EXTEM-ABC).

RESULTS

In WB (platelet count [mean ± SD], 183 ± 37 × 10/μL; plasma fibrinogen concentration, 2.49 ± 0.58 g/L), FFTEG and EXTEM-ABC showed higher MCF (15.7 ± 2.8 mm) than FIBTEM or FIBTEM-S (11.4 ± 3.3 mm, P < 0.001), whereas FIBTEM-ABC and FIBTEM PLUS resulted in lower MCF (9.3 ± 2.8 mm, P < 0.001). In 2 different PRP samples, with platelet counts of 407 ± 80 × 10/μL and 609 ± 127 × 10/μL, FIBTEM-ABC and FIBTEM PLUS reduced platelet contribution to clot strength within 95% confidence interval limits of -1.4 to 0.1 mm and -1.2 to 0.4 mm, respectively. Using all FFPAs it was observed that the Pearson correlation coefficient between plasma fibrinogen concentration and WB MCF was high (range, 0.75-0.93) and significant, regardless of the underlying platelet inhibiting component. Evaluating differences in the interception of regression lines by using analysis of covariance, we compared platelet-poor plasma and both PRP samples within the same assays and found that in contrast to the FIBTEM-ABC and FIBTEM PLUS assays, the FFTEG, EXTEM-ABC, FIBTEM, and FIBTEM-S methods still detected residual platelet activity and grossly overestimated fibrin clot strength in samples with high platelet counts.

CONCLUSIONS

FFPAs based solely on glycoprotein-IIb/IIIa inhibition, such as FFTEG or EXTEM-ABC, are less effective than cytochalasin D-based assays, such as FIBTEM or FIBTEM-S, at inhibiting the platelet component of clot strength. The FIBTEM PLUS assay, and the combination of FIBTEM and abciximab, sufficiently inhibits platelet contribution to clot elasticity. The combination of a glycoprotein-IIb/IIIa receptor blocker and cytochalasin D allows evaluation of functional fibrinogen polymerization without platelet "noise." In a clinical setting, the significance of potent platelet inhibition ensures a more accurate assessment of MCF and therefore the need for fibrinogen supplementation therapy. Further studies are necessary to investigate the application and impact of these tests in a clinical situation.