TEG®6s system measures the contributions of both platelet count and platelet function to clot formation at the site-of-care.

Knowledge of platelet count and function is key to ensuring appropriate hemostatic management. We hypothesized that the novel, portable TEG®6s coagulation assessment system could evaluate the contribution of both platelet count and function to clot formation. Whole-blood samples with variable platelet counts were prepared from healthy volunteers. Platelet function was adjusted using seven concentrations of abciximab and evaluated by light transmission aggregometry (LTA) with TRAP agonist. Maximum amplitude (MA), reaction time (R) and activated clotting time (ACT) were assessed in citrated kaolin (CK), CK with heparinase (CKH), citrated RapidTEG® (CRT), and citrated functional fibrinogen (CFF) assays. Positive correlations were observed between platelet count and CK.MA, CKH.MA, and CRT.MA (p < .0001), and CK.R, CKH.R, and CRT.ACT (p < .05). Platelet count could be accurately quantified in the range 28-91 k/µL, 28-86 k/µL and 28-74 k/µL for CK.MA, CKH.MA, and CRT.MA, respectively. CK.MA, CKH.MA, and CRT.MA showed significant negative relationships with abciximab concentration (p < .001). Platelet function inhibition was detected by all three assays at >68% measured by LTA and quantified in the range 68.4-82% (CK), 69.4-88% (CKH), and 69.7-76% (CRT). This demonstrates the TEG®6s analyzer can accurately evaluate platelet count and function at the site-of-care.

Cartridge-Based Thromboelastography Can Be Used to Monitor and Quantify the Activity of Unfractionated and Low-Molecular-Weight Heparins.

Thromboelastography is increasingly utilized in the management of bleeding and thrombotic complications where heparin management remains a cornerstone. This study assessed the feasibility of the cartridge-based TEG ® 6s system (Haemonetics Corp., Braintree, Massachusetts, United States) to monitor and quantify the effect of unfractionated and low-molecular-weight heparin (UFH and LMWH). Blood samples from healthy donors were spiked with UFH ( n = 23; 0-1.0 IU/mL) or LMWH (enoxaparin; n = 22; 0-1.5 IU/mL). Functional fibrinogen maximum amplitude (CFF.MA), RapidTEG activated clotting time (CRT.ACT), and kaolin and kaolin with heparinase reaction time (CK.R and CKH.R) were evaluated for their correlation with heparin concentrations, as well as the combination parameters ΔCK.R - CKH.R, ratio CK.R/CKH.R, and ratio CKH.R/CK.R. Nonlinear mixed-effect modelling was used to study the relationship between concentrations and parameters, and Bayesian classification modelling for the prediction of therapeutic ranges. CK.R and CRT.ACT strongly correlated with the activity of LMWH and UFH ( p < 0.001). Using combination parameters, heparin activity could be accurately quantified in the range of 0.05 to 0.8 IU/mL for UFH and 0.1 to 1.5 IU/mL for LMWH. CRT.ACT was able to quantify heparin activity at higher concentrations but was only different from the reference range ( p < 0.05) at >0.5 IU/mL for UFH and >1.5 IU/mL for LMWH. Combination parameters classified blood samples into subtherapeutic, therapeutic, and supratherapeutic heparin ranges, with an accuracy of >90% for UFH, and >78% for LMWH. This study suggests that TEG 6s can effectively monitor and quantify heparin activity for LMWH and UFH. Additionally, combination parameters can be used to classify blood samples into therapeutic ranges based on heparin activity.

Rapid point-of-care detection and classification of direct-acting oral anticoagulants with the TEG 6s: Implications for trauma and acute care surgery.

BACKGROUND: The trauma patient on direct oral anticoagulant (DOAC) therapy preinjury presents a challenge in trauma and acute care surgery. Our understanding of these patients is extrapolated from vitamin K antagonists. However, DOACs have different mechanisms of action, effects on laboratory coagulation assays, and reversal strategies. Rapid identification of DOACs in the blood will allow timely reversal of factor Xa inhibitors and direct thrombin inhibitors when necessary. The present study evaluated viscoelastic testing to detect and classify DOACs in patient blood samples. METHODS: This observational, prospective, open-label, multicenter study used point-of-care viscoelastic testing to analyze blood samples taken from patients with and without DOAC treatment, and healthy volunteers. Antifactor Xa and direct thrombin inhibition (DTI) assays were used to establish reference ranges for viscoelastic testing parameters on the TEG 6s system. These ranges were applied to produce a DOAC identification algorithm for patient blood samples. Internal consistency of the measurements, as well as algorithm sensitivity and specificity, was evaluated. RESULTS: Using the TEG 6s system, the R parameter reference range was 0.6 minutes to 1.5 minutes for the Antifactor Xa assay and 1.6 minutes to 2.5 minutes for the DTI assay. Our identification algorithm using these ranges for 2.5 minutes or less has sensitives of 98.3% and 100% for factor Xa inhibitor and direct thrombin inhibitor detection, respectively. Specificity was 100%. Both classes of DOAC were detectable, even when samples were collected during the "trough" between doses of medication. CONCLUSION: Point-of-care viscoelastic testing with TEG 6s can detect and classify DOACs with high sensitivity and specificity. This tool can be used to better determine the need for reversal in trauma and acute care surgery patients and guide optimal surgical timing in the acute setting. LEVEL OF EVIDENCE: Prognostic and epidemiological study, level II.

Determination of non-Vitamin K oral anticoagulant (NOAC) effects using a new-generation thrombelastography TEG 6s system.

Non vitamin K oral anticoagulants (NOACs) do not require regular monitoring but information about their pharmacodynamic effect may be importantin situations like trauma, stroke oremergent surgery. Currently, no standardized point-of-care test is available to evaluate the anticoagulant effects of NOACs. We evaluated the anticoagulant effect of NOACs with the next generation point-of-care TEG assay (TEG® 6S) based on a fully-automated thrombelastography system. We used two TEG® 6S assays, the DTI assay and Anti-Factor Xa (AFXa) assay, to detect anticoagulant effects and classify NOACs. Blood from healthy volunteers (n = 26) was used to obtain a baseline reference range. Data derived from patients on factor Xa inhibitors (FXi) (rivaroxaban and apixaban) (n = 39), and direct thrombin inhibitors (DTIs) (dabigatran) (n = 25) were compared against the reference range for detection of drug effect and drug classification. TEG®6s R-time highly correlated to each NOAC. Presence of NOACs caused elongation of R-time on the AFXa assay compared to the reference range (4.3 ± 1.7 vs. 1.3 ± 0.3 min. for FXi, p < 0.001 and 3.5 ± 1.2 vs. 1.3 ± 0.3 min. for DTI, p < 0.001). R-time on the DTI assay was elongated only in presence of a DTI (3.4 ± 1.0 vs. 1.5 ± 0.2 min, p < 0.001). The cutoff for detection of a DTI effect was an R time of 1.9 min and for anti-Xa effect was 1.95 min. For detection of NOAC therapy, there was ≥92% sensitivity and ≥95% specificity. The automated TEG®6s NOAC assay may be an effective tool to identify an anticoagulant effect from NOAC therapy and facilitate care of patients with bleeding or at risk of bleeding in the event of needing emergency surgery.

New-Generation Thromboelastography: Comprehensive Evaluation of Citrated and Heparinized Blood Sample Storage Effect on Clot-Forming Variables.

CONTEXT: - Thromboelastography (TEG) is a whole blood, real-time analyzer measuring the viscoelastic properties of the hemostasis process and allowing for individualized goal-directed therapy. However, routine use of TEG requires validation of sample storage effect on clot parameters. OBJECTIVES: - To establish the minimum time required for equilibration time and the maximum time for sample storage for all commercially available TEG tests for the new-generation TEG 6s and to determine how those times compare with the older generation TEG 5000. DESIGN: - Citrated and heparinized whole blood samples obtained from 20 healthy donors were analyzed for clot parameters at multiple time points for both the TEG 6s and the TEG 5000. Samples were activated with the citrated multichannel cartridge or the platelet-mapping cartridge in the TEG 6s or with recalcified kaolin in the TEG 5000. RESULTS: - All blood samples yielded TEG parameter results within reference ranges and had a tendency toward hypercoagulable profiles with increased storage time. Sample storage resulted in increased platelet inhibition with significant differences at 4 hours in the platelet-mapping cartridge (arachidonic acid percentage of inhibition, P = .002; adenosine diphosphate percentage of inhibition, P = .02). CONCLUSIONS: - For nonemergent cases or in a central laboratory setting, all tests provided reliable results for up to 4 hours in the citrated multichannel cartridge and for 3 hours for platelet function information in the platelet-mapping cartridge. In emergent/urgent situations in which the sample needs to be run immediately, RapidTEG and functional fibrinogen tests may be preferred.

First report of the point-of-care TEG: A technical validation study of the TEG-6S system.

Thrombelastography (TEG) measured by the TEG5000 Hemostasis Analyzer is an established but the labor-intensive method for assessing global hemostasis. The first true point-of-care TEG, the TEG6s system, uses resonance-frequency viscoelasticity measurements and a disposable multi-channel microfluidic cartridge to assess hemostasis and response to antiplatelet therapy. TEG assays (n = 5,100) were performed on the blood of healthy volunteers (n = 157) and patients undergoing coronary revascularization at three hospitals (n = 300). The results from the TEG6s were compared with the conventional TEG5000 in accordance with Clinical and Laboratory Standards Institute (CLSI) and FDA recommendations. Precision testing was conducted using blood from healthy donors, all assays were run for 5 consecutive days in duplicate using multiple operators, lots, and instruments. Reference ranges were comparable between the TEG systems. Deming regression analysis demonstrated a strong correlation between the two systems for the standard hemostasis tests (R r = 0.932, MA r = 0.972, LY30 r = 0.938). Method comparison analysis showed an acceptable agreement between PlateletMapping (PM) assays for measuring arachidonic acid (indicator of aspirin response)- and adenosine diphosphate (indicator of P2Y12 inhibitor response)-induced platelet aggregation (total agreement = 90%, and 72%, respectively). TEG6s precision testing yielded low variability (CV 0-13%) in all measures. The new point-of-care TEG6s is associated with greater ease of use than the TEG5000 and provides precise results. The results correlated between methods for all variables. TEG6s is a promising device for near-patient hemostasis monitoring and future trials of personalized therapy designed to reduce bleeding and thrombosis.

Multilevel cervical fusion and its effect on disc degeneration and osteophyte formation.

STUDY DESIGN: The effect of single and double cervical fusion on adjacent segments was investigated using a finite element model of the cervical spine. A healthy spine and a cervical spine with a single and double fusion at different levels were analyzed and evaluated. Disc degeneration and osteophyte formation at the endplates and joints can then be addressed. OBJECTIVES: To evaluate the biomechanical effects of cervical fusion on the cervical spine from C3-C7. The goal was to asses the increase of intervertebral disc and bone stress induced by cervical fusion, the effects of single versus double level fusion, and whether the level in which the fusion is performed, might affect the biomechanics of the spine. SUMMARY OF BACKGROUND DATA: Clinical studies have reported that 25% of fusion patients report further degenerative problems within 10 years of fusion. METHODS.: Four finite element models of single fusion at different levels were generated, as well as three additional models for the case of double fusion. The maximum von Mises stresses for anulus, nucleus, and endplates and the motion of the nonfused segments were obtained during lateral bending, flexion, axial torsion, and extension. Each case was compared with the normal cervical spine. RESULTS: Results showed stress increases of up to 96% in the anulus, nucleus, and endplates after fusion. Facet constraining prevents increases in stress during extension. The stresses at all levels tend to be larger for double than for single fusion. CONCLUSIONS: The results of this study quantify the significant increase in the level of stresses below and above the fused segments in the cervical spine. A sustained level of this stress can lead to further discs degeneration and osteophytes.