Investigation of the effect of kaolin and tissue factor-activated citrated whole blood, on clot forming variables, as evaluated by thromboelastography

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.

Reference Range of Kaolin-Activated Thromboelastography (TEG) Values in Healthy Pet Rabbits (Oryctolagus cuniculus)

Thromboelastography (TEG) is a viscoelastic technique that allows the examination of both cellular and plasma protein clotting factors. Thromboelastography helps to investigate the underlying coagulopathy and to monitor therapeutic modalities. Although viscoelastic techniques have been used in human and veterinary medicine, reference ranges in pet rabbits are missing. The objective of this study is to establish the reference-range values of TEG parameters in healthy pet rabbits. 24 healthy pet rabbits of different breeds were included: 16 crossbreeds, four Californians, two lops, one lionhead, and one angora. Four rabbits were less than one year old and 20 were older than one year. Twelve rabbits were neutered females, 10 neutered males, and two were intact females. Health status was assessed through a physical examination, a complete blood work, and a coagulation profile. A TEG 5000 Thromboelastograph Hemostasis System was used with kaolin-activated citrated whole blood. All samples were analysed 30 min postextraction. The TEG reference ranges were reaction time (R) 1.4-6.9 min; clot formation time (K) 0.8-2.2 min; α angle 65.8-82.2 degrees; maximal amplitude (MA) 53.7-73.5 mm; measure of clot strength/firmness (G-value) 5796.6-13,885.9 dyn/cm²; and percentage of clot lysis in 30 min (LY30%) 0-41.5%. This study provides the reference ranges of TEG in pet rabbits.

Citrate does not change viscoelastic haemostatic assays after cardiopulmonary bypass

CONTEXT

Viscoelastic hemostatic assays (VHA) are commonly used to identify specific cellular and humoral causes for bleeding in cardiac surgery patients. Cardiopulmonary bypass (CPB) alterations to coagulation are observable on VHA. Citrated VHA can approximate fresh whole blood VHA when kaolin is used as the activator in healthy volunteers. Some have suggested that noncitrated blood is more optimal than citrated blood for point-of-care analysis in some populations.

AIMS

To determine if storage of blood samples in citrate after CPB alters kaolin activated VHA results.

SETTINGS AND DESIGN

This was a prospective observational cohort study at a single tertiary care teaching hospital.

METHODS AND MATERIAL

Blood samples were subjected to VHA immediately after collection and compared to samples drawn at the same time and stored in citrate for 30, 90, and 150 min prior to kaolin activated VHA both before and after CPB.

STATISTICAL ANALYSIS USED

VHA results were compared using paired T-tests and Bland-Altman analysis.

RESULTS

Maximum clot strength and time to clot initiation were not considerably different before or after CPB using paired T-tests or Bland-Altman Analysis.

CONCLUSIONS

Citrated samples appear to be a clinically reliable substitute for fresh samples for maximum clot strength and time to VHA clot initiation after CPB. Concerns about the role of citrate in altering the validity of the VHA samples in the cardiac surgery population seem unfounded.

Effects of storage time and temperature on thromboelastographic analysis in dogs and horses

BACKGROUND

The accessibility of thromboelastography (TEG) to general practitioners is limited by short sample storage times (30 minutes) and storage temperatures (20-23°C).

OBJECTIVES

We aimed to evaluate the stability of canine and equine citrated blood samples when stored for extended periods of time, both at room temperature (RT) (20-23°C) and refrigerator temperature (FT) (2-7.5°C).

METHODS

Citrated whole blood samples from healthy dogs and horses (n = 10 for each) were stored for 30 minutes (baseline) at RT before TEG analysis. Baseline values for TEG variables R, K, α, MA, LY30, and LY60 were compared with those from samples stored for 2, 8, and 22.5 h, at RT and FT. Results were compared using an ANOVA (P < .05). Total allowable analytical error (TE_a ) based on biological variation data was used to evaluate stability.

RESULTS

In dogs, statistically significant differences included shorter R, longer K, decreased MA, and increased LY60 at various time points and storage temperatures from 2 h onward. Only samples stored for 2 h at FT showed acceptable stability compared with TE_a . In horses, statistically significant differences included shorter R and K, and decreased α, LY30, and LY60 at various time points and storage temperatures from 2 h onward. Samples were not stable at any time compared with TE_a , regardless of the temperature.

CONCLUSIONS

In this study, canine samples could be stored for up to 2 h at FT without affecting TEG results; equine samples should be stored for 30 minutes at RT.

Characterization of analytical errors in thromboelastography interpretation

Introduction

Interpretation of Thromboelastography (TEG) curve involves correlating patient's clinical profile with TEG parameters and the tracing, keeping in mind the potential sources of errors, and hence requires expertise. We aimed to analyse the analytical errors in TEG interpretation due to paucity of literature in this regard.

Material and methods

The retrospective study was conducted in an apex trauma center in North India. Five months of data was reviewed by two laboratory physicians, with differences resolved by consensus. Cases with pre-analytical errors, missing data and TEG runs lasting <10 ​min were excluded. The analytical errors were classified into: preventable, potentially preventable, non-preventable, and non-preventable but care could have been improved.

Results

Out of 440 TEG tracings reviewed, 70 were excluded. An analytical error was present in 60/370 (16.2%) tracings. There were six types analytical errors, of which, tracings of severe hypocoagulable states showing k-time ​= ​0 (33.3%) was the commonest, followed by tracings with spikes at irregular intervals (30%). Of all the analytical errors, 29/60 (48.2%) were preventable and 5/60 (8.3%) were potentially preventable.

Conclusion

Analytical variables that lead to errors in TEG interpretation were identified in about one-sixth of the cases and almost half of them were preventable. Awareness about the common errors amongst clinicians and laboratory physicians is critical to prevent treatment delay and safeguard patient safety.

An overview of the potential sources of diagnostic errors in (classic) thromboelastography curve interpretation and preventive measures

Thromboelastography (TEG), a hemostatic point-of-care assay, provides global information about fibrin formation, platelet activation, and clot retraction in real-time. As it is an operator-dependent technique, error in any phase of the testing process can result in the misinterpretation of the thromboelastogram, and subsequently lead to mismanagement of the patient, wastage of blood products besides increasing the financial burden on the hospital and the patient. The present paper describes the possible errors leading to wrong thromboelastogram interpretation, and the respective preventive measure. In the light of limited resources available for operational challenges in TEG, this review paper can prove to be helpful.

Comparison of native and citrated whole blood samples for rapid thromboelastography in Beagles

OBJECTIVE

To examine the extent to which rapid thromboelastography (r-TEG) could decrease the testing time in comparison with that required for kaolin-activated thromboelastography (TEG), and to compare 2 types of blood samples (ie, native and citrated whole blood [WB]), for determining r-TEG values in healthy dogs.

DESIGN

Prospective observational study.

SETTING

University teaching hospital.

ANIMALS

Sixteen healthy Beagles.

INTERVENTIONS

Kaolin-activated TEG test using citrated WB samples and r-TEG test using native and citrated WB samples were performed in 16 dogs. At 60 minutes after the initial blood sampling, further samples were collected from a subset of 6 dogs in the same manner to evaluate intraindividual repeatability of r-TEG.

MEASUREMENTS AND MAIN RESULTS

The mean time to maximum amplitude (MA) for r-TEG with native and citrated WB samples was recorded as 1313.9 ± 250.9 seconds and 1351.3 ± 264.6 seconds (mean ± SD), respectively, and 1779.9 ± 197.0 seconds for kaolin-activated TEG. Coefficients of variation with native and citrated WB samples for r-TEG values, TEG-activated clotting time, clot formation time, α angle, and MA, were determined to be 13.4% versus 18.8%, 11.1% versus 16.6%, 4.2% versus 5.1%, and 10.0% versus 10.0%, respectively. Intraindividual variations were lower for native WB samples than for citrated WB samples.

CONCLUSIONS

The r-TEG test significantly decreased the mean time to MA compared with the kaolin-activated TEG test. In addition, native WB samples showed lower coefficients of variation and intraindividual variation than citrated WB samples in r-TEG analysis; this suggests that native WB samples can provide more consistent results. Therefore, the r-TEG method using native WB samples is recommended for assessment of dogs' hemostatic status when an early diagnosis is required.

Establishing a protocol for thromboelastography in sea turtles

Thromboelastography (TEG) provides a global evaluation of haemostasis. This diagnostic test is widely used in mammals but has not previously been performed in reptiles, mainly due to the limited availability of taxon-specific reagents. The objective of this pilot study was to establish a protocol to perform TEG in sea turtles. Pooled citrated plasma, stored at −80°C, from four green turtles (Chelonia mydas) was assayed on a TEG 5000. Several initiators were evaluated: kaolin (n=2), RapidTEG (n=2), fresh (n=2) and frozen (n=6) thromboplastin extracted from pooled brain tissue from several chelonian species, human recombinant tissue factor at 1:100 (n=1), Reptilase (n=2), and rabbit thromboplastin (n=1). Both fresh and frozen chelonian thromboplastin were superior in producing quantifiable TEG reaction time compared with all other reagents. These findings are consistent with the lack of an intrinsic pathway in turtles and confirmed a lack of coagulation in the turtle samples in response to mammalian thromboplastin. A TEG protocol was subsequently established for harvested species-specific frozen thromboplastin. The frozen thromboplastin reagent remained stable after one year of storage at −80°C. The developed protocol will be useful as a basis for future studies that aim to understand the pathophysiology of haemostatic disorders in various stranding conditions of sea turtles.

Rapid TEG efficiently guides hemostatic resuscitation in trauma patients

BACKGROUND

Several thrombelastography functional assays have been developed to guide transfusion in injured patients, but how this acceleration of thrombelastography affects its ability to predict massive transfusion is unknown. The objective of this study is to compare citrated native, citrated kaolin, and citrated rapid thromboelastographies for their prediction of massive transfusion after trauma. We hypothesized that citrated native thrombelastography best predicts massive transfusion.

METHODS

Data were collected as part of a prospective study of trauma activation patients. All patients received citrated native, citrated kaolin, or citrated rapid thromboelastographies. Logistic regression was used to assess the predictive performance of different thrombelastography assays for massive transfusion.

RESULTS

Measurements for all three TEG activating systems was available for 343 patients; 57 (16.6%) required a massive transfusion. Compared to citrated rapid thromboelastographies, citrated kaolin thromboelastographies performed better for activated clotting time/rapid and citrated native thromboelastographies for maximum amplitude and angle. Yet, the 95% confidence intervals overlapped considerably, suggesting the citrated rapid thromboelastographies produced comparable results to the other assays for activated clotting time/reaction time, maximum amplitude, and angle.

CONCLUSION

There was substantial overlap in the performance of the different thrombelastography assays, suggesting citrated rapid thrombelastography is a quick and effective method to guide hemostatic resuscitation in trauma patients and does not perform inferiorly to the citrated native or citrated kaolin thrombelastography despite the addition of activation factors.

Development of a fibrinolysis assay for canine plasma

Unbalanced coagulation and fibrinolysis leads to hemorrhage or thrombosis. Thromboelastography has been used to characterize hypo- and hyper-fibrinolysis in dogs, however the technique requires specialized instrumentation and proprietary reagents that limit its availability. The aim of this study was to develop a simple microplate method for assessment of fibrinolysis in canine plasma. Plasma from healthy dogs was mixed in a microwell plate with tissue factor, calcium, phospholipid and tissue plasminogen activator. Light absorbance was measured at regular intervals until return to baseline. Peak optical density (milli-absorption units, mAU), formation velocity (mAU/s), lysis velocity (mAU/s) and area under the curve (mAU.s) were calculated. The influence of potential interferents, variation in fibrinogen and ex vivo addition of heparin and aminocaproic acid on assay performance was determined. Inter-day coefficients of variation were ≤15% for all variables. Bilirubin≤1.88mg/dL and hemoglobin≤0.09mg/dL did not interfere with assay variables. Aminocaproic acid (40μg/mL) and heparin (0.125U/mL) caused almost complete inhibition of fibrinolysis and coagulation, respectively. All variables except lysis velocity (R²=0.08) were associated with fibrinogen concentration (R²>0.8). This assay showed acceptable performance characteristics for measurement of fibrinolysis in normal canine plasma. The assay utilizes small volume citrate plasma samples and readily available instrumentation and reagents, is not influenced by mild to moderate hemolysis or icterus and detects the presence of fibrinolysis inhibitors.

Management of Trauma-Induced Coagulopathy with Thrombelastography

Viscoelastic assays, such as thrombelastography (TEG) and rotational thrombelastometry (ROTEM), have emerged as point-of-care tools that can guide the hemostatic resuscitation of bleeding injured patients. This article describes the role of TEG in contemporary trauma care by explaining this assay's methodology, clinical applications, and result interpretation through description of supporting studies to provide the reader with an evidence-based user's guide. Although TEG and ROTEM are assays based on the same viscoelastic principle, this article is focused on data supporting the use of TEG in trauma, because it is available in trauma centers in North America; ROTEM is mostly available in Europe.

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

Context.—

Thromboelastography (TEG) is a whole blood, real-time analyzer measuring the viscoelastic properties of the hemostasis process and allowing for individualized goal-directed therapy. However, routine use of TEG requires validation of sample storage effect on clot parameters.

Objectives.—

To establish the minimum time required for equilibration time and the maximum time for sample storage for all commercially available TEG tests for the new-generation TEG 6s and to determine how those times compare with the older generation TEG 5000.

Design.—

Citrated and heparinized whole blood samples obtained from 20 healthy donors were analyzed for clot parameters at multiple time points for both the TEG 6s and the TEG 5000. Samples were activated with the citrated multichannel cartridge or the platelet-mapping cartridge in the TEG 6s or with recalcified kaolin in the TEG 5000.

Results.—

All blood samples yielded TEG parameter results within reference ranges and had a tendency toward hypercoagulable profiles with increased storage time. Sample storage resulted in increased platelet inhibition with significant differences at 4 hours in the platelet-mapping cartridge (arachidonic acid percentage of inhibition, P = .002; adenosine diphosphate percentage of inhibition, P = .02).

Conclusions.—

For nonemergent cases or in a central laboratory setting, all tests provided reliable results for up to 4 hours in the citrated multichannel cartridge and for 3 hours for platelet function information in the platelet-mapping cartridge. In emergent/urgent situations in which the sample needs to be run immediately, RapidTEG and functional fibrinogen tests may be preferred.

Heparinase-modified thromboelastography in cats

BACKGROUND

Evaluation of underlying hemostatic function is challenging when feline patients are receiving an anticoagulant medication. Discontinuing the anticoagulant to obtain accurate results for hemostatic testing may lead to thrombotic complications. The addition of heparinase to blood samples may mitigate the effects of exogenous heparin and allow hemostatic testing.

METHODS

Tissue factor (TF)-activated thromboelastography (TEG) was performed using citrated whole blood from 19 cats. Assays were performed using citrated whole blood, with and without addition of unfractionated heparin to a concentration of 0.2 U/mL. For each blood sample, TEG assays were performed using a standard cup and a heparinase-coated cup.

KEY FINDINGS

For TEG variables R, k, α-angle, and MA, mean values were not statistically different when citrated blood was used with standard or heparinase-coated cups. Heparinized blood assayed in standard cups displayed a significantly increased R and k, and significantly decreased α-angle and MA when compared to heparinized blood assayed in heparinase-coated cups. TEG variables for heparinized blood assayed in heparinase cups was not statistically different from those of the citrated whole blood without added heparin.

SIGNIFICANCE

Heparinase modified, TF-activated, TEG reverses heparin effects in feline-citrated blood.

Thromboelastography on plasma reveals delayed clot formation and accelerated clot lyses in HIV-1 infected persons compared with healthy controls

Background

Thromboembolic events among HIV infected persons are a recognized clinical problem but the underlying mechanisms are poorly understood. To assess whether coagulation and fibrinolysis differ between long-term treated HIV infected individuals (HIV+) and healthy controls (CON), we investigated functional plasma coagulation by thrombelastography (TEG) and plasma markers of endothelial and platelet activation.

Methods

In 67 successfully long-term treated HIV+ and 15 CON we analyzed stored plasma samples by TEG, with or without addition of tissue-type plasminogen activator (tPA), and measured levels of C-reactive protein, thrombomodulin, syndecan-1, sVE-cadherin, soluble CD40 ligand (sCD40L), adrenaline and noradrenaline.

Results

Compared to CON, HIV+ had delayed clot formation (reaction (R)-time 14.2 min. vs. 11.2 min., p = 0.0004) and reduced clot formation rapidity (angle 22.6° vs. 48.6 °, p = <0.0001). Clot lyses induced by tPA was accelerated in HIV+ displaying enhanced clot degradation after 30 and 60 min (53.9 % vs. 24.2 %, p < 0.0001 and 77.4 % vs. 59.9 %, p < 0.0001, respectively). sCD40L and TEG R-time correlated negatively in both HIV+ and CON (Rho =−0.502, p < 0.001 and rho =−0.651, p = 0.012).

Discussion

No previous studies have examined plasma coagulation by TEG in HIV, however, we have previously demonstrated that HIV+ display hypocoagulability in whole blood by TEG in accordance with the results of this study. Others have reported of HIV associated changes in the hemostatic system in a pro-coagulant direction based on measurements of isolated components of the coagulation pahways. In disease conditions, the flowing blood may change from “normal” to hyper- or hypocoagulant or to hyper- or hypofibrinolytic. A balance may exist in the flowing blood, i.e. between blood cells and the plasma phase, so that pro-coagulant blood cells are balanced by a hypocoagulable plasma phase; thus alterations that may promote thromboembolic events in the patient may at the same time appear as a hypocoagulable profile when evaluated in vitro.

Conclusion

Plasma from long-term treated HIV infected persons displays a hypocoagulable profile with reduced fibrinolytic resistance as compared to healthy controls.

All the bang without the bucks: Defining essential point-of-care testing for traumatic coagulopathy

BACKGROUND

Rapid assessment and treatment of coagulopathy reduces postinjury morbidity and mortality. Although thrombelastography (TEG) may be more accurate and efficient than conventional coagulation tests, it requires significant financial and personnel investments. We hypothesized that point-of-care international normalized ratio (POC INR) may provide a rapid and accurate alternative to TEG.

METHODS

A retrospective review of sequential trauma patients who underwent both POC INR and rapid TEG (r-TEG) testing upon presentation to a Level I trauma center from July 2012 to December 2013 was performed. POC INR was compared with r-TEG values (R value, K time, α angle, maximum amplitude, percent clot lysis in 30 minutes) and transfusion requirements. Vital signs, admission laboratory values, and injury severity were analyzed. POC INR and venous blood gas testing was performed in the emergency department. All results and Pearson correlations noted were significant if p < 0.05.

RESULTS

We identified 628 trauma patients with concomitant r-TEG and POC INR testing. Median Injury Severity Score (ISS) was 13, 20% arrived in shock (base value < -5), 21% were transfused, and 11% died. POC INR correlated with all r-TEG values, with stronger correlations for patients in shock. POC INR and r-TEG had similar correlations with blood products transfused at 4 hours and 24 hours, but only POC INR predicted substantial bleeding and massive transfusion. POC INR also correlated strongly with standard INR testing. POC INR test duration was less than 1 minute, compared with at least 30 minutes for r-TEG. Total cohort charges for POC INR were estimated at $21,980 versus $396,896 for r-TEG.

CONCLUSION

POC INR testing is faster and cheaper than r-TEG. In addition, POC INR correlates not only with r-TEG values but also with acute blood product transfusions. POC INR provides a practical alternative for rapid coagulopathy assessment in the trauma patient at institutions that lack TEG capability.

LEVEL OF EVIDENCE

Diagnostic study, level III. Therapeutic/care management study, level IV.

Evaluation of thromboelastography in two factor XII-deficient cats

Case summary

The current report describes thromboelastography (TEG) findings in two cats with factor XII (FXII) deficiency. The first cat was diagnosed with bilateral perinephric pseudocysts; hemostatic testing was performed prior to performing renal aspirates. The second cat was healthy; hemostatic testing was performed prior to inclusion into a research project. Both cats had markedly prolonged partial thromboplastin times and hypocoagulable TEG tracings when samples were activated with kaolin. However, when tissue factor (TF) was used to activate the sample, both cats had normal-to-hypercoagulable TEG tracings. The cats each had a subnormal FXII level.

Relevance and novel information

TEG is becoming widely used to investigate hemostasis in veterinary patients, and TEG results in cats with FXII deficiency have not been previously reported. FXII deficiency is the most common hereditary hemostatic defect in cats. While FXII deficiency does not lead to in vivo hemorrhagic tendencies, it can lead to marked prolongation in activated partial thromboplastin and activated clotting times, and cannot be differentiated from true hemorrhagic diatheses without measuring individual factor activity. With the increased use of TEG to evaluate hemostasis in veterinary patients, it is important to recognize the effects of FXII deficiency on this testing modality. The finding of a hypocoagulable kaolin-activated TEG tracing and a concurrent normal TF-activated TEG tracing in samples should prompt clinicians to consider ruling out FXII deficiency.

Association between biomarkers of endothelial injury and hypocoagulability in patients with severe sepsis: a prospective study

Introduction

Patients with severe sepsis often present with concurrent coagulopathy, microcirculatory failure and evidence of vascular endothelial activation and damage. Given the critical role of the endothelium in balancing hemostasis, we investigated single-point associations between whole blood coagulopathy by thrombelastography (TEG) and plasma/serum markers of endothelial activation and damage in patients with severe sepsis.

Methods

A post-hoc multicenter prospective observational study in a subgroup of 184 patients from the Scandinavian Starch for Severe Sepsis/Septic Shock (6S) Trial. Study patients were admitted to two Danish intensive care units. Inclusion criteria were severe sepsis, pre-intervention whole blood TEG measurement and a plasma/serum research sample available from baseline (pre-intervention) for analysis of endothelial-derived biomarkers. Endothelial-derived biomarkers were measured in plasma/serum by enzyme-linked immunosorbent assay (syndecan-1, thrombomodulin, protein C (PC), tissue-type plasminogen activator and plasminogen activator inhibitor-1). Pre-intervention TEG, functional fibrinogen (FF) and laboratory and clinical data, including mortality, were retrieved from the trial database.

Results

Most patients presented with septic shock (86%) and pulmonary (60%) or abdominal (30%) focus of infection. The median (IQR) age was 67 years (59 to 75), and 55% were males. The median SOFA and SAPS II scores were 8 (6 to 10) and 56 (41 to 68), respectively, with 7-, 28- and 90-day mortality rates being 21%, 39% and 53%, respectively. Pre-intervention (before treatment with different fluids), TEG reaction (R)-time, angle and maximum amplitude (MA) and FF MA all correlated with syndecan-1, thrombomodulin and PC levels. By multivariate linear regression analyses, higher syndecan-1 and lower PC were independently associated with TEG and FF hypocoagulability at the same time-point: 100 ng/ml higher syndecan-1 predicted 0.64 minutes higher R-time (SE 0.25), 1.78 mm lower TEG MA (SE 0.87) and 0.84 mm lower FF MA (SE 0.42; all P <0.05), and 10% lower protein C predicted 1.24 mm lower TEG MA (SE 0.31).

Conclusions

In our cohort of patients with severe sepsis, higher circulating levels of biomarkers of mainly endothelial damage were independently associated with hypocoagulability assessed by TEG and FF. Endothelial damage is intimately linked to coagulopathy in severe sepsis.

Trial registration

Clinicaltrials.gov number: NCT00962156. Registered 13 July 2009.

Time impact on non-activated and kaolin-activated blood samples in thromboelastography

Background

The correct methodology of thrombelastography might be influenced by elapsing time. In our study we investigated kaolin activated citrated samples together with non-activated citrated samples in relation to the elapsed times of 0, 15 and 30 minutes to compare both methods and to find out if there is an impact of time on results of thrombelastography.

Methods

Blood samples obtained from 10 healthy volunteers were analyzed after 0, 15 and 30 minutes from sampling with kaolin activation and without activation. Then the results were analysed and compared between the non-activated and the kaolin-activated method.

Results

All blood samples became more hypercoagulable with the time elapsing, both in non-activated and kaolin-activated samples and differences between both groups were found statistically and clinically significant after only 0 minutes.

Conclusions

The non-activated citrated method seems to be reliable and suitable for thrombelastography in non-emergency cases (planned surgical procedures) when we have time to wait 15–30 minutes to get results. In urgent situations a rapid thrombelastography test should be preferred. Although the kaolin-activated method can also be used, results must be interpreted with caution.

Mild induced hypothermia: effects on sepsis-related coagulopathy--results from a randomized controlled trial

INTRODUCTION

Coagulopathy associates with poor outcome in sepsis. Mild induced hypothermia has been proposed as treatment in sepsis but it is not known whether this intervention worsens functional coagulopathy.

MATERIALS AND METHODS

Interim analysis data from an ongoing randomized controlled trial; The Cooling And Surviving Septic shock (CASS) study. Patients suffering severe sepsis/septic shock are allocated to either mild induced hypothermia (cooling to 32-34°C for 24hours) or control (uncontrolled temperature).

TRIAL REGISTRATION

NCT01455116. Thrombelastography (TEG) is performed three times during the first day after study enrollment in all patients. Reaction time (R), maximum amplitude (MA) and patients' characteristics are here reported.

RESULTS

One hundred patients (control n=50 and intervention n=50; male n=59; median age 68years) with complete TEG during follow-up were included. At enrollment, 3%, 38%, and 59% had a hypocoagulable, normocoagulable, and hypercoagulable TEG clot strength (MA), respectively. In the hypothermia group, functional coagulopathy improved during the hypothermia phase, measured by R and MA, in patients with hypercoagulation as well as in patients with hypocoagulation (correlation between ΔR and initial R: rho=-0.60, p<0.0001 and correlation between ΔMA and initial MA: rho=-0.50, p=0.0002). Similar results were not observed in the control group neither for R (rho=-0.03, p=0.8247) nor MA (rho=-0.15, p=0.3115).

CONCLUSION

Mild induced hypothermia did seem to improve functional coagulopathy in septic patients. This improvement of functional coagulopathy parameters during the hypothermia intervention persisted after rewarming. Randomized trials are warranted to determine whether the positive effect on sepsis-related coagulopathy can be transformed to improved survival.

Contact activation of blood coagulation on a defined kaolin/collagen surface in a microfluidic assay

Generation of active Factor XII (FXIIa) triggers blood clotting on artificial surfaces and may also enhance intravascular thrombosis. We developed a patterned kaolin (0 to 0.3 pg/μm(2))/type 1 collagen fibril surface for controlled microfluidic clotting assays. Perfusion of whole blood (treated only with a low level of 4 μg/mL of the XIIa inhibitor, corn trypsin inhibitor) drove platelet deposition followed by fibrin formation. At venous wall shear rate (100 s(-1)), kaolin accelerated onset of fibrin formation by ~100 sec when compared to collagen alone (250 sec vs. 350 sec), with little effect on platelet deposition. Even with kaolin present, arterial wall shear rate (1000 s(-1)) delayed and suppressed fibrin formation compared to venous wall shear rate. A comparison of surfaces for extrinsic activation (tissue factor TF/collagen) versus contact activation (kaolin/collagen) that each generated equal platelet deposition at 100 s(-1) revealed: (1) TF surfaces promoted much faster fibrin onset (at 100 sec) and more endpoint fibrin at 600 sec at either 100 s(-1) or 1000 s(-1), and (2) kaolin and TF surfaces had a similar sensitivity for reduced fibrin deposition at 1000 s(-1) (compared to fibrin formed at 100 s(-1)) despite differing coagulation triggers. Anti-platelet drugs inhibiting P2Y1, P2Y12, cyclooxygenase-1 or activating IP-receptor or guanylate cyclase reduced platelet and fibrin deposition on kaolin/collagen. Since FXIIa or FXIa inhibition may offer safe antithrombotic therapy, especially for biomaterial thrombosis, these defined collagen/kaolin surfaces may prove useful in drug screening tests or in clinical diagnostic assays of blood under flow conditions.

Microparticle-associated tissue factor activity is reduced by inhibition of the complement protein 5 in Neisseria meningitidis-exposed whole blood

Neisseria meningitidis causes fulminant meningococcal sepsis with a massive activation of the coagulation and complement cascades. Bacterial cell envelope molecules from N. meningitidis, particularly lipopolysaccharide (LPS), induce tissue factor (TF) expression. In meningococcal sepsis, TF can be detected on circulating monocytes and microparticles (MPs) within the bloodstream. During infection, Nm activates C5 and C5a, which also is able to induce TF. We evaluated the effect of eculizumab, a C5-blocking monoclonal antibodies (mAb), on cell- and MP-associated TF. Using a lepirudin-anticoagulated whole blood model, we activated the coagulation and complement cascades by N. meningitidis, and investigated the interaction between the cascade systems with special focus on cell-associated TF-expression (mRNA and protein) and MP-associated TF-dependent thrombin and fibrin generation in platelet-free plasma. We also examined the ability of TF-positive MPs to support clot formation in whole blood. In addition, the effect of corn trypsin inhibitor and time-dependent changes on MP-associated functional TF activity was examined. Inhibition of C5 reduced cell-associated TF expression at both gene and protein level, and reduced MP-associated TF-dependent thrombin and fibrin generation in platelet-poor plasma, MP-induced TF-dependent clot formation in whole blood, implying that the complement and coagulation cascades are interplayers in N. meningitidis-mediated activation of these cascades.

Assessing blood coagulation status with laser speckle rheology

We have developed and investigated a novel optical approach, Laser Speckle Rheology (LSR), to evaluate a patient's coagulation status by measuring the viscoelastic properties of blood during coagulation. In LSR, a blood sample is illuminated with laser light and temporal speckle intensity fluctuations are measured using a high-speed CMOS camera. During blood coagulation, changes in the viscoelastic properties of the clot restrict Brownian displacements of light scattering centers within the sample, altering the rate of speckle intensity fluctuations. As a result, blood coagulation status can be measured by relating the time scale of speckle intensity fluctuations with clinically relevant coagulation metrics including clotting time and fibrinogen content. Our results report a close correlation between coagulation metrics measured using LSR and conventional coagulation results of activated partial thromboplastin time, prothrombin time and functional fibrinogen levels, creating the unique opportunity to evaluate a patient's coagulation status in real-time at the point of care.

Determination of thromboelastographic responsiveness in stored single-donor platelet concentrates

BACKGROUND

Thromboelastography (TEG) is widely used in hospitals but less commonly in blood banks for evaluation of platelet (PLT) concentrates (PCs). A TEG-PC assay for testing fresh or stored PLTs must reflect the quality of the PLTs. The added value could be measurement of donor-dependent PLT quality.

STUDY DESIGN AND METHODS

Whole blood (WB) normal values were generated from 100 donors, using standard tests. Nineteen single-donor PCs were evaluated with a TEG-PC assay, using Octaplas as microparticle-free diluent and kaolin or collagen as activator, stored up to 12 days, and also sampled for additional in vitro tests.

RESULTS

WB values showed larger reaction rates (R- and K-times, angle) compared to the reference values and almost similar maximum amplitude (MA). PCs showed usual storage lesion and TEG-PC results showed significant decreasing R- and K-times and increasing angle. Mean MA values remained constant but individual measurements were affected by clot retraction. TEG tracings of two PCs with good quality on Day 12 showed weak to strong clot retraction, while two PCs with poor quality showed moderate clot retraction on Day 1, no clot retraction on Days 5 to 12, and a decreased MA on Day 12. Clot strength (MA) and especially clot retraction represent possibly donor-specific effects.

CONCLUSION

A TEG-PC assay has been developed that is sensitive to storage effects. The assay has the potential to be helpful in selection of PLT donors but needs improvement to be more sensitive, reproducible, and distinctive to determine whose PLTs store poorly and whose store well.

Discrepant coagulation profile in HIV infection: elevated D-dimer but impaired platelet aggregation and clot initiation

OBJECTIVES

In HIV infection, cardiovascular disease (CVD) has emerged as a clinical problem, and elevated D-dimer has been reported. The pathophysiologic mechanisms underlying this remain unclear. We aimed to investigate whether untreated HIV-infected individuals display evidence of functional coagulopathy and whether this was associated with microbial translocation.

DESIGN

The study population consisted of 50 HIV-infected untreated individuals and 50 HIV-infected individuals on combination antiretroviral therapy (cART). Groups were matched for age, sex and current CD4cell count.

METHODS

Coagulation analyses included D-dimer and the functional haemostatic whole blood tests, thromboelastography (TEG) and platelet aggregation (Multiplate, impedance aggregometry). Microbial translocation was assessed by plasma levels of lipopolysaccharide (LPS).

RESULTS

A larger proportion of untreated individuals compared with treated individuals had D-dimer above normal reference range (27.7 vs. 2.2%, P = 0.001). In both treated and untreated individuals, delayed clot initiation with TEG R-time above upper reference range (18 and 28%, respectively, both P < 0.001) and TEG angle below lower reference range [14% (P = 0.004) and 24% (P < 0.001), respectively] was found. In untreated individuals, 64.6% had aggregation response below threshold in at least two of four tests compared with 36.7% in treated individuals (P = 0.010). Untreated individuals with increased D-dimer levels were relatively hypercoagulable by thromboelastography. Furthermore, in untreated patients, a negative association between microbial translocation and platelet aggregation was found.

CONCLUSION

Elevated D-dimer in untreated HIV-infected individuals was confirmed. However, in both untreated and treated individuals, reduced platelet aggregation and clot initiation was found. The impact of reduced platelet function in HIV infection and a potential role of microbial translocation warrant further investigation.

Fresh and citrated whole-blood specimens can produce different thromboelastography results in patients on extracorporeal membrane oxygenation

OBJECTIVES

To compare thromboelastography (TEG) tracings obtained from fresh and citrated whole-blood samples in patients on extracorporeal membrane oxygenation (ECMO) or after cardiopulmonary bypass and in healthy volunteers.

METHODS

Samples of fresh and citrated whole blood were analyzed for 25 patients and 4 healthy volunteers. Thromboelastography analysis was performed in both plain and heparinase cups.

RESULTS

In 5 of 6 patients on ECMO, use of citrated samples resulted in apparent partial or complete heparin reversal. In TEG tracings from patients following cardiopulmonary bypass, there was a slight hypercoagulable appearance in the citrated sample. No differences were noted between fresh and citrated samples from healthy volunteers whose blood was spiked with heparin.

CONCLUSIONS

In some patients on ECMO, use of samples collected in sodium citrate tubes for TEG analysis results in significant artifacts, which could lead to heparin overdosing in these patients.

Evaluation of TEG(®) and RoTEM(®) inter-changeability in trauma patients

BACKGROUND

Massive haemorrhage is a leading cause of preventable deaths in trauma. Traumatic coagulopathy is frequently present early after trauma, and is associated with increased mortality. A number of recent trials suggest that viscoelastic haemostatic assays (VHA), such as thromboelastography and thromboelastometry, are useful tools in guiding transfusion. Treatment algorithms exist for the use of VHAs but are not validated in traumatic haemorrhage. In this study we examined the inter-changeability of two commonly used VHAs, TEG(®) and RoTEM(®).

METHODS

A total of 184 trauma patients over the age of 18, requiring full trauma team activation, were included at three different hospitals in three different countries (Copenhagen, Denmark, San Francisco, CA, USA and Oslo, Norway). Blood samples were drawn immediately upon arrival, and TEG(®) and RoTEM(®) analyzed simultaneously. Correlations were calculated using. Spearman's rank correlation coefficient. Agreement was evaluated by Bland-Altman plots and calculation of limits of agreement.

RESULTS

The mean ISS in the total population was 17, and the mortality was 16.5%. Mean base excess was -2.8 (SD: 4.2). The correlation coefficient for corresponding values for the two devices was 0.24 for the R-time vs CT in all centres combined. For the K-time vs CFT the correlation was 0.48, for the α-angleTEG vs α-angleRoTEM 0.44, and for MA vs MCF 0.76. Limits of agreement exceeded the preset clinically acceptable deviation of 10% for all variables in all centres except for MA/MCF in one centre (Copenhagen). Generally, correlation coefficients were lower and agreement poorer in the one centre (Oslo) where measurements were performed bedside by clinicians.

CONCLUSION

Inter-changeability between TEG(®) and RoTEM(®) is limited in the trauma setting. Agreement seems poorer when clinicians operate the devices. Development and validation of separate treatment algorithms for the two devices is required.

Low hemorrhage-related mortality in trauma patients in a Level I trauma center employing transfusion packages and early thromboelastography-directed hemostatic resuscitation with plasma and platelets

BACKGROUND

Hemorrhage accounts for most preventable trauma deaths, but still the optimal strategy for hemostatic resuscitation remains debated.

STUDY DESIGN AND METHODS

This was a prospective study of adult trauma patients admitted to a Level I trauma center. Demography, Injury Severity Score (ISS), transfusion therapy, and mortality were registered. Hemostatic resuscitation was based on a massive transfusion protocol encompassing transfusion packages and thromboelastography (TEG)-guided therapy.

RESULTS

A total of 182 patients were included (75% males, median age 43 years, ISS of 17, 92% with blunt trauma). Overall 28-day mortality was 12% with causes of death being exsanguinations (14%), traumatic brain injury (72%, two-thirds expiring within 24 hr), and other (14%). One-fourth, 16 and 15% of the patients, received red blood cells (RBCs), plasma, or platelets (PLTs) within 2 hours from admission and 68, 71, and 75%, respectively, of patients transfused within 24 hours received the respective blood products within the first 2 hours. In patients transfused within 24 hours, the median number of blood products at 2 hours was 5 units of RBCs, 5 units of plasma, and 2 units of PLT concentrates. Nonsurvivors had lower clot strength by kaolin-activated TEG and TEG functional fibrinogen and lower kaolin-tissue factor-activated TEG α-angle and lysis after 30 minutes compared to survivors. None of the TEG variables were independent predictors of massive transfusion or mortality.

CONCLUSION

Three-fourths of the patients transfused with plasma or PLTs within 24 hours received these in the first 2 hours. Hemorrhage caused 14% of the deaths. We introduced transfusion packages and early TEG-directed hemostatic resuscitation at our hospital 10 years ago and this may have contributed to reducing hemorrhagic trauma deaths.

Discrepant fibrinolytic response in plasma and whole blood during experimental endotoxemia in healthy volunteers

Background

Sepsis induces early activation of coagulation and fibrinolysis followed by late fibrinolytic shutdown and progressive endothelial damage. The aim of the present study was to investigate and compare the functional hemostatic response in whole blood and plasma during experimental human endotoxemia by the platelet function analyzer, Multiplate and by standard and modified thrombelastography (TEG).

Methods

Prospective physiologic study of nine healthy male volunteers undergoing endotoxemia by means of a 4-hour infusion of E. coli lipopolysaccharide (LPS, 0.5 ng/kg/hour), with blood sampled at baseline and at 4 h and 6 h. Physiological and standard biochemical data and coagulation tests, TEG (whole blood: TEG, heparinase-TEG, Functional Fibrinogen; plasma: TEG±tissue-type plasminogen activator (tPA)) and Multiplate (TRAPtest, ADPtest, ASPItest, COLtest) were recorded. Mixed models with Tukey post hoc tests and correlations were applied.

Results

Endotoxemia induced acute SIRS with increased HR, temperature, WBC, CRP and procalcitonin and decreased blood pressure. It also induced a hemostatic response with platelet consumption and reduced APTT while INR increased (all p<0.05). Platelet aggregation decreased (all tests, p<0.05), whereas TEG whole blood clot firmness increased (G, p = 0.05). Furthermore, during endotoxemia (4 h), whole blood fibrinolysis increased (clot lysis time (CLT), p<0.001) and Functional Fibrinogen clot strength decreased (p = 0.049). After endotoxemia (6 h), whole blood fibrinolysis was reduced (CLT, p<0.05). In contrast to findings in whole blood, the plasma fibrin clot became progressively more resistant towards tPA-induced fibrinolysis at both 4 h and 6 h (p<0.001).

Conclusions

Endotoxemia induced a hemostatic response with reduced primary but enhanced secondary hemostasis, enhanced early fibrinolysis and fibrinogen consumption followed by downregulation of fibrinolysis, with a discrepant fibrinolytic response in plasma and whole blood. The finding that blood cells are critically involved in the vasculo-fibrinolytic response to acute inflammation is important given that disturbances in the vascular system contribute significantly to morbidity and mortality in critically ill patients.

Effects of oral prednisone administration with or without ultralow-dose acetylsalicylic acid on coagulation parameters in healthy dogs

OBJECTIVE

To determine the effects of oral prednisone administration with or without ultralow-dose acetylsalicylic acid on coagulation parameters in healthy dogs and to assess intraindividual variation in thromboelastography results.

ANIMALS

14 healthy research dogs and 10 healthy client-owned dogs.

PROCEDURES

In a randomized controlled trial, research dogs underwent thromboelastography twice (3 days apart), and intraindividual variation in test results was calculated. Dogs were given prednisone (2 mg/kg/d, PO) plus acetylsalicylic acid (0.5 mg/kg/d, PO) or prednisone (2 mg/kg/d, PO) plus a placebo for 14 days, after which thromboelastography and other tests were repeated. Differences from preadministration (baseline) test results between and within groups were compared. In a separate trial, client-owned dogs also underwent thromboelastography twice 2 days apart to assess intraindividual variation in untreated dogs.

RESULTS

Intraindividual variation in thromboelastography results for research dogs was ≤ 10% for maximum amplitude (MA) and α angle. In the research dogs, MA and fibrinogen values significantly increased from baseline, whereas percentage lysis 30 minutes after attainment of the MA as well as antithrombin activity significantly decreased within each group. In the dogs that received prednisone plus a placebo, percentage lysis 60 minutes after attainment of the MA was significantly lower than at baseline. For all parameters for research dogs, there was no difference between groups for change from baseline. Intraindividual variation in findings for client-owned dogs was similar to the variation for research dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Prednisone administration resulted in hypercoagulability in healthy dogs as indicated by an increase in MA and plasma fibrinogen concentration and a decrease in antithrombin activity. Concurrent ultralow-dose acetylsalicylic acid use had no effect on measured thromboelastography values. The high intraindividual variation in some thromboelastography parameters may preclude routine use of this technique in clinical practice.

Thromboembolic complications in Fontan patients: population-based prevalence and exploration of the etiology

After the Fontan procedure, patients face an increased risk for thromboembolic events (TE). The etiology for this increased thrombogenecity is incompletely understood. This study aimed to determine the prevalence of TE in Danish Fontan patients and to bring new insights into the etiology of TE. Using a population-based design, we retrospectively identified all TEs in 210 Fontan patients. Whole blood assays (thromboelastography, thromboelastography functional fibrinogen and Multiplate) reflecting global hemostasis, clot strength and platelet aggregation were analyzed prospectively in 112 patients and plasma was analyzed in 76 patients for biomarkers reflecting endothelial-, glycocalyx-, platelet-, and fibrinolysis function (histone-complexed DNA fragments, Protein C, soluble CD40 ligand, soluble thrombomodulin, syndecan-1, tissue-type plasminogen activator). The results were compared in groups stratified according to age, antithrombotic therapy, TE, and glycocalyx degradation (syndecan-1 < or ≥ median). Correlation between biomarkers and demographic-, anatomical-, clinical- and biochemical parameters was investigated. The prevalence of TE was 8.1 % after a mean follow-up of 8.4 years. None of the stratified groups demonstrated evidence of hypercoagulability in the whole blood assays and no unexpected significant differences were found between the groups. All biomarkers, except protein C, correlated with one another and after stratification of glycocalyx degradation only syndecan-1 levels ≥ median correlated with other biomarkers. The prevalence of TEs was 8.1 % after mean follow-up of 8.4 years. Overall, the hemostatic profile appeared normal, however, in a subset of patients, evidence of some endothelial activation/damage including glycocalyx degradation and fibrinolysis was found, identifying a potentially more thrombogenic group.

Consecutive thrombelastography clot strength profiles in patients with severe sepsis and their association with 28-day mortality: a prospective study

PURPOSE

The aim of this study was to assess associations between consecutive thrombelastography (TEG) profiles and standard coagulation tests and disease severity and mortality in patients with severe sepsis.

MATERIALS AND METHODS

This was a prospective observational study of adults with severe sepsis admitted to the intensive care unit (ICU). Clinical scores/variables, infection, TEG, biochemistry, therapy, and overall mortality were recorded.

RESULTS

Fifty patients (60% men, median age 62 years, 28-day mortality 24%) were included. At admission, 22%, 48%, and 30% had a hypocoagulable, normocoagulable, and hypercoagulable TEG clot strength (maximum amplitude [MA]), respectively. Hypocoagulable patients had higher Sequential Organ Failure Assessment and disseminated intravascular coagulation scores compared with hypercoagulable patients and higher 28-day mortality compared with normocoagulable patients (all P < .05). Most patients (73%-91%) displayed a TEG MA comparable with the admission profile during the initial 4 ICU days or until death/discharge. Patients progressing to hypocoagulable MA had a high early mortality (80%) and hypocoagulable MA independently predicted 28-day mortality (adjusted odds ratio, 4.29 [95% confidence interval, 1.35-13.65], P = .014). In hypocoagulable and hypercoagulable patients, only fibrinogen (P = .041 and P < .001, respectively) contributed independently to clot strength, whereas both platelets (P < .001) and fibrinogen (P < .001) contributed independently to clot strength in normocoagulable patients.

CONCLUSIONS

The ICU admission TEG MA remained constant for several days in patients with severe sepsis and hypocoagulable MA independently predicted 28-day mortality.