Correlation of Thromboelastography with Apparent Rivaroxaban Concentration: Has Point-of-Care Testing Improved?

Clinical guideline on reversal of direct oral anticoagulants in patients with life threatening bleeding

BACKGROUND

Anticoagulation is essential for the treatment and prevention of thromboembolic events. Current guidelines recommend direct oral anticoagulants (DOACs) over vitamin K antagonists in DOAC-eligible patients. The major complication of anticoagulation is serious or life-threatening haemorrhage, which may necessitate prompt haemostatic intervention. Reversal of DOACs may also be required for patients in need of urgent invasive procedures. This guideline from the European Society of Anaesthesiology and Intensive Care (ESAIC) aims to provide evidence-based recommendations and suggestions on how to manage patients on DOACs undergoing urgent or emergency procedures including the treatment of DOAC-induced bleeding.

DESIGN

A systematic literature search was performed, examining four drug comparators (dabigatran, rivaroxaban, apixaban, edoxaban) and clinical scenarios ranging from planned to emergency surgery with the outcomes of mortality, haematoma growth and thromboembolic complications. The GRADE (Grading of Recommendations, Assessment, Development and Evaluation) methodology was used to assess the methodological quality of the included studies. Consensus on the wording of the recommendations was achieved by a Delphi process.

RESULTS

So far, no results from prospective randomised trials comparing two active comparators (e.g. a direct reversal agent and an unspecific haemostatic agent such as prothrombin complex concentrate: PCC) have been published yet and the majority of publications were uncontrolled and observational studies. Thus, the certainty of evidence was assessed to be either low or very low (GRADE C). Thirty-five recommendations and clinical practice statements were developed. During the Delphi process, strong consensus (>90% agreement) was achieved in 97.1% of recommendations and consensus (75 to 90% agreement) in 2.9%.

DISCUSSION

DOAC-specific coagulation monitoring may help in patients at risk for elevated DOAC levels, whereas global coagulation tests are not recommended to exclude clinically relevant DOAC levels. In urgent clinical situations, haemostatic treatment using either the direct reversal or nonspecific haemostatic agents should be started without waiting for DOAC level monitoring. DOAC levels above 50 ng ml-1 may be considered clinically relevant necessitating haemostatic treatment before urgent or emergency procedures. Before cardiac surgery under activated factor Xa (FXa) inhibitors, the use of andexanet alfa is not recommended because of inhibition of unfractionated heparin, which is needed for extracorporeal circulation. In the situation of DOAC overdose without bleeding, no haemostatic intervention is suggested, instead measures to eliminate the DOACs should be taken. Due to the lack of published results from comparative prospective, randomised studies, the superiority of reversal treatment strategy vs. a nonspecific haemostatic treatment is unclear for most urgent and emergency procedures and bleeding. Due to the paucity of clinical data, no recommendations for the use of recombinant activated factor VII as a nonspecific haemostatic agent can be given.

CONCLUSION

In the clinical scenarios of DOAC intake before urgent procedures and DOAC-induced bleeding, practitioners should evaluate the risk of bleeding of the procedure and the severity of the DOAC-induced bleeding before initiating treatment. Optimal reversal strategy remains to be determined in future trials for most clinical settings.

Association of fibrinolysis phenotype with patient outcomes following traumatic brain injury

BACKGROUND

Impaired coagulation is associated with elevated risk of mortality in trauma patients. Prior studies have demonstrated increased mortality in patients with hyperfibrinolysis (HF) and fibrinolysis shutdown (SD). In addition, prior studies have demonstrated no effect of tranexamic acid (TXA) on fibrinolysis phenotypes. We examined the association of admission fibrinolysis phenotype with traumatic brain injury (TBI) patient outcomes.

METHODS

Data were extracted from a placebo-controlled multicenter clinical trial. Patients ≥15 years with TBI (Glasgow Coma Scale score, 3-12) and systolic blood pressure ≥90 mm Hg were randomized in the out-of-hospital setting to receive placebo bolus/placebo infusion (Placebo), 1 gram (g) TXA bolus/1 g TXA infusion (bolus maintenance [BM]); or 2 g TXA bolus/placebo infusion (bolus only [BO]). Fibrinolysis phenotypes on admission were determined by clot lysis at 30 minutes (LY30): SD, ≤0.8%; physiologic, 0.9% to 2.9%; HF, ≥3%. Logistic regression was used to control for age, sex, penetrating injury, Injury Severity Score, maximum head AIS, and TXA treatment group.

RESULTS

Seven hundred forty-seven patients met inclusion criteria. Fibrinolysis shutdown was the most common phenotype in all treatment groups and was associated with increased age, Injury Severity Score, and presence of intracranial hemorrhage (ICH). Inpatient mortality was 15.2% for SD and HF, and 10.6% for physiologic ( p = 0.49). No differences in mortality, disability rating scale at 6 months, acute kidney injury, acute respiratory distress syndrome, or multi-organ failure were noted between fibrinolysis phenotypes.

CONCLUSION

SD is the most common phenotype expressed in moderate to severe TBI. In TBI, there is no association between fibrinolysis phenotype and mortality or other major complications.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Comparison of the Correlation Between Coagulation Indices and Rivaroxaban Concentrations

BACKGROUND

Rivaroxaban has predictable pharmacokinetics and pharmacodynamics. However, monitoring rivaroxaban concentrations should be provided for special patients with hepatic insufficiency, high bleeding risk, and high thrombotic risk.

OBJECTIVE

This study aimed to correlate chromogenic anti-Xa assay, prothrombin time (PT), activated partial thromboplastin time (APTT), thromboelastogram reaction time (TEG R-time), and rivaroxaban concentration measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) (MS-Riva).

METHODS

Peripheral venous blood was collected from recruited patients 30 minutes before and 2 to 4 hours after drug administration. High-performance liquid chromatography-tandem mass spectrometry and chromogenic anti-Xa assay measured rivaroxaban concentration. Different assays were compared by Pearson correlation coefficient and Bland-Altman analysis.

RESULTS

A total of 104 patients with 191 plasma were included in the study. Overall analysis shows that chromogenic anti-Xa assay, PT, APTT, and TEG R-time strongly correlated with MS-Riva (r = 0.986; r = 0.884; r = 0.741; r = 0.739; P < 0.001). Rivaroxaban peak concentration detected by HPLC-MS/MS (MS-peak) showed a very strong correlation with the chromogenic anti-Xa assay (r = 0.977, P < 0.001) and moderate correlation with PT, APTT, and TEG R-time (r = 0.670; r = 0.571; r = 0.481, P < 0.001). Rivaroxaban trough concentration detected by HPLC-MS/MS (MS-trough) correlated strongly with the chromogenic anti-Xa assay (r = 0.884, P < 0.001), weakly with APTT (r = 0.313; P = 0.043), and not significantly with PT and TEG R-time (P = 0.140; P = 0.341).

CONCLUSION AND RELEVANCE

High-performance liquid chromatography-tandem mass spectrometry/MS is the preferred choice for monitoring peak and tough concentrations, followed by anti-Xa, while PT is only suitable for peak concentrations. This study can help the clinicians to better adjust the medication regimen and reduce the risk of recurrence of thrombosis as well as the risk of bleeding.

Management of traumatic cervical epidural hematoma in patients on Xa-inhibitors: a case report and review of the literature

BACKGROUND

Cervical epidural hematoma (CEH) is defined as a collection of blood in the suprameningeal space. Mechanisms of this rare pathology include spontaneous, postsurgical, and traumatic as the main subtypes. This unique case of traumatic CEH represents an even smaller subset of these cases. Management varies by symptom presentation, mechanism of injury, and other contraindications.

CASE PRESENTATION

This case presents a 32 year old African American female on an oral anticoagulant sustaining traumatic cervical hematoma after a motor vehicle collision. Patient complained of neck, abdominal, and back pain. Imaging revealed a cervical spinal hematoma at the level of C3-C6. This case discusses the management of CEH for the general population and in the setting of anticoagulation.

CONCLUSION

Management of each case of CEH must be carefully considered and tailored based on their symptom presentation and progression of disease. As the use of anticoagulation including factor Xa inhibitors becomes more prevalent, there is greater need to understand the detailed pathophysiological aspect of the injuries. Targeted reversal agents such as Prothrombin Concentrate can be used for conservative treatment. Adjunct testing such as thromboelastogram can be used to help guide management.

In vitro effects of Gla-domainless factor Xa analog on procoagulant and fibrinolytic pathways in apixaban-treated plasma and whole blood

BACKGROUND

Andexanet alfa is a Gla-domainless FXa (GDXa) analog used as an antidote to FXa inhibitors. Despite its clinical use, laboratory monitoring for anti-Xa reversal and the effect of andexanet on fibrinolysis has not been explored. We used a GDXa with a serine-to-alanine mutation at position 195 (chymotrypsin numbering) to model the interaction between andexanet and apixaban.

METHODS

Six batches of pooled plasma, and whole blood from healthy volunteers were treated with increasing concentrations of apixaban with/without GDXa. Thrombin generation and plasmin generation (TG and PG) were tested in plasma, and whole blood thrombus formation was tested using thromboelastometry or a flow-chamber system. FXa was also tested in isolation for its ability to support plasmin activation with/without apixaban and GDXa.

RESULTS

Apixaban (250-800 nM) concentration-dependently decreased the velocity and peak of TG in plasma. Apixaban prolonged the onset of thrombus formation in thromboelastometry and flow-chamber tests. GDXa normalized apixaban-induced delays in TG and whole blood thrombus formation. However, GDXa minimally affected the low PG velocity and peak caused by apixaban at higher concentrations (500-800 nM). FXa promoted plasmin generation independent of fibrin that was inhibited by apixaban at supratherapeutic concentrations.

CONCLUSIONS

This study demonstrated the feasibility of assessing coagulation lag time recovery in plasma and whole blood following in vitro apixaban reversal using GDXa, a biosimilar to andexanet. In contrast, GDXa-induced changes in plasmin generation and fibrinolysis were limited in PG and tPA-added ROTEM assays, supporting the endogenous profibrinolytic activity of FXa and its inhibition at elevated apixaban concentrations.

Thromboelastography in the Perioperative Period: A Literature Review

Assessing coagulation status is essential for prompt intervention to reduce morbidity and mortality related to bleeding and thrombotic complications during the perioperative period. Traditional coagulation tests such as platelet count, activated partial thromboplastin time (aPTT), prothrombin time (PT), international normalized ratio (INR), and activated clotting time (ACT) provide only static evaluation. These tests are not designed for assessment of dynamically changing coagulation conditions during the perioperative time. However, viscoelastic coagulation testing such as thromboelastography (TEG) produces a rapid numerical and graphical representation that helps to detect and direct targeted hemostatic therapy. Searching the literature through PubMed, Medline, Ovid, CINAHL, and ClinicalTrials.gov we retrieved 210 studies, which represent the use of TEG in the perioperative period. The included studies were categorized under various settings such as trauma, obstetrics, orthopedics, intensive care unit (ICU), cardiovascular, transplant, and miscellaneous scenarios. TEG showed promising results in trauma surgeries in predicting mortality, hypercoagulability, and bleeding even when it was compared to conventional methods. TEG was also useful in monitoring anticoagulant therapy in orthopedic and obstetric surgeries; however, its role in predicting thrombotic events, hypercoagulability, or complications was questionable. In ICU patients, it showed promising results, especially in the prediction or improvement of sepsis, coagulopathy, thrombotic events, ICU duration, hospital stay, and ventilator duration. TEG parameters effectively predicted hypercoagulation in transplant surgeries. Regarding cardiovascular surgeries, they were effective in the prediction of the need for blood products, coagulopathy, thrombotic events, and monitoring anticoagulation therapy. More randomized clinical trials comparing TEG parameters with standardized tools are needed to produce robust results to standardize its use in different perioperative settings.

The impact of direct oral anticoagulants on viscoelastic testing - A systematic review

BACKGROUND

In case of bleeding patients and in acute care, the assessment of residual direct oral anticoagulant (DOAC) activity is essential for evaluating the potential impact on hemostasis, especially when a timely decision on urgent surgery or intervention is required. Viscoelastic tests are crucial in a modern goal-directed coagulation management to assess patients' coagulation status. However, the role of viscoelastic test to detect and quantify residual DOAC plasma levels is controversially discussed. The aim of this review was to systematically summarize the evidence of viscoelastic tests for the assessment of residual DOAC activity.

METHOD

PubMed, Embase, Scopus, and the Cochrane Library were searched for original articles investigating the effect of rivaroxaban, apixaban, edoxaban, or dabigatran plasma levels on different viscoelastic tests of the adult population from database inception to December 31, 2021.

RESULTS

We included 53 studies from which 31 assessed rivaroxaban, 22 apixaban, six edoxaban, and 29 dabigatran. The performance of viscoelastic tests varied across DOACs and assays. DOAC specific assays are more sensitive than unspecific assays. The plasma concentration of rivaroxaban and dabigatran correlates strongly with the ROTEM EXTEM, ClotPro RVV-test or ECA-test clotting time (CT) and TEG 6s anti-factor Xa (AFXa) or direct thrombin inhibitor (DTI) channel reaction time (R). Results of clotting time (CT) and reaction time (R) within the normal range do not reliable exclude relevant residual DOAC plasma levels limiting the clinical utility of viscoelastic assays in this context.

CONCLUSION

Viscoelastic test assays can provide fast and essential point-of-care information regarding DOAC activity, especially DOAC specific assays. The identification and quantification of residual DOAC plasma concentration with DOAC unspecific viscoelastic assays are not sensitive enough, compared to recommended anti-Xa activity laboratory measurements.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=320629], identifier [CRD42022320629].

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.

Viscoelastic monitoring in trauma resuscitation

BACKGROUND

Traumatic injury results in both physical and physiologic insult. Successful care of the trauma patient depends upon timely correction of both physical and biochemical injury. Trauma-induced coagulopathy is a derangement of hemostasis and thrombosis that develops rapidly and can be fatal if not corrected. Viscoelastic monitoring (VEM) assays have been developed to provide rapid, accurate, and relatively comprehensive depictions of an individual's coagulation profile. VEM are increasingly being integrated into trauma resuscitation guidelines to provide dynamic and individualized guidance to correct coagulopathy.

STUDY DESIGN AND METHODS

We performed a narrative review of the search terms viscoelastic, thromboelastography, thromboelastometry, TEG, ROTEM, trauma, injury, resuscitation, and coagulopathy using PubMed. Particular focus was directed to articles describing algorithms for management of traumatic coagulopathy based on VEM assay parameters.

RESULTS

Our search identified 16 papers with VEM-guided resuscitation strategies in adult patients based on TEG, 12 such protocols in adults based on ROTEM, 1 protocol for children based on TEG, and 2 protocols for children based on ROTEM.

CONCLUSIONS

This review presents evidence to support VEM use to detect traumatic coagulopathy, discusses the role of VEM in trauma resuscitation, provides a summary of proposed treatment algorithms, and discusses pending questions in the field.

A prospective observational study of the rapid detection of clinically-relevant plasma direct oral anticoagulant levels following acute traumatic injury

In urgent clinical situations, such as trauma, urgent surgery or before thrombolysis, rapid quantification of direct oral anticoagulant plasma drug levels is warranted. Using the ClotPro® analyser, we assessed two novel viscoelastic tests for detection of clinically-relevant plasma drug levels in trauma patients. The ecarin clotting time was used to assess the plasma concentration of dabigatran and Russell´s viper venom clotting time to determine the plasma concentration of direct factor Xa inhibitors. In parallel, plasma concentrations were analysed using plasma-based chromogenic assays. A total of 203 simultaneous measurements were performed. Strong to very strong linear correlations were detected between ecarin clotting time and plasma concentration of dabigatran (r = 0.9693), and between Russell´s viper venom clotting time and plasma concentrations of apixaban (r = 0.7391), edoxaban (r = 0.9251) and rivaroxaban (r = 0.8792), all p < 0.001. An ecarin clotting time ≥ 189 seconds provided 100% sensitivity and 90% specificity for detecting plasma dabigatran concentrations ≥ 50 ng.ml^-1 . Corresponding Russell´s viper venom clotting time cut-off values were ≥ 136 seconds for apixaban (80% sensitivity, 88% specificity), ≥ 168 seconds for edoxaban (100% sensitivity, 100% specificity) and ≥ 177 seconds for rivaroxaban (90% sensitivity, 100% specificity). Detection of drug levels ≥ 100 ng.ml^-1 was also investigated: for dabigatran, an ecarin clotting time ≥ 315 seconds yielded 92% sensitivity and 100% specificity; while Russell´s viper venom clotting time cut-offs of 191, 188 and 196 seconds were calculated for apixaban (67% sensitivity, 88% specificity), edoxaban (100% sensitivity, 75% specificity) and rivaroxaban (100% sensitivity, 91% specificity), respectively. We have demonstrated strong positive correlations between plasma drug levels and clotting time values in the specific ClotPro assays. Cut-off values for detecting clinically-relevant drug levels showed high levels of sensitivity and specificity.