Reversal of drug-induced anticoagulation: old solutions and new problems

How do I manage a blood product shortage?

BACKGROUND

The demand for blood products sometimes exceeds the available inventory. Blood product inventories are dependent upon the availability of donors, supplies and reagents, and collection staff. During prolonged extreme shortages, blood centers and transfusion services must alter practices to meet the needs of patients.

STUDY DESIGN AND METHODS

The Association for the Advancement of Blood and Biotherapies Donor and Blood Component Management Subsection compiled some strategies from its blood center and hospital transfusion service members that could be implemented during blood product shortages.

RESULTS

Some strategies that blood centers could use to increase their available inventories include increasing donor recruitment efforts, using alternate types of collection kits, manufacturing low-yield apheresis-derived platelets and/or whole blood-derived platelets, using cold-stored platelets, transferring inventory internally among centers of the same enterprise, using frozen inventory, decreasing standing order quantities, prioritizing allocation to certain patient populations, filling partial orders, and educating customers and blood center staff. Transfusion service strategies that could be implemented to maximize the use of the limited available inventory include increasing patient blood management efforts, using split units, finding alternate blood suppliers, trading blood products with other hospital transfusion services, developing a patient priority list, assembling a hospital committee to decide on triaging priorities, using expired products in extreme situations, and accepting nonconforming products after performing safety checks.

DISCUSSION

Blood centers and transfusion services must choose the appropriate strategies to implement based on their needs.

Advances in symptomatic therapy for left ventricular non-compaction in children

Left ventricular non-compaction is a complex cardiomyopathy and the third largest childhood cardiomyopathy, for which limited knowledge is available. Both pathogenesis and prognosis are still under investigation. Currently, no effective treatment strategy exists to reduce its incidence or severity, and symptomatic treatment is the only clinical treatment strategy. Treatment strategies are constantly explored in clinical practice, and some progress has been made in coping with the corresponding symptoms because the prognosis of children with left ventricular non-compaction is usually poor if there are complications. In this review, we summarized and discussed the coping methods for different left ventricular non-compaction symptoms.

Application of fresh frozen plasma transfusion in the management of excessive warfarin-associated anticoagulation

Warfarin is a commonly used oral anticoagulant. Patients with artificial valve replacement, atrial fibrillation, pulmonary embolism, deep vein thrombosis, and other diseases require long-term anticoagulant oral treatment with warfarin. As warfarin exhibits prompt action with long maintenance time, it has become a key drug for the treatment of patients at risk of developing thrombosis or thromboembolism. Warfarin is a bican coumarin anticoagulant, that exhibits competitive action against vitamin K as its mechanism of action, thereby inhibiting the synthesis of coagulation factors—predominantly the vitamin K-dependent coagulation factors II, VII, IX, and X—in hepatocytes. Long-term warfarin is known to significantly increase the risk of organ bleeding in some patients, while some patients may need to reverse the anticoagulation effect. For instance, patients scheduled for emergency or invasive surgery may require rapid anticoagulation reversal. During such medical circumstances, fresh frozen plasma (FFP) is clinically used for the reversal of excess warfarin-associated anticoagulation, as it contains all the coagulation factors that can alleviate the abnormal blood anticoagulation status in such patients. Accordingly, this article aims to perform an in-depth review of relevant literature on the reversal of warfarin with FFP, and insightful deliberation of the application and efficacy of this clinical intervention.

Plasma trial: Pilot randomized clinical trial to determine safety and efficacy of plasma transfusions

BACKGROUND

Plasma is frequently administered to patients with prolonged INR prior to invasive procedures. However, there is limited evidence evaluating efficacy and safety.

STUDY DESIGN AND METHODS

We performed a pilot trial in hospitalized patients with INR between 1.5 and 2.5 undergoing procedures conducted outside the operating room. We excluded patients undergoing procedures proximal to the central nervous system, platelet counts <40,000/μl, or congenital or acquired coagulation disorders unresponsive to plasma. We randomly allocated patients stratified by hospital and history of cirrhosis to receive plasma transfusion (10-15 cc/kg) or no transfusion. The primary outcome was change in hemoglobin concentration within 2 days of procedure.

RESULTS

We enrolled 57 patients, mean age 56.0, 34 (59.6%) with cirrhosis, and mean INR 1.92 (SD = 0.27). In the intention to treat analysis, there were 10 of 27 (38.5%) participants in the plasma arm with a post procedure INR <1.5 and one of 30 (3.6%) in the no treatment arm (p < .01). The mean INR after receiving plasma transfusion was -0.24 (SD 0.26) lower than baseline. The change from pre-procedure hemoglobin level to lowest level within 2 days was -0.6 (SD = 1.0) in the plasma transfusion arm and -0.4 (SD = 0.6) in the no transfusion arm (p = .29). Adverse outcomes were uncommon.

DISCUSSION

We found no differences in change in hemoglobin concentration in those treated with plasma compared to no treatment. The change in INR was small and corrected to less than 1.5 in minority of patients. Large trials are required to establish if plasma is safe and efficacious.

Clinical protocols for oral anticoagulant reversal during high risk of bleeding for emergency surgical and nonsurgical settings: a narrative review

Background and objectives

Oral anticoagulants prevent thromboembolic events but expose patients to a significant risk of bleeding due to the treatment itself, after trauma, or during surgery. Any physician working in the emergency department or involved in the perioperative care of a patient should be aware of the best reversal approach according to the type of drug and the patient’s clinical condition. This paper presents a concise review and proposes clinical protocols for the reversal of oral anticoagulants in emergency settings, such as bleeding or surgery.

Contents

The authors searched for relevant studies in PubMed, LILACS, and the Cochrane Library database and identified 82 articles published up to September 2020 to generate a review and algorithms as clinical protocols for practical use. Hemodynamic status and the implementation of general supportive measures should be the first approach under emergency conditions. The drug type, dose, time of last intake, and laboratory evaluations of anticoagulant activity and renal function provide an estimation of drug clearance and should be taken into consideration. The reversal agents for vitamin K antagonists are 4-factor prothrombin complex concentrate and vitamin K, followed by fresh frozen plasma as a second-line treatment. Direct oral anticoagulants have specific reversal agents, such as andexanet alfa and idarucizumab, but are not widely available. Another possibility in this situation, but with less evidence, is prothrombin complex concentrates.

Conclusion

The present algorithms propose a tool to help healthcare providers in the best decision making for patients under emergency conditions.

Effect of switching from acenocoumarol to phenprocoumon on time in therapeutic range and INR variability: A cohort study

Background

Treatment with vitamin K antagonists (VKA) requires a high proportion of time in the therapeutic range (TTR) and a low international normalised ratio (INR) variability to be maximally safe and effective. Switching from short-acting acenocoumarol to long-acting phenprocoumon could improve VKA control.

Aims

We assessed whether switching from acenocoumarol to phenprocoumon improves the time in the therapeutic range (TTR) and INR variability.

Methods and results

In a retrospective cohort with data on 236,957 patients-years of VKA management from two first-line anticoagulation clinics in the Netherlands, we identified 124 patients in target range 2–3, 269 patients in target range 2–3.5 and 98 patients in target range 2.5–3.5 who switched from acenocoumarol to phenprocoumon. They were matched in a 1:2 ratio to non-switching controls using propensity score matching. Over the first 180 days after a switch, switchers’ TTR declined 5 (95% CI 1 to 10), 10 (95% CI 7 to 13) and 5 (95% CI 0 to 11) percentage points relative to non-switchers, in target ranges 2–3, 2–3.5 and 2.5–3.5. Anticoagulation was more often supra-therapeutic in switchers, and switchers had a higher INR variability. In the following 180 days, TTR in switchers became 1 (95% CI -4 to 6), 4 (95% CI 0 to 7) and 6 (95% CI 1 to 12) percentage points better than in non-switchers. Switchers’ INRs were much more stable than non-switchers’.

Conclusion

Eventually, a switch from acenocoumarol to phenprocoumon leads to a higher TTR and a lower INR variability. However, this is preceded by a transition period with opposite effects. An improved conversion algorithm could possibly shorten the transition period. Until then, physicians and patients should decide whether switching is worth the increased risk during the transition phase.

Antiplatelets, anticoagulants, and colonoscopic polypectomy

The management of antiplatelet and anticoagulant (ie, antithrombotic) agents is challenging in the periendoscopic setting. In this state-of-the-art update, we review current best practice recommendations focusing on the risk of immediate and delayed postpolypectomy bleeding in the context of drug discontinuation (ie, temporary interruption) and drug continuation. The data regarding polypectomy technique (cold snare vs conventional thermal-based) and prophylactic placement of hemostatic clips are evaluated to assess whether these endoscopic techniques are beneficial in reducing postpolypectomy bleeding. Finally, clinical takeaways are provided to facilitate safer polypectomy among patients on antiplatelet and anticoagulant agents.

Optimization of fibrinogenolytic activity of Solanum tuberosum subtilisin-like protease (StSBTc-3) by response surface methodology

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StSBTc-3 activity is optimized using response surface methodology.

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StSBTc-3 has fibrinogenolytic activity at physiological conditions.

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StSBTc-3 has potential use in biomedical devices.

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rsm package with R is a suitable tool to perform plant protease activity optimizations.

The aim of this study was to optimize in vitro conditions to enhance fibrinogenolytic activity of Solanum tuberosum subtilisin-like protease (StSBTc-3). The effects of StSTBc-3 concentration (0.2–5 μM), pH value (6–10) and temperature (35–50 °C) on fibrinogenolytic activity were studied through response surface methodology (RSM). We obtained a model that predicts the response accurately. The relationship between enzyme concentration and fibrinogenolytic activity was linear, while the main effect from pH and temperature on the response was quadratic. From the RSM generated model the optimum pH was 8 and the optimum temperature was 43 °C, while higher concentrations of enzyme produce higher activities.

Under optimum conditions there were no statistically significant differences between the experimental responses and the ones predicted from the model. This model also predicts the activity under physiological conditions. These results confirm that StSTBc-3 is a good candidate to be considered for therapeutic uses. The generated model will be useful for biotechnological purposes.

Idarucizumab, but not procoagulant concentrates, fully restores dabigatran-altered platelet and fibrin components of hemostasis

BACKGROUND

Comparative studies on the restoration of hemostasis with different reversal agents after dabigatran therapy have not been performed. We compared the efficacy and prothrombotic potential of the specific antidote idarucizumab with that of previously recommended non-specific procoagulant concentrates.

STUDY DESIGN AND METHODS

We explored the in vitro effects of dabigatran (184 ng/mL) on fibrin and platelet-aggregate formation onto a damaged vessel under flow conditions (600 s^-1 ). The reversal mechanisms and efficacy of idarucizumab (0.3-3 mg/mL) were compared with that of the non-specific procoagulant concentrates aPCC (25-75 U/Kg), PCC (70 U/Kg), or rFVIIa (120 μg/Kg). Generation of thrombin and prothrombin fragment (F1 + 2), and thromboelastometry parameters of clot formation were measured.

RESULTS

Dabigatran caused pronounced reductions in fibrin (87%) and platelet interactions (36%) with damaged vessels (p < 0.01) and significantly impaired thrombin generation and thromboelastometric parameters (delayed dynamics and reduced firmness). Idarucizumab completely normalized rates of fibrin and platelet coverage to baseline values in flow studies; and reversed the alterations in thrombin generation, F1 + 2 and thromboelastometry parameters produced by dabigatran. In comparison, aPCC and PCC only partially compensated for the dabigatran-induced alterations in fibrin deposition, but were unable to fully restore them to baseline values. Reversal with aPCC or PCC improved the majority of alterations in coagulation-related tests, but tended to overcompensate thrombin generation kinetics and significantly increased F1 + 2 levels.

CONCLUSION

Idarucizumab antagonizes alterations of direct and indirect biomarkers of hemostasis caused by dabigatran. In our studies, idarucizumab was clearly more efficacious than strategies with non-specific procoagulant concentrates and devoid of the excessive procoagulant tendency observed with the latter.

Management of patients on antithrombotic agents undergoing emergency and elective endoscopy: joint Asian Pacific Association of Gastroenterology (APAGE) and Asian Pacific Society for Digestive Endoscopy (APSDE) practice guidelines

This Guideline is a joint official statement of the Asian Pacific Association of Gastroenterology (APAGE) and the Asian Pacific Society for Digestive Endoscopy (APSDE). It was developed in response to the increasing use of antithrombotic agents (antiplatelet agents and anticoagulants) in patients undergoing gastrointestinal (GI) endoscopy in Asia. After reviewing current practice guidelines in Europe and the USA, the joint committee identified unmet needs, noticed inconsistencies, raised doubts about certain recommendations and recognised significant discrepancies in clinical practice between different regions. We developed this joint official statement based on a systematic review of the literature, critical appraisal of existing guidelines and expert consensus using a two-stage modified Delphi process. This joint APAGE-APSDE Practice Guideline is intended to be an educational tool that assists clinicians in improving care for patients on antithrombotics who require emergency or elective GI endoscopy in the Asian Pacific region.

Management of oral antiplatelet agents and anticoagulation therapy before bronchoscopy

Although, bronchoscopy is a relatively safe procedure, small amount of bleeding in the airway can have serious consequences. Careful consideration of the risks of diagnostic and therapeutic bronchoscopic intervention can help minimize potential complications. With increasing number of patients using antiplatelet and anticoagulation therapies, strategies for minimizing thromboembolic and operative bleeding events need to be included in the risk and benefit analyses. Growing evidence suggests that aspirin is safe and does not increase bleeding during bronchoscopy. In addition, despite small studies reporting that it may be safe to perform bronchoscopic procedures that have low risk for bleeding such as endobronchial ultrasound with transbronchial needle aspiration on clopidogrel, it is still recommended to hold it for 7 days prior to performing elective bronchoscopy. It is recommended to hold vitamin K antagonist, as well as new oral anticoagulation agents prior to bronchoscopy. The timing for pre-procedural discontinuation of anticoagulation therapy and the decision to bridge depend on the agent used, the renal function and the thromboembolic risk. In this review article, we will discuss available data regarding management of anticoagulation and antiplatelet therapy as it applies to bronchoscopic procedures.

Effect of direct oral anticoagulants on the risk of delayed bleeding after gastric endoscopic submucosal dissection

BACKGROUND AND AIM

Anticoagulants are used to prevent thromboembolic events. Direct oral anticoagulants (DOAC) are our new choice; however, their effect on bleeding risk for endoscopic treatment has not been reported. We aimed to assess the clinical effect of DOAC compared to warfarin for gastric endoscopic submucosal dissection (ESD).

METHODS

We retrospectively studied 97 patients on anticoagulants and treated 108 gastric neoplasms with ESD in three referral institutes. Twenty-four patients were taking DOAC, including dabigatran (12), rivaroxaban (11), and apixaban (one) and 73 were taking warfarin.

RESULTS

In the DOAC group, delayed bleeding rate was significantly higher in patients on rivaroxaban than in patients on dabigatran (45% vs 0%, P < 0.05) without relation to heparin bridge therapy (HBT). In the warfarin group, 78% of patients underwent HBT, and delayed bleeding rate was significantly higher in patients with HBT than in those without (36% vs 0%, P < 0.05). Delayed bleeding rate increased as intake of antithrombotic agents increased (P < 0.05). HBT period was shorter (P < 0.05) in DOAC because DOAC achieve the maximum effect quicker, and hospitalization period was shorter (P < 0.05), compared with warfarin. Multivariate analysis showed that HBT (OR, 10.7), rivaroxaban (OR, 6.00) and multiple antithrombotic agents (OR, 4.35) were independent delayed bleeding risk factors.

CONCLUSIONS

The DOAC effect differs in each agent. Dabigatran is a feasible alternative to warfarin for shortening the hospitalization period and decreasing delayed bleeding rate, although rivaroxaban has a significantly higher delayed bleeding risk.

Prothrombin Complex Concentrates for Bleeding in the Perioperative Setting

Prothrombin complex concentrates (PCCs) contain vitamin K-dependent clotting factors (II, VII, IX, and X) and are marketed as 3 or 4 factor-PCC formulations depending on the concentrations of factor VII. PCCs rapidly restore deficient coagulation factor concentrations to achieve hemostasis, but like with all procoagulants, the effect is balanced against thromboembolic risk. The latter is dependent on both the dose of PCCs and the individual patient prothrombotic predisposition. PCCs are approved by the US Food and Drug Administration for the reversal of vitamin K antagonists in the setting of coagulopathy or bleeding and, therefore, can be administered when urgent surgery is required in patients taking warfarin. However, there is growing experience with the off-label use of PCCs to treat patients with surgical coagulopathic bleeding. Despite their increasing use, there are limited prospective data related to the safety, efficacy, and dosing of PCCs for this indication. PCC administration in the perioperative setting may be tailored to the individual patient based on the laboratory and clinical variables, including point-of-care coagulation testing, to balance hemostatic benefits while minimizing the prothrombotic risk. Importantly, in patients with perioperative bleeding, other considerations should include treating additional sources of coagulopathy such as hypofibrinogenemia, thrombocytopenia, and platelet disorders or surgical sources of bleeding. Thromboembolic risk from excessive PCC dosing may be present well into the postoperative period after hemostasis is achieved owing to the relatively long half-life of prothrombin (factor II, 60-72 hours). The integration of PCCs into comprehensive perioperative coagulation treatment algorithms for refractory bleeding is increasingly reported, but further studies are needed to better evaluate the safe and effective administration of these factor concentrates.

Risk stratification, perioperative and periprocedural management of the patient receiving anticoagulant therapy

As a result of the aging US population and the subsequent increase in the prevalence of coronary disease and atrial fibrillation, therapeutic use of anticoagulants has increased. Perioperative and periprocedural management of anticoagulated patients has become routine for anesthesiologists, who frequently mediate communication between the prescribing physician and the surgeon and assess the risks of both thromboembolic complications and hemorrhage. Data from randomized clinical trials on perioperative management of antithrombotic therapy are lacking. Therefore, clinical judgment is typically needed regarding decisions to continue, discontinue, bridge, or resume anticoagulation and regarding the time points when these events should occur in the perioperative period. In this review, we will discuss the most commonly used anticoagulants used in outpatient settings and discuss their management in the perioperative period. Special considerations for regional anesthesia and interventional pain procedures will also be reviewed.

Dose-associated pulmonary complication rates after fresh frozen plasma administration for warfarin reversal

ESSENTIALS: Fresh frozen plasma (FFP) may be associated with a dose-based risk of pulmonary complications. Patients received FFP for warfarin reversal at a large academic hospital over a 3-year period. Almost 20% developed pulmonary complications, and the risk was highest after > 3 units of FFP. The risk of pulmonary complications remained significant in multivariable analysis.

BACKGROUND

Fresh frozen plasma (FFP) is often administered to reverse warfarin anticoagulation. Administration has been associated with pulmonary complications, but it is unclear whether this risk is dose-related. Aims We sought to characterize the incidence and dose relationship of pulmonary complications, including transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI), after FFP administration for warfarin reversal.

METHODS

We performed a structured retrospective review of patients who received FFP for warfarin reversal in the emergency department (ED) of an academic tertiary-care hospital over a 3-year period. Logistic regression was used to explore the relationship between FFP dose and risk of pulmonary events.

RESULTS

Two hundred and fifty-one patients met the inclusion criteria. Overall, 49 patients (20%) developed pulmonary complications, including 30 (12%) with TACO, two (1%) with TRALI, and 17 (7%) with pulmonary edema not meeting the criteria for TACO. Pulmonary complications were significantly more frequent in those who received > 3 units of FFP (34.0% versus 15.6%, 95% confidence interval for risk difference 7.9%-8.9%). After stratification by subtype of complication, only the risk of TACO was statistically significant (28.3% versus 7.6%, 95% confidence interval for risk difference 8.2%-16.6%). In multivariable analysis controlling for age, sex, initial systolic blood pressure, and intravenous fluids given in the ED, > 3 units of FFP remained a significant risk factor for pulmonary complications (odds ratio 2.49, 95% confidence interval 1.21-5.13).

CONCLUSIONS

Almost 20% of patients who received FFP for warfarin reversal developed pulmonary complications, primarily TACO, and this risk increased with > 3 units of FFP. Clinicians should be aware of and prepared to manage these complications.

Perioperative Management of Antithrombotic Therapy in Common Otolaryngologic Surgical Procedures: State of the Art Review

OBJECTIVE

The perioperative management of patients undergoing otolaryngologic procedures is increasingly complicated by the use of newer antithrombotic agents. Furthermore, with advances in anesthesia and surgical technique, otolaryngologists are presented with the challenge of operating on patients with advanced comorbid diseases. The objective of this review is to provide evidence-based recommendations on perioperative antithrombotic management for common otolaryngologic procedures.

DATA SOURCES

PubMed/MEDLINE.

REVIEW METHODS

Selected literature on patient-specific thromboembolic risk, rate of bleeding complications in otolaryngologic procedures, and the interruption of antithrombotic therapy is reviewed and interpreted by expert opinion.

CONCLUSIONS

By stratifying patients into either low thromboembolic risk (≤ 5%) or high thromboembolic risk (> 5%) and interpreting this in the context of procedural bleed risk and potential clinical consequences in the event of a bleed, otolaryngologists can make evidence-based decisions to determine the appropriate perioperative management of antithrombotic therapy.

IMPLICATIONS FOR PRACTICE

When the perioperative management of antithrombotic therapy is being decided, 3 critical factors must be considered systematically: the patient's inherent thromboembolic risk, the risk and potential consequences of bleeding related to the procedure, and the timing of interruption of thromboembolic therapy.

Cutting delays in reversing anticoagulation after intracerebral haemorrhage: three key changes at a UK comprehensive stroke centre

Prothrombin complex concentrate (PCC) reduces the risk of early haematoma expansion after intracerebral haemorrhage in patients taking vitamin K antagonists (VKA-ICH), so must be given without delay. We sought to identify and remove key barriers to rapid administration of PCC at our centre. We describe a single UK comprehensive stroke centre cohort study with mixed retrospective (1/1/2008 to 1/12/2010) and prospective (1/12/2010 to 31/7/2014) participant identification and a survey of UK stroke physicians. Seven hundred and thirteen ICH patients were admitted during the study period. Sixty nine of these patients were VKA-ICH. Patients not admitted on the acute stroke pathway (n=8) or who had palliative care commenced immediately on admission (n=6) were excluded, leaving 55 patients in the final analysis. During 2011/12 we identified and implemented service changes to reduce delays in PCC administration. The primary outcome was the time interval between diagnostic brain scan and commencement of PCC treatment (scan-to-needle time).

Secondary outcomes were the time interval between admission and commencement of PCC (door-to-needle time) and symptom onset and commencement of PCC (onset-to-needle time). Three key barriers were identified to rapid administration of PCC, including haematology consultation, collection of PCC from the transfusion laboratory, and obtaining the laboratory INR result. Our survey indicated that these barriers existed at most UK centres. We implemented point-of-care INR testing, moved PCC to the emergency department, and agreed a protocol to administer PCC autonomously. Our scan-to-needle time more than halved, from a median of 127 min (interquartile range (IQR), 111 to 208 min) prior to service changes to 58 min (IQR 50 to 91 min; p<0.001) afterwards. We have substantially reduced delays in delivering PCC to VKA-ICH patients at our centre and our simple changes could be easily implemented at centres facing similar barriers.

Management of oral anticoagulation in the surgical patient

New oral anticoagulants (NOACs) have recently emerged as an alternative for vitamin K antagonists and are now widely available. Although there is good evidence for their roles in the appropriate clinical settings, so far no reversal agent is currently available. Likewise, there is no readily available laboratory test to quantify drug levels but coagulation assays may provide qualitative information about the presence of some NOACs. We aim to review the current literature regarding the optimal management of oral anticoagulation in the perioperative setting.

Controversies regarding the new oral anticoagulants for stroke prevention in patients with atrial fibrillation

Increasing use of the new oral anticoagulants (NOACs) – dabigatran, rivaroxaban, and apixaban – has prompted considerable discussion in the medical community even as warfarin remains the mainstay of therapy. This article raises 10 controversial issues regarding the use of NOACs for stroke prevention in patients with atrial fibrillation, and offers a review of the latest available evidence. We provide a brief overview of the mechanism and dosing of these drugs, as well as a summary of the key clinical trials that have brought them into the spotlight. Comparative considerations relative to warfarin such as NOAC safety, efficacy, bleeding risk, reversibility, drug-transitioning and use in patients well controlled on warfarin are addressed. Use in select populations such as the elderly, those with coronary disease, renal impairment, or on multiple anti-platelet drugs is also discussed. Finally, we consider such specific issues as comparative efficacy, off-label use, cost, rebound and management during events. Ultimately, the rise of the NOACs to mainstream use will depend on further data and clinical experience amongst the medical community.

Periprocedural management of antithrombotic therapy in hospitalized patients

The management of antithrombotic medications in patients requiring invasive procedures is a common problem in hospital medicine, for which there is limited evidence to guide clinical decision making. Existing guidelines do not address many hospital-based procedures and have not kept pace with the introduction of newer antiplatelet and anticoagulant medications. This article provides a conceptual framework for the periprocedural management of antithrombotic therapy, with a focus on the procedures that hospitalists are most likely to perform and the pharmacology of the common and newer antithrombotic medications.

New anticoagulant and antiplatelet agents: a primer for the gastroenterologist

A large number of patients worldwide receive anticoagulant and antiplatelet agents, collectively known as antithrombotic agents. Several new anticoagulants and antiplatelet agents recently were approved for use. Gastroenterologists may be unfamiliar with the mechanism of action, indications for use, and pharmacokinetics of these newer drugs. In patients undergoing elective and urgent endoscopic procedures, clinicians must be familiar with these medications to optimize outcomes. When the decision is made to continue the newer antithrombotic agents for elective procedures, the clinician must understand the risk that these agents may impart on procedural-induced bleeding. Finally, it is important to understand how to manage these agents in the presence of acute gastrointestinal bleeding. In this article the use of newer antithrombotic agents is reviewed.

The pharmacokinetics of edoxaban for the prevention and treatment of venous thromboembolism

INTRODUCTION

Thromboembolic diseases will become the most important contributors to mortality and morbidity for modern societies. Current antithrombotic strategies using heparins or vitamin K antagonists are inconvenient, with limitations and inherent side effects. A series of new oral anticoagulants with powerful and reliable antithrombotic actions have been developed in the last decade.

AREAS COVERED

Edoxaban is a direct and specific inhibitor of activated factor X, delivered orally. This article reviews literature from PubMed and articles referenced within. The text explores the pharmacological aspects of its antithrombotic action. Pharmacokinetics, metabolism and drug interactions are examined. The review places the results of recent clinical trials that have evaluated the antithrombotic potential of edoxaban versus standard antithrombotic therapies in the prophylaxis and treatment of venous thromboembolism into perspective. The possible relationship between the pharmacokinetic profile of edoxaban and the favorable results in clinical trials is discussed.

EXPERT OPINION

Edoxaban is perceived as a major advance, compared to vitamin K antagonists, in the prevention and treatment of thromboembolic disease given its favorable efficacy, safety, pharmacokinetic profile and renal clearance. The results of ongoing large international trials exploring the prevention of thrombotic complications in patients in different clinical settings should ensure the approval of edoxaban to treat new indications.

Comparative genetics of warfarin resistance

Warfarin and other 4-hydroxycoumarin-based oral anticoagulants targeting vitamin K 2,3-epoxide reductase complex subunit 1 (VKORC1) are administered to humans, mice and rats with different purposes in mind - to act as pesticides in high-dosage baits for killing rodents, but also to save lives when administered in low dosages as antithrombotic drugs in humans. However, high-dosage warfarin used to control rodent populations has resulted in numerous mutations causing warfarin resistance. Currently, six single missense mutations in mice, 12 distinct missense mutations in rats, as well as compound heterozygous or homozygous mutations with up to six distinct missense mutations per Vkorc1 allele have been described. Warfarin resistance missense mutations for human VKORC1 have also been found world-wide, but differ characteristically from those in rodents. In humans, 26 distinct mutations have been characterized, but occur only rarely either in heterozygous or, even rarer, in homozygous form. In this review, we summarize the known VKORC1 missense mutations causing warfarin and other 4-hydroxycoumarin drug resistance, identify genomics databases as new sources of data, explore possible underlying genetic mechanisms, and summarize similarities and differences between warfarin resistant VKORC1 variants in humans and rodents.

Reversal of apixaban induced alterations in hemostasis by different coagulation factor concentrates: significance of studies in vitro with circulating human blood

Apixaban is a new oral anticoagulant with a specific inhibitory action on FXa. No information is available on the reversal of the antihemostatic action of apixaban in experimental or clinical settings. We have evaluated the effectiveness of different factor concentrates at reversing modifications of hemostatic mechanisms induced by moderately elevated concentrations of apixaban (200 ng/ml) added in vitro to blood from healthy donors (n = 10). Effects on thrombin generation (TG) and thromboelastometry (TEM) parameters were assessed. Modifications in platelet adhesive, aggregating and procoagulant activities were evaluated in studies with blood circulating through damaged vascular surfaces, at a shear rate of 600 s(-1). The potential of prothrombin complex concentrates (PCCs; 50 IU/kg), activated prothrombin complex concentrates (aPCCs; 75 IU/kg), or activated recombinant factor VII (rFVIIa; 270 μg/kg), at reversing the antihemostatic actions of apixaban, were investigated. Apixaban interfered with TG kinetics. Delayed lag phase, prolonged time to peak and reduced peak values, were improved by the different concentrates, though modifications in TG patterns were diversely affected depending on the activating reagents. Apixaban significantly prolonged clotting times (CTs) in TEM studies. Prolongations in CTs were corrected by the different concentrates with variable efficacies (rFVIIa≥aPCC>PCC). Apixaban significantly reduced fibrin and platelet interactions with damaged vascular surfaces in perfusion studies (p<0.05 and p<0.01, respectively). Impairments in fibrin formation were normalized by the different concentrates. Only rFVIIa significantly restored levels of platelet deposition. Alterations in hemostasis induced by apixaban were variably compensated by the different factor concentrates investigated. However, effects of these concentrates were not homogeneous in all the tests, with PCCs showing more efficacy in TG, and rFVIIa being more effective on TEM and perfusion studies. Our results indicate that rFVIIa, PCCs and aPCCs have the potential to restore platelet and fibrin components of the hemostasis previously altered by apixaban.

Management of hemorrhage complicated by novel oral anticoagulants in the emergency department: case report from the northwestern emergency medicine residency

Anticoagulation has long complicated the care of hemorrhage in the emergency department and other acute care settings. With the advent of novel anticoagulants such as direct thrombin inhibitors and direct factor Xa inhibitors, the absence of any direct antidote for these medications presents new and difficult challenges in the management of hemorrhagic complications in these patients. We present 2 cases of patients with hemorrhagic complications taking novel oral anticoagulants, their management, and outcomes.

Fresh frozen plasma: the most commonly prescribed hemostatic agent

Although fresh frozen plasma (FFP) is one of the most commonly prescribed therapies in clinical practice throughout the world today, there is little medical evidence available supporting its use. Recent guidelines have called for limiting FFP transfusions. Despite this, FFP use does not seem to be decreasing. The reasons for this are likely to be multifactorial, and may be based on ideas regarding medical practices dating back to Galen and Hippocrates. A review of the history of the development of FFP may shed some light on current clinical practice and guide the direction of future investigations and therapies.

Confronting the chronically anticoagulated, acute care surgery patient as we evolve into the post-warfarin era

There are a growing number of new anticoagulants used as an alternative to warfarin. Surgeons will be confronted with an increasing number of patients who may be on these outpatient medications and must be familiar with their management strategies. The purpose of this review is to examine the mechanisms, monitoring and therapeutic reversal of the non-warfarin antithrombotic agents now so frequently confronting the acute care surgeon.

Prothrombin complex concentrates reduce blood loss in murine coagulopathy induced by warfarin, but not in that induced by dabigatran etexilate

BACKGROUND

Both established oral anticoagulants such as warfarin and newer agents such as dabigatran etexilate (DE) effectively prevent thromboembolic disease, but may provoke bleeding. Limited clinical data exist linking oral anticoagulant reversal and bleeding tendency, as opposed to surrogate laboratory markers.

OBJECTIVE

 To quantify bleeding in warfarin-anticoagulated and DE-anticoagulated mice by tail transection with or without pretreatment with potential reversal agents: prothrombin complex concentrate (PCC); activated PCC (APCC); recombinant factor VIIa (rFVIIa); or murine fresh-frozen plasma (FFP).

METHODS

CD1 mice were given warfarin or DE by gavage, and the effects on in vitro coagulation assays, volume of blood loss and the bleeding time following tail transection injury were evaluated with different reversal agents.

RESULTS

PCC (14.3 IU kg(-1) ), but not rFVIIa (3 mg kg(-1) ) or FFP (12 mL kg(-1) ), normalized blood loss and bleeding time in mice with warfarin-induced elevations of mean prothrombin time at two intensities (prothrombin time ratios of either 4.3 or 24). Neither separate nor combined PCC and/or rFVIIa treatment nor APCC (100 U kg(-1) ) treatment significantly reduced blood loss in mice anticoagulated with 60 mg kg(-1) DE 75 min prior to tail transection. Both combined PCC plus rFVIIa treatment and APCC treatment significantly reduced bleeding time in the DE-treated mice.

CONCLUSIONS

Our data suggest that PCC treatment prevents excess bleeding much more effectively in warfarin-induced coagulopathy than in DE-induced coagulopathy.