Fatality in a patient treated with dabigatran

Non-VKA Oral Anticoagulants: Accurate Measurement of Plasma Drug Concentrations

Non-VKA oral anticoagulants (NOACs) have now widely reached the lucrative market of anticoagulation. While the marketing authorization holders claimed that no routine monitoring is required and that these compounds can be given at fixed doses, several evidences arisen from the literature tend to demonstrate the opposite. New data suggests that an assessment of the response at the individual level could improve the benefit-risk ratio of at least dabigatran. Information regarding the association of rivaroxaban and apixaban exposure and the bleeding risk is available in the drug approval package on the FDA website. These reviews suggest that accumulation of these compounds increases the risk of experiencing a bleeding complication. Therefore, in certain patient populations such as patients with acute or chronic renal impairment or with multiple drug interactions, measurement of drug exposure may be useful to ensure an optimal treatment response. More specific circumstances such as patients experiencing a haemorrhagic or thromboembolic event during the treatment duration, patients who require urgent surgery or an invasive procedure, or patient with a suspected overdose could benefit from such a measurement. This paper aims at providing guidance on how to best estimate the intensity of anticoagulation using laboratory assays in daily practice.

Does the Russell Viper Venom time test provide a rapid estimation of the intensity of oral anticoagulation? A cohort study

BACKGROUND

Dilute Russell Viper Venom Time (DRVV-T) might be useful in urgent settings for screening patients on Non-VKA Oral Anticoagulants (NOACs).

AIM

To compare the accuracy of DRVV-T with gold standard assays for the assessment of pharmacodynamics of dabigatran, rivaroxaban and vitamin K antagonist (VKA) in plasma samples from patients.

METHODS

Sixty rivaroxaban, 48 dabigatran and 50 VKA samples from patients were included. DRVV-T was performed in all groups using STA®-Staclot®DRVV-Screen and -Confirm. For NOACs, PT and aPTT were performed using different reagents while plasma drug concentrations were measured by liquid mass-spectrometry (LC-MS/MS). For VKA, INR was performed using RecombiPlasTin 2G®.

RESULTS

For NOACs, correlations between calibrated STA®-Staclot®DRVV-Confirm and LC-MS/MS (rs=0.88 and 0.97 for rivaroxaban and dabigatran, respectively) were higher than the ones obtained with STA®-Staclot®DRVV-Screen (rs=0.87 and 0.91), PT (rs=0.83 to 0.86) or aPTT (rs=0.84 to 0.89). Bland Altman analyses showed that calibrated DRVV-T methods tend to overestimate plasma concentrations of NOACs. ROC curves revealed that cut-off to exclude supra-therapeutic levels at Ctrough (i.e. 200ng/mL) are different for dabigatran and rivaroxaban. Neither STA®-Staclot®DRVV-Screen nor -Confirm correlated sufficiently with the intensity of VKA therapy (rs=0.35 and 0.52).

CONCLUSIONS

STA®-Staclot®DRVV-Confirm provides a rapid estimation of the intensity of anticoagulation with rivaroxaban or dabigatran without specific calibrators. At Ctrough, thresholds for rivaroxaban and dabigatran can be used to identify supra-therapeutic plasma level. However, this test cannot differentiate the nature of the NOACs. The development of a point-of-care device optimising this method would be of particular interest in emergency situations.

Clinical experience of life-threatening dabigatran-related bleeding at a large, tertiary care, academic medical center: a case series

INTRODUCTION

Dabigatran, an oral direct thrombin inhibitor, is FDA approved for the prevention of stroke in patients with nonvalvular atrial fibrillation. No agent exists for the reversal of dabigatran-related major bleeding. Prothrombin complex concentrate (PCC) has been studied in reversal but was not shown to affect the surrogate markers of bleeding such as the thrombin time, ecarin clotting time, or activated partial thromboplastin time (aPTT). Recombinant factor VIIa (rFVIIa) may provide benefit in patients with life-threatening or major bleeding; however, it has not been studied in dabigatran-related bleeding. PCC and rFVIIa are agents utilized at our institution for major bleeding in patients receiving anticoagulant therapy. Due to the high cost and thrombogenic risk of both rVIIa and PCC and lack of a clear reversal strategy, we reviewed the management of all reported cases of dabigatran-related bleeding.

METHODS

This was a retrospective chart review of patients admitted to UMass Memorial Medical Center with a bleeding event and also receiving dabigatran therapy.

RESULTS

Eleven patients on dabigatran admitted for bleeding were identified. Seven were admitted for an intracranial hemorrhage (ICH) and four for a gastrointestinal hemorrhage (GIH). The baseline characteristics are as follows: mean age was 74.55 years (range, 63-89), and seven were male. Admission mean hemoglobin was 11.88 g/dl (range, 6.1-18), mean international normalized ratio (INR) was 2.2 (range, 1.1-7.1), and mean aPTT was 42.21 s (range, 36-81.4). Interventions received included fresh frozen plasma (n = 6), platelets (n = 3), packed red blood cells (n = 4), rFVIIa (n = 2), intravenous fluids (n = 10), surgical intervention (n = 3), and dialysis (n = 2). No patients received PCC. Four patients survived in the ICH group, and four patients survived in the GIH group.

CONCLUSION

Reversal strategies for dabigatran-related bleeding events at our institution are highly variable. Intracranial hemorrhage in patients on dabigatran was associated with 43 % mortality. Patients with severe dabigatran-related bleeding may benefit from a standardized approach to treatment.

Hip arthroplasty fatality related to dabigatran induced gastrointestinal haemorrhage

We report a fatality due to massive gastrointestinal haemorrhage in a patient receiving prophylactic dabigatran etexilate following a total hip replacement. A 79-year-old woman was commenced on dabigatran for venous thromboembolic prophylaxis following a total hip replacement. She presented again four days after surgery with haematemesis and hypotension but her coagulopathy could not be corrected, leading to her death. This case highlights the lack of reversal agent for dabigatran etexilate that resulted in this fatal complication.

Pathology consultation on monitoring direct thrombin inhibitors and overcoming their effects in bleeding patients

OBJECTIVES

Direct thrombin inhibitors (DTIs), a relatively new class of anticoagulants, present several challenges regarding monitoring of their anticoagulant effects and overcoming bleeding associated with their use. The aim of this article is to (1) briefly present the pharmacologic properties of currently available DTIs, (2) discuss approaches to laboratory assessment of these drugs, and (3) review management of bleeding associated with their use.

METHODS

Published literature on DTIs, including clinical trials, case reports, and experimental animal models, was reviewed. The primary authors also reviewed their first-hand experiences with DTI anticoagulation.

RESULTS

Based on the literature review and the practical experiences of the authors, suggestions for the monitoring of DTIs and algorithmic approaches for the management of DTI-associated bleeding were developed.

CONCLUSIONS

Routine coagulation assays (eg, the prothrombin time) show a relatively poor correlation with the degree of anticoagulation and DTI drug concentrations. Newer assays, such as the ecarin clotting time and dilute thrombin time, may be more useful in assessing DTI anticoagulation, but these assays are not yet widely available. Low-grade DTI-associated bleeds are best managed with cessation of the drug and supportive care, while higher-grade and/or life-threatening bleeds may best be reversed by active drug removal (eg, via the administration of activated charcoal or hemodialysis). At present there is little evidence to suggest that transfusion products such as factor concentrates or thawed plasma are of any particular benefit in DTI reversal; however, these products may play a supportive role in the management of bleeding.