Therapie mit Dabigatran

Update on Direct Oral AntiCoagulants (DOACs)

Recent findings require an update of previous recommendations for the perioperative use of Direct Oral AntiCoagulants (DOACs). A break in preoperative treatment of 24-96 hours is recommended based on the pharmacokinetic profiles of DOACs and depends on individual patient characteristics, their renal and possibly liver function, and their surgery-related risk of bleeding. In cases of renal or hepatic insufficiency, whether to extend the preoperative interruption of IIa- and Xa-inhibitors is a clinical decision that must be reached on an individual patient basis. In cases of epidural or spinal anaesthesia, more conservative pausing-intervals are recommended due to the risk of persistent neurologic deficits (e.g., paraplegia) following the development of spinal subdural and epidural haematomas. Elective surgery should be postponed according to these recommendations. Preoperative "bridging" with LMWH (more precisely referred to as "switching") should be omitted due to a significantly increased risk of bleeding. In addition, the incidence of perioperative thromboembolic risks, such as DVT, PE, and stroke, are no different whether interruption or "switching" is undertaken. Postoperatively, the DOACs can be reinstituted within the first 24 hours. In cases of major surgery or if there is a higher risk of bleeding, resumption of DOACS should only begin after 24-72 hours. In patients with an elevated thromboembolic risk, transient postoperative LMWH administration can be recommended during this period.Interaction of DOACs with other drugs usually occurs during the absorption, transport and elimination of these drugs. Therefore, substance- specific restrictions and recommendations should be observed during these times. In everyday clinical practice, webbased, independent information portals on drug-interactions are very helpful in providing safe and rapid information about potential interactions when DOACs are used in combination with other drugs, especially during perioperative management.Non-adherence to medications is a worldwide problem that has dangerous and costly consequences. Present data suggest that persistence is the primary factor that supports adherence. Despite the adherence data presented in the DOACS approval studies (e.g., persistence in the treatment of acute venous thromboembolism has been reported to be between 94-99%), the first registries and meta-analyses provide sobering results regarding the incidence of persistence and the success rate of interventions designed to improve adherence with DOACs in cases of long-term usage.

Kidney and haemostasis

Renal insufficiency is characterized by thrombocytopathy, caused by the accumulation of water soluble and protein bound waste products of protein metabolism, which are not adequately eliminated by the kidney. The kidneys also excrete drugs and their metabolites, which accumulate if dosages are not adjusted to the renal function and may cause clinically relevant bleeding (i. e. synthetic penicillins, vitamin K antagonists, new oral anticoagulants). Therefore, each patients kidney function (GFR) ought to be evaluated by the KDIGO guidelines. The survival of chronic renal patients is lowered by increasing cardiovascular complications. Particularly frequent is non-valvular atrial fibrillation. The recommended prophylaxis with vitamin K antagonists for renal insufficiency is hampered by increased bleeding as well as by augmented (coronary) vascular and valvular calcification. It is not known yet whether prophylaxis with vitamin K may prevent this complication. Conclusion: Because new oral anticoagulants are equally or even more effective and cause less bleeding, they may be favoured in future and even in end-stage renal failure if more is known about dosing, safety and efficacy. The measurement of serum FGF 23 concentration may be helpful as a marker for their use.

[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.

[Platelet aggregation inhibitors and anticoagulants during ophthalmic interventions]

In ophthalmology many patients undergo surgical treatment who need to take anticoagulant medication due to cardiovascular diseases. The proper handling of these drugs requires both correct assessment of the risk of thromboembolism as well as the rating of the risk of surgery-related hemorrhages. While there are established recommendations for estimation of the risk of thromboembolism based on a large body of prospective randomized trials, data regarding the evaluation of the related complications secondary to ophthalmic surgery are limited. In comparison to other surgical procedures, most interventions in ophthalmic surgery tend to have a relatively low risk of bleeding; therefore, in general there is no need to convert or discontinue anticoagulant drugs in patients undergoing opthalmic surgery. The sparse data available justifying the abrupt termination of anticoagulation are contrary to the approach currently widely distributed in clinical practice. This overview covers the relevant knowledge of the perioperative use of anticoagulant drugs. In addition, the data on the risk of hemorrhage in ophthalmological procedures are presented and discussed.

The modification of the thrombin generation test for the clinical assessment of dabigatran etexilate efficiency

A new oral anticoagulant, dabigatran etexilate (DE, a prodrug of direct thrombin inhibitor (DTI) dabigatran), has been used clinically to prevent thrombosis. The assessment of dabigatran efficiency is necessary in some clinical cases, such as renal insufficiency, risk of bleeding, and drug interactions. However, a specific thrombin generation test (TGT) that is one of the most informative and sensitive to anticoagulant therapy (calibrated automated thrombinography (САТ)) shows a paradoxical increase of test parameters, such as endogenous thrombin potential (ETP) and peak thrombin, in patients receiving DE. The paradoxical behaviour of ETP and peak thrombin in these patients in the presence of DTIs is mostly caused by a decrease in the activity of thrombin in the α₂-macroglobulin-thrombin complex that is used as a calibrator in CAT. For a correct estimation of the TGT parameters in patient’s plasma containing DTIs we proposed to use our previously described alternative calibration method that is based on the measurement of the fluorescence signal of a well-known concentration of the reaction product (7-amino-4-methylcoumarin). In this study, the validity of such approach was demonstrated in an ex vivo study in patients with knee replacement and two special patients with multiple myeloma, who received DE for thrombosis prophylaxis.

[New oral anticoagulants for prophylaxis of stroke. Results of an expert conference on practical use in geriatric patients]

Geriatric patients with non-valvular atrial fibrillation (AF) are increasingly being treated with novel oral anticoagulants (NOAC) to prevent ischemic stroke. This article highlights the outcome of an expert meeting on the practical use of NOAC in elderly patients. An interdisciplinary group of experts discussed the current situation of stroke prevention in geriatric patients and its practical management in daily clinical practice. The topic was examined through focused impulse presentations and critical analyses as the basis for the expert consensus. The key issues are summarized in this paper. The European Society of Cardiology (ESC) guidelines from 2012 for the management of patients with non-valvular AF recommend NOAC as the preferred treatment and vitamin K antagonists (VKA) only as an alternative option. Currently, the NOAC factor Xa inhibitors apixaban and rivaroxaban and the thrombin inhibitor dabigatran are more commonly used in clinical practice for patients with AF. Although these drugs have many similarities and are often grouped together it is important to recognize that the pharmacology and dose regimes differ between compounds. Especially n elderly patients NOAC drugs have some advantages compared to VKA, e.g. 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 geriatric patients requires weighing the serious risk of stroke against an equally high risk of major bleeding and pharmacoeconomic considerations. Geriatric patients in particular have the greatest benefit from NOAC, which can also be administered in cases of reduced renal function. Regular control of the indications is indispensable, as also for all other medications of the patient. The use of NOAC should certainly not be withheld from geriatric patients who have a clear need for oral anticoagulation.

[Direct oral anticoagulation and gastrointestinal bleeding: Interventional therapy management]

BACKGROUND

More and more patients are being treated with direct oral anticoagulants (DOAC). Under treatment with DOACs gastrointestinal bleeding appears to occur more frequently, particularly in the lower gastrointestinal tract, compared to treatment with vitamin K antagonists (e.g. warfarin).

OBJECTIVE

A possible approach should now be elaborated in a joint effort by gastroenterologists and cardiologists.

MATERIAL AND METHODS

A selective literatue search was carried out and own experiences were also included.

RESULTS

The decision to perform procoagulant therapy by slowly injecting 30-50 IU prothrombin complex concentrate (PPSB) per kg body weight intravenously depends on various factors and should be assessed critically. Specific antidotes are awaiting approval. After a bleeding episode potentially controllable and reversible triggers must be excluded (e.g. drug interactions and renal impairment). The risk of recurrent bleeding and the risk of thromboembolic events have to be weighed against each other before deciding to readminister an anticoagulant and its form. Dose reduction and changing to apixaban (in reduced dosage) are options for risk reduction and vitamin K antagonists can also be considered.

DISCUSSION

It is still unclear what role specific antidotes will play.

[Consensus statement: Stroke prevention in nonvalvular atrial fibrillation in special consideration of the new direct oral anticoagulants]

The introduction of new direct oral anticoagulants has changed the treatment of nonvalvular atrial fibrillation. However, these changes are not yet fully reflected in current guidelines.This consensus statement, endorsed by six Austrian medical societies, provides guidance to current prophylactic approaches of thromboembolic events in nonvalvular atrial fibrillation on the basis of current evidence and published guidelines. Furthermore, some special subjects are treated, like changes in laboratory parameters and their interpretation under treatment with direct oral anticoagulants, treatment of bleedings, approach to operations, cardioversion and ablation, and specific neurological aspects. For a CHA2DS2-VASc-Score of ≥ 2, anticoagulation is recommended with a high level of evidence (1A). At the end of the consensus statement, recommendations for a number of specific patient subgroups can be found, in order to help treating physicians to arrive at appropriate therapeutic decisions.

Direct oral anticoagulants – laboratory monitoring

Die zum niedermolekularen Heparin (NMH) ähnliche Pharmakokinetik der DOAKs (Direkte Orale Antikoagulanzien) ermöglicht im klinischen Alltag den Austausch dieser Substanzen unter Beibehaltung der Anwendungsfrequenz. Vor allem bei nicht sicherer oder nicht möglicher oraler Anwendung von DOAKs erfolgt die parenterale Gabe von NMH. Die benötigte Karenzzeit vor Interventionen oder Operationen ist für beide Anwendungen präzise darstellbar. Beide Substanzklassen werden, wo nötig, durch ähnliche Labortests überwacht.

Ein generelles therapiebegleitendes Gerinnungsmonitoring, wie es seit vielen Jahrzehnten unter Verwendung von Vitamin-K Antagonisten üblich ist, ist unter Einnahme der neuen Xa- und Thrombin-Inhibitoren nicht erforderlich. Treten bei Patienten, die mit den DOAK behandelt werden, spezielle klinische Situationen auf (z.B. notfallmäßige Operationen oder Interventionen, akute Blutungssituation, akutes Organversagen), so können für den behandelnden Arzt Informationen über die Wirkspiegel im Plasma des Patienten die Einschätzung des Blutungsrisikos erleichtern. Da die DOAKs an zentraler Stelle in das Gerinnungssystem eingreifen, zeigen sie eine Interferenz mit den globalen Gerinnungstesten wie z.B. Thromboplastinzeit (TPZ; Quick/INR), aktivierte partielle Thromboplastinzeit (aPTT) und Thrombinzeit (TZ)(nur Thrombininhibitoren!) und speziellen gerinnungsphysiologischen Untersuchungen. Die Veränderungen in der Gerinnungsdiagnostik sind sowohl abhängig vom Wirkmechanismus des DOAK und der entsprechenden Halbwertszeit als auch vom Zeitpunkt der Tabletteneinnahme, der Dosierung und vom dem im Gerinnungslabor verwendetem Testsystem/Reagenz. Zur Interpretation der hämostaseologischen Messergebnisse muss dem behandelnden Arzt und dem Labormediziner bekannt sein, welches DOAK zu welchem Zeitpunkt eingenommen wurde. Weiters muss die Empfindlichkeit (Dosis-Wirkungskurve) des jeweiligen verwendeten Testsystems berücksichtigt werden. Mit den Globaltesten der Gerinnung können unter Behandlung mit DOAK lediglich abschätzende (semi-quantitative) Aussagen getroffen werden:

Liegt unter Einnahme von Rivaroxaban die Thromboplastinzeit (Quick / INR) im Normbereich (vorausgesetzt es wurde im Labor ein auf Rivaroxaban empfindliches Reagenz, z.B. Neoplastin Plus benutzt), so kann gefolgert werden, dass eine klinisch relevante Restwirkung von Rivaroxaban im Patientenplasma unwahrscheinlich ist. Unter Einnahme von Dabigatran weist eine aPTT >80 sec im Talspiegel auf ein erhöhtes Blutungsrisiko hin, eine im Normbereich liegende TZ lässt auf die Abwesenheit von Dabigatran im Plasma schließen.

Für die Quantifizierung der Plasmakonzentration von anti-Xa Inhibitoren stehen speziell auf die jeweilige Substanz kalibrierte chromogene anti-Xa-Teste zur Verfügung. Für die Quantifizierung der Plasmakonzentration von Dabigatran kann die kalibrierte verdünnte Thrombinzeit (Hemoclot®) eingesetzt werden. Eine Messung der Medikamentenkonzentrationen ist im klinischen Alltag jedoch bislang routinemäßig nicht vorgesehen, da die gemessenen Plasmakonzentrationen klinisch derzeit nicht für den einzelnen Patienten interpretiert werden können. Insgesamt muss der Einsatz hämostaseologischer Labormethoden zum Nachweis von DOAKS den lokalen Gegebenheiten entsprechend geplant und immer wieder (z. B. bei Reagenzienwechsel) zwischen Labor und Klinik abgestimmt werden.

Direct oral anticoagulants--interference with laboratory tests and mechanism of action

Direct oral anticoagulants (DOACs) have been established and already registered for clinical use on a wide basis in the United States and Europe. Different from the vitamin K antagonists (VKA), their mode of action is based on the direct inhibition of the single coagulation enzymes factor Xa or IIa. Other laboratory tests of hemostasis, such as the global tests prothrombin time (PT/INR) and activated partial thromboplastin time (APTT), or various functional coagulation assays involving generation of factor Xa or IIa for their endpoints, can be negatively influenced by the presence of the anticoagulant in the test sample. This interference has been well documented for rivaroxaban, apixaban, and dabigatran and is most prominent during the first hours after intake of the respective agent. Thus, the potential influence of DOACs has always to be considered when interpreting abnormal functional coagulation assays.

Perioperative management issues of direct oral anticoagulants

The treatment repertoire of oral anticoagulation has changed dramatically over the past few years from one class of vitamin K1 antagonists to an increasing number of direct oral anticoagulants (DOACs). Clinicians are confronted with the problem of managing patients on novel agents in the critical setting before, during, and after surgery, where the risk of bleeding and thrombosis are increased simultaneously. Randomized clinical data are insufficient to date, but clinical exposure enlarges the body of experience. The following review considers perioperative management issues in various categories, including minor elective surgery, major elective surgery, and acute surgery. This review is a credo to personalized medicine where the patient's underlying thromboembolic risk status, the potential bleeding risk, or actual hemorrhagic manifestation determine the selection of multi-modal targeted management strategies.

Management of dabigatran-induced bleeding: expert statement

The interdisciplinary group of experts has compiled a clinical guidance for manifest dabigatran-induced haemorrhage and envisaged invasive interventions on patients under dabigatran. It recommends an escalation of treatment measures as summarized in a pocket guide (see electronic supplementary material online and insert in the print issue).