Sonic Estimation of Elasticity via Resonance: A New Method of Assessing Hemostasis

Sonorheometry Device Thresholds in Liver Transplantation: An Observational Retrospective Study

BACKGROUND

Liver transplantation (LT) remains a potentially haemorrhagic procedure whose perioperative bleeding and transfusion could be better monitored using point-of-care devices. Quantra® is a device based on sonorheometry to assess whole blood clot formation. Our aims were to describe Quantra® parameters during LT and to study their correlations with standard laboratory parameters, and to determine Quantra® cut-off values for thrombocytopenia, hypofibrinogenemia and coagulation factors' deficit.

METHODS

In 34 patients undergoing LT, blood samples were collected before surgical incision, 15 min after the beginning of the anhepatic phase, and 15 min after arterial revascularization of the graft.

RESULTS

Clotting time (CT) was well correlated with prothrombin (PT) ratio and activated partial thromboplastin time (aPTT) ratio. Platelet contribution to clot stiffness (PCS) was correlated with platelets (ρ = 0.82, p < 0.001) and fibrinogen contribution clot stiffness (FCS) with fibrinogen (Fg) (ρ = 0.74, p < 0.001). CT predicted a PT ratio < 30% with an area under the curve (AUC) of 0.93 (95% CI 0.87-0.98; p < 0.001). PCS predicted a platelet count < 50 G/L with an AUC of 0.87 (95% CI 0.76-0.98, p < 0.001). FCS predicted a Fg < 1.0, 1.2 or 1.5 g/L, with an AUC of 0.86 (95% CI 0.77-094, p < 0.001), 0.82 (95% CI 0.74-0.91, p < 0.001) and 0.88 (95% CI 0.82-0.95, p < 0.001), respectively.

CONCLUSION

Quantra® provides a rapid assessment of haemostasis during LT.

Viscoelastic Testing Methods

Viscoelastic testing methods examine the real-time formation of a clot in a whole blood sample, and include thromboelastography (TEG), rotational thromboelastometry (ROTEM), and several other testing platforms. They allow for concurrent assessment of multiple aspects of clotting, including plasmatic coagulation factors, platelets, fibrinogen, and the fibrinolytic pathway. This testing is rapid and may be performed at the point-of-care, allowing for prompt identification of coagulopathies to guide focused and rational administration of blood products as well as the identification of anticoagulant effect. With recent industry progression towards user-friendly, cartridge-based, portable instruments, viscoelastic testing has emerged in the 21st century as a powerful tool to guide blood transfusions in the bleeding patient, and to identify and treat both bleeding and thrombotic conditions in many operative settings, including trauma surgery, liver transplant surgery, cardiac surgery, and obstetrics. In these settings, the use of transfusion algorithms guided by viscoelastic testing data has resulted in widespread improvements in patient blood management as well as modest improvements in select patient outcomes. To address the increasingly wide adoption of viscoelastic methods and the growing number of medical and laboratory personnel tasked with implementing, performing, and interpreting these methods, this chapter provides an overview of the history, physiology, and technology behind viscoelastic testing, as well as a practical review of its clinical utility and current evidence supporting its use. Also included is a review of testing limitations and the contextual role played by viscoelastic methods among all coagulation laboratory testing.

Retrospective study assessing outcomes in cardiac surgery after implementation of Quantra

BACKGROUND

The Quantra QPlus System is a cartridge-based device with a unique ultrasound technology that can measure the viscoelastic properties of whole blood during coagulation. These viscoelastic properties correlate directly with hemostatic function. The primary objective of this study was to assess blood product utilization in cardiac surgery patients before and after the implementation of the Quantra QPlus System.

METHODS

Yavapai Regional Medical Center implemented the Quantra QPlus System to aid in their efforts to reduce the transfusion of allogenic blood products and improve outcomes in patients undergoing cardiac surgery. A total of 64 patients were enrolled prior to the utilization of the Quantra (pre-Quantra cohort), and 64 patients were enrolled after (post-Quantra cohort). The pre-Quantra cohort had been managed via standard laboratory assays along with physician discretion for transfusion decisions. The utilization of blood products and frequency of transfusions were compared and analyzed between the two cohorts. (using the Student's t-test) RESULTS: The implementation of the Quantra resulted in a change in the pattern of blood product utilization leading to a demonstrated decrease in the amount of blood products transfused and the associated costs. The amount of FFP transfused was significantly decreased by 97% (P = 0.0004), whereas cryoprecipitate decreased by 67% (P = 0.3134), platelets decreased by 26% (P = 0.4879), and packed red blood cells decreased by 10% (P = 0.8027) however these trends did not reach statistical significance. The acquisition cost of blood products decreased by 41% for total savings of roughly $40,682.

CONCLUSIONS

Use of the Quantra QPlus System has the potential to improve patient blood management and decrease costs. STUDY REGISTERED AT CLINICALTRIALS.GOV: NCT05501730.

Questions about COVID-19 associated coagulopathy: possible answers from the viscoelastic tests

Abnormal coagulation parameters are often observed in patients with coronavirus disease 2019 (COVID-19) and the severity of derangement has been associated with a poor prognosis. The COVID-19 associated coagulopathy (CAC) displays unique features that include a high risk of developing thromboembolic complications. Viscoelastic tests (VETs), such as thromboelastometry (ROTEM), thromboelastography (TEG) and Quantra Hemostasis Analyzer (Quantra), provide "dynamic" data on clot formation and dissolution; they are used in different critical care settings, both in hemorrhagic and in thrombotic conditions. In patients with severe COVID-19 infection VETs can supply to clinicians more information about the CAC, identifying the presence of hypercoagulable and hypofibrinolysis states. In the last year, many studies have proposed to explain the underlying characteristics of CAC; however, there remain many unanswered questions. We tried to address some of the important queries about CAC through VETs analysis.

Shear Elastic Coefficient of Normal and Fibrinogen-Deficient Clotting Plasma Obtained with a Sphere-Motion-Based Acoustic-Radiation-Force Approach

Blood coagulation is a process involving several chemical reactions governed by coagulation factors, during which the shear elastic coefficient, μ, varies as the medium transitions from liquid to gel phase. This work used ultrasound to measure μ during the clotting of human plasma samples by tracking the motion of a glass sphere located inside a cuvette filled with the plasma. A 2.03 MHz ultrasonic system generated an impulsive acoustic radiation force acting on the sphere, and a 4.89 MHz pulse-echo ultrasonic system tracked the sphere displacement induced by that force. Measurements of μ were determined by fitting a μ-dependent theoretical model to the motion waveform of the sphere immersed in clotting normal plasma and plasma samples with fibrinogen (FI) concentrations of 1.2 (FI-deficiency) and 3.6 (FI-normal) g/L. For normal plasma, μ started at 14.22 Pa and increased rapidly until 2 min, then slowly until it reached 210.23 Pa at 35 min after the clotting process started. A similar trend was exhibited in plasma samples with FI concentrations of 1.2 and 3.6 g/L, with μ reaching 120.55 and 679.42 Pa, respectively. A theoretical model, related to the kinetics of clot-structure formation, describes the time changes of μ for the clotting plasma samples. The sphere-motion-based acoustic-radiation-force approach allowed us to measure the shear elastic coefficient during the coagulation process of plasma samples with normal and deficient FI concentrations. Our results suggest that the method used in this study is capable of being used to detect bleeding disorders.

Efficacy of sonorheometry point of the care device in determining low fibrinogen levels in pregnant blood: an invitro dilution and reconstitution study

Quantra® Hemostasis Analyzer is a Point of the care device that uses ultrasound technology to assess clot formation. In this study, we establish how Quantra® system performs compared to conventional coagulation tests at low levels of fibrinogen in the blood obtained from pregnant women. 24 mL blood was obtained from each healthy parturient. Blood was analyzed for Quantra® variables (Q): Clot time (CT), Clot stiffness (CS), platelet contribution to CS (PCS), fibrinogen contribution to CS (FCS), and conventional coagulation (CL) tests: PT, aPTT, INR, Factor VIII and fibrinogen. 6 ml blood were centrifuged to obtain pregnant plasma. 30 mL of saline was added to 10 mL of blood to simulate crystalloid resuscitation (DB) and was evaluated for Q and CL. Fractions of pregnant plasma, or nonpregnant plasma (Blood Bank) was added to DB to obtain 15% and 30% clotting factor enriched samples. 4 ml of DB was added to 4 ml of original blood (1:1) to obtain the final sample (resus). Each of the samples were analyzed for Q and CL parameters. Regression analysis and Receiving Characteristics Curves were used to study the relationship between Quantra variables and CL tests. There were remarkably high linear correlations between Fibrinogen and CS (R = 0.93, P < 0.001), fibrinogen and FCS (R = 0.77, P < 0.001). An FCS value 2.45 (sensitivity of 79.2 and specificity of 97.3%), and CS value 10.85 hPa (sensitivity of 83% and specificity of 100%) predicted fibrinogen of 200 mg/dL. This study demonstrates a good correlation between Quantra® CS, FCS and serum fibrinogen.Clinical Trial Number: NCT04301193.

Comparison of the resonance sonorheometry based Quantra® system with rotational thromboelastometry ROTEM® sigma in cardiac surgery - a prospective observational study

BACKGROUND

Measures of the sonorheometry based Quantra® viscoelastic hemostatic analyzer (HemoSonics, LCC, Charlottesville, VA, USA) were compared with corresponding results of the ROTEM® sigma device (Instrumentation Laboratory, Bedford, MA, USA).

METHODS

In thirty-eight patients scheduled for elective cardiac surgery between December 2018 and October 2019, blood samples were taken after induction of anesthesia (sample 1) and after heparin neutralization (sample 2) and measured on Quantra (QPlus® Cartridge) and ROTEM sigma (ROTEM® sigma complete + hep Cartridge). Clot times and clot stiffness values were recorded. Clot stiffness values of ROTEM amplitudes (A in mm) were converted to shear modulus (G) in hectoPascal (hPa): G (hPa) = (5 x A)/(100-A). Additionally, time-to-results was recorded. Spearman rank test correlation and Bland Altman analysis were performed.

RESULTS

Clot stiffness parameters of the Quantra correlated strongly with corresponding measurements of the ROTEM with r = 0.93 and 0.94 for EXTEM A10 vs CS and r = 0.94 and 0.96 for FIBTEM A10 vs FCS for sample 1 and 2, respectively. Quantra clot time correlated strongly with ROTEM INTEM CT with r = 0.71 for sample 1 and r = 0.75 for sample 2. However, Bland Altman analysis showed no agreement in all compared assays of both methods. The median time to delivery of first and complete results was significantly shorter for Quantra (412 and 658 s) compared to ROTEM sigma (839 and 1290 s).

CONCLUSIONS

The Quantra showed a strong correlation with the ROTEM sigma for determining clot times and clot stiffness and the parameters assess similar aspects of clot development. However, these parameters are not directly interchangeable and implicate that separate cut-off values need to be established for users of the Quantra device. Word count: 278.

TRIAL REGISTRATION

The study was retrospectively registered with ClinicalTrials.gov (ID: NCT04210830 ) at December 20th 2019.

Viscoelastic hemostatic assays: Update on technology and clinical applications

Viscoelastic hemostatic assays (VHA) are point of care tests that allow for a global assessment of coagulation using whole blood. The technology to allow this assessment has evolved from the original thromboelastography (TEG, Haemonetic, Boston, MA) to now include thromboelastometry (ROTEM, Instrumentation Laboratory, Bedford, MA), and, most recently, the Quantra Hemostasis Analyzer (Hemosonics, Charlottesville, VA). Diagnosis and treatment algorithms incorporating viscoelastic hemostatic tests for bleeding patients in a variety of clinical situations have now been developed. The original ROTEM and TEG technologies have been updated with emphasis placed on a cartridge-based technologies. Results from the new devices show good correlation with those from the previous versions of the devices, while cartridge-based technology has increased device stability and enhanced portability to the bedside. In this article, we will review recent advances in TEG and ROTEM technology and introduce the Quantra Hemostasis Analyzer device.

Dynamic assessment of plasma clotting in samples with distinct fibrinogen concentrations using impulsive acoustic radiation force

While some diseases reduce fibrinogen concentration, others increase the amount of this clotting factor in the blood. Some studies have shown that the fibrinogen concentration in the blood is related to the stiffness of the formed clot. Hence, the aim of this study was to employ an ultrasonic method based on impulsive acoustic radiation force (IARF) to identify the fibrinogen concentration (coagulation factor I) in a plasma sample by means of peak-displacement (PD), time of peak-displacement (TPD), and shear modulus (μ) as well as to identify the change of plasma samples during the clot formation process. The IARF-based ultrasonic system transmitted bursts with a frequency of 2.03 MHz, duration of 246.31 µs, amplitude of 118 VPP, and pulse with 1.25 Hz repetition frequency to generate an IARF on a glass sphere (2.99 mm in diameter and 2500 kg/m3 in density) embedded in a plasma sample, causing a displacement that was monitored by a pulse-echo system with a center frequency of 4.89 MHz. The values of the shear moduli were 124.14 ± 3.02, 556.99 ± 11.76, and 670.39 ± 9.77 Pa, for fibrinogen concentrations of 1.2, 2.4, and 3.6 g/L 20 to 36 min after the beginning of the coagulation process. The TPD values obtained in the same period were 5.28 ± 0.09, 3.03 ± 0.02, and 2.83 ± 0.01 s. The results indicate that an IARF-based ultrasonic system can be used clinically because it uses small amounts of plasma and has the ability to detect differences in PD, TPD, and μ as a function of fibrinogen concentrations.

Basic principles of viscoelastic testing

BACKGROUND

Viscoelastic testing is a method of hemostatic analysis that provides a real-time, holistic view of ex vivo clotting. It allows for examination of both cellular and plasma protein contributions to clotting including platelet number and function, fibrin(ogen) function, and coagulation factor function. The method assesses physical clot properties during the transition of blood from a liquid to a gel state, either by measurement of clot shear modulus using physical force transduction or by measurement of clot resonance frequency using sonometric interrogation. Results are reported in a live trace, with different trace parameters reflecting different contributors to hemostasis. These reported parameters vary between testing platforms.

RESULTS

In the United States, there are several commonly used Food and Drug Administration (FDA)-approved viscoelastic instruments available on the market. Those instruments that use sonometric clot assessment are more recently available and allow for improved portability for use near the patient's bedside. These instruments generally feature different reagent kits that allow more specific interrogation of different hemostatic pathways. Viscoelastic testing can predict the results of traditional plasma-based coagulation assays and has the added benefit of detecting hypercoagulability and severe hyperfibrinolysis. Implementation of viscoelastic testing in many clinical settings is becoming widespread and has proven to be efficacious in reducing blood transfusion rates in many settings. An impact on overall mortality and morbidity has not yet been demonstrated.

CONCLUSION

This article provides a narrative review of the basic principles of viscoelastic testing, including the science and technology behind the method, as well as currently available testing platforms and reagents.

The quantra hemostasis analyzer compared to thromboelastography (TEG) in the surgical oncologic population: A prospective observational trial

BACKGROUND

Management of coagulopathy during major oncologic surgery can be multifactorial and challenging. Viscoelastic assays (VEAs) can be useful in providing vital data about the mechanism of coagulopathy in these dynamic circumstances.

OBJECTIVES

A prospective nonrandomized observational study with the aim of describing the coagulation parameters of patients undergoing major oncologic surgery using the Quantra® and TEG® 5000 systems. Our secondary objectives included the correlation between Quantra and TEG parameters, and the times to result for both technologies.

METHODS

This study included 74 adults undergoing oncologic surgery with an anticipated blood loss of more than 500 ml. For each subject, whole blood samples for each device were collected at multiple points perioperatively for comparison.

RESULTS

Correlation coefficients between Quantra and TEG parameters were 0.8 and above, indicating a very strong correlation (p < .001). Correlation coefficients between conventional laboratory tests and Quantra ranged from 0.74 to 0.83, indicating a moderate correlation (p < .001). The mean time to obtain results and total processing time was shorter for Quantra in comparison to TEG.

CONCLUSIONS

Quantra parameters strongly correlated with TEG parameters; however, Quantra parameters were available in shorter amount of time as it is specifically designed as a closed point of care device.

Viscoelastic Haemostatic Assays in Cardiovascular Critical Care

The initiation and management of anticoagulation is a fundamental practice for a wide variety of indications in cardiovascular critical care, including the management of patients with acute MI, stroke prevention in patients with AF or mechanical valves, as well as the prevention of device thrombosis and thromboembolic events with the use of mechanical circulatory support and ventricular assist devices. The frequent use of antiplatelet and anticoagulation therapy, in addition to the presence of concomitant conditions that may lead to a propensity to bleed, such as renal and liver dysfunction, present unique challenges. The use of viscoelastic haemostatic assays provides an additional tool allowing clinicians to strike a delicate balance of attaining adequate anticoagulation while minimising the risk of bleeding complications. In this review, the authors discuss the role that viscoelastic haemostatic assay plays in cardiac populations (including cardiac surgery, heart transplantation, extracorporeal membrane oxygenation, acute coronary syndrome and left ventricular assist devices), and identify areas in need of further study.

Resonant acoustic rheometry for non-contact characterization of viscoelastic biomaterials

Resonant Acoustic Rheometry (RAR) is a new, non-contact technique to characterize the mechanical properties of soft and viscoelastic biomaterials, such as hydrogels, that are used to mimic the extracellular matrix in tissue engineering. RAR uses a focused ultrasound pulse to generate a microscale perturbation at the sample surface and tracks the ensuing surface wave using pulse-echo ultrasound. The frequency spectrum of the resonant surface waves is analyzed to extract viscoelastic material properties. In this study, RAR was used to characterize fibrin, gelatin, and agarose hydrogels. Single time point measurements of gelled samples with static mechanical properties showed that RAR provided consistent quantitative data and measured intrinsic material characteristics independent of ultrasound parameters. RAR was also used to longitudinally track dynamic changes in viscoelastic properties over the course of fibrin gelation, revealing distinct phase and material property transitions. Application of RAR was verified using finite element modeling and the results were validated against rotational shear rheometry. Importantly, RAR circumvents some limitations of conventional rheology methods and can be performed in a high-throughput manner using conventional labware. Overall, these studies demonstrate that RAR can be a valuable tool to noninvasively quantify the viscoelastic mechanical properties of soft hydrogel biomaterials.

Hemostasis in Coronavirus Disease 2019-Lesson from Viscoelastic Methods: A Systematic Review

Hemostatic unbalance is often observed in patients with coronavirus disease 2019 (COVID-19), and patients with severe disease are at high risk of developing thromboembolic complications. Viscoelastic methods (VEMs), including thrombelastography (TEG) and thromboelastometry (TEM), provide data on the nature of hemostatic disturbance. In this systematic review, we assessed the performance of TEG and TEM in the assessment of blood coagulation and fibrinolysis in patients with COVID-19. PubMed, Scopus, Web of Science Core Collection, medRxiv, and bioRxiv were systematically searched for clinical studies evaluating TEG and/or TEM variables in COVID-19 individuals. Ten studies, with a total of 389 COVID-19 patients, were included, and VEMs were performed in 292 of these patients. Most patients (90%) presented severe COVID-19 and required mechanical ventilation. TEG and TEM variables showed that these patients displayed hypercoagulability and fibrinolysis shutdown, despite the use of appropriate thromboprophylaxis. However, the mechanism underlying these phenomena and their clinical significance in COVID-19 patients who developed thrombosis are still not clear. Further studies are warranted if VEMs might help to identify those at highest risk of thrombotic events and who therefore may derive the greatest benefit from antithrombotic therapy.

Massive Hemorrhage: The Role of Whole Blood Viscoelastic Assays

Viscoelastic whole blood tests are increasingly used to guide hemostatic therapy in bleeding patients in the perioperative, trauma, and obstetric settings. Compared with standard laboratory tests of hemostasis, they have a shorter turnaround time and provide simultaneous information on various aspects of clot formation and lysis. The two available brands TEG (thromboelastography) and ROTEM (rotational thromboelastometry) provide devices that are either manually operated or fully automated. The automation allows for the assays to be used as point-of-care tests increasing their usefulness in massively bleeding patients with rapidly changing hemostatic profiles. While the number of research papers on the subject and the number of published treatment algorithms increase rapidly, the influence of the use of these devices on patient outcome needs yet to be established. In this article, we first review the technology of these devices and the parameters provided by the assays. Next, we present the problems encountered when choosing cut-off values that trigger intervention. Furthermore, we discuss the studies examining their influence on clinical outcomes, and finally, we briefly highlight some of the most important limitations and pitfalls inherent to these assays.

Unique Approach to Quality Assurance in Viscoelastic Testing

Background

The Quantra QPlus System is a novel viscoelastic testing (VET) device designed for the management of coagulation function in critical care settings. The system is indicated and approved for use at the point-of-care and designed for use by nonlaboratory personnel.

Methods

We describe the comprehensive set of internal QC checks implemented in the Quantra and demonstrate the system’s unique capabilities made possible by its ultrasound core technology. Single- and multisite precision testing were performed following Clinical Laboratory Standards Institute guidelines and included multiple days of testing, multiple instruments, multiple lots of cartridges and controls, and multiple operators.

Results

Percent CVs for total imprecision were 3.6% to 8.0% for all measured parameters. CVs for replicate imprecision (“repeatability”) were 2.7% to 7.7% for all measured parameters. Replicate imprecision was the largest component of variability for most parameters.

Conclusions

The Quantra QPlus System is a new-generation cartridge-based VET device that can operate with reduced oversight from the central laboratory while easily integrating into the Individualized Quality Control Plan framework.

Hemostatic Testing in Critically Ill Infants and Children

Children with critical illness frequently manifest imbalances in hemostasis with risk of consequent bleeding or pathologic thrombosis. Traditionally, plasma-based tests measuring clot formation by time to fibrin clot generation have been the "gold standard" in hemostasis testing. However, these tests are not sensitive to abnormalities in fibrinolysis or in conditions of enhanced clot formation that may lead to thrombosis. Additionally, they do not measure the critical roles played by platelets and endothelial cells. An added factor in the evaluation of these plasma-based tests is that in infants and young children plasma levels of many procoagulant and anticoagulant proteins are lower than in older children and adults resulting in prolonged clot generation times in spite of maintaining a normal hemostatic "balance." Consequently, newer assays directly measuring thrombin generation in plasma and others assessing the stages hemostasis including clot initiation, propagation, and fibrinolysis in whole blood by viscoelastic methods are now available and may allow for a global measurement of the hemostatic system. In this manuscript, we will review the processes by which clots are formed and by which hemostasis is regulated, and the rationale and limitations for the more commonly utilized tests. We will also discuss selected newer tests available for the assessment of hemostasis, their "pros" and "cons," and how they compare to the traditional tests of coagulation in the assessment and management of critically ill children.

Production of acoustic radiation force using ultrasound: methods and applications

INTRODUCTION

Acoustic radiation force (ARF) is used in many biomedical applications. The transfer of momentum in acoustic waves can be used in a multitude of ways to perturb tissue and manipulate cells.

AREAS COVERED

This review will briefly cover the acoustic theory related to ARF, particularly that related to application in tissues. The use of ARF in measurement of mechanical properties will be treated in detail with emphasis on the spatial and temporal modulation of the ARF. Additional topics covered will be the manipulation of particles with ARF, correction of phase aberration with ARF, modulation of cellular behavior with ARF, and bioeffects related to ARF use.

EXPERT COMMENTARY

The use of ARF can be tailored to specific applications for measurements of mechanical properties or correction of focusing for ultrasound beams. Additionally, noncontact manipulation of particles and cells with ARF enables a wide array of applications for tissue engineering and biosensing.

Comparison of Coagulation Parameters in Arterial and Venous Blood in Cardiac Surgery Measured Using the Quantra System

Objective:

Perioperative coagulation testing often is performed with arterial samples even though device reference ranges typically are established in venous samples. Although limited studies exist comparing coagulation parameters across sampling sites, viscoelastic testing devices have demonstrated some differences. The objective of this study was to compare coagulation parameters determined using the Quantra System for venous and arterial samples.

Design:

Prospective, observational study.

Setting:

Tertiary care university hospital.

Participants:

The study comprised 30 adult patients undergoing cardiac surgery.

Interventions:

Paired arterial and venous samples were obtained at 2 of the following time points: baseline, during bypass, or after protamine reversal of heparin. Quantra measurements included Clot Time (CT), Heparinase Clot Time (CTH), Clot Time Ratio (CTR), Clot Stiffness (CS), and Fibrinogen (FCS) and Platelet (PCS) Contributions to clot stiffness.

Measurements and Main Results:

The relationship and agreement between matched data pairs were established and statistical analysis was performed via paired t tests. CTR, CS, FCS, and PCS were unaffected by the sampling site, whereas CT and CTH demonstrated statistically significant differences between arterial and venous samples (p < 0.001). Arterial clot times were prolonged relative to the venous ones with a mean percent error of 14.2 % and 11.9 %, respectively. These results are in general agreement with those reported for other viscoelastic testing devices.

Conclusions:

This study demonstrates that Quantra clot stiffness-based parameters (CS, FCS, PCS) are unaffected by sampling site, whereas the clot time parameters (CT and CTH) show good correlation in the presence of a bias. CTR, a ratio of CT and CTH, also is unaffected.

A Novel Device for the Evaluation of Hemostatic Function in Critical Care Settings

Major surgical procedures often result in significant intra- and postoperative bleeding. The ability to identify the cause of the bleeding has the potential to reduce the transfusion of blood products and improve patient care. We present a novel device, the Quantra Hemostasis Analyzer, which has been designed for automated, rapid, near-patient monitoring of hemostasis. The Quantra is based on Sonic Estimation of Elasticity via Resonance Sonorheometry, a proprietary technology that uses ultrasound to measure clot time and clot stiffness from changes in viscoelastic properties of whole blood during coagulation. We present results of internal validation and analytical performance testing of the technology and demonstrate the ability to characterize the key functional components of hemostasis.