Rivaroxaban and hemostasis in emergency care

Micellar liquid chromatography determination of rivaroxaban in plasma and urine. Validation and theoretical aspects

A Micellar Chromatographic method to determine rivaroxaban in plasma and urine has been developed. The samples were dissolved in the mobile phase (SDS 0.05 M - 1-propanol 12.5%, phosphate buffered at pH 7) and 20 μL directly injected, avoiding the extraction and purification steps. Using a C18 column and running under isocratic mode at 1 mL/min, analyte was eluted without interference from the matrix in <6.0 min. The detection absorbance wavelength was set to 250 nm. The procedure was validated by Food and Drug Administration guidelines in terms of: system suitability, calibration range (0.05-5 mg/L), linearity, sensitivity, robustness, carry-over effect, specificity, accuracy (-11.1 to 4.2%), precision (<19.9%), stability and analysis of incurred samples. The method was found reliable, practical, easy-to-conduct, rapid, relatively eco-friendly, safe, inexpensive, widely available and with a high sample throughput. The method was applied to the analysis of incurred samples, including incurred sample reanalysis, to verify that the instrumentation works correctly. In addition, the constants of the different partition equilibria occurring in the column were elucidated in order to have a better comprehension of the theoretical aspects of the retention mechanism. A moderately strong association between rivaroxaban and the stationary phase and the micelles was found, weakened by short chain alcohol.

Real-world monitoring of direct oral anticoagulants in clinic and hospitalization settings

Background:

The monitoring of the effects of direct oral anticoagulants may be beneficial during emergencies and adverse events. We aimed to explore direct oral anticoagulant monitoring in “real-world” settings, in which monitoring methods are limited and loading time can be estimated based on only patient reports.

Methods:

In 164 patients, plasma anti-Xa activity was assessed using a STA^®-Liquid Anti-Xa reagent (Diagnostica Stago, Asnieres, France), and prothrombin time was measured using HemosIL^® RecombiPlasTin 2G (Instrumentation Laboratory, Bedford, MA, USA). The loading time was calculated according to the previous dosing time reported by the patient. In the clinic setting, rivaroxaban and apixaban were administered to 103 patients with atrial fibrillation and a blood sample was tested once during a clinic visit. In the hospitalization setting, edoxaban was administered to 61 patients undergoing arthroplasty for prophylaxis of a venous thrombosis and blood samples were tested 3 and 18 h after the last intake.

Results:

Plasma Xa activity in the clinical setting ranged widely (rivaroxaban: 1.1–424.4 ng/mL, apixaban: 15.4–469.2 ng/mL) during the 11.7 ± 7.0 h following the previous dose. The values varied over a wide range (up to a factor of 2) at the same loading time, especially around the peak period. The plasma anti-Xa activity of rivaroxaban and apixaban showed linear correlations with prothrombin time (R² = 0.828 and 0.717, respectively). Edoxaban administration prolonged the prothrombin time by only 1.6 ± 1.1 s from the trough to the peak, to a degree that was negatively correlated with age, but not with plasma creatinine level, creatinine clearance, or body mass index.

Conclusion:

In real-world settings, plasma anti-Xa monitoring should be interpreted considering the wide variations in data, reflecting the variability in patient-reported loading time and interpatient variability.

Clinical pearls: Laboratory assessments of direct oral anticoagulants (DOACS)

Direct oral anticoagulants (DOACS) are being used for stroke prevention in patients with atrial fibrillation as well as for prophylaxis and treatment of venous thromboembolism. Clinicians who treat, or may encounter, patients with DOAC exposure, should be aware of the limitations of coagulation testing in this setting, and seek counsel from their laboratory to understand the effects of DOACS on coagulation results. Generally, assays that employ clot based principles, or methods that require thrombin or Factor Xa activation or substrates may be affected by the presence of DOACS. The clinical laboratory should have an algorithmic testing plan for adequately assessing the presence of all DOACS and readily provide this information to clinicians. We describe Clinical Pearls for DOAC assessment using common and esoteric coagulation testing.

Rivaroxaban-induced chest wall spontaneous expanding hematoma

Rivaroxaban is an oral direct Factor Xa inhibitor approved in the European Union and the United Sates for the single-drug treatment of several thromboembolic diseases in adults. Ιt has been evaluated in large phase III clinical trials and has been found to have similar efficacy and safety with standard therapy. Herein, is described a very rare case of a rivaroxaban-induced spontaneous expanding chest wall hematoma, that required surgical intervention, in a breast cancer patient. Use of the Naranjo adverse drug reaction probability scale indicated a probable relationship (score of 7) between the patient's development of hematoma and treatment with rivaroxaban. Physicians should be cautious when prescribing rivaroxaban in groups of patients associated with increased bleeding risk such as patients with impaired renal or hepatic function, hypertension, coronary heart disease, heart failure, patients with certain types of cancers and patients receiving concomitant medications which may alter the pharmacokinetic or pharmacodymamic parameters of rivaroxaban. Anticoagulant treatment should be tailored to each individual patient weighing the bleeding risk against the risk of recurrent thrombosis.

Use of rivaroxaban in patients with stroke

Rivaroxaban, an inhibitor of Factor Xa, is a direct oral anti-coagulant that has been found to be non-inferior to warfarin in preventing cerebral ischemia in patients with non-valvular atrial fibrillation and in the subgroup of patients with a history of the previous stroke or transient ischemic attack. Vascular neurologists in daily clinical practice may encounter patients taking rivaroxaban or patients who may benefit from its use. In this paper, we review the current clinical indications, contraindications, and clinical management guidelines for rivaroxaban while providing a special focus on neurological aspects and expert opinions on rivaroxaban therapy management in various situations that a neurologist may encounter when treating patients with an ischemic stroke (including those requiring intravenous or intra-arterial reperfusion therapy) and patients with an intracerebral hemorrhage. Since data from clinical trials and real-life data are missing in some clinical situations, strong recommendations are not always available. Nevertheless, practical guidelines should be adopted to maximize benefits from this oral anti-coagulant.

Microfluidic coagulation assay for monitoring anticoagulant therapy in acute stroke patients

Reliable detection of anticoagulation status in patients treated with non-vitamin K antagonist oral anticoagulants (NOACs) is challenging but of importance especially in the emergency setting. This study evaluated the potential of a whole-blood clotting time assay based on Surface Acoustic Waves (SAW-CT) in stroke-patients. The SAW-technology was used for quick and homogenous recalcification of whole blood inducing a surface-activated clotting reaction quantified and visualised by real-time fluorescence microscopy with automatic imaging processing. In 20 stroke or transient ischaemic attack (TIA)-patients taking NOACs kinetics of SAW-CT were assessed and correlated to other coagulation parameters (PT, aPTT) and NOAC-plasma concentration measured by tandem mass spectrometry (LC-MS/MS). In 225 emergency patients with suspicion of acute stroke or TIA, SAW-CT values were assessed. Mean (± SD) SAW-CT in non-anticoagulated stroke patients (n=180) was 124 s (± 21). In patients on dabigatran or rivaroxaban, SAW-CT values were significantly higher 2 and 8 hours (h) after intake rising up to 267 seconds (s) (dabigatran, 2 h after intake) and 250 s (rivaroxaban, 8 h after intake). In patients on apixaban, SAW-CT values were only moderately increased 2 h after intake (SAW-CT 153 s). In emergency patients, SAW-CT values were significantly higher in NOAC and vitamin K antagonist (VKA)-treated as compared to non-anticoagulated patients. In conclusion, the SAW-CT assay is capable to monitor anticoagulant level and effect in patients receiving dabigatran, rivaroxaban and the VKA phenprocoumon. It has a limited sensitivity for apixaban-detection. If specific SAW-CT results were used as cut-offs, SAW-CT yields high diagnostic accuracy to exclude relevant rivaroxaban and dabigatran concentrations in stroke-patients.

Identification of incident poisoning, fracture and burn events using linked primary care, secondary care and mortality data from England: implications for research and surveillance

BACKGROUND

English national injury data collection systems are restricted to hospitalisations and deaths. With recent linkage of a large primary care database, the Clinical Practice Research Datalink (CPRD), with secondary care and mortality data, we aimed to assess the utility of linked data for injury research and surveillance by examining recording patterns and comparing incidence of common injuries across data sources.

METHODS

The incidence of poisonings, fractures and burns was estimated for a cohort of 2 147 853 0-24 year olds using CPRD linked to Hospital Episode Statistics (HES) and Office for National Statistics (ONS) mortality data between 1997 and 2012. Time-based algorithms were developed to identify incident events, distinguishing between repeat follow-up records for the same injury and those for a new event.

RESULTS

We identified 42 985 poisoning, 185 517 fracture and 36 719 burn events in linked CPRD-HES-ONS data; incidence rates were 41.9 per 10 000 person-years (95% CI 41.4 to 42.4), 180.8 (179.8-181.7) and 35.8 (35.4-36.1), respectively. Of the injuries, 22 628 (53%) poisonings, 139 662 (75%) fractures and 33 462 (91%) burns were only recorded within CPRD. Only 16% of deaths from poisoning (n=106) or fracture (n=58) recorded in ONS were recorded within CPRD and/or HES records. None of the 10 deaths from burns were recorded in CPRD or HES records.

CONCLUSIONS

It is essential to use linked primary care, hospitalisation and deaths data to estimate injury burden, as many injury events are only captured within a single data source. Linked routinely collected data offer an immediate and affordable mechanism for injury surveillance and analyses of population-based injury epidemiology in England.