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BioMed Research International
Volume 2014 (2014), Article ID 616405, 14 pages
Preventive Strategies against Bleeding due to Nonvitamin K Antagonist Oral Anticoagulants
1Department of Anesthesiology, CHU Dinant-Godinne UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), NAmur Research Institute of Life Sciences (NARILIS), 5530 Yvoir, Belgium
2Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), NAmur Research Institute of Life Sciences (NARILIS), University of Namur, 5000 Namur, Belgium
3Department of Hematology, CHU Dinant-Godinne UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), NAmur Research Institute of Life Sciences (NARILIS), 5530 Yvoir, Belgium
4Department of Internal Medicine, CHU Dinant-Godinne UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), NAmur Research Institute of Life Sciences (NARILIS), 5530 Yvoir, Belgium
5Department of Pharmacy, CHU Dinant-Godinne UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), NAmur Research Institute of Life Sciences (NARILIS), 5530 Yvoir, Belgium
6Université Catholique de Louvain, Louvain Drug Research Institute, Clinical Pharmacy Research Group, 1200 Brussels, Belgium
7Hematology Laboratory, CHU Dinant-Godinne UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), NAmur Research Institute of Life Sciences (NARILIS), 5530 Yvoir, Belgium
Received 28 February 2014; Accepted 14 April 2014; Published 16 June 2014
Academic Editor: Helen Mani
Copyright © 2014 Lessire Sarah et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Dabigatran etexilate (DE), rivaroxaban, and apixaban are nonvitamin K antagonist oral anticoagulants (NOACs) that have been compared in clinical trials with existing anticoagulants (warfarin and enoxaparin) in several indications for the prevention and treatment of thrombotic events. All NOACs presented bleeding events despite a careful selection and control of patients. Compared with warfarin, NOACs had a decreased risk of intracranial hemorrhage, and apixaban and DE (110 mg BID) had a decreased risk of major bleeding from any site. Rivaroxaban and DE showed an increased risk of major gastrointestinal bleeding compared with warfarin. Developing strategies to minimize the risk of bleeding is essential, as major bleedings are reported in clinical practice and specific antidotes are currently not available. In this paper, the following preventive approaches are reviewed: improvement of appropriate prescription, identification of modifiable bleeding risk factors, tailoring NOAC’s dose, dealing with a missed dose as well as adhesion to switching, bridging and anesthetic procedures.
Nonvitamin K antagonist oral anticoagulants (NOACs)  have been approved by the European Commission, as an alternative to vitamin K antagonists (VKAs) and parenteral anticoagulants, for the following indications: prevention of venous thromboembolism (VTE) in adult patients undergoing elective hip or knee surgery (apixaban [2–4], dabigatran etexilate (DE) [5–7], and rivaroxaban [8–11]), prevention of stroke and systemic embolism in adult patients with nonvalvular atrial fibrillation (NVAF) (apixaban , DE , and rivaroxaban ), treatment and secondary prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE) in adults (rivaroxaban and DE [15, 16]), and prevention of atherothrombotic events after an acute coronary syndrome with elevated cardiac biomarkers, combined with a single or dual antiplatelet therapy (acetylsalicylic acid alone or associated with clopidogrel or ticlopidine) (rivaroxaban [17, 18]). In NVAF trials, NOACs proved to be either superior or noninferior to warfarin for the prevention of stroke and systemic embolus [12–14]. Several guidelines (European Society of Cardiology, American College of Chest Physicians, and Canadian Cardiovascular Society) recommend NOACs as broadly preferable to VKAs in most patients with NVAF. This will lead to a wider use of NOACs in the future.
Compared with warfarin, the NOACs showed less risk of intracranial hemorrhage, and apixaban and DE (110 mg bid) showed less risk of major bleeding from any site [12–14]. Unfortunately, rivaroxaban and DE had an increased risk of gastrointestinal (GI) bleeding compared with warfarin. Apixaban was associated with fewer GI bleeding compared with warfarin, but it was not statistically significant .
Bleeding events were reported despite a regular monitoring of adverse events, a strong medication adherence and a careful selection of patients in the pivotal clinical trials (exclusion of patients with assumed poor compliance, bleeding risks, renal insufficiency, etc.). Extension of adverse events into clinical practice is currently under research and postmarketing registers, like the GLORIA-AF registry, are recruiting [20, 21].
The aim of this review is to highlight the bleeding risks with NOACs in the clinical practice and to broach different prevention strategies to minimize these adverse events.
2. NOACs and Major Bleeding
Large randomized controlled trials (RCT) allowing head-to-head comparison between NOACs are not available. Only indirect comparison on bleeding can be proposed since the three pivotal NOAC trials contain a common comparator (i.e., adjusted-dose warfarin). Even so there are limits in the conclusiveness of such comparisons, like differences in the study populations (differences in reporting age, renal function, exclusion criteria, and additional risk factors), in the definition of adverse events, in study protocols (open or double-blind design) and in time in therapeutic range (TTR) of the international normalized ratio (INR) values among these RCTs. In the three pivotal trials comparing NOACs with warfarin, evidence of the validation of the stated INR was not provided. This makes cross-trial comparisons difficult [30–32].
Few data exist regarding the safety of NOACs in clinical practice, and the available information reflects the limitations of post-authorization studies, such as reporting bias. Recent evidence provides contradiction to earlier safety reports that suggested that the major bleeding rates in patients receiving NOACs in clinical practice did not exceed the rates reported in the pivotal trials [21, 33].
McConeghy et al. evaluated DE adverse event reports with a reported bleeding event and/or reported fatal outcome compared with warfarin . This retrospective analysis of the FDA Adverse Event Reporting System (FAERS) database suggested increased odds of bleed-related mortality in clinical practice with dabigatran compared with the clinical trials .
The bleeding reports were driven by patients who were older, renally impaired, acutely injured, and had low body weight. These patients were underrepresented in the RELY trial and may have higher risks of dabigatran-induced bleeding. Furthermore, reports from FAERS showed underreporting bias .
For rivaroxaban, the following clinical characteristics were associated with an increased risk for major GI bleeding : concurrent aspirin or nonsteroidal anti-inflammatory drugs (NSAID) use, prior vitamin K antagonist use, decreased creatinine clearance, prior stroke, transient ischemic attack or systemic embolization, sleep apnea, cigarette smoking, chronic obstructive pulmonary disease, male gender, patient treated with histamine-2 receptor antagonist or proton pump inhibitor (PPI), and prior upper and lower GI bleeding. Most of these characteristics were also associated with an increased risk of major GI bleeding in patients treated with warfarin .
Concerning apixaban, Hylek et al. recently analyzed the bleeding events of all patients who received at least one dose of a study drug in the ARISTOTLE trial. All major bleedings (defined by the criteria of the International Society on Thrombosis and Haemostasis (ISTH)) that appear from the time of the first dose until 2 days after the last dose was received were included . Apixaban, compared with warfarin, was associated with a 31% reduction of first major bleeding and with half of the death within 30 days following a major hemorrhage. Independent factors associated with first major hemorrhage were: older age, prior hemorrhage, prior stroke or transient ischemic attack (TIA), diabetes, lower creatinine clearance, and decreased hematocrit. Female gender and liver disease were more associated with apixaban randomization, compared with warfarin. A subgroup analysis showed that patients with renal dysfunction and low body weight had a greater reduction in bleeding with apixaban versus warfarin than in patients with normal renal function and higher body weight.
The use of aspirin and nonsteroidal anti-inflammatory drugs (NSAID) with apixaban increased independently the risk of major bleeding by around 30% .
Based on the RE-LY trial, DE 150 mg BID, combined with a single or dual antiplatelet therapy, increased the rate of extracranial bleeding .
3. Prevention of Major Bleeding in Patients Receiving NOACs
The following preventive strategies are achievable to reduce the incidence rate of NOAC-related major bleeding:(1)improving appropriate prescription,(2)identifying modifiable bleeding risk factors,(3)improving individual benefit-risk by tailoring NOACs dose,(4)dealing with a missed dose,(5)adhering to switching procedures,(6)adhering to bridging procedures,(7)adhering to anesthetic recommendations.
3.1. Improving Appropriate Prescription
3.1.1. Off-Label Use or Misuse
The off-label use or misuse of NOACs means a use outside an appropriate indication or at inappropriate doses. For example the off label uses of DE are: age 80 years, patients with liver or kidney disease, with previous bleeding, with previous ischemic heart disease or severe renal impairment, patients with a CHADS2 score of 0 and patients with coadministration of systemic ketoconazole, cyclosporine, itraconazole, tacrolimus, dronedarone and aspirin [36–41].
Misuse is frequent (between 8.0 and 43.5%) and can induce supratherapeutic anticoagulation with a potential risk of severe or even fatal bleeding [36–38]. A lack of consensus in NVAF’s definition and the complexity of dose regimens for different indications and populations (as illustrated in Table 2) can lead to inadequate prescriptions.
3.1.2. Renal Function
Several cases of severe bleedings (often leading to death) have been reported in older patients under DE . Renal failure was the most recurrent risk factor associated with bleedings in these elderly patients and should therefore be reassessed during the treatment if clinically indicated (fluctuating renal function, diuretic use, and hypovolemia).
In clinical trials of DE and rivaroxaban for NVAF, drug eligibility and dosing were determined by using the Cockcroft-Gault equation to estimate creatinine clearance (CrCl), a measure of renal function. The modification of diet in renal disease (MDRD) equation (used to estimate glomerular filtration rate (eGFR)) leads, in low GFR values, to a surestimated renal function in comparison with the Cockcroft-Gault equation [46, 47]. Thus, by using the MDRD equation, many elderly patients with AF would either become incorrectly eligible for these drugs or would receive higher doses than required. Regulatory authorities and drug companies recommend therefore the use of the Cockcroft-Gault equation instead of the MDRD-derived eGFR to calculate eligibility for NOACs and adapted dose for elderly patients with AF.
By opening DE capsules, the bioavailability reaches 75% and increases highly the bleeding risk . Therefore, gastrostomies and jejunostomies are not advised with DE.
For rivaroxaban, Moore et al. studied its relative bioavailability when administered as a whole tablet orally or as a crushed tablet mixed with applesauce or water suspension through a nasogastric tube (NGT) or a gastrostomy. There was no difference in both pharmacokinetics, so that they concluded to a safe administration for rivaroxaban through a NGT or gastrostomy .
To the best of our knowledge, there is currently no data available for apixaban.
3.1.4. Patient with Low Body Weight
Despite recent data suggesting that the clearance of anticoagulants increases with weight, the optimal dosing strategies for most anticoagulants remain unknown . This uncertainty is mainly relevant for anticoagulants with fixed-dosing regimen such as NOACs, in contrast to anticoagulants for which efficacy monitoring is routinely required (i.e., VKAs).
In the RE-LY study, the overall mean weight of patient was 82.6 kg (ranging from 32 to 222 kg) with 17.1% of patients weighing above 100 kg. A tendency of increasing dabigatran concentrations with decreasing body weight was found . There is very limited clinical experience in patients with a body weight 50 kg. In this population, no dose adjustment is advised but a close clinical surveillance is recommended by the different authorities [43, 50].
A study with 48 healthy participants assessed the influence of extremes of body weight (50 kg and 120 kg) on the pharmacokinetics (PK) of rivaroxaban 10 mg OD as compared with normally weighted patients (80 kg). The results show that the of rivaroxaban was increased by 24% in subjects weighing 50 kg while the area under the curve (AUC) was unaffected (difference is 25%) by body weight. The 24% increase in in patients with low body weight resulted in a small (15%) increase in prolongation of prothrombin time (PT), which was not considered as clinically relevant . However, this was performed with STA Neoplastin CI+, a reagent with a moderate sensitivity to rivaroxaban. In a population pharmacokinetic/pharmacodynamics (PK-PD) modeling study, there was a clear increase in the volume of distribution interrelated with weight and probably due to secondary increase of body volume . Based on these findings, a higher exposure to rivaroxaban could be expected in patients with low body weight and, consequently, a higher risk of bleeding with a standard dose. However, these preliminary data need confirmations in larger studies. Similarly to dabigatran, no dose adjustment is currently proposed by the European and American agencies in patients with extreme body weight (50 kg or 120 kg) .
Apixaban has also been evaluated in patients with extreme body weight. A 30% and 20% increase in and AUC, respectively, has been seen in patients weighing 50 kg . These modifications were considered as modest and unlikely to be clinically meaningful. However, further evaluation of clinical data is warranted. Since the body weight seems to have a modest effect on apixaban exposure, the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) recommend dose adjustment in patients weighing 60 kg (2.5 mg BID instead of 5 mg BID) in the presence of additional risk factors, namely, age 80 years or serum creatinine 1.5 mg/dL [54, 55].
3.1.5. Patients with Impaired Hepatic Function
Hepatic impairment may alter the pharmacokinetics of drugs that are metabolized by the liver, such as rivaroxaban and apixaban . Data on the use of NOACs in hepatic impairment are scarce and mainly restricted to single-dose studies in a limited number of subjects with mild or moderate hepatic impairment. In addition, patients with elevated liver enzymes and/or bilirubin levels were excluded from clinical trials. The manufacturer’s recommendations for rivaroxaban, apixaban, and DE regarding impaired hepatic function are based on both Child-Pugh classification and liver-related exclusion criteria applied in clinical trials .
Stangier et al. found no influence of moderate hepatic impairment on pharmacokinetic, pharmacodynamics and safety profile of DE following administration of a single 150 mg dose in 24 subjects . However, patients with elevated liver enzymes above 2 times the upper limit of normal (ULN) were excluded from clinical trials . The Summary of Product Characteristics of the European Commission (EU-SmPC) contraindicates the use of DE in patients with hepatic impairment or liver disease expected to have any impact on survival .
In contrast to dabigatran, liver metabolism is an important route of elimination for FXa inhibitors. Approximately two-thirds of the administered rivaroxaban dose is metabolized by the liver via CYP3A4, 2J2, and CYP-independent mechanisms to inactive metabolites . The AUC following administration of a single dose of rivaroxaban 10 mg was increased by 2.27-fold in patients with moderately impaired liver function (Child-Pugh B). Moderate but not mild hepatic impairment reduced total body clearance of rivaroxaban and led to pharmacodynamics effects . Therefore, EMA contraindicates its use in case of hepatic disease associated with coagulopathy and clinically relevant bleeding risk including cirrhotic patients with Child Pugh B and C.
Apixaban undergoes liver metabolism mainly via CYP3A4/5, but other isoenzymes are also involved . Data on the use of apixaban in patients with moderate hepatic impairment (Child Pugh B) show that AUC increased slightly by 1.09-fold when a 5 mg single dose was administered . Apixaban should be used with caution in patients with elevated liver enzymes (ALT/AST 2 ULN) or total bilirubin 1.5 ULN because those were excluded from clinical trials. The EMA recommends to perform liver function test prior to initiating apixaban and to use it with caution in patients with moderate and severe hepatic impairment. Apixaban is contraindicated in patients with hepatic disease associated with coagulopathy and clinically relevant bleeding risk .
In conclusion, limited data indicate that the PK and PD of NOACs such as rivaroxaban or apixaban can be modified in moderate hepatic impairment, in contrast to dabigatran. Further evaluations are needed to better support clinicians in their decision process. Evaluations of liver function are recommended before prescribing NOACs and regularly during treatment in patients with possible liver impairment.
3.1.6. Drug Interactions
In addition to these specific populations, NOACs have also drug interactions with P-glycoprotein substrates or CYP3A4 inhibitors that may highly increase their plasma concentrations and hence bleeding risks. Table 3 summarizes drug-drug interactions reported in the literature as well as recommendations for dose adaptation and contraindications for the EU-SmPC and FDA prescribing guidelines [26–28].
3.2. Identifying Modifiable Bleeding Risk Factors
Identification of modifiable and nonmodifiable bleeding risk factors will help to ascertain and manage the risk of major bleeding. This can be performed before NOAC’s initiation using validated bleeding scores like the International Society of Thrombosis and Hemostasis bleeding assessment tool . The HAS-BLED score is a tool designed for assessing bleeding risks during anticoagulation. Despite debate in the literature on its ability to predict any clinically relevant bleeding, it may be useful for this purpose [61, 62]. For example, a HAS-BLED score 3 indicates high risk for hemorrhage and suggests that modifiable risk factors affecting bleeding should be reviewed and corrected (e.g., blood pressure, hepatic/renal function, INR, antiplatelet agents, NSAIDs, alcohol ingestion, and selective serotonin reuptake inhibitors (SSRI)).
The EMA has introduced new contraindications for all NOACs since September 2013. This statement mentions that a screening of injuries and sicknesses that may lead to major bleeding is required before starting NOAC therapies. This can be a current or recent gastrointestinal bleeding, suspected or known esophageal varicose veins, any malignancy with high bleeding risks (e.g., colon cancer), recent cerebral, spine or ophthalmic injuries, recent intracranial hemorrhage, arteriovenous malformations, vascular aneurysm, or major intraspinal and intracranial vascular anomalies .
Careful attention must be directed to renal protective strategies for patients under DE. These patients should know that concurrent medications (e.g., NSAIDs) or clinical comorbidities (e.g., dehydration) can deteriorate their renal function, and, as consequence, increase and prolong dabigatran anticoagulant effect .
3.3. Improving Individual Benefit-Risk by Tailoring NOAC’s Dose
A reanalysis of the RE-LY study has shown that bleeding outcomes were correlated with dabigatran plasma concentrations . Demographic characteristics (mainly age and previous stroke) played the strongest role in determining risk of clinical events. In addition, the authors concluded that for patients at highest risk for events, such as the very elderly and/or those with poor renal function, an adjustment of dabigatran dose to optimize exposure might improve benefit-risk ratio if they are at either extreme of the concentration range.
The EU-SmPC mentions that exceeding the 90th percentile of NOAC’s trough level is considered to be associated with an increased risk of bleeding. For example, patients treated with 150 mg dabigatran BID for stroke prevention in NVAF have a 90th percentile of dabigatran plasma concentrations measured at trough (10–16 hours (h) after the previous dose) about 200 ng/mL .
Moreover, estimation of plasma drug concentrations can also be interesting to identify high responders which are at risk of bleeding . Pharmacokinetic studies showed that dabigatran has considerable variation in plasma drug concentrations . Most patients will obtain an adequate plasma level when given a fixed dose. But a measurable proportion will either achieve an insufficient or a supratherapeutic drug level [66–68]. Furthermore, medication adherence is not better than 50% in unmonitored conditions [64, 69], meaning that losing track of the patients during long-term (often life-long) treatment can be worrying. For these reasons, searching for the optimal dose in patients at risk of supra- or infratherapeutic plasma level can improve the efficacy and safety of NOACs. In addition, without a structured organization, there will be no routine check on side effects, tolerance, and adherence [64, 69].
To prevent massive bleeding, biological monitoring would be valuable in the following situations [64, 68, 70, 71]:(i)before urgent surgery or procedure (with the last administration in the last 24 h, or more, if CrCl 50 mL/min),(ii)before fibrinolytic therapy of acute ischemic stroke,(iii)for bridging therapy,(iv)for patients with multiple risk factors for NOAC’s accumulation (i.e., patients older than 75 years, drug-drug interactions as with frequently used medication like amiodarone and verapamil, extreme body weight (50–60 kg and 110–120 kg), hepatic impairment, and renal impairment),(v)for patients with renal impairment (progressive decrease of renal function, acute decrease due to dehydration, antibiotics administration, etc.),(vi)in complex management of dual or triple antithrombotic therapies (e.g., patients with AF undergoing percutaneous coronary intervention or dual platelet inhibitors added to NOACs).
Therefore, it is essential to know the timing of NOAC’s administration and the timing of blood sampling when interpreting results of a coagulation assay in a NOAC treated patient.
For example, coagulation assay results will differ if blood samples are taken 2 hours after DE intake (peak level) compared with blood sampling 12 hours after ingestion of the same dose. A French group (GIHP: Groupe d’Intérêt en Hémostase Périopératoire) proposed the following cut-off for the perioperative management of DE and rivaroxaban (Table 4): 30 ng/mL: the operation may take place; between 30 and 200 ng/mL: therapeutic zone; between 200 and 400 ng/mL: minor hemorrhagic risk; 400 ng/mL: major hemorrhagic risk .
For apixaban, there is no data regarding the plasma trough or max level versus bleeding or recurrence of thrombosis. Pharmacokinetic studies revealed that apixaban plasma concentrations varied modestly between peak and trough and were mainly comprised within the range of 100–300 ng/mL .
The recent recommendation of the International Society of Thrombosis and Hemostasis (ISTH) mentions that the activated partial thromboplastin time (aPTT) and prothrombin time (PT) can be used in emergency situations to determine the relative intensity of anticoagulation due to DE and rivaroxaban, respectively . However, aPTT and PT should not be used to quantify the drug plasma concentration. Further studies are required to determine the relative sensitivity of aPTT and PT reagents in order to give more specific recommendations. In addition, aPTT and PT are global assays which are not reflecting peripheral concentrations of NOACs, especially at high plasma concentrations .
PT is not sensitive enough to estimate apixaban plasma concentrations. Furthermore, depending on the reagent, it may be normal with apixaban therapeutic concentration. Even for the most sensitive reagents, it may only inform the clinician if the patient is taking the drug.
As thrombin time (TT) is too sensitive to dabigatran , it is advisable to use a calibrated diluted thrombin time (dTT) with dabigatran standards to estimate dabigatran plasma concentration . Therefore, Hemoclot thrombin inhibitor (HTI) is a rapid, linear, standardized, and calibrated assay which determines precisely plasma concentrations of dabigatran .
3.4. Dealing with a Missed Dose
To minimize the risk of bleeding, keep in mind that patients on DE for NVAF or on rivaroxaban for NVAF and VTE prevention should never take a double dose at the same time. If the missed dose is within 6 hours for dabigatran and within 12 hours for rivaroxaban, patients should take the forgotten capsule immediately. Otherwise, if the time is exceeded, they should just go on with the treatment without taking any capsule.
The only exception concerns VTE treatment with rivaroxaban, where patients may take simultaneously 2 tablets of 15 mg to ensure a total daily dose of 30 mg.
For apixaban, there is no time schedule. Patients should just take the forgotten capsule immediately and go on with the treatment .
3.5. Adherence to Switching Procedures
To avoid hypercoagulability during a switching procedure, it is important to consider NOAC’s pharmacokinetics and patient comorbidities.
When VKAs are switched to NOACs, VKAs should be discontinued and NOACs should be started as soon as the INR is lower than 2 .
Inversely, if DE is switched to VKAs, physicians need to consider the renal function before starting VKAs. Creatinine clearance (CrCl) influences the delay of VKA’s introduction, which in this case, precedes dabigatran arrest (from 3 days to 1 day, if CrCl is over 50 mL/min, between 30 and 50 mL/min or between 15 and 30 mL/min, resp.). NOACs interfere with an elevated INR, so that a better reflect of VKA on the INR will appear only after 2 days of NOAC’s arrest .
To switch from NOACs to parenteral anticoagulants, these last ones should be started when the next dose of NOACs is due . Inversely, NOACs should be started at the same time or up to 2 hours before the next parenteral anticoagulant dose. For intravenous unfractionated heparin, NOACs should be started at the time of discontinuation of the infusion.
3.6. Adherence to Bridging Procedures
The aim of bridging procedures is to avoid thromboembolic events in patients at high risk during the perioperative period.
Only one prospective study has recently evaluated the peri-interventional NOAC management in unselected patients from daily care . Outcomes and bleeding risks were compared for different types of procedure (minimal, minor, or major) in patients under NOACs. In 22% of the patients, NOACs were not interrupted, and in 30%, the gap in NOAC’s intake was bridged with heparin. The rest of the patients underwent an interruption of NOACs of maximal 3 perioperative days. Major procedures had the highest cardiovascular and major bleeding complications. Interestingly, the bridging therapy did not reduce cardiovascular events but led to higher rates of major bleeding complications compared with no bridging. But these bleedings were similar to VKA patients who had bridging therapy before invasive procedures.
However, a selection bias resulted from a more frequent use of bridging therapy in severe procedure (most physicians anticipated the increased cardiovascular risk in patients undergoing major procedure). This can explain why cardiovascular and bleeding events were more frequent in major procedures .
They concluded that a continuation or short interruption of NOACs is safe for most invasive procedures and that patients with cardiovascular risks undergoing major procedure may benefit from bridging therapy, with as a consequence a higher bleeding risk. As the bridging therapy with heparin does not reduce the risk of cardiovascular events, a benefit-risk evaluation is needed to target the appropriate candidates who could benefit from it.
NOACs are sometimes interrupted perioperatively without bridging procedure. In this case, a postoperative resumption balanced between bleeding and thromboembolic risk needs to be defined. Spyropoulos and Douketis proposed a management based on studies assessing DE as thromboprophylaxis after orthopedic surgery and on the RELY trial. These authors suggest that NOACs should be resumed 24 hours after low bleeding risk surgery and 48–72 hours after high bleeding risk surgery. In patients with high thrombotic risk, consider a reduced dose of NOACs on the evening after surgery (DE) and on the first postoperative day (DE, rivaroxaban, and apixaban). Further studies are necessary to validate the safety of this approach .
3.7. Adherence to Anesthetic Recommendations
Anesthesia recommendations are available to decrease bleeding risks during perioperative procedures (e.g., regional anesthesia), especially in neuraxial anesthesia, which has potential risk of spinal hematoma [71, 84, 85].
Extreme caution is recommended with neuraxial blockade for rivaroxaban and apixaban. For DE, the manufacturer advise against its use .
For regional nerve blockade, ultrasound is a valuable tool to optimize catheter placement and decrease accidental vascular puncture .
Postprocedure anticoagulation (e.g., after removing indwelling catheter) should be restarted after 8 hours minus the time to reach maximum activity () (8 hours equal to the time to establish a stable clot) .
4. Absence of Antidote
The absence of antidote for NOACs emphasizes the importance of implementing strategies to prevent massive bleeding.
NOACs have a relatively short half-life, so that stopping the drug in patients without altered renal or liver function could be already valuable to eliminate it.
In large randomized controlled trial (RCT), the number of fatal bleedings was similar between NOACs and warfarin groups, despite absence of antidote for NOACs [12–14]. Strategies against life-threatening bleedings under NOACs are needed in any cases. Currently, there is no high-quality evidence in the clinical management of severe bleedings under NOACs but rather experience-related management. Animals and in vitro studies are guiding treatment approaches. The discussed effectiveness of nonspecific reversal therapies must be counterbalanced with their increased thrombotic risk [88–90].
A recent paper has presented the management and outcome of major bleeding during treatment with DE or warfarin .
Dickneite and Hoffman  reviewed the currently available data of PCC’s use in reversing NOAC’s anticoagulant effects. Because of different study models, the results are not entirely consistent. Some studies used 3F-PCCs, which contain high concentrations of coagulation factors II, IX and X and low and/or variable amounts of FVII. Other studies used 4F-PCCs, which additionally contain high levels of FVII. Due to their ability to raise the levels of these factors and consequently enhance thrombin generation in in vitro models, their utility to overcome the anticoagulant effects of FIIa and FXa inhibitors is plausible. But using PCCs to attempt to overcome the effect of an inhibitor is more complicated than simply replacing factors that are deficient. For example, the still present dabigatran will continue to inhibit thrombin activity, even if PCCs are supplied and lead to thrombin formation.
Effectiveness and appropriate doses of PCCs still need to be established, especially when there appear variations in the ability of different PCCs to reverse NOAC’s anticoagulant effects .
Only one of the available 4F-PCCs is able to reverse anticoagulation due to dabigatran and rivaroxaban. The others are more selective for dabigatran or rivaroxaban. These differences can be due to the wide variation in the amount of factors II, VII, IX and X, of antithrombotic proteins (proteins C and S) and also of anticoagulants, such as heparin and antithrombin, among the different PCCs. For the 3F-PCCs, two of them were able to normalize increased bleeding time following dabigatran administration, but the effect was short-lasting in comparison with 4F-PCC. This can be explained by the smaller amount of FVII in 3F-PCCs and its short half-life compared with the other factors. Activated PCCs seem to enhance more the parameters of thrombin generation to supratherapeutic levels than nonactivated PCCs, but it may be consequently at greater risk of thrombosis. Thrombin generation appears to have the best predictive value in the reversal of NOAC’s anticoagulant effect.
Anyway, even if some PCCs seem promising in reversing anticoagulation due to NOACs, their effectiveness needs still to be studied in bleeding human patients .
Piccini et al. analyzed the management and outcomes of major bleeding events in patients treated with rivaroxaban versus warfarin, using data from the ROCKET AF trial . Among high-risk patients with AF who experienced major bleeding, there was a reduction in fresh frozen plasma and PCC’s use in the rivaroxaban group compared with the warfarin group .
Other alternatives exist to treat major bleedings in patients who do not respond to supportive measures. For dabigatran, due to its important renal excretion, hemodialysis can be proposed but with limited clinical experience [94–96]. Hemodialysis can also be discussed if a patient has renal insufficiency and needs an emergent surgery that cannot be delayed .
If NOAC’s intake is recent, oral activated charcoal may also be effective .
Different specific antidotes are currently under evaluation. For DE, the antidote is a humanized selective and specific monoclonal antibody fragment (aDabi-Fab), which has no effect on other molecules. A recent study compared its ex vivo reversal effect with PCC, aPCC, and rFVIIa in a dabigatran anticoagulated liver trauma experimental model. Coagulation was assessed by thromboelastometry (TEM), global coagulation assays and diluted thrombin time. Interestingly, rFVIIa (90 and 180 microgrammes/kg) had no significant effect on coagulation parameters, but aDabi-Fab (60 and 120 mg/kg), PCC and aPCC (30 and 60 IU/kg) were effective in reducing the anticoagulation effects of dabigatran (TEM parameters and PT). In contrast, aDabi-Fab was the only reversal agent that normalized aPTT .
Andexanet alpha (PRT064445), a truncated form of enzymatically inactive factor Xa, is a universal reversal agent for all anti-Xa inhibitors. It reverses the inhibition of factor Xa dose-dependently, correcting the prolonged ex vivo clotting times due to anti-Xa inhibitors [98, 99].
Another antidote currently under research is aripazine (PER977), a small synthetic molecule that bounds several NOACs in animal studies, without significant adverse events. It reverses the anticoagulant activity of all clinically used NOACs in the rat-tail injury model and also in a human ex vivo model, using aPTT and anti-Xa analysis to measure its reversal effect [98, 99].
In the absence of specific antidotes, it is important to assess the degree of emergency and the patient characteristics (which type of NOAC, timing of the last dose, drugs interactions, comorbidities, site of bleeding, etc.) . If possible, delay the surgery until the NOAC reaches trough concentration.
A hospital-wide policy for the management of NOAC’s related bleedings should be easily accessible for every health worker involved in the patient’s care.
NOACs are indisputably an important step forward in the field of anticoagulation. However, an inappropriate use can possibly lead to a higher risk of bleeding. This highlights the importance of strengthening education of health care professionals and patients, that is, with regard to dose adjustment, modalities of administration, choice of anticoagulant, and compliance guidance. Modifiable bleeding risk factors should also be screened and reviewed before initiation of NOACs. Individual benefit-risk might be improved in some clinical settings or patient subpopulations (patients at risk of supra- or infratherapeutic plasma level) by tailoring a dose following coagulation monitoring. Adherence to switching, bridging, resuming, and anesthetic recommendations is crucial to allow an optimal management of patient.
Anticoagulation with NOACs has still risks and requires strong adherence from the patient’s side and careful supervision from the physician’s side. Furthermore, since February 2012, the EMA has imposed the development of an education pack for patients and prescribers with regard to the safety and effectiveness of NOACs.
A well-structured organization will help to improve the control on side effects, tolerance, and adherence.
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publication of this paper.
Lessire Sarah, Dincq Anne-Sophie, Gourdin Maximilien, and Mullier François contributed equally.
- S. Husted, R. De Caterina, F. Andreotti, et al., “Non-vitamin K antagonist oral anticoagulants (NOACs): no longer new or novel,” Journal of Thrombosis and Haemostasis, vol. 111, no. 5, 2014.
- M. R. Lassen, A. Gallus, G. E. Raskob, G. Pineo, D. Chen, and L. M. Ramirez, “Apixaban versus enoxaparin for thromboprophylaxis after hip replacement,” The New England Journal of Medicine, vol. 363, no. 26, pp. 2487–2498, 2010.
- M. R. Lassen, G. E. Raskob, A. Gallus, G. Pineo, D. Chen, and P. Hornick, “Apixaban versus enoxaparin for thromboprophylaxis after knee replacement (ADVANCE-2): a randomised double-blind trial,” The Lancet, vol. 375, no. 9717, pp. 807–815, 2010.
- M. R. Lassen, G. E. Raskob, A. Gallus, G. Pineo, D. Chen, and R. J. Portman, “Apixaban or enoxaparin for thromboprophylaxis after knee replacement,” The New England Journal of Medicine, vol. 361, no. 6, pp. 594–604, 2009.
- B. I. Eriksson, O. E. Dahl, M. H. Huo et al., “Oral dabigatran versus enoxaparin for thromboprophylaxis after primary total hip arthroplasty (RE-NOVATE II): a randomised, double-blind, non-inferiority trial,” Thrombosis and Haemostasis, vol. 105, no. 4, pp. 721–729, 2011.
- B. I. Eriksson, O. E. Dahl, N. Rosencher et al., “Oral dabigatran etexilate vs. subcutaneous enoxaparin for the prevention of venous thromboembolism after total knee replacement: the RE-MODEL randomized trial,” Journal of Thrombosis and Haemostasis, vol. 5, no. 11, pp. 2178–2185, 2007.
- B. I. Eriksson, O. E. Dahl, N. Rosencher et al., “Dabigatran etexilate versus enoxaparin for prevention of venous thromboembolism after total hip replacement: a randomised, double-blind, non-inferiority trial,” The Lancet, vol. 370, no. 9591, pp. 949–956, 2007.
- B. I. Eriksson, L. C. Borris, R. J. Friedman et al., “Rivaroxaban versus enoxaparin for thromboprophylaxis after hip arthroplasty,” The New England Journal of Medicine, vol. 358, no. 26, pp. 2765–2775, 2008.
- A. K. Kakkar, B. Brenner, O. E. Dahl et al., “Extended duration rivaroxaban versus short-term enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a double-blind, randomised controlled trial,” The Lancet, vol. 372, no. 9632, pp. 31–39, 2008.
- M. R. Lassen, W. Ageno, L. C. Borris et al., “Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty,” The New England Journal of Medicine, vol. 358, no. 26, pp. 2776–2786, 2008.
- A. G. Turpie, M. R. Lassen, B. L. Davidson et al., “Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty (RECORD4): a randomised trial,” The Lancet, vol. 373, no. 9676, pp. 1673–1680, 2009.
- C. B. Granger, J. H. Alexander, J. J. McMurray, et al., “Apixaban versus warfarin in patients with atrial fibrillation,” The New England Journal of Medicine, vol. 365, pp. 981–992, 2011.
- M. Barry, “Dabigatran versus warfarin in patients with atrial fibrillation,” The New England Journal of Medicine, vol. 361, no. 27, p. 2674, 2009.
- M. R. Patel, K. W. Mahaffey, J. Garg et al., “Rivaroxaban versus warfarin in nonvalvular atrial fibrillation,” The New England Journal of Medicine, vol. 365, no. 10, pp. 883–891, 2011.
- E. Investigators, R. Bauersachs, S. D. Berkowitz, et al., “Oral rivaroxaban for symptomatic venous thromboembolism,” The New England Journal of Medicine, vol. 363, pp. 2499–2510, 2010.
- H. R. Büller, M. H. Prins, A. W. A. Lensing et al., “Oral rivaroxaban for the treatment of symptomatic pulmonary embolism,” The New England Journal of Medicine, vol. 366, no. 14, pp. 1287–1297, 2012.
- J. Mega, E. Braunwald, S. Mohanavelu et al., “Rivaroxaban versus placebo in patients with acute coronary syndromes (ATLAS ACS-TIMI 46): a randomised, double-blind, phase II trial,” The Lancet, vol. 374, no. 9683, pp. 29–38, 2009.
- J. L. Mega, E. Braunwald, S. D. Wiviott, et al., “Rivaroxaban in patients with a recent acute coronary syndrome,” The New England Journal of Medicine, vol. 366, pp. 9–19, 2012.
- E. M. Hylek, C. Held, J. H. Alexander, et al., “Major bleeding in patients with atrial fibrillation receiving apixaban or warfarin in the ARISTOTLE trial: predictors, characteristics, and clinical outcomes,” Journal of the American College of Cardiology, 2014.
- J. Harenberg, S. Marx, O. E. Dahl, et al., “Interpretation of endpoints in a network meta-analysis of new oral anticoagulants following total hip or total knee replacement surgery,” Thrombosis and Haemostasis, vol. 108, pp. 903–912, 2012.
- M. R. Southworth, M. E. Reichman, and E. F. Unger, “Dabigatran and postmarketing reports of bleeding,” The New England Journal of Medicine, vol. 368, pp. 1272–1274, 2013.
- C. Frost, S. Nepal, J. Wang, et al., “Safety, pharmacokinetics and pharmacodynamics of multiple oral doses of apixaban, a factor Xa inhibitor, in healthy subjects,” British Journal of Clinical Pharmacology, vol. 76, pp. 776–786, 2013.
- W. Mueck, J. Stampfuss, D. Kubitza, and M. Becka, “Clinical pharmacokinetic and pharmacodynamic profile of rivaroxaban,” Clinical Pharmacokinetics, vol. 53, pp. 1–16, 2014.
- J. Stangier and A. Clemens, “Pharmacology, pharmacokinetics, and pharmacodynamics of dabigatran etexilate, an oral direct thrombin inhibitor,” Clinical and Applied Thrombosis/Hemostasis, vol. 15, supplement 1, pp. 9S–16S, 2009.
- A. Tamigniau, J. Douxfils, J. B. Nicolas, et al., “Why, when and how to monitor new oral anticoagulants,” Revue Médicale Suisse, vol. 10, pp. 326–333, 2014.
- H. Heidbuchel, P. Verhamme, M. Alings, et al., “European Heart Rhythm Association Practical Guide on the use of new oral anticoagulants in patients with non-valvular atrial fibrillation,” Europace, vol. 15, pp. 625–651, 2013.
- E. Nutescu, I. Chuatrisorn, and E. Hellenbart, “Drug and dietary interactions of warfarin and novel oral anticoagulants: an update,” Journal of Thrombosis and Thrombolysis, vol. 31, no. 3, pp. 326–343, 2011.
- J. M. Walenga and C. Adiguzel, “Drug and dietary interactions of the new and emerging oral anticoagulants,” International Journal of Clinical Practice, vol. 64, no. 7, pp. 956–967, 2010.
- G. Pernod, P. Albaladejo, A. Godier, et al., “Management of major bleeding complications and emergency surgery in patients on long-term treatment with direct oral anticoagulants, thrombin or factor-Xa inhibitors: proposals of the working group on perioperative haemostasis (GIHP)—March 2013,” Archives of Cardiovascular Diseases, vol. 106, pp. 382–393, 2013.
- R. De Caterina, S. Husted, L. Wallentin, et al., “Vitamin K antagonists in heart disease: current status and perspectives (Section III). Position paper of the ESC Working Group on Thrombosis—task Force on Anticoagulants in Heart Disease,” Thrombosis and Haemostasis, vol. 110, pp. 1087–1107, 2013.
- L. Poller, J. Jespersen, S. Ibrahim, and A. Pattison, “European Action on A. Phase III studies on novel oral anticoagulants for stroke prevention in atrial fibrillation: a look beyond the excellent results: a rebuttal,” Journal of Thrombosis and Haemostasis, vol. 11, pp. 1203–1205, 2013.
- J. Desai, J. M. Kolb, J. I. Weitz, and J. Aisenberg, “Gastrointestinal bleeding with the new oral anticoagulants—defining the issues and the management strategies,” Thrombosis and Haemostasis, vol. 110, pp. 205–212, 2013.
- “Pradaxa-H-C-829-X-13: ePAR—assessment Report—extension,” 2011, http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Assessment_Report_-_Variation/human/000829/WC500110875.pdf.
- K. W. McConeghy, A. Bress, D. M. Qato, C. Wing, and E. A. Nutescu, “Evaluation of dabigatran bleeding adverse reaction reports in the FDA adverse event reporting system during the first year of approval,” Pharmacotherapy, 2014.
- J. W. Eikelboom, L. Wallentin, S. J. Connolly et al., “Risk of bleeding with 2 doses of dabigatran compared with warfarin in older and younger patients with atrial fibrillation: an analysis of the randomized evaluation of long-term anticoagulant therapy (RE-LY) Trial,” Circulation, vol. 123, no. 21, pp. 2363–2372, 2011.
- K. Kirley, D. M. Qato, R. Kornfield, R. S. Stafford, and G. C. Alexander, “National trends in oral anticoagulant use in the United States, 2007 to 2011,” Circulation Cardiovascular Quality and Outcomes, vol. 5, pp. 615–621, 2012.
- S. L. Lim and E. Maxwell, “An audit of dabigatran etexilate prescribing in Victoria,” Medical Journal of Australia, vol. 198, pp. 314–315, 2013.
- R. Sorensen, G. Gislason, C. Torp-Pedersen, et al., “Dabigatran use in Danish atrial fibrillation patients in 2011: a Nationwide Study,” BMJ Open, vol. 3, article e002758, 2013.
- B. Carley, S. Griesbach, T. Larson, and K. Krueger, “Assessment of dabigatran utilization and prescribing patterns for atrial fibrillation in a physician group practice setting,” The American Journal of Cardiology, vol. 113, pp. 650–654, 2014.
- C. Escobar and V. Barrios, “Dabigatran and bleeding risk: the importance of a correct prescription,” The Journal of Emergency Medicine, 2013.
- A. Troncoso and E. Diogene, “Dabigatran and rivaroxaban prescription for atrial fibrillation in Catalonia, Spain: the need to manage the introduction of new drugs,” European Journal of Clinical Pharmacology, vol. 70, pp. 249–250, 2014.
- “European Medicine Agency—xarelto: summary of Product Characteristics,” 2013, http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Product_Information/human/000944/WC500057108.pdf.
- “European Medicine Agency—pradaxa: summary of Product Characteristics,” 2013, http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Product_Information/human/000829/WC500041059.pdf.
- “European Medicine Agency—eliquis: summary of Product Characteristics,” 2014, http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Product_Information/human/002148/WC500107728.pdf.
- W. Pfeilschifter, S. Luger, R. Brunkhorst, E. Lindhoff-Last, and C. Foerch, “The gap between trial data and clinical practice—an analysis of case reports on bleeding complications occurring under dabigatran and rivaroxaban anticoagulation,” Cerebrovascular Disease, vol. 36, pp. 115–119, 2013.
- A. Hellden, I. Odar-Cederlof, G. Nilsson, et al., “Renal function estimations and dose recommendations for dabigatran, gabapentin and valaciclovir: a data simulation study focused on the elderly,” BMJ Open, vol. 3, article e002686, 2013.
- P. K. Maccallum, R. Mathur, S. A. Hull, et al., “Patient safety and estimation of renal function in patients prescribed new oral anticoagulants for stroke prevention in atrial fibrillation: a Cross-Sectional Study,” BMJ Open, vol. 3, article e003343, 2013.
- K. Moore, S. Vaidyanathan, C. Damaraju, and L. Fields, “The relative bioavailability of single-dose rivaroxaban, a novel oral anticoagulant and a selective direct factor Xa inhibitor, administered orally (as a whole or crushed tablet) and via nasogastric tube (as a crushed tablet suspension),” Pharmacotherapy, vol. 32, article 2, 2012.
- J. P. Patel, L. N. Roberts, and R. Arya, “Anticoagulating obese patients in the modern era,” British Journal of Haematology, vol. 155, no. 2, pp. 137–149, 2011.
- “Pradaxa: full Prescribing Information,” 2013, http://www.accessdata.fda.gov/drugsatfda_docs/label/2013/022512s017lbl.pdf.
- D. Kubitza, M. Becka, M. Zuehlsdorf, and W. Mueck, “Body weight has limited influence on the safety, tolerability, pharmacokinetics, or pharmacodynamics of rivaroxaban (BAY 59-7939) in healthy subjects,” Journal of Clinical Pharmacology, vol. 47, no. 2, pp. 218–226, 2007.
- W. Mueck, B. I. Eriksson, K. A. Bauer et al., “Population pharmacokinetics and pharmacodynamics of rivaroxaban—an oral, direct factor Xa inhibitor—in patients undergoing major orthopaedic surgery,” Clinical Pharmacokinetics, vol. 47, no. 3, pp. 203–216, 2008.
- V. V. Upreti, J. Wang, Y. C. Barrett, et al., “Effect of extremes of body weight on the pharmacokinetics, pharmacodynamics, safety and tolerability of apixaban in healthy subjects,” British Journal of Clinical Pharmacology, vol. 76, pp. 908–916, 2013.
- “Food and Drug Administration—eliquis: full Prescribing Information,” 2014, http://www.accessdata.fda.gov/drugsatfda_docs/label/2012/202155s000lbl.pdf.
- “Food and drug Administration—eliquis: clinical Pharmacology & Biopharmaceutical Review(s),” 2014, http://www.accessdata.fda.gov/drugsatfda_docs/nda/2012/202155Orig1s000ClinPharmR.pdf.
- J. Stangier, H. Stähle, K. Rathgen, W. Roth, and K. Shakeri-Nejad, “Pharmacokinetics and pharmacodynamics of dabigatran etexilate, an oral direct thrombin inhibitor, are not affected by moderate hepatic impairment,” Journal of Clinical Pharmacology, vol. 48, no. 12, pp. 1411–1419, 2008.
- J. Graff and S. Harder, “Anticoagulant therapy with the oral direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban and the thrombin inhibitor dabigatran etexilate in patients with hepatic impairment,” Clinical Pharmacokinetics, vol. 52, pp. 243–254, 2013.
- D. Kubitza, A. Roth, M. Becka, et al., “Effect of hepatic impairment on the pharmacokinetics and pharmacodynamics of a single dose of rivaroxaban, an oral, direct Factor Xa inhibitor,” British Journal of Clinical Pharmacology, vol. 76, pp. 89–98, 2013.
- C. E. Frost, Z. Yu, J. Wang, et al., “Single-dose safety and pharmacokinetics of apixaban in subjects with mild or moderate hepatic impairment,” Clinical Pharmacology & Therapeutics, vol. 85, supplement 1, article PI-84, p. S34, 2009.
- F. Rodeghiero, A. Tosetto, T. Abshire et al., “ISTH/SSC bleeding assessment tool: a standardized questionnaire and a proposal for a new bleeding score for inherited bleeding disorders,” Journal of Thrombosis and Haemostasis, vol. 8, no. 9, pp. 2063–2065, 2010.
- S. Apostolakis, D. A. Lane, H. Buller, and G. Y. Lip, “Comparison of the CHADS2, CHA2DS2-VASc and HAS-BLED scores for the prediction of clinically relevant bleeding in anticoagulated patients with atrial fibrillation: the AMADEUS trial,” Thrombosis and Haemostasis, vol. 110, pp. 1074–1079, 2013.
- S. Burgess, N. Crown, M. L. Louzada, G. Dresser, R. B. Kim, and A. Lazo-Langner, “Clinical performance of bleeding risk scores for predicting major and clinically relevant non-major bleeding events in patients receiving warfarin,” Journal of Thrombosis and Haemostasis, vol. 11, pp. 1647–1654, 2013.
- P. A. Reilly, T. Lehr, S. Haertter, et al., “The effect of dabigatran plasma concentrations and patient characteristics on the frequency of ischemic stroke and major bleeding in atrial fibrillation patients: the RE-LY Trial (Randomized Evaluation of Long-Term Anticoagulation Therapy),” Journal of the American College of Cardiology, vol. 63, pp. 321–328, 2014.
- H. Ten Cate, “Monitoring new oral anticoagulants, managing thrombosis, or both?” Thrombosis and Haemostasis, vol. 107, no. 5, pp. 803–805, 2012.
- K.-H. Liesenfeld, T. Lehr, C. Dansirikul et al., “Population pharmacokinetic analysis of the oral thrombin inhibitor dabigatran etexilate in patients with non-valvular atrial fibrillation from the RE-LY trial,” Journal of Thrombosis and Haemostasis, vol. 9, no. 11, pp. 2168–2175, 2011.
- G. Freyburger, G. MacOuillard, S. Labrouche, and F. Sztark, “Coagulation parameters in patients receiving dabigatran etexilate or rivaroxaban: two observational studies in patients undergoing total hip or total knee replacement,” Thrombosis Research, vol. 127, no. 5, pp. 457–465, 2011.
- H. Mani and E. Lindhoff-Last, “Main considerable factors for correct laboratory test interpretation under DOA treatment,” Thrombosis Journal, vol. 11, article 22, 2013.
- M. M. Samama, “Coagulation Assays in Patients with New Oral Anticoagulants (NOACs): why? When?” Drug Development Research, vol. 74, article 7, 2013.
- H. Ten Cate, “New oral anticoagulants: discussion on monitoring and adherence should start now!,” Thrombosis Journal, vol. 11, article 8, 2013.
- T. Baglin, D. Keeling, and S. Kitchen, “Effects on routine coagulation screens and assessment of anticoagulant intensity in patients taking oral dabigatran or rivaroxaban: guidance from the British Committee for Standards in Haematology,” British Journal of Haematology, vol. 159, pp. 427–429, 2012.
- A. G. Turpie, R. Kreutz, J. Llau, B. Norrving, and S. Haas, “Management consensus guidance for the use of rivaroxaban—an oral, direct factor Xa inhibitor,” Thrombosis and Haemostasis, vol. 108, pp. 876–886, 2012.
- T. Baglin, A. Hillarp, A. Tripodi, I. Elalamy, H. Buller, and W. Ageno, “Measuring Oral Direct Inhibitors (ODIs) of thrombin and factor Xa: a recommendation from the Subcommittee on Control of Anticoagulation of the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis,” Journal of Thrombosis and Haemostasis, 2013.
- Y. C. Barrett, J. Wang, Y. Song et al., “A randomised assessment of the pharmacokinetic, pharmacodynamic and safety interaction between apixaban and enoxaparin in healthy subjects,” Thrombosis and Haemostasis, vol. 107, no. 5, pp. 916–924, 2012.
- J. Douxfils, F. Mullier, S. Robert, C. Chatelain, B. Chatelain, and J.-M. Dogné, “Impact of dabigatran on a large panel of routine or specific coagulation assays: laboratory recommendations for monitoring of dabigatran etexilate,” Thrombosis and Haemostasis, vol. 107, no. 5, pp. 985–997, 2012.
- J. Douxfils, C. Chatelain, B. Chatelain, J.-M. Dogné, and F. Mullier, “Impact of apixaban on routine and specific coagulation assays: a practical laboratory guide,” Thrombosis and Haemostasis, vol. 110, pp. 283–294, 2013.
- J. Douxfils, A. Tamigniau, B. Chatelain, et al., “Comparison of calibrated chromogenic anti-Xa assay and PT tests with LC-MS/MS for the therapeutic monitoring of patients treated with rivaroxaban,” Thrombosis and Haemostasis, vol. 110, pp. 723–731, 2013.
- M. V. Huisman, G. Y. H. Lip, H.-C. Diener, M. Brueckmann, J. Van Ryn, and A. Clemens, “Dabigatran etexilate for stroke prevention in patients with atrial fibrillation: resolving uncertainties in routine practice,” Thrombosis and Haemostasis, vol. 107, no. 5, pp. 838–847, 2012.
- T. H. Baron, P. S. Kamath, and R. D. McBane, “Management of antithrombotic therapy in patients undergoing invasive procedures,” The New England Journal of Medicine, vol. 368, pp. 2113–2124, 2013.
- S. A. Kozek-Langenecker, “Perioperative management issues of direct oral anticoagulants,” Seminars in Hematology, 2014.
- A. Liew and J. Douketis, “Perioperative management of patients who are receiving a novel oral anticoagulant,” Internal and Emergency Medicine, vol. 8, pp. 477–484, 2013.
- P. Sié, C. M. Samama, A. Godier et al., “Surgery and invasive procedures in patients on long-term treatment with direct oral anticoagulants: thrombin or factor-Xa inhibitors. Recommendations of the Working Group on perioperative haemostasis and the French Study Group on thrombosis and haemostasis,” Archives of Cardiovascular Diseases, vol. 104, no. 12, pp. 669–676, 2011.
- A. C. Spyropoulos and J. D. Douketis, “How I treat anticoagulated patients undergoing an elective procedure or surgery,” Blood, vol. 120, pp. 2954–2962, 2012.
- J. Beyer-Westendorf, V. Gelbricht, K. Forster, et al., “Peri-interventional management of novel oral anticoagulants in daily care: results from the prospective Dresden NOAC registry,” European Heart Journal, 2014.
- W. Gogarten, E. Vandermeulen, H. Van Aken, S. Kozek, J. V. Llau, and C. M. Samama, “Regional anaesthesia and antithrombotic agents: recommendations of the European Society of Anaesthesiology,” European Journal of Anaesthesiology, vol. 27, no. 12, pp. 999–1015, 2010.
- J. H. Levy, D. Faraoni, J. L. Spring, J. D. Douketis, and C. M. Samama, “Managing new oral anticoagulants in the perioperative and intensive care unit setting,” Anesthesiology, vol. 118, pp. 1466–1474, 2013.
- J. V. Llau and R. Ferrandis, “New anticoagulants and regional anesthesia,” Current Opinion in Anaesthesiology, vol. 22, no. 5, pp. 661–666, 2009.
- N. Rosencher, M.-P. Bonnet, and D. I. Sessler, “Selected new antithrombotic agents and neuraxial anaesthesia for major orthopaedic surgery: management strategies,” Anaesthesia, vol. 62, no. 11, pp. 1154–1160, 2007.
- S. Kaatz and M. Crowther, “Reversal of target-specific oral anticoagulants,” Journal of Thrombosis and Thrombolysis, vol. 36, pp. 195–202, 2013.
- S. Kaatz, P. A. Kouides, D. A. Garcia et al., “Guidance on the emergent reversal of oral thrombin and factor Xa inhibitors,” American Journal of Hematology, vol. 87, no. 1, pp. S141–S145, 2012.
- D. M. Siegal, D. A. Garcia, and M. A. Crowther, “How I treat target-specific oral anticoagulant-associated bleeding,” Blood, vol. 123, pp. 1152–1158, 2014.
- A. Majeed, H. G. Hwang, S. J. Connolly, et al., “Management and outcomes of major bleeding during treatment with dabigatran or warfarin,” Circulation, vol. 128, pp. 2325–2332, 2013.
- G. Dickneite and M. Hoffman, “Reversing the new oral anticoagulants with prothrombin complex concentrates (PCCs): what is the evidence?” Thrombosis and Haemostasis, vol. 111, pp. 189–198, 2014.
- J. P. Piccini, J. Garg, M. R. Patel, et al., “Management of major bleeding events in patients treated with rivaroxaban vs. warfarin: results from the ROCKET AF trial,” European Heart Journal, 2014.
- J. Van Ryn, J. Stangier, S. Haertter et al., “Dabigatran etexilate—a novel, reversible, oral direct thrombin inhibitor: interpretation of coagulation assays and reversal of anticoagulant activity,” Thrombosis and Haemostasis, vol. 103, no. 6, pp. 1116–1127, 2010.
- M. R. Wanek, E. T. Horn, S. Elapavaluru, S. C. Baroody, and G. Sokos, “Safe use of hemodialysis for dabigatran removal before cardiac surgery,” Annals of Pharmacotherapy, vol. 46, article e21, 2012.
- T. E. Warkentin, P. Margetts, S. J. Connolly, A. Lamy, C. Ricci, and J. W. Eikelboom, “Recombinant factor VIIa (rFVIIa) and hemodialysis to manage massive dabigatran-associated postcardiac surgery bleeding,” Blood, vol. 119, no. 9, pp. 2172–2174, 2012.
- O. Grottke, J. van Ryn, H. M. Spronk, and R. Rossaint, “Prothrombin complex concentrates and a specific antidote to dabigatran are effective ex-vivo in reversing the effects of dabigatran in an anticoagulation/liver trauma experimental model,” Critical Care, vol. 18, article R27, 2014.
- G. Lu, F. R. DeGuzman, S. J. Hollenbach, et al., “A specific antidote for reversal of anticoagulation by direct and indirect inhibitors of coagulation factor Xa,” Nature Medicine, vol. 19, pp. 446–451, 2013.
- C. Ward, G. Conner, G. Donnan, A. Gallus, and S. McRae, “Practical management of patients on apixaban: a consensus guide,” Thrombosis Journal, vol. 11, article 27, 2013.
- A. Majeed and S. Schulman, “Bleeding and antidotes in new oral anticoagulants,” Best Practice & Research Clinical Haematology, vol. 26, pp. 191–202, 2013.