Detection of elevated INR by thromboelastometry and thromboelastography in warfarin treated patients and healthy controls

Multichannel resonant acoustic rheometry system for quantification of coagulation of multiple human plasma samples

Resonant Acoustic Rheometry (RAR), a newly developed ultrasound-based technique for non-contact characterization of soft viscoelastic materials, has shown promise for quantitative viscoelastic assessment of temporally changing soft biomaterials in real time, and may be used to monitor blood coagulation process. Here, we report the development of a novel, multichannel RAR (mRAR) system for simultaneous measurements of multiple temporally evolving samples and demonstration of its use for monitoring the coagulation of multiple small-volume plasma samples. The mRAR system was constructed using an array of 4 custom-designed ultrasound transducers at 5.0 MHz and a novel electronic driving system that controlled the generation of synchronized ultrasound pulses for real time assessment of multiple samples simultaneously. As a proof-of-concept of the operation of the mRAR system, we performed tests using pooled normal human plasma samples and anti-coagulated plasma samples from patients treated with warfarin with a range of International Normalized Ratio (INR) values as well-characterized samples with different coagulation kinetics. Our results show that simultaneous tracking of dynamic changes in 4 plasma samples triggered by either kaolin or tissue factor was achieved for the entire duration of coagulation. The mRAR system captured distinct changes in the samples and identified parameters including the clotting start time and parameters associated with the stiffness of the final clots that were consistent with INR levels. Data from this study demonstrate the feasibility of the mRAR system for efficient characterization of the kinetic coagulation processes of multiple plasma samples.

The coagulopathy underlying rotational thromboelastometry derangements in trauma patients: a prospective observational multicenter study

BACKGROUND

Viscoelastic hemostatic assays such as rotational thromboelastometry (ROTEM®) are used to guide treatment of trauma induced coagulopathy. We hypothesized that ROTEM derangements reflect specific coagulation factor deficiencies after trauma.

METHODS

Secondary analysis of a prospective cohort study in six European trauma centers in patients presenting with full trauma team activation. Patients with dilutional coagulopathy and patients on anticoagulants were excluded. Blood was drawn on arrival for measurement of ROTEM®, coagulation factor levels and markers of fibrinolysis. ROTEM® cut-off values to define hypocoagulability were: EXTEM clotting time (CT) >80s, EXTEM clot amplitude after 5 minutes (CA5) <40mm, EXTEM lysis at 30 minutes (Li30) <85%, FIBTEM clot amplitude after 5 minutes (CA5) <10mm and FIBTEM lysis at 30 minutes (Li30) <85%. Based on these, patients were divided into 7 deranged ROTEM® profiles and compared to the reference group (ROTEM® values within reference range). The primary endpoint was coagulation factors levels and fibrinolysis.

RESULTS

Of 1828 patients, 40% had ROTEM® derangements 40.0%, most often consisting of a combined decrease in EXTEM and FIBTEM CA5, that was present in 217 (11.9%) patients. While an isolated EXTEM CT>80s had no impact on mortality, all other ROTEM® derangements were associated with increased mortality. Also, coagulation factor levels in this group were similar to patients with a normal ROTEM®. Of coagulation factors, decrease was most apparent for fibrinogen (with a nadir of 0.78 g/L) and for factor V levels (with a nadir of 22.8%). In addition, increased fibrinolysis can be present when LI30 is normal but EXTEM and FIBTEM CA5 is decreased.

CONCLUSION

Coagulation factor levels and mortality in the group with an isolated clotting time prolongation is similar to patients with a normal ROTEM ®. Other ROTEM ® derangements are associated with mortality and reflect a depletion of fibrinogen and factor V. Increased fibrinolysis can be present when lysis after 30 minutes is normal.

"In Less than No Time": Feasibility of Rotational Thromboelastometry to Detect Anticoagulant Drugs Activity and to Guide Reversal Therapy

Anticoagulant drugs (i.e., unfractionated heparin, low-molecular-weight heparins, vitamin K antagonists, and direct oral anticoagulants) are widely employed in preventing and treating venous thromboembolism (VTE), in preventing arterial thromboembolism in nonvalvular atrial fibrillation (NVAF), and in treating acute coronary diseases early. In certain situations, such as bleeding, urgent invasive procedures, and surgical settings, the evaluation of anticoagulant levels and the monitoring of reversal therapy appear essential. Standard coagulation tests (i.e., activated partial thromboplastin time (aPTT) and prothrombin time (PT)) can be normal, and the turnaround time can be long. While the role of viscoelastic hemostatic assays (VHAs), such as rotational thromboelastometry (ROTEM), has successfully increased over the years in the management of bleeding and thrombotic complications, its usefulness in detecting anticoagulants and their reversal still appears unclear.

Thromboelastography: a review for radiologists and implications on periprocedural bleeding risk

Thromboelastography (TEG) and rotational thromboelastometry are emerging technologies that are gaining increasing acceptance in the medical field to evaluate the coagulation status of patients on an individual level by assessing dynamic clot formation. TEG has been proven to reduce blood product use as well as improve patient outcomes in a variety of medical settings, including trauma and surgery due to the expediated nature of the test as well as the ability to determine specific deficiencies present in whole blood that are otherwise undetectable with traditional coagulation studies. Currently, no guidelines or recommendations are in place for the utilization of TEG in interventional or diagnostic radiology although access to TEG has become increasingly common in recent years. This manuscript presents a review of prior literature on the technical aspects of TEG as well as its use in various fields and explains the normal TEG-tracing parameters. Common hemodynamic abnormalities and their effect on the TEG tracing are illustrated, and the appropriate treatments for each abnormality are briefly mentioned. TEG has the potential to be a useful tool for determining the hemodynamic state of patients in both interventional and diagnostic radiology, and further research is needed to determine the value of these tests in the periprocedural setting.

Anticoagulation Monitoring for Perioperative Physicians

From preoperative medications to intraoperative needs to postoperative thromboprophylaxis, anticoagulants are encountered throughout the perioperative period. This review focuses on coagulation testing clinicians utilize to monitor the effects of these medications.

Rotational thromboelastometry and conventional coagulation tests in patients undergoing major cardiac or aortic surgery: a retrospective single-center cohort study

Algorithms for treatment of diffuse bleeding in cardiac surgery are based on intervention thresholds of coagulation tests, such as rotational thromboelastometry (ROTEM) or conventional laboratory tests. The relationship between these two approaches is unclear in patients with increased risk of coagulation abnormalities. We retrospectively analyzed the data of 248 patients undergoing major cardiac and/or aortic surgery. ROTEM and conventional laboratory tests were performed simultaneously after termination of cardiopulmonary bypass and protamine administration to investigate the extrinsic and intrinsic system, and to determine deficiencies in platelets and fibrinogen. We evaluated the association between ROTEM and conventional tests by linear regression analysis and compared the frequency of exceeding established thresholds for clinical intervention. Significant linear associations between ROTEM 10 min after the start of coagulation, and plasma fibrinogen concentration or platelet count (FIBTEM A10, R² = 0.67, p < 0.001; EXTEM A10, R² = 0.47, p < 0.001) were obtained. However, the 95% prediction intervals exceeded clinically useful ranges (92–233 mg/dL fibrinogen at the intervention threshold of FIBTEM A10 = 10 mm; 14 × 10³–122 × 10³/µL platelets at the intervention threshold of EXTEM A10 = 40 mm). The association between EXTEM and INR (R² = 0.23), and INTEM and aPTT (R² = 0.095) was poor. The frequency of exceeding intervention thresholds and, consequently, of triggering treatment, varied markedly between ROTEM and conventional tests (p < 0.001 for all comparisons). The predictability of conventional coagulation test results by ROTEM is limited, thus hampering the interchangeability of methods in clinical practice.

Viscoelastometry for detecting oral anticoagulants

Background

Determination of anticoagulant therapy is of pronounced interest in emergency situations. However, routine tests do not provide sufficient insight. This study was performed to investigate the impact of anticoagulants on the results of viscoelastometric assays using the ClotPro device.

Methods

This prospective, observational study was conducted in patients receiving dabigatran, factor Xa (FXa)-inhibitors, phenprocoumon, low molecular weight heparin (LMWH) or unfractionated heparin (UFH) (local ethics committee approval number: 17–525-4). Healthy volunteers served as controls. Viscoelastometric assays were performed, including the extrinsic test (EX-test), intrinsic test (IN-test) Russel’s viper venom test (RVV-test), ecarin test (ECA-test), and the tissue plasminogen activator test (TPA-test).

Results

70 patients and 10 healthy volunteers were recruited. Clotting time in the EX-test (CT_EX-test) was significantly prolonged versus controls by dabigatran, FXa inhibitors and phenprocoumon. CT_IN-test was prolonged by dabigatran, FXa inhibitors and UFH. Dabigatran, FXa inhibitors and UFH significantly prolonged CT_RVV-test in comparison with controls (median 200, 207 and 289 vs 63 s, respectively; all p < 0.0005). Only dabigatran elicited a significant increase in CT_ECA-test compared to controls (median 307 vs 73 s; p < 0.0001). CT_ECA-test correlated strongly with dabigatran plasma concentration (measured by anti-IIa activity; r = 0.9970; p < 0.0001) and provided 100% sensitivity and 100% specificity for detecting dabigatran. Plasma concentrations (anti-XA activity) of FXa inhibitors correlated with CT_RVV-test (r = 0.7998; p < 0.0001), and CT_RVV-test provided 83% sensitivity and 64% specificity for detecting FXa inhibitors.

Conclusions

In emergency situations, ClotPro viscoelastometric assessment of whole-blood samples may help towards determining the presence and type of anticoagulant class that a patient is taking.

Trial registration

German clinical trials database ID: DRKS00015302.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-021-00267-w.

Impact of Dabigatran Treatment on Rotation Thromboelastometry

A rapid and reliable assessment of the dabigatran effect is desirable in dabigatran treated patients with uncontrolled bleeding or before acute surgery. The aim of this study was to study the anticoagulant effects of dabigatran in patients with atrial fibrillation (AF) as assessed by the whole blood assays ROTEM, and how data from these methods correlate to plasma dabigatran concentrations measured by Hemoclot. ROTEM was performed with ROTEM Gamma (Pentapharm GmbH, Munich, Germany). The assays used in our study were Ex-tem and In-tem assay. Plasma dabigatran concentrations were determined by hemoclot thrombin inhibitor assay (Hyphen BioMed, France) at trough and post-dose in 27 patients on dabigatran 150 mg BID. Median plasma dabigatran concentrations at trough were 74 ng/mL (11.2–250) and post-dose (2 h after ingestion) 120 ng/mL (31–282). The ROTEM clotting time (CT) and maximum clot firmnes (MCF) correlated strongly with dabigatran concentrations when activated with the reagents Ex-tem (p < 0.0001) and In-tem (p < 0.0001). In summary, in our study, we have found that the ROTEM variable CT and MCF, when activated with triggers Ex-tem and In-tem, has a strong and highly significant correlation with the plasma dabigatran concentration in a real-life population of AF-patients and could thereby be an alternative to estimate dabigatran concentration in emergency situations. However, additional studies are needed to further validate these findings.

Coagulation Effect of Sugammadex as Determined by Thromboelastography in a Randomized Controlled Study of Surgical Patients

Introduction: Sugammadex has been shown to be associated with prolongation of prothrombin time and activated partial thromboplastin time. However, it is not known whether it could be associated with enhancing postoperative hypocoagulation. The objective of this study was to analyze the effect of 4 mg/kg of sugammadex on thromboelastography (TEG) parameters in surgical patients. Methods: After Institutional Review Board approval, a prospective double-blinded randomized controlled study was conducted between September 2016 and April 2017. Sixty adult patients scheduled for laparoscopic abdominal surgery were randomly allocated to receive either sugammadex 4 mg/kg (sugammadex group) or pyridostigmine 0.15 mg/kg in combination with glycopyrrolate 0.4 mg (control group) to reverse rocuronium-induced neuromuscular blockade at the completion of surgery. Blood samples were collected three time points; After the final suture of surgery (baseline) (T1), and at 10 min (T2) and 1 h (T3) after administration of the study drug. Whole blood was analyzed by TEG using TEG 5000 (Hemonetics Corp, Braintree, MA, USA). The primary endpoints were comparison of coagulation time (K, time to 20 mm clot amplitude), R (reaction time), alpha angle, and maximal amplitude (MA) between two groups. Results: Coagulation time was significantly prolonged in sugammadex group after 10 min of the study drug administration compared to control group (mean value 1.3 ± 0.4 vs. 1.5 ± 0.4, P = 0.03). However, R, alpha angle and MA value were not different between two groups. Conclusions: Sugammadex 4 mg/kg showed an increase in coagulation time in surgical patients. Physician should aware the potential enhancement of hypocoagulation by sugammadex in the setting of high risk of postoperative bleeding.

Rotational thromboelastometry results are associated with care level in COVID-19

High prevalence of thrombotic events in severely ill COVID-19 patients have been reported. Pulmonary embolism as well as microembolization of vital organs may in these individuals be direct causes of death. The identification of patients at high risk of developing thrombosis may lead to targeted, more effective prophylactic treatment. The primary aim of this study was to test whether rotational thromboelastometry (ROTEM) at admission indicates hypercoagulopathy and predicts the disease severity, assessed as care level, in COVID-19 patients. The study was designed as a prospective, observational study where COVID-19 patients over 18 years admitted to hospital were eligible for inclusion. Patients were divided into two groups depending on care level: (1) regular wards or (2) wards with specialized ventilation support. Conventional coagulation tests, blood type and ROTEM were taken at admission. 60 patients were included; age 61 (median), 67% men, many with comorbidities (e.g. hypertension, diabetes). The ROTEM variables Maximum Clot Firmness (EXTEM-/FIBTEM-MCF) were higher in COVID-19 patients compared with in healthy controls (p < 0.001) and higher in severely ill patients compared with in patients at regular wards (p < 0.05). Our results suggest that hypercoagulopathy is present early in patients with mild to moderate disease, and more pronounced in severe COVID-19 pneumonia. Non-O blood types were not overrepresented in COVID-19 positive patients. ROTEM variables showed hypercoagulopathy at admission and this pattern was more pronounced in patients with increased disease severity. If this feature is to be used to predict the risk of thromboembolic complications further studies are warranted.

Thromboelastometry-guided anticoagulation reversal in a patient with ventricular assist device with intracranial hemorrhage

Intracranial hemorrhage (ICH) is a known complication in patients with ventricular assist devices (VAD). We present a case of a 42-year-old male with a VAD and on warfarin who presented to the emergency department with ICH necessitating anticoagulant reversal. An attenuated dose of 15 units/kg of 4-factor prothrombin complex-concentrates (4F-PCC) was given and the patient's coagulation profile was subsequently assessed using rotational thromboelastometry (ROTEM®) to determine appropriateness of reversal. ROTEM® analysis showed adequate reversal at the time of assessment and the patient ultimately returned home without further functional deficits, highlighting the role of ROTEM® to guide anticoagulation reversal in the VAD patient population.

A European consensus statement on the use of four-factor prothrombin complex concentrate for cardiac and non-cardiac surgical patients

Modern four-factor prothrombin complex concentrate was designed originally for rapid targeted replacement of the coagulation factors II, VII, IX and X. Dosing strategies for the approved indication of vitamin K antagonist-related bleeding vary greatly. They include INR and bodyweight-related protocols as well as fixed dose regimens. Particularly in the massively bleeding trauma and cardiac surgery patient, four-factor prothrombin complex concentrate is used increasingly for haemostatic resuscitation. Members of the Transfusion and Haemostasis Subcommittee of the European Association of Cardiothoracic Anaesthesiology performed a systematic literature review on four-factor prothrombin complex concentrate. The available evidence has been summarised for dosing, efficacy, drug safety and monitoring strategies in different scenarios. Whereas there is evidence for the efficacy of four-factor prothrombin concentrate for a variety of bleeding scenarios, convincing safety data are clearly missing. In the massively bleeding patient with coagulopathy, our group recommends the administration of an initial bolus of 25 IU.kg^-1 . This applies for: the acute reversal of vitamin K antagonist therapy; haemostatic resuscitation, particularly in trauma; and the reversal of direct oral anticoagulants when no specific antidote is available. In patients with a high risk for thromboembolic complications, e.g. cardiac surgery, the administration of an initial half-dose bolus (12.5 IU.kg^-1 ) should be considered. A second bolus may be indicated if coagulopathy and microvascular bleeding persists and other reasons for bleeding are largely ruled out. Tissue-factor-activated, factor VII-dependent and heparin insensitive point-of-care tests may be used for peri-operative monitoring and guiding of prothrombin complex concentrate therapy.

Tracing the Lines: A Review of Viscoelastography for Emergency Medicine Clinicians

BACKGROUND

Viscoelastography (VE) is an established method to identify coagulopathies in various disease processes. Clinical decisions can be made with real-time tracings and quantitative values at the bedside. Thromboelastography (TEG®) and rotational thromboelastometry (ROTEM®) have been utilized in several disease states with clinical varying success.

OBJECTIVES

This review will summarize the literature and provide recommendations pertaining to major disease processes where VE may be beneficial, including trauma, anticoagulation reversal, liver disease, acute ischemic stroke, and acquired brain injuries.

DISCUSSION

VE has a role in many emergency medicine patients encountered by clinicians. Reduced mortality, decreased blood product utilization, and prognostication ability makes VE an intriguing tool that can be utilized by providers to improve patient care.

CONCLUSION

This review serves as a way for emergency medicine clinicians to utilize VE in their practice and provides an insightful literature overview.

Thromboelastography Reaction-Time Thresholds for Optimal Prediction of Coagulation Factor Deficiency in Trauma

BACKGROUND

Coagulopathy is common in multitrauma patients and repletion of procoagulant factor deficiency with fresh frozen plasma (FFP) improves hemostasis. Optimal kaolin-thromboelastography thresholds for FFP transfusion in trauma patients have not been well established.

STUDY DESIGN

Adult trauma patients with an Injury Severity Score ≥15 were included in this retrospective observational cohort study. The primary end point was area under the receiver operating characteristic curve (AUROC) for reaction time (R-time) to detect procoagulant factor deficiency, as reflected by an elevated international normalized ratio (INR) or aPTT. Test characteristics for the optimal R-time threshold calculated in our study were compared against thresholds recommended by the American College of Surgeons for FFP transfusion.

RESULTS

Six hundred and ninety-four pairs of thromboelastography and conventional coagulation tests were performed in 550 patients, with 144 patients having additional pairs of tests after the first hour. The R-time was able to detect procoagulant factor deficiency (INR ≥1.5 AUROC 0.80; 95% CI, 0.75 to 0.85; aPTT ≥40 seconds AUROC 0.85; 95% 0.80 to 0.89) and severe procoagulant factor deficiency (INR ≥2.0 AUROC 0.82; 95% CI, 0.73 to 0.99; aPTT ≥60 seconds AUROC 0.89; 95% CI, 0.81 to 0.98) with good accuracy. Optimal thresholds to maximize sensitivity and specificity were 3.9 minutes for detection of INR ≥1.5, 4.1 minutes for detection of aPTT ≥40 seconds, 4.3 minutes for detection of INR ≥2.0, and 4.3 for detection of aPTT ≥60 seconds. Currently recommended R-time thresholds for FFP transfusion had 100% specificity for detecting procoagulant factor deficiency, but low sensitivity (3% to 7%).

CONCLUSIONS

R-time can detect procoagulant factor deficiency in multitrauma patients with good accuracy, but currently recommended R-time thresholds are highly specific and not sensitive. Use of low-sensitivity thresholds might result in undertreatment of many patients with procoagulant factor deficiency.

A prospective study on the correlation between thromboelastometry and standard laboratory tests - influence of type of surgery and perioperative sampling times

This prospective study aimed at investigating the influence of surgery type and perioperative sampling times on the correlations between rotational thromboelastometry (ROTEM) parameters and standard laboratory coagulation tests assessing comparable coagulation phases. Patients undergoing glioblastoma multiforme resection (GBR group, n = 60) or laparoscopic colon cancer resection (CCR group, n = 40) were prospectively included. Blood samples for ROTEM and laboratory assessments were consecutively drawn within 24-hours prior to surgery (baseline), and at 2, 24 and 48-hours after surgery. Correlations between perioperative ExTEM clotting-time (CT-exTEM) and prothrombin time (PT), and between FibTEM maximum clot firmness (MCF-fibTEM) with and plasma fibrinogen (pFB) concentration (Clauss method), were evaluated using the Spearman's rho test. The efficiency of recommended cut-offs of CT-exTEM (>75 s) and MCF-fibTEM (<10 mm) for predicting a prolonged PT (>15 s) or a low pFB (<2 g/L), respectively, was assessed using Receiver-Operator Characteristic curves. Correlations between CT-exTEM and PT were weak in GBR (rho = 0.25 [0.12-0.38], p < .01), and very weak in CCR (rho = 0.06 [-0.12-0.27]). Those between MCF-fibTEM and pFB, were strong in both GBR (rho = 0.69 [0.61-0.76], p < .01) and CCR (rho = 0.70 [0.60-0.78], p < .01). These correlations remained largely unchanged over the studied perioperative period in both groups. Recommended CT-exTEM and MCF-fibTEM cut-offs had poor sensitivity for predicting a prolonged PT (17% [8-31]) or a low pFB (46% [32-62]), without group-related differences. Neither the type of surgery nor the perioperative sampling times had a significant influence on the correlations between ROTEM parameters and standard laboratory tests. ClinicalTrials.gov ID: NCT02652897.

The role of evidence-based algorithms for rotational thromboelastometry-guided bleeding management

Rotational thromboelastometry (ROTEM) is a point-of-care viscoelastic method and enables to assess viscoelastic profiles of whole blood in various clinical settings. ROTEM-guided bleeding management has become an essential part of patient blood management (PBM) which is an important concept in improving patient safety. Here, ROTEM testing and hemostatic interventions should be linked by evidence-based, setting-specific algorithms adapted to the specific patient population of the hospitals and the local availability of hemostatic interventions. Accordingly, ROTEM-guided algorithms implement the concept of personalized or precision medicine in perioperative bleeding management (‘theranostic’ approach). ROTEM-guided PBM has been shown to be effective in reducing bleeding, transfusion requirements, complication rates, and health care costs. Accordingly, several randomized-controlled trials, meta-analyses, and health technology assessments provided evidence that using ROTEM-guided algorithms in bleeding patients resulted in improved patient’s safety and outcomes including perioperative morbidity and mortality. However, the implementation of ROTEM in the PBM concept requires adequate technical and interpretation training, education and logistics, as well as interdisciplinary communication and collaboration.

Advances in monitoring anticoagulant therapy

Anticoagulant drugs directly or indirectly influence coagulation factors preventing fibrin formation, thus preventing blood clotting. They are classified into two groups according to the mode of application, namely parenteral and oral drugs. Among the latter, vitamin K antagonists (most often warfarin) were most widely used for almost a century. In recent years new oral anticoagulant drugs have become available that directly target either factor IIa or Xa (direct oral anticoagulants, DOACs). The proportion of patients to whom DOACs are prescribed is increasing because clinical studies have proved they are at least as effective and safe as vitamin K antagonists. Some of the anticoagulant drugs require regular laboratory monitoring, while others only need assessment of blood drug levels in specific clinical situations. This chapter provides an overview of appropriate laboratory tests used for either regular laboratory monitoring of therapy or occasional assessment of the anticoagulant effect of both parenteral and oral anticoagulant drugs used in clinical practice.

Monitoring of coagulation by intraoperative thromboelastometry of liver transplantation in a patient using warfarin – case report

Introduction

Case report

Discussion

[Monitoring of coagulation by intraoperative thromboelastometry of liver transplantation in a patient using warfarin - case report]

INTRODUCTION

Advanced hepatic disease may - in addition to the widely recognized hemorrhagic complications - occur with thrombotic events. We describe the case of a cirrhotic patient taking warfarin and whose coagulation management during liver transplantation was guided by thromboelastometry (ROTEM^®).

CASE REPORT

A 56 year-old male patient diagnosed with alcohol cirrhosis using warfarin (2.5mg.day^-1) for partial portal vein thrombosis with the International Normalized Ratio (INR) of 2.14. At the beginning of surgery, the ROTEM^® parameters were all normal. In the anhepatic phase, EXTEM and INTEM remained normal, but FIBTEM showed reduction of amplitude after 10min and maximum clot firmness. Finally, in the neohepatic phase, there was a slight alteration in the hypocoagulability of most of the parameters of the EXTEM, INTEM and FIBTEM, besides a notable correction of the Coagulation Time (CT) in HEPTEM compared to the CT of the INTEM. Therefore, the patient did not receive any transfusion of blood products during surgery and in the postoperative period, being discharged on the 8th postoperative day.

DISCUSSION

Coagulation deficit resulting from cirrhosis distorts INR as a parameter of anticoagulation adequacy and as a determinant of the need for blood transfusion. Thus, thromboelastometry can provide important information for patient management.

Thromboelastography as a Predictor of Outcomes Following Liver Transplantation

BACKGROUND

Thromboelastography (TEG) has been used perioperatively during liver transplantation (LT) to provide a real-time global hemostasis assessment for targeted blood product replacement. We aimed to analyze the relationship between post-LT TEG results and outcomes.

METHODS

We retrospectively analyzed patients undergoing LT from November 2008 to December 2014 at Mayo Clinic Florida. All 441 single-organ 1st-time LT patients aged ≥18 years requiring post-LT intensive care unit management were included. TEG parameters including r time, k time, α angle, and maximum amplitude were measured regularly during the first 24 hours after LT. Outcomes included return to the operating room secondary to bleeding, length of hospitalization, survival, and early allograft dysfunction.

RESULTS

A prolonged and/or lengthening r time, k time, and r+k time were all independently associated with increased length of hospitalization after LT. Increased maximum amplitude on the first post-LT TEG was associated with early allograft dysfunction. No notable associations of TEG parameters with survival or return to operating room were observed.

CONCLUSIONS

The association of absolute and temporal TEG value changes with increased length of hospitalization and early allograft dysfunction suggests that TEG may have a role in identifying patients at high risk for these outcomes.

Warfarin monitoring with viscoelastic haemostatic assays, thrombin generation, coagulation factors and correlations to Owren and Quick prothrombin time

The anticoagulant warfarin is commonly monitored with prothrombin time (PT). Viscoelastic haemostatic assays (VHA) are primarily used in situations of acute bleeding to guide haemostatic therapy. Much research has focused on VHA monitoring of new oral anticoagulants. However, many patients are still anticoagulated with warfarin and effect of warfarin anticoagulation on VHA is uncertain. The aim of this study was to assess warfarin anticoagulation on three different VHA and compare these findings with prothrombin time (PT), coagulation factor analyses and a thrombin generation assay (TGA). Citrated whole blood was drawn from 80 patients admitted for routine PT-INR Owren. VHA analysis with ROTEM (EXTEM, INTEM and FIBTEM), ReoRox (Fibscreen 1 and 2) and Sonoclot (gbACT+) was performed. Blood was also drawn for plasma analysis with PT (PT-INR Owren and PT Quick), TGA and analysis of factors I, II, VII, IX and X. Extrinsically activated VHA, including ROTEM EXTEM and FIBTEM Clotting Time (CT) and ReoRox Fibscreen1 and 2 clot onset time 1 correlated moderately with PT-INR Owren , with R 0.66-0.71. These four variables were likely to be prolonged above reference interval in patients with prolonged PT-INR Owren >1.2. Two patients with normal ROTEM CTs had Owren PT-INRs >1.5. Warfarin affects extrinsically activated VHA variables of initial clotting. The role of VHA for clinical decision-making in patients planned for invasive procedures, such as spinal/epidural anaesthesia needs further study. None of the recent guidelines on regional anaesthesia include VHA testing to define adequate haemostasis.

In vitro investigation of the effects of exogenous sugammadex on coagulation in orthopedic surgical patients

Background

Previous studies have shown that sugammadex resulted in the prolongation of prothrombin time and activated partial thromboplastin time. In this study, we aimed to investigate the in vitro effects of exogenous sugammadex on the coagulation variables of whole blood in healthy patients who underwent orthopedic surgery.

Methods

The effects of sugammadex on coagulations were assessed using thromboelastography (TEG) in kaolin-activated citrated blood samples taken from 14 healthy patients who underwent orthopedic surgery. The in vitro effects of three different concentrations of sugammadex (42, 193, and 301 μg mL^− 1) on the TEG profiles were compared with those of the control (0 μg mL^− 1). Previous studies indicated that these exogenous concentrations correspond to the approximate maximum plasma concentrations achieved after the administration of 4, 16, and 32 mg kg^− 1 sugammadex to healthy subjects.

Results

Increased sugammadex concentrations were significantly associated with reduced coagulation, as evidenced by increases in reaction time (r), coagulation time, and time to maximum rate of thrombus generation (TMRTG), and decreases in the angle, maximum amplitude, and maximum rate of thrombus generation. Compared with the control, the median percentage change (interquartile range) in the TEG values of the samples treated with the highest exogenous sugammadex concentration was the greatest for r, 53% (26, 67.3%), and TMRTG, 48% (26, 59%).

Conclusions

This in vitro study suggests that supratherapeutic doses of exogenous sugammadex might be associated with moderate hypocoagulation in the whole blood of healthy subjects.

Trial registration

identifier: UMIN000029081, registered 11 September 2017.

Position of the French Working Group on Perioperative Haemostasis (GIHP) on viscoelastic tests: What role for which indication in bleeding situations?

PURPOSE

Viscoelastic tests (VETs), thromboelastography (TEG^®) and thromboelastometry (ROTEM^®) are global tests of coagulation performed on whole blood. They evaluate the mechanical strength of a clot as it builds and develops after coagulation itself. The time required to obtain haemostasis results remains a major problem for clinicians dealing with bleeding, although some teams have developed a rapid laboratory response strategy. Indeed, the value of rapid point-of-care diagnostic devices such as VETs has increased over the years. However, VETs are not standardised and there are few recommendations from the learned societies regarding their use. In 2014, the recommendations of the International Society of Thrombosis and Haemostasis (ISTH) only concerned haemophilia. The French Working Group on Perioperative haemostasis (GIHP) therefore proposes to summarise knowledge on the clinical use of these techniques in the setting of emergency and perioperative medicine.

METHODS

A review of the literature.

PRINCIPAL FINDINGS

The role of the VETs seems established in the management of severe trauma and in cardiac surgery, both adult and paediatric. In other situations, their role remains to be defined: hepatic transplantation, postpartum haemorrhage, and non-cardiac surgery. They must be part of the global management of haemostasis based on algorithms defined in each centre and for each population of patients. Their position at the bedside or in the laboratory is a matter of discussion between clinicians and biologists.

CONCLUSION

VETs must be included in algorithms. In consultation with the biology laboratory, these devices should be situated according to the way each centre functions.

Optical sensing of anticoagulation status: Towards point-of-care coagulation testing

Anticoagulant overdose is associated with major bleeding complications. Rapid coagulation sensing may ensure safe and accurate anticoagulant dosing and reduce bleeding risk. Here, we report the novel use of Laser Speckle Rheology (LSR) for measuring anticoagulation and haemodilution status in whole blood. In the LSR approach, blood from 12 patients and 4 swine was placed in disposable cartridges and time-varying intensity fluctuations of laser speckle patterns were measured to quantify the viscoelastic modulus during clotting. Coagulation parameters, mainly clotting time, clot progression rate (α-angle) and maximum clot stiffness (MA) were derived from the clot viscoelasticity trace and compared with standard Thromboelastography (TEG). To demonstrate the capability for anticoagulation sensing in patients, blood samples from 12 patients treated with warfarin anticoagulant were analyzed. LSR clotting time correlated with prothrombin and activated partial thromboplastin time (r = 0.57-0.77, p<0.04) and all LSR parameters demonstrated good correlation with TEG (r = 0.61-0.87, p<0.04). To further evaluate the dose-dependent sensitivity of LSR parameters, swine blood was spiked with varying concentrations of heparin, argatroban and rivaroxaban or serially diluted with saline. We observed that anticoagulant treatments prolonged LSR clotting time in a dose-dependent manner that correlated closely with TEG (r = 0.99, p<0.01). LSR angle was unaltered by anticoagulation whereas TEG angle presented dose-dependent diminution likely linked to the mechanical manipulation of the clot. In both LSR and TEG, MA was largely unaffected by anticoagulation, and LSR presented a higher sensitivity to increased haemodilution in comparison to TEG (p<0.01). Our results establish that LSR rapidly and accurately measures the response of various anticoagulants, opening the opportunity for routine anticoagulation monitoring at the point-of-care or for patient self-testing.

Targeted Coagulation Management in Severe Trauma: The Controversies and the Evidence

Hemorrhage in the setting of severe trauma is a leading cause of death worldwide. The pathophysiology of hemorrhage and coagulopathy in severe trauma is complex and remains poorly understood. Most clinicians currently treating trauma patients acknowledge the presence of a coagulopathy unique to trauma patients-trauma-induced coagulopathy (TIC)-independently associated with increased mortality. The complexity and incomplete understanding of TIC has resulted in significant controversy regarding optimum management. Although the majority of trauma centers utilize fixed-ratio massive transfusion protocols in severe traumatic hemorrhage, a widely accepted "ideal" transfusion ratio of blood to blood products remains elusive. The recent use of viscoelastic hemostatic assays (VHAs) to guide blood product replacement has further provoked debate as to the optimum transfusion strategy. The use of VHA to quantify the functional contributions of individual components of the coagulation system may permit targeted treatment of TIC but remains controversial and is unlikely to demonstrate a mortality benefit in light of the heterogeneity of the trauma population. Thus, VHA-guided algorithms as an alternative to fixed product ratios in trauma are not universally accepted, and a hybrid strategy starting with fixed-ratio transfusion and incorporating VHA data as they become available is favored by some institutions. We review the current evidence for the management of coagulopathy in trauma, the rationale behind the use of targeted and fixed-ratio approaches and explore future directions.

Relative effects of plasma, fibrinogen concentrate, and factor XIII on ROTEM coagulation profiles in an in vitro model of massive transfusion in trauma

Massive traumatic haemorrhage is aggravated through the development of trauma-induced coagulopathy, which is managed by plasma transfusion and/or fibrinogen concentrate administration. It is yet unclear whether these treatments are equally potent in ensuring adequate haemostasis, and whether additional factor XIII (FXIII) administration provides further benefits. In this study, we compared ROTEM whole blood coagulation profiles after experimental massive transfusion with different transfusion regimens in an in vitro model of dilution- and transfusion-related coagulopathy. Healthy donor blood was mixed 1 + 1 with six different transfusion regimens. Each regimen contained RBC, platelet concentrate, and either fresh frozen plasma (FFP) or Ringer's acetate (RA). The regimens were further augmented through addition of a low- or medium-dose fibrinogen concentrate and FXIII. Transfusion with FFP alone was insufficient to maintain tissue-factor activated clot strength, coincidental with a deficiency in fibrin-based clot strength. Fibrinogen concentrate conserved, but did not improve coagulation kinetics and overall clot strength. Only combination therapy with FFP and low-dose fibrinogen concentrate improved both coagulation kinetics and fibrin-based clot strength. Administration of FXIII did not result in an improvement of clot strength. In conclusion, combination therapy with both FFP and low-dose fibrinogen concentrate improved clotting time and produced firm clots, representing a possible preferred first-line regimen to manage trauma-induced coagulopathy when RBC and platelets are also transfused. Further research is required to identify optimal first-line transfusion fluids for massive traumatic haemorrhage.

Thromboelastometry: Relation to the severity of liver cirrhosis in patients considered for liver transplantation

The severity of liver disease is assessed by scoring systems, which include the conventional coagulation test prothrombin time-the international normalized ratio (PT-INR). However, PT-INR is not predictive of bleeding in liver disease and thromboelastometry (ROTEM) has been suggested to give a better overview of the coagulation system in these patients. It has now been suggested that coagulation as reflected by tromboelastomety may also be used for prognostic purposes. The objective of our study was to investigate whether thrombelastometry may discriminate the degree of liver insufficiency according to the scoring systems Child Pugh and Model for End-stage Liver Disease (MELD).Forty patients with chronic liver disease of different etiologies and stages were included in this observational cross-sectional study. The severity of liver disease was evaluated using the Child-Pugh score and the MELD score, and blood samples for biochemistry, conventional coagulation tests, and ROTEM were collected at the time of the final assessment for liver transplantation. Statistical comparisons for the studied parameters with scores of severity were made using Spearman correlation test and receiver-operating characteristic (ROC) curves.Spearman correlation coefficients indicated that the thromboelastometric parameters did not correlate with Child-Pugh or MELD scores. The ROC curves of the thromboelastometric parameters could not differentiate advanced stages from early stages of liver cirrhosis.Standard ROTEM cannot discriminate the stage of chronic liver disease in patients with severe chronic liver disease.

Monitoring of antivitamin K-dependent anticoagulation in rodents - Towards an evolution of the methodology to detect resistance in rodents

Vitamin K antagonists are used as rodenticides for pest control management. In rodents, prothrombin time is used to monitor their effect despite its limits and the emergence of many coagulation methods. The aim of this study is to explore different coagulation monitoring methods in order to propose the best method and the best parameter to monitor vitamin K antagonists effect in rodents. The coagulation function was thus monitored with global coagulation assays and specialty assays after difethialone administration in rats. Despite many parameters obtained by thromboelastometry, only clotting time and clot formation time obtained by ExTEM were modified. Their evolution was fast with doubling time respectively of 4.0h and 3.7h but their increases were delayed with a lag time higher than 8h. Conversely, prothrombin time evolution presented a lag time of only 2h, but a higher doubling time of 7.2h. The measurements of factor VII and X activities were the most sensitive assays to monitor vitamin K antagonists effect with almost no lag time and the fastest evolution. Nevertheless, factor X was shown to be the only key factor driving prothrombin time. Monitoring factor X activity enables to follow most effectively the anticoagulation status in rats after rodenticides administration.

Novel Diagnostic and Monitoring Tools in Stroke: an Individualized Patient-Centered Precision Medicine Approach

Central to the pathogenesis of ischaemic stroke are the normally protective processes of platelet adhesion and activation. Experimental evidence has shown that the ligand-receptor interactions in ischaemic stroke represent a thrombo-inflammatory cascade, which presents research opportunities into new treatment. However, as anti-platelet drugs have the potential to cause severe side effects in ischaemic stroke patients (as well as other vascular disease patients), it is important to carefully monitor the risk of bleeding and risk of thrombus in patients receiving treatment. Because thrombo-embolic ischaemic stroke is a major health issue, we suggest that the answer to adequate treatment is based on an individualized patient-centered approach, inline with the latest NIH precision medicine approach. A combination of viscoelastic methodologies may be used in a personalized patient-centered regime, including thromboelastography (TEG®) and the lesser used scanning electron microscopy approach (SEM). Thromboelastography provides a dynamic measure of clot formation, strength, and lysis, whereas SEM is a visual structural tool to study patient fibrin structure in great detail. Therefore, we consider the evidence for TEG® and SEM as unique means to confirm stroke diagnosis, screen at-risk patients, and monitor treatment efficacy. Here we argue that the current approach to stroke treatment needs to be restructured and new innovative thought patterns need to be applied, as even approved therapies require close patient monitoring to determine efficacy, match treatment regimens to each patient's individual needs, and assess the risk of dangerous adverse effects. TEG® and SEM have the potential to be a useful tool and could potentially alter the clinical approach to managing ischaemic stroke. As envisaged in the NIH precision medicine approach, this will involve a number of role players and innovative new research ideas, with benefits that will ultimately only be realized in a few years. Therefore, with this ultimate goal in mind, we suggest that an individualized patient-orientated approach is now available and therefore already within our ability to use.

Prophylactic plasma and platelet transfusion in the critically Ill patient: just useless and expensive or even harmful?

It is still common practice to correct abnormal standard laboratory test results, such as increased INR or low platelet count, prior to invasive interventions, such as tracheostomy, central venous catheter insertion or liver biopsy, in critically ill patients. Data suggest that 30-90 % of plasma transfused for these indications is unnecessary and puts the patient at risk. Plasma transfusion is associated with a high risk of transfusion-associated adverse events such as transfusion-associated circulatory overload (TACO), transfusion-related lung injury (TRALI), transfusion-related immunomodulation (TRIM), and anaphylaxis/allergic reactions. Therefore, the avoidance of inappropriate plasma transfusion bears a high potential of improving patient outcomes. The prospective study by Durila et al., published recently in BMC Anesthesiology, provides evidence that tracheostomies can be performed without prophylactic plasma transfusion and bleeding complications in critically ill patients despite increased INR in case of normal thromboelastometry (ROTEM) results. Thromboelastometry-based restrictive transfusion management helped avoid unnecessary plasma and platelet transfusion, and should reduce the incidence of transfusion-related adverse events and transfusion-associated hospital costs. Therefore, the authors believe that thromboelastometry-based strategies should be implemented to optimize patient blood management in perioperative medicine.