Recommendations for the emergency management of complications associated with the new direct oral anticoagulants (DOACs), apixaban, dabigatran and rivaroxaban

Acute ischemic stroke and measurement of apixaban and rivaroxaban: an observational cohort implementation study

Background

Treatment with intravenous thrombolysis for acute ischemic stroke is contraindicated with intake of apixaban/rivaroxaban in the last 48 hours. Recent European Stroke Organization guidelines suggest that thrombolysis can be considered if anti-factor Xa activity (AFXa) is <0.5 × 103 IU/L with low-molecular-weight (LMWH) or unfractionated heparin (UFH) calibrated assays. Some centers also use apixaban/rivaroxaban-calibrated AFXa assays to identify patients with low drug concentrations.

Objectives

To prospectively evaluate the first year of implementation of drug-calibrated AFXa assays at our center with 2500 yearly admittances with suspected stroke.

Methods

Samples were analyzed on Sysmex CS-5100 instruments with Innovance anti-Xa reagents. Thrombolysis could be considered with drug concentrations <25 μg/L. Patients were registered in an institutionally approved quality register. Outcomes included (1) the number of patients receiving thrombolysis after drug measurement, (2) turn-around time for drug concentration measurements, and (3) sensitivity of LMWH/UFH AFXa to apixaban and rivaroxaban.

Results

Apixaban or rivaroxaban was measured in 148 samples, and 4 patients who previously would have been ineligible for thrombolysis were treated with thrombolysis. In total, thrombolysis was administered in 123 patient episodes in the study period. The median turn-around time for the drug measurements was 38 minutes. Apixaban concentrations of 25 μg/L and 50 μg/L corresponded to LMWH/UFH AFXa of 0.13 and 0.27 × 103 IU/L, respectively. There were too few rivaroxaban results for regression analysis.

Conclusion

Implementation of apixaban and rivaroxaban measurements led to a small increase in the number of patients receiving thrombolysis. Excluding significant concentrations of apixaban or rivaroxaban using LMWH/UFH AFXa may be feasible.

Population pharmacokinetics of apixaban in a real-life hospitalized population from the OptimAT study

This study aimed to characterize apixaban pharmacokinetics (PKs) and its variability in a real-world clinical setting of hospitalized patients using a population PK (PopPK) approach. Model-based simulations helped to identify factors that affect apixaban exposure and their clinical significance. A classic stepwise strategy was applied to determine the best PopPK model for describing typical apixaban PKs in hospitalized patients from the OptimAT study (n = 100) and evaluating the associated variability and influencing factors. Apixaban exposure under specific conditions was assessed using the final model. A two-compartment model with first-order absorption and elimination best described the data. The developed PopPK model revealed a major role of renal function and a minor role of P-glycoprotein phenotypic (P-gp) activity in explaining apixaban variability. The final model indicated that a patient with stage 4 chronic kidney disease (creatinine clearance [CLcr] = 15-29 mL/min) would have a 45% higher drug exposure than a patient with normal renal function (CLcr >90 mL/min), with a further 12% increase if the patient was also a poor metabolizer of P-gp. A high interindividual variability in apixaban PKs was observed in a real-life setting, which was partially explained by renal function and by P-gp phenotypic activity. Target apixaban concentrations are reached under standard dosage regimens, but overexposure can rapidly occur in the presence of cumulative factors warranting the development of a predictive tool for tailoring apixaban exposure and its clinical utility in at-risk patients.

Intravenous Thrombolysis in Patients With Ischemic Stroke and Recent Ingestion of Direct Oral Anticoagulants

Importance

International guidelines recommend avoiding intravenous thrombolysis (IVT) in patients with ischemic stroke who have a recent intake of a direct oral anticoagulant (DOAC).

Objective

To determine the risk of symptomatic intracranial hemorrhage (sICH) associated with use of IVT in patients with recent DOAC ingestion.

Design, Setting, and Participants

This international, multicenter, retrospective cohort study included 64 primary and comprehensive stroke centers across Europe, Asia, Australia, and New Zealand. Consecutive adult patients with ischemic stroke who received IVT (both with and without thrombectomy) were included. Patients whose last known DOAC ingestion was more than 48 hours before stroke onset were excluded. A total of 832 patients with recent DOAC use were compared with 32 375 controls without recent DOAC use. Data were collected from January 2008 to December 2021.

Exposures

Prior DOAC therapy (confirmed last ingestion within 48 hours prior to IVT) compared with no prior oral anticoagulation.

Main Outcomes and Measures

The main outcome was sICH within 36 hours after IVT, defined as worsening of at least 4 points on the National Institutes of Health Stroke Scale and attributed to radiologically evident intracranial hemorrhage. Outcomes were compared according to different selection strategies (DOAC-level measurements, DOAC reversal treatment, IVT with neither DOAC-level measurement nor idarucizumab). The association of sICH with DOAC plasma levels and very recent ingestions was explored in sensitivity analyses.

Results

Of 33 207 included patients, 14 458 (43.5%) were female, and the median (IQR) age was 73 (62-80) years. The median (IQR) National Institutes of Health Stroke Scale score was 9 (5-16). Of the 832 patients taking DOAC, 252 (30.3%) received DOAC reversal before IVT (all idarucizumab), 225 (27.0%) had DOAC-level measurements, and 355 (42.7%) received IVT without measuring DOAC plasma levels or reversal treatment. The unadjusted rate of sICH was 2.5% (95% CI, 1.6-3.8) in patients taking DOACs compared with 4.1% (95% CI, 3.9-4.4) in control patients using no anticoagulants. Recent DOAC ingestion was associated with lower odds of sICH after IVT compared with no anticoagulation (adjusted odds ratio, 0.57; 95% CI, 0.36-0.92). This finding was consistent among the different selection strategies and in sensitivity analyses of patients with detectable plasma levels or very recent ingestion.

Conclusions and Relevance

In this study, there was insufficient evidence of excess harm associated with off-label IVT in selected patients after ischemic stroke with recent DOAC ingestion.

Direct oral anticoagulants (DOACs): From the laboratory point of view

Direct oral anticoagulants (DOACs) represent a new generation of drugs that have been increasingly used in the prevention and treatment of thromboembolic states. According to the mechanism of anticoagulant action, DOACs are divided into two groups: direct inhibitors of thrombin (dabigatran) and direct inhibitors of activated factor X (FXa) (rivaroxaban, apixaban, edoxaban, betrixaban). Compared to the vitamin K antagonists, DOACs are superior in terms of onset of action, pharmacokinetic and pharmacodynamics properties and fixed daily dose without the need for routine coagulation monitoring. Despite these advantages, there are clinical conditions in which laboratory measurement of DOACs should be performed. Although DOACs have an impact on screening haemostasis assays (prothrombin time, PT; activated partial thromboplastin time, aPTT; and thrombin time, TT), these tests are not appropriate for quantifying drug levels. Therefore, specific quantitative methods (LC-MS/MS as a gold standard method for all DOACs, coagulometric and chromogenic assays for dabigatran, and chromogenic anti-Xa assays with drug-specific calibrators for inhibitors of FXa) should only be used for determination of DOACs concentration. The aim of this review is to present all aspects of laboratory assessment of DOACs, including pre-analytical, analytical and post-analytical factors in the overall testing process with a special accent on the available specific quantitative methods for measurement of DOACs in circulation.

Spontaneous epidural hematoma induced by rivaroxaban: A case report and review of the literature

Background:

Trauma is the most frequent reason for epidural bleeding. However, numerous investigation had discovered that anticoagulants such as rivaroxaban could cause epidural hematoma. Here, we present a case of epidural hematoma in young man who got rivaroxaban as treatment of deep vein thrombosis.

Case Description:

A 27-year-old male with a history of deep vein thrombosis and one month of rivaroxaban medication presented with seizure and loss of consciousness following a severe headache. A CT scan of the head revealed epidural bleeding, and emergency blood clot removal was performed. As a reversal, prothrombin complex was utilized.

Conclusion:

Rivaroxaban has the potential to cause an epidural hemorrhage. Reversal anticoagulant should be administered before doing emergency surgery.

Thrombolysis in an Acute Ischemic Stroke Patient on Direct Anticoagulant Therapy Outside of the Traditional Time Window: A Case Report

A stroke is a life-threatening medical condition that could be disabling if left untreated. Intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) can be effective when initiated in an acute stroke, but their benefit is time-dependent and their use may be restricted by contraindications (CIs) such as anticoagulation therapy. The critical therapeutic time window, which was previously limited to 4.5-6 hours, is now extended to 24 hours in selected patients due to the development of advanced neuroimaging techniques. Herein, we discuss the case of a 50-year-old patient on rivaroxaban who developed acute ischemic stroke (AIS) and was treated successfully with intravenous recombinant tissue plasminogen activator thrombolysis more than six hours after the time he was last seen well (LSW). Our case demonstrates the importance of advanced neuroimaging techniques in identifying AIS candidates for IVT and/or MT with late or unknown time windows as well as the importance of case-by-case assessment when challenged by theoretical contraindications for thrombolysis.

Prevalence, contributory factors and severity of medication errors associated with direct-acting oral anticoagulants in adult patients: a systematic review and meta-analysis

PURPOSE

This study aimed to estimate the prevalence, contributory factors, and severity of medication errors associated with direct acting oral anticoagulants (DOACs).

METHODS

A systematic review and meta-analysis were undertaken by searching 11 databases including Medline, Embase, and CINHAL between January 2008 and September 2020. The pooled prevalence of errors and predictive intervals were estimated using random-effects models using Stata software. Data related to error causation were synthesised according to Reason's accident causation model.

RESULTS

From the 5205 titles screened, 32 studies were included which were mostly based in hospitals and included DOAC treatment for thromboembolism and atrial fibrillation. The proportion of study population who experienced either prescription, administration, or dispensing error ranged from 5.3 to 37.3%. The pooled percentage of patients experiencing prescribing error was 20% (95% CI 15-25%; I² = 96%; 95% PrI 4-43%). Prescribing error constituted the majority of all error types with a pooled estimate of 78% (95%CI 73-82%; I² = 0) of all errors. The common reported causes were active failures including wrong drug, and dose for the indication. Mistakes such as non-consideration of renal function, and error-provoking conditions such as lack of knowledge were common contributing factors. Adverse events such as potentially fatal intracranial haemorrhage or patient deaths were linked to the errors but causality assessments were often missing.

CONCLUSIONS

Despite their favourable safety profile, DOAC medication errors are common. There is a need to promote multidisciplinary working, guideline-adherence, training, and education of healthcare professionals, and the use of theory-based and technology-facilitated interventions to minimise errors and maximise the benefits of DOACs usage in all settings.

PROTOCOL

A protocol developed as per PRISMA-P guideline is registered under PROSPERO ID = CRD42019122996.

Acute Stroke Treatment in an Anticoagulated Patient: When Is Thrombolysis an Option?

Purpose of Review

Direct oral anticoagulants (DOACs: the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban and the direct thrombin inhibitor dabigatran) are the mainstay of stroke prevention in patients with non-valvular atrial fibrillation (AF). Nevertheless, there is a residual stroke risk of 1–2% per year despite DOAC therapy. Intravenous thrombolysis (IVT) reduces morbidity in patients with ischemic stroke and improves functional outcome. Prior DOAC therapy is a (relative) contraindication for IVT but emerging evidence supports its use in selected patients.

Recent Findings

Recent observational studies highlighted that IVT in patients on prior DOAC therapy seems feasible and did not yield major safety issues. Different selection criteria and approaches have been studied including selection by DOAC plasma levels, non-specific coagulation assays, time since last intake, and prior reversal agent use. The optimal selection process is however not clear and most studies comprised few patients.

Summary

IVT in patients taking DOAC is a clinically challenging scenario. Several approaches have been proposed without major safety issues but current evidence is weak. A patient-oriented approach balancing potential benefits of IVT (i.e., amount of salvageable penumbra) against expected bleeding risk including appropriate monitoring of anticoagulant activity seem justified.

Impact of centrifugation time and pneumatic tube transport on plasma concentrations of direct oral anticoagulants

INTRODUCTION

Rapid results are needed when plasma concentrations of direct oral anticoagulants (DOACs) are required in acute clinical settings. We evaluated the impact of centrifugation time and pneumatic tube transport on DOAC plasma concentrations with the overall aim of reducing turnaround time.

METHODS

Blood samples were spiked with rivaroxaban, apixaban or dabigatran in a low and a high concentration prior to centrifugation for 25 minutes (3163 g) or 5 minutes (3000 g) (n = 20 for each DOAC). Both samples spiked with DOACs (n = 20 for each DOAC) and patient samples (n = 25 in total) were transported manually or by pneumatic tube system samples.

RESULTS

For samples spiked with DOAC, statistically significant differences in DOAC plasma concentrations were found between centrifugation times for rivaroxaban in low (P < .05) and high (P < .05) concentrations. Relative bias was below 9% for all DOACs. Statistically significant differences were found between modes of transportation for rivaroxaban (P < .01) and dabigatran (P < .01) in high concentrations. Relative bias was 4%-23% for all DOACs. For patient samples, no statistically significant differences were found between modes of transportation, and relative bias was below 12% for all DOACs.

CONCLUSION

Minor, clinically insignificant, differences regarding centrifugation times were found in DOAC plasma concentrations. Importantly, no significant differences were found according to transportation modes for samples collected from patients. Although statistically significant differences were found depending on mode of transportation of spiked samples, relative bias was clinically acceptable. Thus, reduced centrifugation time and pneumatic tube transport should be considered to reduce turnaround time for rapid measurement of DOAC plasma concentrations.

Direct (new) oral anticoagulants (DOACs): Drawbacks, bleeding and reversal

BACKGROUND AND OBJECTIVE

Direct (new) Oral Anticoagulants (DOACs) have emerged as a contemporary and promising option in the treatment of thromboses and VTE, while protecting the coagulation cascade against untoward bleeding events. They are used in the management and prophylaxis of Venous Thromboembolism (VTE) and other thrombotic diseases. The most prominent complication of these agents is bleeding. These agents have similar or lower rates of major intracranial hemorrhages, while they had a higher risk of major gastrointestinal bleeding when compared to warfarin. This manuscript is aimed to revise and update the literature findings to outline the side effects of DOACs in various clinical scenarios.

METHODS

A narrative review of currently published studies was performed. Online database searches were performed for clinical trials published before July 2021, on the efficacy and adverse effects attributed to the anticoagulant treatment, especially DOACs. A literature search via electronic databases was carried out, beginning with the usage of the agents in the Western Languages papers. The search terms initially included direct (new) oral anticoagulants, dabigatran, rivaroxaban, apixaban, edoxaban, idarucizumab, andexanet, prothrombin complex concentrates, and fresh frozen plasma. Papers were examined for methodological soundness before being included.

RESULTS

Severe bleeding episodes require aggressive interventions for successful management. Therefore, bleeding should be evaluated in special regard to the location and rate of hemorrhage, and total volume of blood loss. Patient's age, weight and organ dysfunctions (e.g., kidney/liver failure or chronic respiratory diseases) directly affect the clinical course of overdose.

CONCLUSION

Management recommendations for hemorrhage associated with DOAC use vary, depending on the class of the culprit agent (direct thrombin inhibitor vs. FXa inhibitor), the clinical status of the patient (mild/ moderate vs. severe/life-threatening), and capabilities of the institution. Specific reversal agents (i.e., idarucizumab and andexanet alfa) can be used if available, while prothrombin complex concentrates, fresh frozen plasma and/ or tranexamic acid can also be employed as nonspecific replacement agents in the management of DOAC-related bleeding diathesis.

Recanalisation therapies for acute ischaemic stroke in patients on direct oral anticoagulants

Direct oral anticoagulants (DOACs) have emerged as primary therapeutic option for stroke prevention in patients with atrial fibrillation. However, patients may have ischaemic stroke despite DOAC therapy and there is uncertainty whether those patients can safely receive intravenous thrombolysis or mechanical thrombectomy. In this review, we summarise and discuss current knowledge about different approaches to select patient. Time since last DOAC intake-as a surrogate for anticoagulant activity-is easy to use but limited by interindividual variability of drug pharmacokinetics and long cut-offs (>48 hours). Measuring anticoagulant activity using drug-specific coagulation assays showed promising safety results. Large proportion of patients at low anticoagulant activity seem to be potentially treatable but there remains uncertainty about exact safe cut-off values and limited assay availability. The use of specific reversal agents (ie, idarucizumab or andexanet alfa) prior to thrombolysis is a new emerging option with first data reporting safety but issues including health economics need to be elucidated. Mechanical thrombectomy appears to be safe without any specific selection criteria applied. In patients on DOAC therapy with large vessel occlusion, decision for intravenous thrombolysis should not delay thrombectomy (eg, direct thrombectomy or immediate transfer to a thrombectomy-capable centre recommended). Precision medicine using a tailored approach combining clinicoradiological information (ie, penumbra and vessel status), anticoagulant activity and use of specific reversal agents only if necessary seems a reasonable choice.

Differences in risk factors for anticoagulant-related nephropathy between warfarin and direct oral anticoagulants: Analysis of the Japanese adverse drug event report database

Limited information is available on anticoagulant-related nephropathy (ARN). We therefore reviewed the Japanese Adverse Drug Event Report database to investigate kidney injury (KI) in patients administered warfarin or direct oral anticoagulants (DOACs) and sought to clarify the risk factors for ARN. KI risk in warfarin users was associated with male sex (odds ratio [OR], 1.70; 95% confidence interval [CI], 1.35-2.13; P < .01) and age ≥80 years (OR, 1.35; 95% CI, 1.07-1.72; P = .01). KI risk in DOAC users was associated with body weight ≥80 kg (OR, 1.60; 95% CI, 1.01-2.53; P = .04) and use of dabigatran (OR, 1.61; 95% CI, 1.09-2.37; P < .01). Our findings suggest that risk factors for ARN differ between warfarin and DOACs and that these risk factors may be associated with bleeding risk. Therefore, the risk of ARN may be decreased by better managing bleeding risk in patients taking anticoagulants.

Prior Anticoagulation in Patients with Ischemic Stroke and Atrial Fibrillation

OBJECTIVE

The aim was to evaluate, in patients with atrial fibrillation (AF) and acute ischemic stroke, the association of prior anticoagulation with vitamin K antagonists (VKAs) or direct oral anticoagulants (DOACs) with stroke severity, utilization of intravenous thrombolysis (IVT), safety of IVT, and 3-month outcomes.

METHODS

This was a cohort study of consecutive patients (2014-2019) on anticoagulation versus those without (controls) with regard to stroke severity, rates of IVT/mechanical thrombectomy, symptomatic intracranial hemorrhage (sICH), and favorable outcome (modified Rankin Scale score 0-2) at 3 months.

RESULTS

Of 8,179 patients (mean [SD] age, 79.8 [9.6] years; 49% women), 1,486 (18%) were on VKA treatment, 1,634 (20%) on DOAC treatment at stroke onset, and 5,059 controls. Stroke severity was lower in patients on DOACs (median National Institutes of Health Stroke Scale 4, [interquartile range 2-11]) compared with VKA (6, [2-14]) and controls (7, [3-15], p < 0.001; quantile regression: β -2.1, 95% confidence interval [CI] -2.6 to -1.7). The IVT rate in potentially eligible patients was significantly lower in patients on VKA (156 of 247 [63%]; adjusted odds ratio [aOR] 0.67; 95% CI 0.50-0.90) and particularly in patients on DOACs (69 of 464 [15%]; aOR 0.06; 95% CI 0.05-0.08) compared with controls (1,544 of 2,504 [74%]). sICH after IVT occurred in 3.6% (2.6-4.7%) of controls, 9 of 195 (4.6%; 1.9-9.2%; aOR 0.93; 95% CI 0.46-1.90) patients on VKA and 2 of 65 (3.1%; 0.4-10.8%, aOR 0.56; 95% CI 0.28-1.12) of those on DOACs. After adjustments for prognostic confounders, DOAC pretreatment was associated with a favorable 3-month outcome (aOR 1.24; 1.01-1.51).

INTERPRETATION

Prior DOAC therapy in patients with AF was associated with decreased admission stroke severity at onset and a remarkably low rate of IVT. Overall, patients on DOAC might have better functional outcome at 3 months. Further research is needed to overcome potential restrictions for IVT in patients taking DOACs. ANN NEUROL 2021;89:42-53.

Diagnostic performance of coagulation indices for direct oral anticoagulant concentration

INTRODUCTION

Different coagulation indices for direct oral anticoagulants (DOACs) exist in clinical practice, but limited data are available for the diagnostic power of these indices. This review and meta-analysis aims to explore the diagnostic value of coagulation indices for DOACs.

MATERIALS AND METHODS

PubMed, Web of Science, EMBASE, Clinical Trials.gov, and the Cochrane Library were searched from inception of each database to 15 February 2020. Studies reporting a relationship between coagulation indices and the gold standard (liquid chromatography/tandem mass spectrometry) were included in the analysis.

RESULTS

Sixteen articles from 9169 citations evaluating the performance of coagulation indices were included in this review. A total of 236, 273, 273 rivaroxaban samples were included to assess the diagnostic power of anti-Xa activity (AXA), prothrombin time (PT), combined PT and activated partial thromboplastin time, respectively. A total of 268 dabigatran samples were included to assess the diagnostic performance of diluted thromboplastin time (dTT). AXA calibrated by rivaroxaban showed a sensitivity of 0.98 (95% confidence interval (CI): 0.91-0.99) and a specificity of 0.98 (95% CI: 0.94-0.99) at the threshold of 30 ng/mL. For dabigatran, the combined sensitivity of dTT was 0.76 (95% CI: 0.66-0.84) and combined specificity was 0.97 (95% CI: 0.92-0.99).

CONCLUSIONS

DOAC-specific calibrated AXA was a good index to indicate concentration for rivaroxaban and apixaban. More studies on edoxaban and betrixaban are in need. Diluted TT, thrombin inhibitor assay, and ecarin-based assays were potential to measure dabigatran concentration. Due to the limited data, results should be validated in the future.

A Case of Liver Failure Due to Dabigatran Treated with Venovenous Hemodiafiltration and Idarucizumab

Dabigatran etexilate, a direct thrombin inhibitor, was recently introduced in clinical use to prevent thromboembolic events in patients with risk factors (such as non-valvular atrial fibrillation or deep vein thrombosis). Dabigatran is not recommended in patients with creatinine clearance below 30 mL/min. More than 85% of the drug is eliminated by the renal route while the remaining part via the enteral route. Acute renal failure can result in an unexpected increase in serum levels of Dabigatran. In elderly, renal dysfunction, co-morbidity, and concomitant intake of different drugs could make the dosage of Dabigatran challenging. We present a case of an elderly man who suffered a severe accidental dabigatran intoxication with acute liver toxicity recovered after dialytic treatment and Idarucizumab.

Can an anti-Xa assay for unfractionated heparin be used to assess the presence of rivaroxaban in critical situations?

OBJECTIVE

Although rivaroxaban has recently become widely used for thrombosis treatment, it is difficult for clinicians to make clinical decisions in critical situations, such as emergent surgery or interventions, because a specific anti-Xa assay is not available in many laboratories. This study assessed the relationships between rivaroxaban-specific anti-factor Xa activity (AXA) and unfractionated heparin (UFH)-specific AXA and determined the cutoff level for UFH-specific AXA in critical situations for patients undergoing rivaroxaban therapy.

METHODS

Thirty-eight blood samples were collected from patients with cancer-associated thrombosis receiving rivaroxaban therapy. All samples were assessed using both rivaroxaban-specific and UFH-specific anti-Xa assays. Routine coagulation studies, including prothrombin time (PT) and activated partial thromboplastin time, were also conducted on the samples.

RESULTS

A positive dose-dependent correlation between rivaroxaban-specific and UFH-specific AXA was evident (R = 0.97; P < .0001). Rivaroxaban-specific AXA was also positively correlated with PT (R = 0.95; P < .0001) but only weakly with activated partial thromboplastin time (R = 0.67; P < .0001). Patients with plasma rivaroxaban concentrations <100 ng/mL were found to have UFH-specific AXA <1.41 IU/mL and PT <17.3 seconds, with sensitivities of 100% and 93.3% and specificities of 87.0% and 95.7%, respectively.

CONCLUSIONS

Our study demonstrates that UFH-calibrated AXA correlates strongly with plasma rivaroxaban concentration. This assay appears to be sensitive to the presence of rivaroxaban, which may be advantageous in the setting of assessing drug levels for critical events. These findings suggest that if a rivaroxaban-specific anti-Xa assay is unavailable, the chromogenic anti-Xa assay for UFH may be useful to assess the anticoagulant effects of rivaroxaban.

Limitations of Specific Coagulation Tests for Direct Oral Anticoagulants: A Critical Analysis

Background

During treatment with direct oral anticoagulants (DOAC), coagulation assessment is required before thrombolysis, surgery, and if anticoagulation reversal is evaluated. Limited data support the accuracy of DOAC‐specific coagulation assays around the current safe‐for‐treatment threshold of 30 ng/mL.

Methods and Results

In 481 samples obtained from 96 patients enrolled at a single center, DOAC concentrations were measured using Hemoclot direct thrombin inhibitor assay, Biophen direct thrombin inhibitor assay or ecarin clotting time for dabigatran, chromogenic anti‐Xa assay (AXA) for factor Xa inhibitors (rivaroxaban, apixaban) and ultraperformance liquid chromatography–tandem mass spectrometry as reference. All dabigatran‐specific assays had high sensitivity to concentrations >30 ng/mL, but specificity was lower for Hemoclot direct thrombin inhibitor assay (78.2%) than for Biophen direct thrombin inhibitor assay (98.9%) and ecarin clotting time (94.6%). AXA provided high sensitivity and specificity for rivaroxaban, but low sensitivity for apixaban (73.8%; concentrations up to 82 ng/mL were misclassified as <30 ng/mL). If no DOAC‐specific calibration for AXA is available, results 2‐fold above the upper limit of normal indicate relevant rivaroxaban concentrations. For apixaban, all elevated results should raise suspicion of relevant anticoagulation.

Conclusions

DOAC‐specific tests differ considerably in diagnostic performance for concentrations close to the currently accepted safe‐for‐treatment threshold. Compared with Biophen direct thrombin inhibitor assay and ecarin clotting time, limited specificity of Hemoclot direct thrombin inhibitor assay poses a high risk of unnecessary anticoagulation reversal or treatment delays in patients on dabigatran. While AXA accurately detected rivaroxaban, the impact of low apixaban levels on the assay was weak. Hence, AXA results need to be interpreted with extreme caution when used to assess hemostatic function in patients on apixaban.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifiers: NCT02371044, NCT02371070.

Monitoring of low dabigatran concentrations: diagnostic performance at clinically relevant decision thresholds

The direct oral anticoagulant dabigatran does not require therapeutic drug monitoring, however emergency measurements are gaining importance. Current assays feature good performance at intermediate and high dabigatran concentrations but show limited accuracy at low concentrations. This area requires more attention as clinical decision threshold values currently lie at 30 and 50 ng/ml. The objective of the study was to evaluate and compare diagnostic performance of dabigatran assays at these thresholds. Dabigatran concentrations of 293 plasma samples taken from 50 patients were measured with the INNOVANCE direct thrombin inhibitor assay (DTI) from Siemens, the Biophen direct thrombin inhibitor assay (BDTI), the BDTI using a low range calibrator (BDTI-low), the Hemoclot direct thrombin inhibitor assay (HTI) and an ecarin clotting time assay (ECT). Assay results were compared to ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and test characteristics were calculated for thresholds of 30 and 50 ng/ml. DTI, BDTI-low and ECT showed very strong correlation and high agreement with UPLC-MS/MS and an improved determination of low dabigatran concentrations. ROC curve analyses revealed very high accuracy at the 30/50 ng/ml thresholds for DTI (AUC = 0.989/0.995), BDTI-low (AUC = 0.980/0.991) and ECT (AUC = 0.990/0.996) measurements. Sensitivity and specificity in detecting were calculated for DTI (98/92%), BDTI-low (87/95%), ECT (97/96%), BDTI (99/82%) and HTI (86/89%) measurements. Compared to the previously available HTI and BDTI, both novel assays, DTI and BDTI-low, reliably determine low dabigatran plasma concentrations around the clinical decision thresholds with very high sensitivity and specificity.

Impact of rivaroxaban plasma concentration on perioperative red blood cell loss

BACKGROUND

This study investigates the impact of preoperative calculated rivaroxaban (RXA) plasma concentration on perioperative red blood cell (RBC) loss.

STUDY DESIGN AND METHODS

In this retrospective single-center study, we identified patients with RXA intake according to a preoperative determination of RXA levels within 96 hours before surgery. RXA plasma concentration at the beginning of surgery was then calculated from the last RXA intake using a single-compartment pharmacokinetic model with four categories of RXA concentration (≤20, 21-50, 51-100, and >100 μg/L). Patients were classified into surgery with high (≥500 mL) or low (<500 mL) expected blood loss. Perioperative bleeding was determined by calculating RBC loss.

RESULTS

We analyzed 308 surgical interventions in 298 patients during the period from January 2012 to July 2018. Among patients undergoing surgery with low expected blood loss, RBC loss varied from 164 mL (standard deviation [SD], 189) to 302 mL (SD, 397) (p = 0.66), and no association of calculated RXA concentration with RBC loss was observed. In patients undergoing surgery with high expected blood loss, we found a significant correlation of calculated RXA concentration with RBC loss (Pearson's correlation coefficient, 0.29; p = 0.002). RBC loss increased with rising RXA concentration from 575 mL (SD, 365) at RXA concentration of 20 μg/L or less up to 1400 mL (SD, 1300) at RXA concentration greater than 100 μg/L. RXA concentration greater than 100 μg/L was associated with a significant increase of in RBC loss of 840 mL (95% confidence interval, 360-1300; p < 0.001). Transfusion of RBC and fresh frozen plasma units tended to increase in patients with RXA concentrations greater than 100 μg/L. The proportion of patients treated with prothrombin complex concentrate and coagulation factor XIII concentrate increased significantly with higher RXA concentrations.

CONCLUSION

Only in surgery with high expected blood loss, a calculated RXA concentration of greater than 100 μg/L was associated with a significant increase of perioperative RBC loss.

Direct-Acting Oral Anticoagulants and Their Reversal Agents-An Update

Background: Over the last ten years, a new class of drugs, known as the direct-acting oral anticoagulants (DOACs), have emerged at the forefront of anticoagulation therapy. Like the older generation anticoagulants, DOACs require specific reversal agents in cases of life-threatening bleeding or the need for high-risk surgery. Methods: Published literature was searched, and information extracted to provide an update on DOACS and their reversal agents. Results: The DOACs include the direct thrombin inhibitor—dabigatran, and the factor Xa inhibitors—rivaroxaban, apixaban, edoxaban, and betrixaban. These DOACs all have a rapid onset of action and each has a predictable therapeutic response requiring no monitoring, unlike the older anticoagulants, such as warfarin. Two reversal agents have been approved within the last five years: idarucizumab for the reversal of dabigatran, and andexanet alfa for the reversal of rivaroxaban and apixaban. Additionally, ciraparantag, a potential “universal” reversal agent, is currently under clinical development. Conclusions: A new generation of anticoagulants, the DOACs, and their reversal agents, are gaining prominence in clinical practice, having demonstrated superior efficacy and safety profiles. They are poised to replace traditional anticoagulants including warfarin.

Clinical presentation, diagnostic findings and management of cerebral ischemic events in patients on treatment with non-vitamin K antagonist oral anticoagulants - A systematic review

Background

Non-vitamin K antagonist oral anticoagulants (NOAC) are equally or potentially superior in terms of effectiveness in the prevention of ischemic stroke and carry a lower associated risk of intracranial hemorrhage compared to Vitamin K antagonists. Nevertheless, ischemic strokes also occur in patients who are being treated with NOAC. In those particular patients, knowledge about the underlying stroke etiology, clinical presentation, acute management, and complication rates is scarce.

Objective

Systematic literature review to provide a comprehensive clinical overview in terms of presentation, laboratory, imaging parameters and outcomes of patients suffering from acute cerebral ischemic events (i.e. TIA and acute ischemic stroke) while on treatment with a NOAC. Only if available, comparison to VKA is presented which was not the primary focus of this analysis.

Data sources

PubMed/MEDLINE, Scopus and EMBASE from January 1, 2006, to November 20, 2018.

Study eligibility criteria

52 studies providing detailed information on a total of 12247 patients were included. We excluded case reports and case series with less than five patients.

Study appraisal and synthesis method

We systematically assessed study quality using a bias tool and pooled consistent data.

Results

Existing data indicates milder stroke severity and smaller infarct size of acute ischemic stroke on treatment with NOAC compared to stroke occurrence on Vitamin K antagonists (VKA). Established risk factors for ischemic events also play a role in stroke while on NOACs, albeit the underlying etiology remains poorly understood. Intravenous thrombolysis and endovascular therapy seem to be safe and effective, but patient selection for recanalization therapies is challenging.

Limitations

Limited quality of published data, duplicate cases, statistical issues of data pooling, possible incomplete retrieval of identified research and reporting bias might have limited our findings.

Conclusions

Acute ischemic events despite treatment with NOAC therapy are insufficiently investigated.

Systematic review registration number

PROSPERO: CRD42018074853.

Management of patients with stroke treated with direct oral anticoagulants

Since their market approval, direct oral anticoagulants (DOACs) are being increasingly used for stroke prevention in patients with atrial fibrillation. However, the management of DOAC-treated patients with stroke poses several challenges for physicians in everyday clinical practice, both in the acute setting and in long-term care. This has spurred extensive research activity in the field over the past few years, which we review here.

Non-Vitamin K Oral Anticoagulants Associated Bleeding and Its Antidotes

Oral anticoagulant-associated intracerebral hemorrhage (OAC-ICH) accounts for nearly 20% of all ICH. The number of patients with an indication for oral anticoagulant therapy (OAT) increases with increasing age. OAT became less complicate with the introduction of non-vitamin K oral anticoagulants (NOAC) OAT because of easier handling, favorable risk-benefit profile, reduced rates of ICH compared to vitamin K antagonists and no need for routine coagulation testing. Consequently, despite a better safety profile of NOAC the number of patients with OAC-ICH will increase. The mortality and complication rates of OAC-ICH are high and therefore they are the most feared complication of OAT. Immediate normalization of coagulation is the main goal and therefore knowledge of pharmacodynamics and coagulation status is essential. Laboratory measurements of anticoagulant activity in NOAC patients is challenging as specific tests are not widely available. More accessible tests such as the prothrombin time and activated partial thromboplastin time have important limitations. In dabigatran-associated ICH 5 g Idarucizumab should be administered. In rivaroxaban and apixaban-associated ICHs administration of andexanet alpha should be considered. Prothrombin complex concentrate may be considered if andexanet alpha is not available or in case of an ICH associated with edoxaban.

Point-of-care coagulation testing for reducing in-hospital delay in thrombolysis

Background:

The confirmation of prothrombin time international normalized ratio by a central laboratory often delays intravenous thrombolysis in patients with acute ischemic stroke.

Objectives:

We investigated the feasibility, reliability, and usefulness of point-of-care determination of prothrombin time international normalized ratio for stroke thrombolysis.

Methods:

Among 312 patients with ischemic stroke, 202 who arrived at the emergency room within 4.5 h of stroke onset were enrolled in the study. Patients with lost orders for point-of-care testing for the prothrombin time international normalized ratio or central laboratory testing for the prothrombin time international normalized ratio (n = 47) were excluded. We compared international normalized ratio values and the time interval from arrival to the report of test results (door-to-international normalized ratio time) between point-of-care testing for the prothrombin time international normalized ratio and central laboratory testing for the prothrombin time international normalized ratio. In patients who underwent thrombolysis, we compared the time interval from arrival to thrombolysis (door-to-needle time) between the current study population and historic cohort at our center.

Results:

In the 155 patients included in the study, the median door-to-international normalized ratio time was 9.0 min (interquartile range, 5.0–12.0 min) for point-of-care testing for the prothrombin time international normalized ratio and 46.0 min (interquartile range, 38.0–55.0 min) for central laboratory testing for the prothrombin time international normalized ratio (p < 0.001). The intraclass correlation coefficient between point-of-care testing for the prothrombin time international normalized ratio and central laboratory testing for the prothrombin time international normalized ratio was 0.975 (95% confidence interval: 0.966–0.982). Forty-nine of the 155 patients underwent intravenous thrombolysis. The door-to-needle time was significantly decreased after implementation of point-of-care testing for the prothrombin time international normalized ratio (median, 23.0 min; interquartile range, 16.0–29.8 vs median, 46.0 min; interquartile range, 33.5–50.5 min).

Conclusion:

Utilization of point-of-care testing for the prothrombin time international normalized ratio was feasible in the management of patients with acute ischemic stroke. Point-of-care testing for the prothrombin time international normalized ratio was quick and reliable and had a pivotal role in expediting thrombolysis.

Consensus Guides on Stroke Thrombolysis for Anticoagulated Patients from Japan: Application to Other Populations

Development of direct oral anticoagulants and their antidotes has led to the need to reconsider the eligibility of acute stroke patients who have been taking oral anticoagulants for intravenous thrombolysis. Officially authorized Japanese guidelines on this issue were revised twice at the time of approval for clinical use of direct oral anticoagulants and idarucizumab, a specific reversal agent for dabigatran. A unique recommendation in the latest Japanese clinical guides was that thrombolysis can be recommended if the time of the last dose of direct oral anticoagulants exceeds 4 hours and if commonly available anticoagulation markers are normal or subnormal, i.e., international normalized ratio of prothrombin time <1.7 and activated partial thromboplastin time <1.5 times the baseline value (≤40 seconds only as a guide). These criteria are partly supported by the findings of domestic multicenter and single-center surveys that symptomatic or asymptomatic intracranial hemorrhage following thrombolysis was rare under the conditions of the criteria. Even for dabigatran users, stroke thrombolysis can be considered without pretreatment by idarucizumab if patients meet the above criteria. If not, direct mechanical thrombectomy can be considered without pretreatment by idarucizumab or thrombolysis, and use of idarucizumab, followed immediately by thrombolysis, can be considered only when thrombectomy cannot be quickly performed. These clinical guides are practical and to some extent economical, but they have some limitations, including lack of corroborating information from sufficient numbers of relevant cases. The guides will be further modified based on the results of future research.

Acute subdural hematoma in patients on oral anticoagulant therapy: management and outcome

OBJECTIVE Isolated acute subdural hematoma (aSDH) is increasing in older populations and so is the use of oral anticoagulant therapy (OAT). The dramatic increase of OAT-with direct oral anticoagulants (DOACs) as well as with conventional anticoagulants-is leading to changes in the care of patients who present with aSDH while receiving OAT. The purpose of this study was to determine the management and outcome of patients being treated with OAT at the time of aSDH presentation. METHODS In this single-center, retrospective study, the authors analyzed 116 consecutive cases involving patients with aSDH treated from January 2007 to June 2016. The following parameters were assessed: patient characteristics, admission status, anticoagulation status, perioperative management, comorbidities, clinical course, and outcome as determined at discharge and through 6 months of follow-up. Oral anticoagulants were classified as thrombocyte inhibitors, vitamin K antagonists, and DOACs. Patients were stratified based on which type of medication they were taking, and subgroup analyses were performed. Predictors of unfavorable outcome at discharge and follow-up were identified. RESULTS Of 116 patients, 74 (64%) had been following an OAT regimen at presentation with aSDH. The patients who were taking oral anticoagulants (OAT group) were significantly older (OR 12.5), more often comatose 24 hours postoperatively (OR 2.4), and more often had ≥ 4 comorbidities (OR 3.2) than patients who were not taking oral anticoagulants (no-OAT group). Accordingly, the rate of unfavorable outcome was significantly higher in patients in the OAT group, both at discharge (OR 2.3) and at follow-up (OR 2.2). Of the patients in the OAT group, 37.8% were taking a thrombocyte inhibitor, 54.1% a vitamin K antagonist, and 8.1% DOACs. In all cases, OAT was stopped on discovery of aSDH. For reversal of anticoagulation, patients who were taking a thrombocyte inhibitor received desmopressin 0.4 μg/kg, 1-2 g tranexamic acid, and preoperative transfusion with 2 units of platelets. Patients following other oral anticoagulant regimens received 50 IU/kg of prothrombin complex concentrates and 10 mg of vitamin K. There was no significant difference in the rebleeding rate between the OAT and no-OAT groups. The in-hospital mortality rate was significantly higher for patients who were taking a thrombocyte inhibitor (OR 3.3), whereas patients who were taking a vitamin K antagonist had a significantly higher 6-month mortality rate (OR 2.7). Patients taking DOACs showed a tendency toward unfavorable outcome, with higher mortality rates than patients on conventional OAT or patients in the vitamin K antagonist subgroup. Independent predictors for unfavorable outcome at discharge were comatose status 24 hours after surgery (OR 93.2), rebleeding (OR 9.8), respiratory disease (OR 4.1), and infection (OR 11.1) (Nagelkerke R² = 0.684). Independent predictors for unfavorable outcome at follow-up were comatose status 24 hours after surgery (OR 12.7), rebleeding (OR 3.1), age ≥ 70 years (OR 3.1), and 6 or more comorbidities (OR 3.1, Nagelkerke R² = 0.466). OAT itself was not an independent predictor for worse outcome. CONCLUSIONS An OAT regimen at the time of presentation with aSDH is associated with increased mortality rates and unfavorable outcome at discharge and follow-up. Thrombocyte inhibitor treatment was associated with increased short-term mortality, whereas vitamin K antagonist treatment was associated with increased long-term mortality. In particular, patients on DOACs were seriously affected, showing more unfavorable outcomes at discharge as well as at follow-up. The suggested medical treatment for aSDH in both OAT and no-OAT patients seems to be effective and reasonable, with comparable rebleeding and favorable outcome rates in the 2 groups. In addition, prior OAT is not a predictor for aSDH outcome.

Choosing a particular oral anticoagulant and dose for stroke prevention in individual patients with non-valvular atrial fibrillation: part 2

The choice of oral anticoagulant (OAC) for patients with atrial fibrillation (AF) may be influenced by individual clinical features or by patterns of risk factors and comorbidities. We reviewed analyses of subgroups of patients from trials of vitamin K antagonists vs. non-vitamin K oral anticoagulants (NOACs) for stroke prevention in AF with the aim to identify patient groups who might benefit from a particular OAC more than from another. In addition, we discuss the timing of initiation of anticoagulation. In the second of a two-part review, we discuss the use of NOAC for stroke prevention in the following subgroups of patients with AF: (vii) secondary stroke prevention in patients after stroke or transient ischaemic attack (TIA), (viii) patients with acute stroke requiring thrombolysis or thrombectomy, (ix) those initiating or restarting OAC treatment after stroke or TIA, (x) those with renal impairment on dialysis, (xi) the elderly, (xii) those at high risk of gastrointestinal bleeding, and (xiii) those with hypertension. In addition, we discuss adherence and compliance. Finally, we present a summary of treatment suggestions. In specific subgroups of patients with AF, evidence supports the use of particular NOACs and/or particular doses of anticoagulant. The appropriate choice of treatment for these subgroups will help to promote optimal clinical outcomes.

Can the anticoagulant effects of dabigatran be reversed?

Idarucizumab is a humanized monoclonal antibody fragment for reversal of the anticoagulant effects of dabigatran. This drug can be used for patients who need emergency surgery or invasive procedures, as well as those with life-threatening or uncontrolled bleeding.

Lupus-anticoagulant testing at NOAC trough levels

Non-vitamin K antagonist oral anticoagulants (NOAC), including rivaroxaban, apixaban or dabigatran, regularly show relevant effects on coagulation tests, making the interpretation of results difficult. The aim of this study was to evaluate possible interferences of NOACs in trough level concentrations in lupus anticoagulant (LA) testing. Citrate plasma specimens of 30 healthy volunteers were spiked with rivaroxaban, apixaban or dabigatran in four plasma concentration levels at or below trough NOAC levels. The NOAC concentration was measured using dedicated surrogate concentration tests and a stepwise diagnostic procedure for LA-testing was applied using screening, mixing and confirmatory testing. Results were compared to NOAC-free specimens. Starting with a plasma concentration of 12.5 ng/ml, dabigatran-spiked specimens showed significant prolongations in the lupus anticoagulant-sensitive activated partial thromboplastin time (aPTT-LA) as well as in the Dilute Russell viper venom time (dRVVT), leading to 43.3% false positives in confirmatory testing in the dRVVT. In contrast, rivaroxaban, beginning with 7.5 ng/ml, exclusively affected dRVVT-based tests. In confirmatory tests, 30.0% of rivaroxaban-spiked specimens showed false positive results. Starting with 18.75 ng/ml apixaban, a significant prolongation of the dRVVT and up to 20.7% false positives in confirmatory tests were found. In contrast to other NOACs tested, apixaban did not present with a dose-dependent increase of the dRVVT ratio. In conclusion, the rate of false positive results in LA-testing is unacceptably high at expected trough levels of NOACs. Even at plasma concentrations below the LLOQ of commercially available surrogate tests, LA testing is best avoided in patients with NOAC therapy.

Rivaroxaban plasma levels in acute ischemic stroke and intracerebral hemorrhage

OBJECTIVE

Information about rivaroxaban plasma level (RivLev) may guide treatment decisions in patients with acute ischemic stroke (AIS) and intracerebral hemorrhage (ICH) taking rivaroxaban.

METHODS

In a multicenter registry-based study (Novel Oral Anticoagulants in Stroke Patients collaboration; ClinicalTrials.gov: NCT02353585) of patients with stroke while taking rivaroxaban, we compared RivLev in patients with AIS and ICH. We determined how many AIS patients had RivLev ≤ 100ng/ml, indicating possible eligibility for thrombolysis, and how many ICH patients had RivLev ≥ 75ng/ml, making them possibly eligible for the use of specific reversal agents. We explored factors associated with RivLev (Spearman correlation, regression models) and studied the sensitivity and specificity of international normalized ratio (INR) thresholds to substitute RivLev using cross tables and receiver operating characteristic curves.

RESULTS

Among 241 patients (median age = 80 years, interquartile range [IQR] = 73-84; median time from onset to admission = 2 hours, IQR = 1-4.5 hours; median RivLev = 89ng/ml, IQR = 31-194), 190 had AIS and 51 had ICH. RivLev was similar in AIS patients (82ng/ml, IQR = 30-202) and ICH patients (102ng/ml, IQR = 51-165; p = 0.24). Trough RivLev_{(≤137ng/ml)} occurred in 126/190 (66.3%) AIS and 34/51 (66.7%) ICH patients. Among AIS patients, 108/190 (56.8%) had RivLev ≤ 100ng/ml. In ICH patients, 33/51 (64.7%) had RivLev ≥ 75ng/ml. RivLev was associated with rivaroxaban dosage, and inversely with renal function and time since last intake (each p < 0.05). INR ≤ 1.0 had a specificity of 98.9% and a sensitivity of 25.7% to predict RivLev ≤ 100ng/ml. INR ≥ 1.4 had a sensitivity of 59.3% and specificity of 90.1% to predict RivLev ≥ 75ng/ml.

INTERPRETATION

RivLev did not differ between patients with AIS and ICH. Half of the patients with AIS under rivaroxaban had a RivLev low enough to consider thrombolysis. In ICH patients, two-thirds had a RivLev high enough to meet the eligibility for the use of a specific reversal agent. INR thresholds perform poorly to inform treatment decisions in individual patients. Ann Neurol 2018;83:451-459.

Laboratory testing in patients treated with direct oral anticoagulants: a practical guide for clinicians

Click to hear Dr Baglin's perspective on the role of the laboratory in treatment with new oral anticoagulants SUMMARY: One of the key benefits of the direct oral anticoagulants (DOACs) is that they do not require routine laboratory monitoring. Nevertheless, assessment of DOAC exposure and anticoagulant effects may become useful in various clinical scenarios. The five approved DOACs (apixaban, betrixaban, dabigatran etexilate, edoxaban and rivaroxaban) have different characteristics impacting assay selection and the interpretation of results. This article provides an updated overview on (i) which test to use (and their advantages and limitations), (ii) when to assay DOAC levels, (iii) how to interpret the results relating to bleeding risk, emergency situations and perioperative management, and (iv) what is the impact of DOACs on routine and specialized coagulation assays. Assays for anti-Xa or anti-IIa activity are the preferred methods when quantitative information is useful, although the situations in which to test for DOAC levels are still debated. Different reagent sensitivities and variabilities in laboratory calibrations impact assay results. International calibration standards for all specific tests for each DOAC are needed to reduce the inter-laboratory variability and allow inter-study comparisons. The impact of the DOACs on hemostasis testing may cause false-positive or false-negative results; however, these can be minimized by using specific assays and collecting blood samples at trough concentrations. Finally, prospective clinical trials are needed to validate the safety and efficacy of proposed laboratory thresholds in relation to clinical decisions. We offer recommendations on the tests to use for measuring DOACs and practical guidance on laboratory testing to help patient management and avoid diagnostic errors.

[Anticoagulation in geriatric patients with atrial fibrillation : With what and for whom no more?]

Based on established risk scores, such as the CHA₂DS₂-VASc score, the indications for oral anticoagulation are given for patients over 65 years old with atrial fibrillation and even more so for patients over 75 years old. Before beginning anticoagulation a geriatric assessment for evaluation of the cognitive ability, the activities of daily living and the risk of falling should be made because of the known complications of anticoagulation. Geriatric patients with non-valvular atrial fibrillation (AF) are increasingly being treated with non-vitamin K antagonist oral anticoagulants (NOAC) to prevent ischemic stroke. The European Society for Cardiology (ESC) guidelines for the management of AF recommended NOACs as the preferred treatment and vitamin K antagonists (VKA) only as an alternative option. Meanwhile, apixaban, rivaroxaban, and edoxaban as factor Xa inhibitors and dabigatran as a thrombin inhibitor, are more commonly used in clinical practice in patients with AF. Although, these drugs have pharmacodynamics and pharmacokinetic similarities and are often grouped together, it is important to recognize that the pharmacology and dose regimens differ between compounds. Especially in elderly patients the new drugs have interesting advantages compared to VKA, i. e., less drug-drug interactions with concomitant medication and a more favorable risk-benefit ratio mostly driven by the reduction of bleeding. Treatment of anticoagulation in elderly patients requires weighing the serious risk of stroke with an equally high risk of major bleeding and pharmacoeconomic considerations. The easier practicality of NOACs in routine practice must be emphasized as no international normalized ratio (INR) monitoring is necessary and the interruption of treatment for planned interventions is uncomplicated. A regular monitoring of the indications for NOACs is indispensable (as for all other medications). Especially elderly patients have the greatest benefit from NOAC along with a low renal elimination rate and they should certainly not be withheld from elderly patients who have a clear need for oral anticoagulation.

Measurement of dabigatran: previously demonstrated Hemoclot® Thrombin Inhibitor assay reagent instability on Sysmex CS-2100i is no longer an issue

The Hemoclot^® Thrombin Inhibitor (HTI) assay has been recommended for measurement of dabigatran concentrations in specific clinical situations. Traditionally, reagents for biochemical assays are prepared from instructions found in the package insert. For the HTI reagents the manufacturer recommends incubating the reagents much longer than indicated in the package insert. These recommendations are added to the application sheets designed for different analyzers. Many clinicians and laboratory personnel may be unaware of the discrepancy between the two instructions, resulting in incorrect handling of the reagents. The aim of this study was to investigate the effect of the two different preparation methods on reagent stability and test results. For the standard concentration range, reagent stability on Sysmex CS-2100i was only two hours instead of the eight hours indicated by the producer when following package insert instructions (incubation time: 15 min). Stability was increased to five hours when following the application sheet (incubation time: 60 min). Two years later, the study was repeated using samples of patients treated with dabigatran etexilate. This time, reagent stability was at least six hours. Since the reagent composition was unchanged, the increased stability could be due to changed logistics by the supplier, with stock and transfer closer by. Previously demonstrated HTI reagent instability is no longer an issue at our laboratory. The reliability of results of clinical studies in which the assay has been used is potentially compromised.

Spontaneous Intracerebral Hemorrhage

Although commonly arising from poorly controlled hypertension, spontaneous intracerebral hemorrhage may occur secondary to several other etiologies. Clinical presentation to the emergency department ranges from headache with vomiting to coma. In addition to managing the ABCs, the crux of emergency management lies in stopping hematoma expansion and other complications to prevent clinical deterioration. This may be achieved primarily through anticoagulation reversal, blood pressure, empiric management of intracranial pressure, and early neurosurgical consultation for posterior fossa hemorrhage. Patients must be admitted to intensive care. The effects of intracerebral hemorrhage are potentially devastating with very poor prognoses for functional outcome and mortality.

Intravenous Thrombolysis in Patients with Stroke Taking Rivaroxaban Using Drug Specific Plasma Levels: Experience with a Standard Operation Procedure in Clinical Practice

Background and Purpose

Standard operating procedures (SOP) incorporating plasma levels of rivaroxaban might be helpful in selecting patients with acute ischemic stroke taking rivaroxaban suitable for IVthrombolysis (IVT) or endovascular treatment (EVT).

Methods

This was a single-center explorative analysis using data from the Novel-Oral-Anticoagulants-in-Stroke-Patients-registry (clinicaltrials.gov:NCT02353585) including acute stroke patients taking rivaroxaban (September 2012 to November 2016). The SOP included recommendation, consideration, and avoidance of IVT if rivaroxaban plasma levels were <20 ng/mL, 20‒100 ng/mL, and >100 ng/mL, respectively, measured with a calibrated anti-factor Xa assay. Patients with intracranial artery occlusion were recommended IVT+EVT or EVT alone if plasma levels were ≤100 ng/mL or >100 ng/mL, respectively. We evaluated the frequency of IVT/EVT, door-to-needle-time (DNT), and symptomatic intracranial or major extracranial hemorrhage.

Results

Among 114 acute stroke patients taking rivaroxaban, 68 were otherwise eligible for IVT/EVT of whom 63 had plasma levels measured (median age 81 years, median baseline National Institutes of Health Stroke Scale 6). Median rivaroxaban plasma level was 96 ng/mL (inter quartile range [IQR] 18‒259 ng/mL) and time since last intake 11 hours (IQR 4.5‒18.5 hours). Twenty-two patients (35%) received IVT/EVT (IVT n=15, IVT+EVT n=3, EVT n=4) based on SOP. Median DNT was 37 (IQR 30‒60) minutes. None of the 31 patients with plasma levels >100 ng/mL received IVT. Among 14 patients with plasma levels ≤100 ng/mL, the main reason to withhold IVT was minor stroke (n=10). No symptomatic intracranial or major extracranial bleeding occurred after treatment.

Conclusions

Determination of rivaroxaban plasma levels enabled IVT or EVT in one-third of patients taking rivaroxaban who would otherwise be ineligible for acute treatment. The absence of major bleeding in our pilot series justifies future studies of this approach.

Comparison of different laboratory tests in the evaluation of hemorrhagic risk of patients using rivaroxaban in the critical care setting: diagnostic accuracy study

Background

Rivaroxaban is a direct oral anticoagulant designed to dispense with the necessity of laboratory monitoring. However, monitoring rivaroxaban levels is necessary in certain clinical conditions, especially in the critical care setting.

Methods

This is a diagnostic accuracy study evaluating sensitivity and specificity of prothrombin time (PT), activated partial thromboplastin time (aPTT), and Dilute Russell viper venom time (dRVVT), to evaluate the hemorrhagic risk in patients taking rivaroxaban. The study used a convenience sample of 40 clinically stable patients using rivaroxaban to treat deep vein thrombosis or atrial fibrillation admitted in a private hospital in Brazil, compared to a group of 60 healthy controls. The samples from patients were collected two hours after the use of the medication (peak) and two hours before the next dose (trough).

Results

The correlation with the plasmatic concentration measured by anti-FXa assay was higher for PT and dRVVTS. The PT and aPTT tests presented higher specificity, while dRVVT was 100% sensible.

Conclusions

There was a strong correlation between the tests and the plasma concentration of the drug. Additionally, our results demonstrated the potential use of dRVVT as a screening test in the emergency room and the need of a second test to improve specificity.