In vitro evaluation of a new viscoelastometry-based point-of-care analyzer

INTRODUCTION

The VCM is a point-of-care analyzer using a new viscoelastometry technique for rapid assessment of hemostasis on fresh whole blood. Its characteristics would make it suitable for use in austere environments. The purpose of this study was to evaluate the VCM in terms of repeatability, reproducibility and interanalyzer correlation, reference values in our population, correlation with standard coagulation assays and platelet count, correlation with the TEG5000 analyzer and resistance to stress conditions mimicking an austere environment.

METHODS

Repeatability, reproducibility, and interanalyzer correlation were performed on quality control samples (n = 10). Reference values were determined from blood donor samples (n = 60). Correlations with standard biological assays were assessed from ICU patients (n = 30) and blood donors (n = 60) samples. Correlation with the TEG5000 was assessed from blood donor samples. Evaluation of vibration resistance was performed on blood donor (n = 5) and quality control (n = 5) samples.

RESULTS

The CVs for repeatability and reproducibility ranged from 0% to 11%. Interanalyzer correlation found correlation coefficients (r2) ranging from 0.927 to 0.997. Our reference values were consistent with those provided by the manufacturer. No robust correlation was found with conventional coagulation tests. The correlation with the TEG5000 was excellent with r2 ranging from 0.75 to 0.92. Resistance to stress conditions was excellent.

CONCLUSION

The VCM analyzer is a reliable, easy-to-use instrument that correlates well with the TEG5000. Despite some logistical constraints, the results suggest that it can be used in austere environments. Further studies are required before its implementation.

Targeted fibrinogen concentrate use in severe traumatic haemorrhage

OBJECTIVE

Fibrinogen is one of the first coagulation factors to be depleted during traumatic haemorrhage, and evidence suggests hypofibrinogenaemia leads to poor outcomes. A number of fibrinogen replacement products are currently available, with no clear consensus on the ideal product to use in severe traumatic haemorrhage. We hypothesised that it will be possible to rapidly administer fibrinogen concentrate (FC) guided by rotational thromboelastometry (ROTEM) FIBTEM A5 in patients presenting with trauma haemorrhage.

METHODS

We examined 36 consecutive patients with trauma admitted to a level 1 trauma centre in Australia who received FC as part of their initial resuscitation. ROTEM analysis was conducted at various time points from emergency department (ED) admission to 48 hours after admission. The primary outcome was time to administration of FC after identification of hypofibrinogenaemia using ROTEM FIBTEM A5. Data were collected on quantity and timing of product transfusion, demographics, Injury Severity Score and laboratory values of coagulation. Spearman rank order correlation was used to determine the correlation between FIBTEM A5 and Clauss fibrinogen (FibC).

RESULTS

Thirty-six patients received FC as their initial form of fibrinogen replacement during the study. Patients were hypofibrinogenaemic by both FIBTEM A5 (6 mm) and FibC (1.7 g/L) on presentation to the ED. It took a median of 22 minutes (IQR, 17-30 minutes) from time of a FIBTEM A5 analysis to FC administration. Both parameters increased significantly (P < 0.05) by 24 hours after admission.

CONCLUSION

This study suggests that administration of FC represents a rapid and feasible method to replace fibrinogen in severe traumatic haemorrhage. However, the optimal method for replacing fibrinogen in traumatic haemorrhage is controversial and large multicentre randomised controlled trials are needed to provide further evidence. This study provided baseline data to inform the design of further clinical trials investigating fibrinogen replacement in traumatic haemorrhage.

Thromboelastography on-the-go: Evaluation of the TEG 6s device during ground and high-altitude Aeromedical Evacuation with extracorporeal life support

BACKGROUND

Coagulation monitoring capabilities during transport are limited. Thromboelastography (TEG) is a whole-blood clotting test measuring clot formation, stabilization, and fibrinolysis and is traditionally performed in a laboratory. We evaluated a new point-of-care TEG analyzer, TEG 6s (Haemonetics, Braintree, MA), in a large animal model of combat-relevant trauma managed with extracorporeal life support during ground and high-altitude aeromedical evacuation. The objective was to compare TEG 6s used during transport versus the predicate device, TEG 5000, used in the laboratory. We hypothesized that TEG 6s would be comparable with TEG 5000 during dynamically changing transport conditions.

METHODS

Thromboelastography parameters (R, K, angle, MA, LY30) derived by TEG 6s and TEG 5000 were compared during transport of 8 swine. TEG 6s was transported with animals during ground transport and flight. TEG 5000 was stationary in an adjacent building. TEG 6s activated clotting time (ACT) was compared with a Hemochron Junior ACT analyzer (Accriva Diagnostics, San Diego, CA). Statistics were performed using SAS 9.4 with Deming regressions, Spearman correlations, and average differences compared.

RESULTS

Correlation between devices was stronger at sea-level (R, r = 0.7413; K, r = 0.7115; angle, r = 0.7192; MA, r = 0.8386; LY30, r = 0.9099) than during high-altitude transport (R, r = 0.4787; K, r = 0.4007; angle, r = 0.3706; MA, r = 0.6573; LY30, r = 0.8481). Method agreement was comparable during stationary operation (R, r = 0.7978; K, r = 0.7974; angle, r = 0.7574; MA, r = 0.7841; LY30, r = 0.9140) versus ground transport (R, r = 0.7927; K, r = 0.6246; angle, r = 0.6967; MA, r = 0.9163; LY30, r = 0.8603). TEG 6s ACT trended higher than Hemochron ACT when subjects were heparinized (average difference, 1,442 ± 1,703 seconds) without a methodological difference by Deming regression.

CONCLUSION

Mobile TEG 6s during ground and altitude transport is feasible and provides unprecedented information to guide coagulation management. Future studies should assess the precision and accuracy of TEG 6s during transport of critically ill.

Quasi-static acoustic tweezing thromboelastometry

Essentials Blood coagulation measurement during contact with an artificial surface leads to unreliable data. Acoustic tweezing thromboelastometry is a novel non-contact method for coagulation monitoring. This method detects differences in the blood coagulation state within 10 min. Coagulation data were obtained using a much smaller sample volume (4 μL) than currently used.

SUMMARY

Background Thromboelastography is widely used as a tool to assess the coagulation status of critical care patients. It allows observation of changes in material properties of whole blood, beginning with early stages of clot formation and ending with clot lysis. However, the contact activation of the coagulation cascade at surfaces of thromboelastographic systems leads to inherent variability and unreliability in predicting bleeding or thrombosis risks. Objectives To develop acoustic tweezing thromboelastometry as a non-contact method for perioperative assessment of blood coagulation. Methods Acoustic tweezing is used to levitate microliter drops of biopolymer and human blood samples. By quasi-statically changing the acoustic pressure we control the sample drop location and deformation. Sample size, deformation and location are determined by digital imaging at each pressure. Results Simple Newtonian liquid solutions maintain a constant, reversible location vs. deformation curve. In contrast, the location/deformation curves for gelatin, alginate, whole blood and blood plasma uniquely change as the samples solidify. Increasing elasticity causes the sample to deform less, leading to steeper stress/strain curves. By extracting a linear regime slope, we show that whole blood or blood plasma exhibits a unique slope profile as it begins to clot. By exposing blood samples to pro- or antithrombotic agents, the slope profile changes, allowing detection of hyper- or hypocoagulable states. Conclusions We demonstrate that quasi-static acoustic tweezing can yield information about clotting onset, maturation and strength. The advantages of small sample size, non-contact and rapid measurement make this technique desirable for real-time monitoring of blood coagulation.

The TEG®6s on Shaky Ground? A Novel Assessment of the TEG®6s Performance under a Challenging Condition

Thromboelastography® (TEG®) is used to guide clinical decision-making across many medical and surgical subspecialties. Advances in this field have resulted in analyzers becoming increasingly user friendly, and have led to a reduction in the possibility of user error. The new TEG®6s does not come with the warnings of vibration and movement avoidance of its predecessor. It was decided to test the capability of this device while being subject to motion. TEG®6s machine 1 was placed in an environment free from motion. TEG®6s machine 2 was placed on a flatbed platelet agitator, which would expose the device to sudden and continual motion. Blood from the same healthy volunteer was pipetted into cartridges and inserted into both machines. Testing was commenced on machine 2 simultaneously with the agitator being activated. Visual and numerical data were collected. All measured parameters were significantly different (p < .05) between the motion and motion-free groups apart from CK R-Time, CRT R-Time, CRT Angle, and CRT Ly30. The TEG®6s results differ significantly when the analyzer is exposed to a set amount of motion. Such motion should be avoided if results are to be relied upon.

Platelet Function Tests: Preanalytical Variables, Clinical Utility, Advantages, and Disadvantages

Platelet function tests are mainly used in the diagnostic work-up of platelet disorders. During the last decade, the additional use of platelet function tests to evaluate the effect of antiplatelet therapy has also emerged in an attempt to identify patients with an increased risk of arterial thrombosis. Furthermore, platelet function tests are increasingly used to measure residual effect of antiplatelet therapy prior to surgery with the aim of reducing the risk of bleeding. To a limited extend, platelet function tests are also used to evaluate hyperaggregability as a potential marker of a prothrombotic state outside the setting of antiplatelet therapy. This multifaceted use of platelet function tests and the development of simpler point-of-care tests with narrower application have increased the use of platelet function testing and also facilitated the use of platelet function tests outside the highly specialized laboratories. The present chapter describes the preanalytical variables, which should be taken into account when planning platelet function testing. Also, the most widely used platelet function tests are introduced, and their clinical utility and their relative advantages and disadvantages are discussed.

Targeting blood products transfusion in trauma: what is the role of thromboelastography?

Viscoelastic hemostatic assays (VHAs), mainly thromboelastography (TEG) and the rotational thromboelastometry (ROTEM), provide global information on clot formation and dissolution at patient bedside, allowing fast identification of coagulation disorders. In trauma patients, VHAs are able to predict massive transfusion and mortality. These devices might also be used for applying targeted administration of procoagulant factors (e.g. fibrinogen concentrate) as an alternative to or in addition to using predefined fixed ratios of red blood cells: platelets: fresh frozen plasma/cryoprecipitate. These goal-directed, individualized treatment algorithms seem to reduce blood product transfusion without deleterious effects on patient outcome. Nevertheless, a clear outcome benefit of using VHAs remains to be demonstrated in trauma patients.

Optical Thromboelastography to evaluate whole blood coagulation

Measurement of blood viscoelasticity during clotting provides a direct metric of haemostatic conditions. Therefore, technologies that quantify blood viscoelasticity at the point-of-care are invaluable for diagnosing coagulopathies. We present a new approach, Optical Thromboelastography (OTEG) that measures the viscoelastic properties of coagulating blood by evaluating temporal laser speckle fluctuations, reflected from a few blood drops. During coagulation, platelet-fibrin clot formation restricts the mean square displacements (MSD) of scatterers and decelerates speckle fluctuations. Cross-correlation analysis of speckle frames provides the speckle intensity temporal autocorrelation, g2 (t), from which MSD is deduced and the viscoelastic modulus of blood is estimated. Our results demonstrate a close correspondence between blood viscoelasticity evaluated by OTEG and mechanical rheometry. Spatio-temporal speckle analyses yield 2-dimensional maps of clot viscoelasticity, enabling the identification of micro-clot formation at distinct rates in normal and coagulopathic specimens. These findings confirm the unique capability of OTEG for the rapid evaluation of patients' coagulation status and highlight the potential for point-of-care use.

[Clinical management of disorders hemostasis-related with obstetric complications]

BACKGROUND

The aim of the study was the reduction of adverse pregnancy outcomes in women with gestational and genetically determined changes in the hemostatic system.

PATIENTS AND METHODS

The study group comprised 98 patients with obstetric complications on the background of changes in the parameters of coagulation screening. In 63 pregnant women, hemostatic disorders were not corrected, in 35 patients medical tactic defined clinical situation and the results of laboratory and instrumental studies of the hemostatic system.

RESULTS

Hereditary thrombophilia detected in 85% of patients with obstetric complications. Carriage of the rare allele of MTHFR-677 2-fold increased risk of adverse pregnancy outcomes; heterozygous carriers of polymorphism PAI-1 - 1.5 times more. The prognostic parameters thrombelastographic (sensitivity 80%, specificity 82%) were higher than in laboratory tests. To determine the most predictive of adverse pregnancy outcome has a density of fibrin clot--the maximum amplitude.

CONCLUSIONS

In women with obstetric complications associated with disturbances in the hemostatic system, medical diagnostic tactics using c thrombelastographic evaluates all stages of coagulation and fibrinolysis, allows you to select a reasonable pathogenetic anticoagulant therapy and reduce the number of adverse pregnancy outcomes.

[Influence of temperature on spatial fibrin clot formation process in thrombodynamics]

In this study we have investigated the process of spatial fibrin clot formation in non-steered platelet-free plasma at the temperatures from 20°C to 43°C using thrombodynamics - the novel in vitro hemostasis assay, which imitates the process of hemostatic clot growth in vivo. During data processing the following parameters were calculated: initial (V i ) and stationary (V st ) rates of clot growth which characterize initiation and propagation phases of clotting process, and clot size on the 30 th minute. The temperature dependence of extrinsic and intrinsic tenase activities, which determine values of the initial and stationary clot growth rates, respectively, have been also measured. It was established that the temperature lowering from 37°C to 24°C extends mainly on the initiation phase of clot growth, while the stationary rate of clot growth changes insignificantly. Meanwhile none of the thrombodynamics parameters shows the dramatic change of plasma coagulation system condition at the temperature of 24°C (acute hypothermia). Using the thrombodynamics assay an assumption, that the temperature lowering does not change the state of plasma hemostasis system significantly has been confirmed.

Assessment of hemostaseologic alterations induced by hyperbaric oxygen therapy using point-of-care analyzers

BACKGROUND

Exposure to hyperbaric conditions influences the coagulation system. Thromboembolic events and disseminated intravascular coagulation were observed.

OBJECTIVES

To detect the effects of a hyperbaric environment on the human coagulation system using the point-of-care coagulation analyzers Multiplate and ROTEM.

PATIENTS/METHODS

20 patients were included. Each received 90 minutes of oxygen intermittently at 2.4 atmospheres absolute, as per the TS 240-90 wound-healing protocol. Blood samples were taken before and after hyperbaric exposure and ROTEM, Multiplate and standard laboratory assays were subsequently performed.

RESULTS

ROTEM showed a significant increase of the maximum clot firmness (EXTEM MCF; p < 0.05) and the thromboelastometric platelet component of the clot firmness (MCF(EXTEM) - MCF(FIBTEM); p < 0.01). Multiplate showed a platelet activation mediated by thrombin (AU TRAP-test; p < 0.05) and by arachidonic acid (AUC ASPI-test; p < 0.01). Standard laboratory assays revealed a lower activated partial thromboplastin time (p < 0.05) and a higher leukocyte count (p < 0.05). No further changes were detected. A t-test was performed after testing if data followed normal distribution.

CONCLUSIONS

ROTEM and Multiplate were able to detect an activation of platelets after HBO2 therapy via thrombin and arachidonic acid pathways. Previously reported fibrinolysis could not be confirmed.

Perspectives on thromboelastography

The knowledge of these sources of error together with strict methodology assure reliable results and avoid what some authors consider limitations of the test. These so-called limitations are actually due to incomplete information or insufficient experience. It is our opinion that the key for success when using TEG is to use the test in those cases for which it has been indicated. Also, the fact that TEG is a global test of coagulation should be kept in mind and therefore the need for additional hemostatic tests should be evaluated when applicable (Fig.3). According to this review, the established applications of TEG are as follows: (1) detection of hypercoagulable states, particularly in the postoperative period and for patients with malignancies; (2) management of patients who are administered intravenous heparin; (3) monitoring the coagulation state during liver transplantation; (4) monitoring the coagulation state and management of patients during cardiopulmonary bypass; and (5) diagnosis and treatment of hematologic dysfunctions, particularly hemophilia. Management of patients under warfarin administration, as well as monitoring of the adjustment of subcutaneous heparin prophylaxis in several surgical procedures, should probably belong to this list, but further studies are needed to confirm these roles. Used by experienced hands, TEG is a valuable hemostatic test, the future of which is already present.

Influence of hydroxyethyl starch (HES) 130/0.4 on hemostasis as measured by viscoelastic device analysis: a systematic review

PURPOSE

Hydroxyethyl starch solutions (HES) are plasma volume expanders which affect hemostasis. Newer HES 130/0.4 is said to be safer. Reevaluation of published evidence is necessary after the recent retraction of studies.

METHODS

Systematic review of studies assessing HES 130/0.4 effects on hemostasis by thrombelastography (TEG, ROTEM) or Sonoclot (SCR) in comparison with crystalloid or albumin control fluids was performed. Only studies which provided statistical comparisons between study fluids were analyzed. Studies were divided into in vitro or in vivo hemodilution studies. We assessed study quality, HES effects which differed significantly from controls, values outside normal range, degree of hemodilution, and cumulative HES dose.

RESULTS

Seventeen in vitro and seven in vivo hemodilution studies were analyzed. Four studies reported quality control measures. Nineteen studies (all 15 ROTEM studies, 3 of 5 in vitro TEG, and 1 of 2 SCR studies) showed a significant hypocoagulatory effect of HES 130/0.4 on clot formation, while clotting time was not uniformly affected. Three in vivo TEG studies with low HES doses or cancer patients found mixed or nonsignificant results. In studies which provided normal ranges (n = 9), more values were outside normal ranges in the HES than in the control groups (87/122 vs. 58/122, p < 0.001). Dose effects were apparent in the in vitro studies, which investigated higher dilutions up to 80%. In vivo studies were fewer and did not investigate doses >40 ml/kg.

CONCLUSIONS

HES 130/0.4 administration results in a weaker and smaller clot. Until results from well-designed clinical trials are available, safer fluids should be chosen for patients with impaired coagulation.

[Thromboelastography]

Coagulopathies of various origins have been mentioned among the leading causes of morbidity in hospitals all over the world. Time-consuming coagulation assays delay the diagnosis and response to a dynamic pathology. The need to analyse whole blood for the accurate identification of coagulopathies has led to a revival of interest in thromboelastography (TEG). This simple test can be performed at the bedside using non-anticoagulated blood, and enables complex assessment of extrinsic and intrinsic pathways of coagulation and fibrinolysis. TEG can be also used to predict postoperative bleeding and/or organ dysfunction. TEG has been widely used in research, but poor understanding of the technique has limited its clinical use. Controversies regarding the relationship between traditional tests and TEG have made the bedside use of TEG less popular than it should be. In the review, the authors discuss details of the process and practical aspects of its use in clinical settings.

Correlation between rotation thrombelastometry ROTEM analysis and standard haemostatic parameters during liver transplantation

BACKGROUND

The determination of the correlations between simultaneously performed rotation thrombelastometry ROTEM analysis and standard haemostatic analysis during liver transplantations is indispensable for performing an adequate perioperative haemostatic monitoring.

METHODS

Perioperative haemostatic monitoring was performed to 30 patients undergoing orthotopic liver transplantation (13 male (42%) and 17 female (58%), age: (mean +/- SD; 21 +/- 17 years). Standard coagulation parameters (PT, APTT, FIB) were assessed chronometrically on STA-Compact Analyzer (Diagnostica Stago - La Roche), rotation thrombelastometry analyses - on ROTEM analyzer (Petapharm GmbH) and platelets (PLT) - on Cell Dyn 3700 (Abbott Diagnostica), MAPSS technology.

RESULTS

A protocol was successfully developed for the implementation of perioperative haemostatic control during orthotopic liver transplantations, performing parallel thrombelastometric and standard haemostatic analyses. Significant correlation was established between PT(INR) and EXTEM_CFT ( r = 0.834; p < 0.001) and between APTT and INTEM_CFT (r = 0.707; p < 0.001) in the preoperative period (R1). The correlation was reduced to insignificant during the intraoperative periods (R2-R5) and two hours postoperatively (R6). Significant correlation was determined between PLT/INTEM and between FIB/MCF_FIBTEM during all perioperative periods (R1 -R6).

CONCLUSIONS

The correlations found in the present study suggest to perform the haemoststic liver transplantation monitoring through a parallel systematic analysis of both standard and rotation thrombelastometry parameters and confirm the ROTEM method as preferable and highly informative.

[Reducing the frequency of fresh frozen donor plasma transfusion on the basis of the results of thromboelastographic study in neurosurgical patients with intraoperative blood loss]

The paper gives the results of a study of the time course of changes in the major laboratorily determined hemostatic parameters, as well as the main characteristics of a thromboelastographic curve in 95 neurosurgical patients who developed significant intraoperative blood loss at surgery. The patients were divided into 2 comparable groups: 1) a decision on fresh frozen donor plasma transfusion was taken only on the basis of laboratory parameters; 2) this was done on the basis of thromboelastographic data. In Group 2, the frequency of fresh frozen donor plasma transfusion proved to be 4 times less than that in Group 1. The use of thromboelastography to evaluate the hemostatic system during operations with a significant blood loss volume permits a reduction in the frequency of fresh frozen donor plasma, without deteriorating the results of treatment.

[Thromboelastometry--a new method supporting the therapeutical decisions in the coagulopathy based on the Hartet's thromboelastography]

Thromboelastometry is a diagnostic method presenting in graphs and numbers the dynamics of hemostasis and physical properties of the clot forming. Thromboelastometry allows quick and complete assessment of clotting and fibrinolysis mechanism respecting share of coagulation and fibrinolytic factors and also platelets. Interpretation is based on comparative analysis of model data from computer memory with graphs and numeric data that present clot formation and fibrinolysis in time periods. Graphic presentation of quality and dynamics of coagulation process allow to understand its disorders caused for different reasons, like coagulation factors deficiency, thrombocytopenia, massive bleeding and transfusion or sometimes hypothermia. Measuring device used for thromboelastometry is mobile and makes possible to test blood by a patient bed. By introducing specialist reagents that activate clotting in vitro it is possible to shorten the diagnostic period to 15 minutes therefore multiple patient hemostasis controls can be achieved in real time. Quick diagnostic and possibility of assessment an influence of applied treatment on coagulation process allow to make proper therapeutic decisions in patients with coagulopathy. Hemostasis image and reference to clinical situation might be helpful in diagnosis if there is a surgical bleeding or there is a bleeding released by coagulation and fibrinolytic disorders. Thromboelastometry contributes not only to widen knowledge about complex mechanics of coagulation disorders but also to reduce usage of blood and its products. Thromboelastograhic examinations play a major role in the documentation of coagulation disorders treatment. In order to widen use of this method in clinical practice the algorithms are created, based on thromboelastometry and thromboelatograhy results. These can indicate type and quantity of blood products and medicines that are necessary to administer. Thromboelastometry is applied in many medical disciplines like cardiothoracic surgery, transplant surgery, obstetrics, multiorgan failures, vascular surgery and intensive care. In this method specialistic laboratory education is unnecessary.

[Thromboelastography as a method for preoperative screening for the hemostatic system in neurosurgical patients]

The paper analyzes the use of a method of thromboelastography (TEG) as a screening technique of diagnosing hemostatic disorders in risk-group neurosurgical patients: hemostatic disorders detectable from the data of routine laboratory tests; the administration of anticoagulants and desaggresants, the use of anticonvulsants causing impairments in the hemostatic system, hematological diseases, and hepatic cirrhosis. As compared with the routine laboratory tests, TEG is shown to diagnose hemostatic disorders accurately and promptly and to monitor the efficiency of their therapy.

Use of a thrombelastograph platelet mapping assay for diagnosis of clopidogrel resistance: a case report

A 62-year-old woman presented to the emergency department with sudden collapse, intractable ventricular fibrillation, and an inferior wall myocardial infarction (MI). An emergent cardiac catheterization showed a totally occluded right coronary artery (RCA). A bare-metal stent was placed in the stenosis, resulting in thrombolysis in myocardial infarction (TIMI)-III flow with 0% residual stenosis. Four days after stenting, the patient developed chest pain. A repeat cardiac catheterization showed a totally occluded stent. The patient was subsequently tested using a thrombelastograph (TEG) Platelet Mapping assay to exclude clopidogrel resistance. The assay confirmed the patient to be non-responsive to clopidogrel for the inhibition of platelet ADP receptors. In an attempt to increase ADP inhibition, the ADP antagonist was changed to ticlopidine. Further testing was confounded by the presence of abciximab; however, the patient has remained free of cardiac events.

Platelet hyperreactivity in response to on- and off-pump coronary artery bypass grafting

Hypercoagulability has been reported after off-pump coronary artery bypass grafting (OPCAB) compared with patients undergoing standard coronary artery bypass grafting (CABG) with cardiopulmonary bypass. The aim of this study was to evaluate the changes in platelet reactivity in response to cardiac surgery, both OPCAB and CABG. Platelet reactivity was monitored pre- and postoperatively (days 1 and 4) in elective OPCAB (n = 29) and CABG (n = 24) patients using the maximal amplitude (MA) parameter obtained with thrombelastography. Platelet reactivity was also examined at 1 month in 30 of the 53 patients. Twenty-three percent of the patients (12/53) had a preoperative MA value above normal reference value (MA > 69 mm). By postoperative day 4, 88% of the patients presented with an MA > 69 mm, and significant increases in MA were shown in both groups (p < .0001). Of the 30 patients examined at 1 month after surgery, 75% of the patients with high preoperative MA (6/8) remained at this level. In contrast, only 4.5% of patients with normal preoperative MA (1/22) presented with high MA at day 30. MA has previously been shown to correlate with the incidence of thrombotic and ischemic complications and this study identified 23% of patients needing coronary bypass surgery to be at high risk for recurrent ischemic events at 1 month after surgery, based on the MA. These results suggest that a more aggressive antithrombotic treatment might be warranted for patients undergoing coronary artery bypass grafting, both OPCAB and CABG, presenting with a high MA pre- and postsurgery.

ROTEM analysis: a significant advance in the field of rotational thrombelastography

At the turn of the century, a significant advance in the rapidly expanding field of rotational thrombelastography (ROTEG), known at present as thrombelastometry or ROTEM analysis, was developed at the Ludwig-Maximillian University in Munich. The measuring unit is operated by a laptop computer. There are four temperature-controlled measuring channels in which the global assays not only detect coagulation factor defects but also platelet function, abnormal fibrinogen polymerisation, anticoagulant defects and hyperfibrinolysis. ROTEM has steadily increased in popularity, particularly because of its well-established application as a diagnostic aid at the point of care in the critical care situation. It also provides a useful guide in the choice of an appropriate therapeutic option in the bleeding patient, reducing costs by avoiding administration of costly component therapy such as fresh-frozen plasma, cryoprecipitate, platelet concentrates or antifibrinolytic agents. As well as being useful in monitoring anticoagulant therapy and the use of pharmacological agents, ROTEM is a valuable research tool in the field of hypercoagulability, fibrinolysis, factor XIII activity and the ultimate phases of the blood coagulation process.

Effects of modified ultrafiltration on coagulation as measured by the thromboelastograph

Hemodilution during cardiopulmonary bypass (CPB) continues to be a cause of morbidity associated with coagulation dysfunction, bleeding, and allogeneic blood transfusion. Clot formation and strength have been shown to impact bleeding and transfusions. Strategies to reduce hemodilution may be negated based on the course of the cardiac procedure itself. Modified ultrafiltration (MUF) is commonly used in pediatric cardiac surgery; however, it is not well accepted in adult surgery. This study aimed to evaluate clot formation and strength, bleeding, and transfusions in adult subjects undergoing MUF. Nineteen subjects having primary coronary artery bypass, aortic, or mitral valve surgeries were recruited and randomized to having MUF (n = 10) or no-MUF (n = 9) performed after the termination of CPB. Five time points for data collection were designated: T1, baseline/induction; T2, termination CPB; T3, post-MUF; T4, post-protamine; T5, 24 hours postoperative. Subjects randomized to MUF had 1505 +/- 15.8 mL of effluent removed, and no-MUF subjects had the CPB remnants processed with a cell salvage device. There was no statistical difference seen in 24-hour chest tube output, thromboelastograph values, or allogeneic transfusions at any time point between MUF and no-MUF subjects. There was a significant difference between MUF and no-MUF in the number of autologous cell salvage units processed (1.3 +/- .48 vs. 2.9 +/- .78, p = .0013) and end of procedure net fluid balance (+2003 +/- 1211 vs. +4194 +/- 1276 mL, p = .001), respectively. Estimated plasma loss from the cell salvage device was 477.6 mL greater in the no-MUF group. In primary adult cardiac procedures, MUF did not change coagulation values as measured by thromboelastography, number of allogeneic unit transfusions, or chest tube output at 24 hours postoperatively. There was a significant difference in autologous cell salvage units processed and end of procedure net fluid balance that benefited MUF subjects.

Peculiar whole blood rotation thromboelastometry (Rotem) profile in 40 sideropenic anaemia patients

The ROtation ThromboElastoMetry analyser (ROTEM, Pentapharm, Munich, Germany) is useful for studying whole blood (WB) clot formation and lysis. Reduction of haematocrit (HCT) has been reported to influence traditional thromboelastography parameters without compromising "in vitro" blood coagulation. We performed this case-control study to evaluate ROTEM profiles in sideropenic anaemia patients with different degrees of reduction of HCT levels. Forty consecutively referred patients with sideropenic anaemia were enrolled. A group of 40 healthy age and gender matched subjects acted as a control. The influence of HCT on ROTEM was assessed in the study population and in a model of artificially reconstituted blood with modified HCT values. Cases presented significantly increased levels of maximum clot firmness (MCF) as compared to controls (p < 0.001) mimicking a sort of "hypercoagulable profile". However, thrombin generation tests failed to detect an increase in thrombin generation in cases as compared to controls. A statistically significant inverse linear correlation between HCT and MCF (p < 0.0001) was found. In addition, ROTEM profiles following "in vitro" manipulation of HCT confirmed the inverse linear correlation between HCT and MCF found in the study population. In conclusion, the increased clot firmness found by ROTEM in anaemic patients is likely to be related to the method in itself rather than representing a marker of hypercoagulability "in vivo". Since ROTEM is widely used by anaesthesiologists when deciding the optimisation of products supplementation during surgery, attention should be paid in the case of anaemic patients taking depending on the peculiar thrombo-elastography profile found.

Long-term extracorporeal circulation management: the role of low- and high-range heparin ACT tests

Modern management of extracorporeal circulation, especially during long-term support of post-cardiac surgical patients, remains challenging and requires optimal care of the patient's fluid balance and coagulation hemostasis for its successful outcome. The activated clotting time assay is one of the tests used to manage extracorporeal circulation and is available in a low- and high-range level. The question of which assay is more appropriate for procedures that require low to moderate heparin dosing is still unclear. We report our experience with a neonate diagnosed with hypoplastic left heart syndrome who needed emergent extracorporeal membrane oxygenation support for 13 days after Norwood stage I palliation using a Sano shunt. Although successful, bleeding complications prompted us to review our strategy for management of coagulation hemostasis.

Rotational thrombelastometry for the bedside monitoring of recombinant hirudin

BACKGROUND

Recombinant hirudin is used as an alternative anticoagulant, particularly in patients with heparin-induced thrombocytopenia type II. However, bedside monitoring for hirudin is not available. The present study aims to evaluate rotational thrombelastometry regarding its suitability to detect the effects of recombinant hirudin on whole blood coagulation. Hirudin was added to whole blood samples from healthy donors (n=5) and thrombelastometry variables resulting from activation of samples with tissue factor, ellagic acid, and ecarin were determined.

METHODS

Hirudin (0.1-10 microg/ml) was added to citrated blood. Thereafter, rotational thrombelastometry was performed by initiating coagulation via recalcification and addition of tissue factor, ellagic acid, and ecarin, respectively, using the commercially available assays.

RESULTS

In the absence of hirudin, clotting times (CT) induced by ellagic acid, tissue factor, and ecarin, respectively, were 141.7+/-18.0, 54.0+/-7.6, and 64.5+/-4.1 s. Increasing concentrations of hirudin led to dose-dependent prolongation of the clotting time with the three activators. All assays were capable to detect hirudin concentrations in the range of 0.5-5 microg/ml. At a final hirudin concentration of 1 microg/ml, clotting time increased to 268.0+/-25.1, 84.0+/-9.3, and 107.5+/-9.9 s, respectively, with the above-mentioned activators. The other thrombelastographic variables, including clot formation time, angle alpha, and maximum clot firmness, were not altered by hirudin at concentrations up to 5 microg/ml.

CONCLUSIONS

Our study demonstrates the suitability of rotational thrombelastometry to detect anticoagulant effects of recombinant hirudin.

Influence of polymorphonuclear leukocytes on the plasma clot formation as evaluated by thromboelastometry (ROTEM®)

OBJECTIVE

It has been emphasized that polymorphonuclear leukocytes (PMN) participate in the regulation of coagulation. However, the mechanisms of action are not clear. Besides a procoagulant activity, anticoagulant or fibrinolytic properties are attributed to these cells. To explore their global effect, we have studied their involvement in the clot formation with thromboelastometry, which gives global view over the clotting process, in particular on the structure of the clot and on the kinetic of its formation.

METHODS

PMN were isolated from healthy blood donors and resuspended into autologous platelet-free plasma. The ROTEM device was used. Coagulation was triggered only by adding calcium chloride. Thromboelastometric profiles of PMN-rich plasma (PMN-RP) were compared with autologous platelet-rich (PRP) and platelet-poor plasma (PPP). The inhibition of both tissue factor and intrinsic pathways was also studied.

RESULTS AND CONCLUSIONS

The procoagulant activity of resting PMN was demonstrated as the initiation of fibrin formation with PMN-RP was significantly faster compared with both PRP and PPP. The kinetic of plasma clotting was remarkably improved with PMN-RP compared with PPP. However, the clot with PMN-RP had the same poor viscoelastical properties as PPP. Thromboelastometry gives a new point of view in the involvement of PMN in coagulation, in the absence of any PMN pre-activation. Their impact was centred on the kinetic and the facilitation of the clot formation.

Hydroxyethyl starch enhances fibrinolysis in human plasma by diminishing α2-antiplasmin–plasmin interactions

Hydroxyethyl starch (HES) solutions are effective volume expanders but are also associated with poorly understood coagulopathy. Enhanced fibrinolysis following dilution with HES has been demonstrated. This investigation sought to identify the interactions of HES with critical fibrinolytic/antifibrinolytic enzymes. Normal plasma or plasmas deficient in factor XIII, thrombin activatable fibrinolysis inhibitor or alpha2-antiplasmin were either not diluted or were diluted 20% with 0.9% NaCl, 5% human albumin, high-molecular-weight HES (HES 450) or low-molecular-weight HES (HES 130). Plasma was activated with celite and exposed to 75 IU/ml tissue-type plasminogen activator. Coagulation growth/disintegration kinetics were determined with thrombelastography. Compared with undiluted plasma, diluted plasma had a significant decrease in the clot lysis time and the time to maximum rate of lysis in all plasma types except in alpha2-antiplasmin-deficient plasma. The hierarchy of the decrease in clot lysis time and time to maximum rate of lysis was HES 450 = HES 130 > 5% human albumin = 0.9% NaCl. In conclusion, HES dilution enhances fibrinolysis by diminishing alpha2-antiplasmin-plasmin interactions. Further laboratory and clinical investigation is warranted to better define the mechanisms by which HES enhances clot disintegration and to find new therapeutic roles for HES to either prevent or treat thrombosis.

Thromboelastographic profiles as a tool for thrombotic risk in digestive tract cancer

BACKGROUND

Quantification of the magnitude of thrombotic risk associated with malignancy and with anti-cancer therapy is indispensable to use anticoagulant drugs which selectively interfere with haemostatic mechanisms protecting patients from venous thromboembolism (VTE) and probably from tumor progression. However, none of activation coagulation markers has any predictive value for the occurrence of the thrombotic events in one individual patient. Current clotting methods can't reveal the overall dynamic clot formation; in contrast thromboelastographic methods specifically assess overall coagulation kinetics and its strength in whole blood.

AIM

Objective of study was to evaluate if the activation of coagulation as eventually revealed by ROTEM thromboelastometry could assess an hypercoagulable state in surgical neoplastic patients.

PATIENTS AND METHODS

Fifty consecutive patients with carcinoma of the digestive tract in preoperative period (23 M, 27 F aging 61.5 (45-79 years) and 147 healthy subjects (71 M, 76 F) were studied. A recent thromboelastometric method based on thrombelastography after Hartert was employed. Measurements were performed on ROTEM Coagulation Analyzer. The continuous coagulation data from 50 min course were transformed into dynamic velocity profiles of WB clot formation.

RESULTS

Standard parameters (CT, CFT, MCF) of cancer patients were similar to controls. CT (in cancer patients): females 50 s (38.3-58.7), males 50 s (42-71.2) vs 51 s (42-59), p = 0.1210 / 53 s (42-74.8), p = 0.1975 (in controls). CFT (in cancer patients): females 72 s (32- 92.4), males 80 s (50.2- 128.7) vs 78 s (62-100), p = 0.0128 / 80 s (59-124.4), p = 0.9384 (in controls). MCF (in cancer patients): females 70 mm (59.9-82.5), males 63 mm (56-73.7) vs 69 mm (59-95.8), p = 0.9911 / 69 mm (53.6-90), p = 0.0135 (in controls). Females showed a higher MaxVel when compared to males. The MaxVel was increased in cancer patients: females 19 mm /100 s (14.3-49.5) males 18 mm / 100 s (11-27) vs 15 mm 100 s (11.8-22), p < 0.001 / 13 mm / 100 s (10-21.8), p < 0.001 in controls. The t-MaxVel was shortened in cancer patients: females 65s (48.6-112.8), males 81s (50.1-135.9) vs 115s (56.8-166), p < 0.001 / 115 s (59.8-180.8), p = 0.0002 in controls. The AUC was increased in cancer patients: females 6451 mm 100(5511-8148), males 5984 mm 100 (5119-6899) vs 5778 mm 100 (4998-6655), p < 0.001 / 5662 mm 100 (4704-6385), p = 0.0105.

CONCLUSION

Unlike other assays measuring variations in a single component during coagulation, the thrombelastographic method records a profile of real-time continuous WB clot formation, and may provide extensive informations on haemostasis in neoplastic patients before surgery.

Hemostatic Function in Healthy Pregnant and Preeclamptic Women: An Assessment Using the Platelet Function Analyzer (PFA-100??) and Thromboelastograph??

BACKGROUND

The PFA-100 is a point-of-care platelet function analyzer which measures the speed of formation of a platelet plug in vitro, expressed as closure time (CT) in seconds. This device could potentially be used to assess primary hemostasis prior to regional anesthesia. In this prospective, observational study we sought to establish 95% reference intervals for PFA-100 and Thromboelastograph (TEG) values for our normal pregnant population, before comparing the PFA and TEG in measuring platelet function in preeclamptic and healthy pregnant women at term, using confidence interval analysis and analysis of variance.

METHODS

Routine hematologic and coagulation tests were performed along with von Willebrand Factor, CT, and TEG measurements. Results are expressed as mean (sd).

RESULTS

Increased severity of preeclampsia was associated with increasing prolongation of CT, even in the presence of normal platelet counts. In severe preeclampsia, the PFA-100 CT (mean (sd): 155 (65) s) exceeded the 95% reference interval of the control group (70-139 s). In contrast, TEG maximum amplitude (MA) in severe preeclampsia (mean (sd): 71 (8) mm) remained within the 95% reference interval for MA in normal pregnancy (64-82 mm).

CONCLUSION

We conclude that impairment of primary hemostatic function with increasing severity of preeclampsia was recorded by the PFA-100 but not the TEG.

Diagnosis of early coagulation abnormalities in trauma patients by rotation thrombelastography

BACKGROUND

Reagent-supported thromboelastometry with the rotation thrombelastography (e.g. ROTEM) is a whole blood assay that evaluates the visco-elastic properties during blood clot formation and clot lysis. A hemostatic monitor capable of rapid and accurate detection of clinical coagulopathy within the resuscitation room could improve management of bleeding after trauma.

OBJECTIVES

The goals of this study were to establish whether ROTEM correlated with standard coagulation parameters to rapidly detect bleeding disorders and whether it can help to guide transfusion.

METHODS

Ninety trauma patients were included in the study. At admission, standard coagulation assays were performed and ROTEM parameters such as clot formation time (CFT) and clot amplitude (CA) were obtained at 15 min (CA(15)) with two activated tests (INTEM, EXTEM) and at 10 min (CA(10)) with a test analyzing specifically the fibrin component of coagulation (FIBTEM).

RESULTS

Trauma induced significant modifications of coagulation as assessed by standard assays and ROTEM. A significant correlation was found between prothrombin time (PT) and CA(15)-EXTEM (r = 0.66, P < 0.0001), between activated partial thromboplastin time and CFT-INTEM (r = 0.91, P < 0.0001), between fibrinogen level and CA(10)-FIBTEM (r = 0.85, P < 0.0001), and between platelet count and CA(15)-INTEM (r = 0.57, P < 0.0001). A cutoff value of CA(15)-EXTEM at 32 mm and CA(10)-FIBTEM at 5 mm presented a good sensitivity (87% and 91%) and specificity (100% and 85%) to detect a PT > 1.5 of control value and a fibrinogen less than 1 g L(-1), respectively.

CONCLUSIONS

ROTEM is a point-of-care device that rapidly detects systemic changes of in vivo coagulation in trauma patients, and it might be a helpful device in guiding transfusion.

Quantifying the effect of antiplatelet therapy: a comparison of the platelet function analyzer (PFA-100) and modified thromboelastography (mTEG) with light transmission platelet aggregometry

BACKGROUND

Antiplatelet therapy with aspirin and clopidogrel is known to confer protection against ischemic events. Increasing numbers of patients are presenting for surgery while taking these drugs. This may lead to an increase in perioperative blood loss, particularly in those who have a heightened response to the drugs. Identifying these patients preoperatively would allow us to plan appropriate management.

METHODS

The antiplatelet effect of aspirin and/or clopidogrel was measured using two point-of-care monitors: the platelet function analyzer (PFA-100; Dade, Miami, FL) and the modified thromboelastograph (mTEG; Haemoscope Corp., Niles, IL). This was compared with optical light transmission aggregometry.

RESULTS

All people taking aspirin displayed a definitive aspirin effect on aggregometry (n = 20). Ninety percent of these were identified by modified thromboelastography (n = 18). Seventy percent were identified by the platelet function analyzer (n = 14). Fifty percent of people taking clopidogrel displayed a definitive response to the drug on aggregometry. Seventy percent of these were identified on modified thromboelastography (n = 7). None were identified by the platelet function analyzer. There was good agreement between the results of the aggregometry and modified thromboelastography in clopidogrel patients (kappa = 0.81).

CONCLUSION

The search for a point-of-care monitor of platelet function has been the focus of much research. This study has shown that the modified thromboelastograph can be used for monitoring the effect of clopidogrel as well as aspirin. It potentially has a wide scope to be used for the monitoring of effectiveness of therapy as well as a possible predictor of perioperative bleeding.

Dose titration of recombinant factor VIIa using thromboelastograph monitoring in a child with hemophilia and high titer inhibitors to factor VIII: a case report and brief review

The administration of recombinant factor VIIa (rFVIIa) is complicated by a wide inter-subject variation in response, a short half-life, evolving indications for use, and the absence of a test that has been shown to correlate with clinical effect. This report describes a method used to titrate rFVIIa to thromboelastography (TEG) parameters in a difficult to manage hemophilic patient with high titer inhibition to factor VIII. The current concepts of monitoring rFVIla administration in hemophiliacs and uncontrolled hemorrhage in cardiac surgery are briefly reviewed.

Transfusion triggers in orthotopic liver transplantation: a comparison of the thromboelastometry analyzer, the thromboelastogram, and conventional coagulation tests

OBJECTIVES

The Thromboelastogram (TEG; Haemoscope Corporation, Niles, IL) and the ROTEM thromboelastometry analyzer (Pentapharm GmbH, Munich, Germany) are coagulation monitors that measure the viscoelastic changes accompanying whole-blood coagulation generation and lysis. It is not clear whether TEG and ROTEM transfusion algorithms suggest similar blood component intervention. This study aims to report the extent to which administration of platelets, fresh frozen plasma, and cryoprecipitate would be indicated using protocol-dictated interventions by the Rotem, TEG, and conventional coagulation screens during orthotopic liver transplantation (OLT).

DESIGN

Prospective observational study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients undergoing orthotopic liver transplantation.

INTERVENTIONS

Coagulation was managed with native TEG protocols. Additional samples for kaolin TEG, kaolin heparinase TEG, Rotem in-TEM, Rotem hep-TEM, Rotem fib-TEM, full blood count, prothrombin time, and Clauss fibrinogen assays were taken at 5 fixed operative stages.

MEASUREMENTS AND MAIN RESULTS

Results were reviewed and protocol-indicated interventions recorded. There was moderate agreement between Clauss fibrinogen and Rotem fib-TEM assays about fulfilling fibrinogen transfusion criteria (kappa = 0.42, p < or = 0.05). Agreement between TEG and Rotem to transfuse platelets was fair (Rotem in-TEM/native heparinase TEG, kappa = 0.33, Rotem in-TEM/kaolin heparinase TEG, kappa = 0.28). There was moderate agreement between Rotem in-TEM and prothrombin time (kappa = 0.42), and poor agreement between other tests about the point to administer fresh frozen plasma.

CONCLUSIONS

Transfusion practice is likely to differ according to the method of coagulation monitoring used. A prospective case-matched study using the viscoelastic tests used in this study would be beneficial in determining the optimal therapy. Rotem fib-TEM monitoring may improve hemostasis management.

Validation of rotation thrombelastography in a model of systemic activation of fibrinolysis and coagulation in humans

BACKGROUND

Thrombelastography (TEG) is a whole blood assay to evaluate the viscoelastic properties during blood clot formation and clot lysis. Rotation thrombelastography (e.g. ROTEM) has overcome some of the limitations of classical TEG and is used as a point-of-care device in several clinical settings of coagulation disorders. Endotoxemia leads to systemic activation of the coagulation system and fibrinolysis in humans.

OBJECTIVES

We validated whether ROTEM is sensitive to endotoxin induced, tissue factor-triggered coagulation and fibrinolysis and if its measures correlate with biohumoral markers of coagulation and fibrinolysis.

PATIENTS AND METHODS

Twenty healthy male volunteers participated in this randomized placebo-controlled trial. Volunteers received either 2 ng kg(-1) National Reference Endotoxin or saline.

RESULTS

Endotoxemia significantly shortened ROTEM clotting time (CT) by 36% (CI 0.26-0.46; P < 0.05) with a strong inverse correlation with the peak plasma levels of prothrombin fragments (F(1 + 2)) (r = -0.83, P < 0.05). Additionally, endotoxin infusion enhanced maximal lysis (ML) 3.9-fold (CI: 2.5-5.2) compared with placebo or baseline after 2 h (P < 0.05). Peak ML and peak tissue plasminogen activator (t-PA) values correlated excellently (r = 0.82, P < 0.05). ROTEM parameters clot formation time and maximal clot firmness were not affected by LPS infusion, whereas platelet function analyzer (PFA-100) closure times decreased.

CONCLUSIONS

Rotation thrombelastography (ROTEM) detects systemic changes of in vivo coagulation activation, and importantly it is a point of care device, which is sensitive to changes in fibrinolysis in humans. The ex vivo measures CT and ML correlate very well with established in vivo markers of coagulation activation (F(1 + 2)) and fibrinolysis (t-PA), respectively.

Urokinase induced fibrinolysis in thromboelastography: a model for studying fibrinolysis and coagulation in whole blood

BACKGROUND

The contact system (CS) proteins, factor XII and prekallikrein are thought to have roles in blood coagulation and fibrinolysis. Recent research has suggested that the CS proteins might be more important in fibrinolysis and cell function than in coagulation. Most studies on fibrinolysis have used plasma or euglobulin assays, ignoring the influence of cellular elements of blood on the fibrinolytic process.

OBJECTIVE AND METHODS

In order to study both coagulation and fibrinolysis in whole blood (WB), we have developed a thromboelastography (TEG) assay to investigate both coagulation and fibrinolysis in the same blood sample. In this assay, named urokinase (UK) induced fibrinolysis in thromboelastography (UKIFTEG), TEG is performed on recalcified citrated WB in the presence of UK. Large variations in Ly60 (percentage lysis 60 min after clot formation) were obtained between different donors with the same UK concentration. The UKIFTEG assay was therefore performed using UK concentrations that gave Ly60 values in the approximate range of 20-40%.

RESULTS

The effect of CS activation was investigated in the presence or absence of celite (10 mg mL(-1) blood). Celite shortened the clotting time (CT), and increased Ly60 values. Factor XIIa (FXIIa) and plasma kallikrein (KK) produced concentration dependent reductions in CT (significant at concentrations of 1303 and 2600 ng mL(-1) blood, respectively) and increased Ly60 values (significant at concentrations of 652 and 1300 ng mL(-1) blood, respectively).

CONCLUSIONS

Our results show that CS activation and both FXIIa and KK produce reductions in clotting time and enhanced fibrinolysis in UKIFTEG.

Multi-centre investigation on reference ranges for ROTEM thromboelastometry

Reagent-supported thromboelastometry (TEM) with the ROTEM Whole Blood Haemostasis Analyser is an enhancement of thromboelastography, a method that is increasingly used for the point of care monitoring of acute perioperative bleeding disorders. We investigated the reference ranges of two activated tests (INTEM and EXTEM) and a test analysing specifically the fibrin component of coagulation (FIBTEM) in a multi-centre approach. The reference ranges obtained for the clotting time (CT), clot formation time (CFT), alpha angle (ALP), maximum clot firmness (MCF) and clot lysis parameters were comparable from centre to centre. INTEM: CT equals; 137-246 s, CFT equals; 40-100 s, MCF equals; 52-72 mm. EXTEM: CT equals; 42-74 s, CFT equals; 46-148 s, MCF equals; 49-71 mm. FIBTEM: MCF equals; 9-25 mm. ROTEM whole blood coagulation correlated weakly with a trend towards enhanced coagulation in females compared with males and in advanced age. The repeatability (within-run imprecision) of the results was dependent on the test with the following coefficients of variation: 1-5% (clot firmness, alpha angle), 3-12% (CT, CFT), 6-13% (FIBTEM clot firmness). Citrated blood samples were stable for ROTEM analysis stored within 6 h from drawing. In summary, the data showed that ROTEM thromboelastometry yields consistent values between centres and that providing general orientating reference ranges seems to be possible.

Thrombelastography/thromboelastometry

The term thrombelastograph (TEG) was used to describe the trace produced from the measurement of the viscoelastic changes associated with fibrin polymerization. Recently the term rotational thromboelastometry has been applied to the output of the ROTEM instrument. Since its first description in 1948, the TEG/ROTEM has been successfully used in the near patient assessment of haemostasis. The greatest use has been the application of TEG-guided transfusion of blood components in hepatic and more widely in cardiac surgery. Recent years have seen a renewed interest in the technology with applications for both pharmaceutical monitoring and patient screening being described. The present review gives a broad overview of the developments and applications related to thrombelastography/thromboelastometry.

Comparison of modified Thrombelastograph and Plateletworks whole blood assays to optical platelet aggregation for monitoring reversal of clopidogrel inhibition in elective surgery patients

Clinically monitoring recovery from clopidogrel and nonsteroidal anti-inflammatory drug (NSAID) inhibition requires whole blood assays corresponding to a standard methodology such as platelet-rich plasma aggregation monitored optically (OPA). We compared OPA, using an ED 50 dose of adenosine diphosphate activation, with 2 whole blood assays, Plateletworks (PWA) and modified Thrombelastograph (TEG). Two sets of assays were performed on 43 surgery patients while on clopidogrel and off clopidogrel to determine the reversal of absolute and relative inhibition. The modified TEG had Spearman correlations with OPA for absolute (rho = .424; P = .006) and relative inhibition (rho = .742; P < .0001). PWA correlations with OPA gave absolute (rho = .28; P = .08) and relative inhibition (rho = .46; P = .004) values. Bland-Altman analysis indicated agreement of both tests with OPA, showing constant biases of about 18% and some dependency on mean magnitude error. Cohen effect size thresholds defined nonresponders as < 7.7% clopidogrel inhibition relative to baseline recovery of full platelet function. Apparent nonresponse to clopidogrel or lack of platelet recovery did not correlate with statin or NSAID therapies. These PWA and modified TEG whole blood assays could prove useful for monitoring the reversal of clopidogrel and NSAID inhibition before surgery. More important, these assays done at baseline and after beginning clopidogrel therapy could monitor the effectiveness for the individual patients with cardiovascular disease and help identify the need for alternative therapies.

Maniabilité et intérêts potentiels du thromboélastomètre modifié (Rotem™) dans le monitorage extemporané de l'hémostase en réanimation

OBJECTIVE

Preliminary assessment of a rotary thromboelastometer (Rotem) in the haemostasis monitoring in ICU.

STUDY DESIGN

Prospective, open.

PATIENTS AND METHODS

The device: the Rotem is a rotary thromboelastometer, which measures continuously and retranscribes numerically viscoelastic properties of a clot after an in vitro haemostasis activation. 83 patients with various haemostasis disorders that 122 blood samples have been subjected to a double analysis: extemporaneous by Rotem and at the laboratory for conventional haemostasis tests (aPTT, PT, fibrinogen, platelets). We assessed Rotem's manipulation duration, time for the first results. We compared Rotem variables with conventional haemostasis parameters and haemostasis diagnosis with each method.

RESULTS

Mean Rotem manipulation duration was measured at 2 minutes 51 seconds+/-1 minute 48 seconds and time for results at 13+/-6 minutes. Plasma fibrinogen level was strongly correlated with the kinetic of clot formation (CFT) and the maximun clot firmness (MCF) measured by Rotem (R>0.7, coefficient of Pearson). Platelets were strongly correlated with MCF. The PT and aPTT had a weak correlation with Rotem parameters (R< or =0.53). The diagnosis concordance between the two techniques was good with a pondered kappa coefficient measured at 0.68. Hypocoagulability thromboelastographic profile with Rotem was in agreement with conventional parameters diagnosis in 92 percent of cases. Hypercoagulability thromboelastographic profile was associated with a significant increase of conventional parameters (supranormal value in 78%). Normal thromboelastography profile was associated with normal conventional parameters in 49%. Different reagents used on several simultaneous tests specified the thromboelastographic diagnosis. A diagnostic algorithm showed the interest of the Rotem for the prediction of conventional test results.

CONCLUSION

Rotem is an easy manipulation device whose concordant and rapid results allow its emergency use in the framework of haemorrhagic situations. It also allows an approach of hypercoagulability states so that the therapeutic implication remains to evaluate. The Rotem offers a dynamic multifactorial approach on total blood of haemostasis that is what makes it a prime aid of haemostasis monitoring, in complement of usual analytic haemostasis evaluation.

Using thrombelastography to determine the efficacy of the platelet glycoprotein IIb/IIIa antagonist, roxifiban, on platelet/fibrin-mediated clot dynamics in humans

The effect of platelet glycoprotein IIb/IIIa antagonists on the dynamics of platelet/fibrin clot formation and strength was determined using thrombelastography (TEG) under conditions of recalcification or tissue factor addition. In the present investigation, the effect of roxifiban (class I) on ex vivo clot dynamics using recalcified blood was tested in normal, healthy volunteers (n = 7) dosed with 1 mg BID roxifiban for 9 days. Roxifiban inhibited platelet aggregation induced by 20 mumol/l adenosine diphosphate by 60-90% but did not significantly affect any of the TEG parameters either at peak, trough, or subtrough drug levels. Addition of 30 nmol/l roxifiban free acid (XV459; which is ineffective by itself to modify TEG parameters) to human blood obtained from roxifiban-treated subjects resulted in 45-60% (P < 0.01) inhibition of clot strength (maximum amplitude), 90-100% (P < 0.01) inhibition of initial kinetic of clot development (angle alpha), and 50-70% (P < 0.01) inhibition of early clot initiation (K). These data suggest that a subthreshold blood level of 40-50 nmol/l roxifiban active form was achieved in those subjects, as estimated from an in vitro calibration with XV459. These data indicate (not studied) that roxifiban, at a targeted clinical dosing regimen, failed to achieve sufficient exposure to modulate platelet-mediated clot retraction.

Thrombelastograph (TEG) analysis of platelet gel formed with different thrombin concentrations

Autologous blood transfusion is the safest and most successful way to decrease transfusion-related risks such as postoperative infections, allo-immunization, and short- and long-term immunosuppression. In addition, these fibrin sealants are known to provide coagulation support at the surgical site and act as an adjunct to the control of postoperative bleeding. The physical formation of autologous platelet fibrin gel clot is dependent on both the common pathway of the coagulation cascade and platelet activation. Platelet gel can help provide control of intraoperative and postoperative bleeding. The Thrombelastograph Hemostasis Analyzer (TEG) measures the viscoelastic properties of a clot as it forms. Based on the information that the TEG provides, it promises to be a good choice for point of care measurement of the integrity of thrombus formed by platelet gels. Bovine blood from a single donor was sequestered into platelet-rich plasma and was made into platelet gel using calcium and three different concentrations of thrombin. The platelet gel samples were then analyzed with the TEG analyzer. The results for MA, tMA, CI, and angle were recorded and statistical analysis was performed to accept or reject the null hypothesis, which is: There is no difference between TEG parameters when analyzing platelet gels formed with calcium chloride, platelet-rich plasma and three different concentrations of thrombin A one-way analysis of variance test was performed between thrombin concentrations for MA (p = 0.19), tMA (p = 0.443), CI (p = 0.257), and angle (p = 0.323). The results showed that thrombin concentration did not affect the MA, tMA, CI, or angle as measured by the TEG analyzer. The null hypothesis was accepted. Based on a one-way analysis of variance test for MA, tMA, CI, and angle there was no significant statistical difference for the TEG samples in this experiment as reported with a 95% confidence interval.

Is platelet function as measured by Thrombelastograph monitoring in whole blood affected by platelet inhibitors?

Platelet inhibitors, especially the glycoprotein (GP) IIb/IIIa receptor antagonists, have demonstrated their effectiveness in reducing the acute ischemic complications of percutaneous coronary intervention (PCI) and in improving clinical outcomes in patients with acute coronary crisis. Three common platelet inhibitors observed in emergent cardiopulmonary bypass (CPB) for failed PCI are abciximab, eptifibatide, and tirofiban. An in vitro model was constructed in two parts to determine whether platelet aggregation inhibition induced by platelet inhibitors would be demonstrated by the Thrombelastograph (TEG) monitor when compared with baseline samples with no platelet inhibitor. In part A, 20 mL of fresh whole blood was divided into four groups: group I = baseline, group A = abcix-imab microg/mL, group E = eptifibatide ng/mL, and group T = tirofiban ng/mL. Platelet inhibitor concentrations in whole blood were derived starting with reported serum concentrations with escalation to achieve 80% platelet inhibition using the Medtronic hemoSTATUS and/or Lumi-aggregometer. A concentration range determined by our in vitro tests were chosen for each drug using concentrations achieving less than, equal to, or greater than 80% platelet inhibition. In part B, TEG analysis was then performed using baseline and concentrations for each drug derived in part A. Parameters measured were clot formation reaction time (R), coagulation time (K), maximum amplitude (MA) and alpha angle (A). Groups E1000 and E2000 extended R over control by 37% and 23%, respectively (p = 0.01 and 0.03). Groups E1000 and E2000 increased K times by 45% and 58% (p = .02 and .04). T160 samples prolonged K by 20% (p = 0.01). The angle or clot strength (A) was decreased in groups T160 and E1000 by 23% (+ 7.06 SD) and 18% (+ 11.23 SD), respectively (p = 0.001 and 0.01). The MA decrease was statistically significant in the T160, E1000 and E2000 by 9%, 6% and 13% respectively (p = 0.01). Samples treated with abciximab were comparable to control values for all parameters measured. Although statistical significance could be demonstrated with some parameters, sensitivity was only observed at increased doses and was not seen with all agents tested. In our in vitro model, the TEG monitor was unable to demonstrate clinically significant differences in platelet function and may not be reflective of platelet function in samples which have been treated with these GP IIb/IIIa inhibitors.

Quantifying platelet gel coagulation using Sonoclot and Thrombelastograph hemostasis analyzer

Little in vitro research exists discussing platelet gel composition and the resulting strength and degradation characteristics using point-of-care technologies. There must be a quantifiable way of determining the structural integrity of the resulting formed platelet gel thrombus. The Thrombelastograph Hemostasis Analyzer (TEG) and Sonoclot measure the elasticity of a clot as it forms and subsequently degrades naturally. The objective of this study was to determine the application of TEG and Sonoclot technologies as point-of-care devices for technicians using platelet gel therapy. The collected bovine blood was anticoagulated with CPD and processed using a previously published plasma sequestration protocol, using normal saline as a wash solution. The resulting platelet-rich plasma was stored in a sequestration bag in a water bath to maintain the blood temperature at 37 degrees C. Sequestered bovine platelet-rich plasma was made into platelet gel using three different thrombin concentrations. A total of 30 experiments were performed on the platelet gel product using both the TEG and the Sonoclot. We discovered that 6 of the Sonoclot tests and 15 of the TEG tests were valid. None of the TEG clot signatures and nine of the Sonoclot signatures were discovered to be invalid. A chi2 test was performed on the resultant data. The value of the chi2 test was calculated to be 12.86, which translated into a p value of less than 0.001. Despite the vast use and growing popularity of platelet gels, a method in which to quantify platelet gels has yet to be reported. There remains a possibility that gels formed with different concentrations of components may prove useful in different areas of surgery or their uses may expand to a broader spectrum of medicine. However, technology to quantify platelet gels must first be standardized. On the basis of the data collected in this study, it was determined that the TEG and the Sonoclot are not equally capable of analyzing platelet gel clots. The TEG is a valid means for analysis, whereas the Sonoclot provided unreliable analysis based on a Chi-squared test.

Coagulation status and complications of pregnancy

INTRODUCTION

There is much interest in the relationship between coagulation status and complications of pregnancy. The thrombelastograph (TEG) has been proposed as a useful, inexpensive tool to screen for patients with hypercoagulable states.

MATERIALS AND METHODS

We investigated 588 unselected pregnant women at booking, obtaining blood samples for TEG and thrombophilia investigation. Pregnancy outcome data was recorded.

RESULTS

We found significant correlations between TEG parameters and the Prothrombin time (PT) and Activated Partial Thromboplastin time (APTT) (p<0.01) and with plasma Antithrombin level (p<0.01). There was no correlation between TEG and other thrombophilic defects (protein C, protein S, Factor V Leiden mutation, Prothrombin G20210A mutation, MTHFR C677T mutation and Lupus Anticoagulant). There was a significant association of TEG parameters with mid-trimester loss (MTL) but not with other adverse pregnancy outcomes.

CONCLUSIONS

The correlation between TEG and PT, APTT and antithrombin level supports its value in providing a global measure of haemostasis. Coagulation status at booking is associated with increased risk of MTL but not with complications occurring later in pregnancy.

Plateletworks platelet function test compared to the thromboelastograph for prediction of postoperative outcomes

Approximately 3.5 million units of platelets are transfused in the United States each year to patients undergoing open-heart surgery with cardiopulmonary bypass (CPB). CPB is a known contributor to platelet loss and platelet dysfunction leading to disruption of hemostasis. Impaired hemostasis results in excess bleeding in 5-25% of all patients undergoing CPB. For this reason, it may be beneficial to measure platelet number and function in these patients. The purpose of this study was to compare the Plateletworks platelet function analyzer to the thromboelastograph (TEG) in predicting postoperatiave hemostatic outcomes as measured by blood product use and chest tube (CT) drainage. This study consisted of 35 adult patients undergoing cardiac surgery with cardiopulmonary bypass at Rush-Presbyterian-Saint Luke's Medical Center (RPSLMC). The Plateletworks and TEG tests were performed preoperatively, after protamine was given, and 24 hours postoperatively on all patients. Plateletworks demonstrated a statistically significant change in platelet function as shown by the adenosine diphosphate (ADP) reagent tube from the preoperative period to the removal of the aortic cross clamp (p = .011). The TEG did not demonstrate a significant change in the k-time and maximum amplitude (MA), but did show a significant change in the alpha-angle from the pre-operative to postoperatiave sample (p = .035). A correlation was found between Plateletworks collagen reagent tubes preoperatively and CT drainage (p = .048, r -0.324). No statistical correlation was established between TEG parameters and CT drainage at any time interval. TEG preoperative MA showed a correlation to receipt of blood products (p = .016). When comparing the Plateletworks to the TEG in this study, the Plateletworks system was a more useful predictor of blood product use and chest tube drainage.

The predictive value of modified computerized thromboelastography and platelet function analysis for postoperative blood loss in routine cardiac surgery

Hemorrhage after cardiopulmonary bypass (CPB) remains a clinical problem. Point-of-care tests to identify hemostatic disturbances at the bedside are desirable. In the present study, we evaluated the predictive value of two point-of-care tests on postoperative bleeding after routine cardiac surgery. Prospectively, 255 consecutive patients were studied to compare the ability of modified thromboelastography (ROTEG) as well as a platelet function analyzer (PFA-100) to predict postoperative blood loss. Measurements were performed at three time points: preoperatively, during CPB, and after protamine administration with three modified thromboelastography and PFA tests. The best predictors of increased bleeding tendency were the tests performed after CPB. The angle alpha is the best predictor (area under the receiver operating characteristic curve 0.69) and, in combination with the adenosine diphosphate-PFA test, the predictive accuracy is enhanced (area under the receiver operating characteristic curve 0.73). The negative predictive value for the angle alpha is 82%, although the positive predictive value is small (41%). Thromboelastography is a better predictor than PFA. In routine cardiac surgery, impaired hemostasis as identified by point-of-care tests does not inevitably lead to hemorrhage postoperatively. However, patients with normal test results are unlikely to bleed for hemostatic reasons. Bleeding in these patients is probably caused surgically. The high negative predictive value supports early identification and targeted treatment of surgical bleeding by distinguishing it from a significant coagulopathy.

IMPLICATIONS

Thrombelastography and platelet function analysis in routine cardiac surgery demonstrate high negative predictive values for postoperative bleeding, which supports early identification and targeted treatment of surgical bleeding by distinguishing it from a significant coagulopathy. The positive predictive values are small. The best predictors are thrombelastography values obtained after cardiopulmonary bypass.