Protamine reversal of low molecular weight heparin: clinically effective. Blood Coagul Fibrinolysis. 2011;22:565-570. [PMID: 21959588 DOI: 10.1097/mbc.0b013e3283494b3c]

Anticoagulation reversal (vitamin K, prothrombin complex concentrates, idarucizumab, andexanet-α, protamine)

Bleeding events are common in patients prescribed anticoagulants and can have devastating consequences. Several specific and nonspecific agents have been developed to reverse the effects of anticoagulant drugs or toxins. Vitamin K, as the oldest of these antidotes, specifically counteracts the effects of pharmaceuticals and rodenticides designed to deplete stores of vitamin K-dependent factors. In cases of life-threatening bleeding, the addition of prothrombin complex concentrates (PCCs) allows for the immediate replacement of coagulation factors. While the use of PCCs has been extended to the non-specific reversal of the effects of newer direct oral anticoagulants, the specific agents idarucizumab, targeting dabigatran and andexanet-α, binding factor Xa inhibitors, have recently been developed and are being preferentially recommended by most guidelines. However, despite having rapid effects on correcting coagulopathy, there is to date a lack of robust evidence establishing the clear superiority of direct oral anticoagulant-specific reversal agents over PCCs in terms of haemostatic efficacy, safety or mortality. For andexanet-α, a potential signal of increased thromboembolic risks, comparatively high costs and low availability might also limit its use, even though emerging evidence appears to bolster its role in intracranial haemorrhage. Protamine is the specific agent for the reversal of unfractionated heparin anticoagulation used mainly in cardiovascular surgery. It is much less effective for low molecular weight heparin fragments and is usually reserved for cases with life-threatening bleeding.

Ultra-Early Hemostatic Therapy for Acute Intracerebral Hemorrhage: An Updated Review

Intracerebral hemorrhage (ICH) is the second most common type of stroke, accounting for approximately 10-20% of all strokes, and is linked to severe neurological disability and death. Since the most accurate predictor of outcome in patients with ICH is hematoma volume, there is a great need for pharmacologic therapy that can reduce hematoma expansion and resultant mass effect and edema. This is especially critical within the ultra-early window of 3-4 hours after the presentation. Hemostatic therapies are exceptionally important for those patients taking antiplatelet or anticoagulant medications to reverse the effects of these medications and therefore prevent hematoma expansion. Furthermore, the recent publication of the 2023 Guideline for the Management of Patients with Aneurysmal Subarachnoid Hemorrhage by the American Heart Association/American Stroke Association, the first update to the guidelines since 2012, underscores the importance of optimizing anticoagulation reversal for this population. The purpose of this selective, nonsystematic review is to examine current literature regarding the use of hemostatic therapies in ICH, with particular attention paid to antiplatelet, anticoagulation, and antifibrinolytic therapies.

Reversal and resumption of anticoagulants in patients with anticoagulant-associated intracerebral hemorrhage

The use of anticoagulants has become more frequent due to the progressive aging population and increased thromboembolic events. Consequently, the proportion of anticoagulant-associated intracerebral hemorrhage (AAICH) in stroke patients is gradually increasing. Compared with intracerebral hemorrhage (ICH) patients without coagulopathy, patients with AAICH may have larger hematomas, worse prognoses, and higher mortality. Given the need for anticoagulant reversal and resumption, the management of AAICH differs from that of conventional medical or surgical treatments for ICH, and it is more specific. Understanding the pharmacology of anticoagulants and identifying agents that can reverse their effects in the early stages are crucial for treating life-threatening AAICH. When patients transition beyond the acute phase and their vital signs stabilize, it is important to consider resuming anticoagulants at the right time to prevent the occurrence of further thromboembolism. However, the timing and strategy for reversing and resuming anticoagulants are still in a dilemma. Herein, we summarize the important clinical studies, reviews, and related guidelines published in the past few years that focus on the reversal and resumption of anticoagulants in AAICH patients to help implement decisive diagnosis and treatment strategies in the clinical setting.

Caltrop-like Small-Molecule Antidotes That Neutralize Unfractionated Heparin and Low-Molecular-Weight Heparin In Vivo

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are widely applied for surgical procedures and extracorporeal therapies, which, however, suffer bleeding risk. Protamine, the only clinically approved antidote, can completely neutralize UFH, but only partially neutralizes LMWHs, and also has a number of safety drawbacks. Here, we show that caltrop-like multicationic small molecules can completely neutralize both UFH and LMWHs. In vitro and ex vivo assays with plasma and whole blood and in vivo assays with mice and rats support that the lead compound is not only superior to protamine by displaying higher neutralization activity and broader therapeutic windows but also biocompatible. The effective neutralization dose and the maximum tolerated dose of the lead compound are determined to be 0.4 and 25 mg/kg in mice, respectively, suggesting good promise for further preclinical studies.

Management of Complications of Balloon Pulmonary Angioplasty

Since the publication of the first case series reporting the outcomes of patients with chronic thromboembolic pulmonary hypertension who underwent treatment with balloon pulmonary angioplasty more than 30 years ago, significant improvements to the procedural technique have made balloon pulmonary angioplasty (BPA) a safe and effective therapy that we know today. Nevertheless, BPA carries a small risk of complications, which require rapid recognition and immediate management. The most commonly seen complications associated with BPA include pulmonary vascular injury and reperfusion pulmonary edema.

Investigation of the anticoagulant activity of cyclic sulfated glycosaminoglycan mimetics

Thrombotic disorders are among the leading causes of deaths worldwide. Anticoagulants are frequently prescribed for their prevention and/or treatment. Current anticoagulants, which target either thrombin or factor Xa, are plagued with a number of drawbacks, the most important of which is the increased risk of internal bleeding. To develop better antithrombotic agents, the anticoagulant activity of cyclic glycosaminoglycan mimetics was evaluated. Human plasma clotting assays and enzyme inhibition assays were exploited to evaluate the anticoagulant activity of sulfated β-cyclodextrin (SBCD) and its three analogs: sulfated α-cyclodextrin, β-cyclodextrin, and methylated β-cyclodextrin. In normal human plasma, SBCD selectively doubled the activated partial thromboplastin time (APTT) at ∼9 μg/mL, with no effect on prothrombin time (PT) at the same concentration. Likewise, SBCD doubled APTT at ∼9 μg/mL and at ∼8 μg/mL in antithrombin-deficient plasma and heparin cofactor II-deficient plasma, respectively. Interestingly, the three SBCD derivatives were inactive at the highest concentrations tested which highlighted the importance of the sulfate groups and the size of the molecule. Enzyme assays revealed that SBCD inhibits factor XIa (FXIa) with an IC50 value of ∼20 μg/mL and efficacy of near 100%. SBCD did not inhibit other related proteins including thrombin, factor IXa, factor Xa, factor XIIa, factor XIIIa, plasmin, chymotrypsin, or trypsin at the highest concentrations tested demonstrating a significant selectivity. In Michaelis-Menten kinetics, SBCD decreased the VMAX and increased the KM of FXIa hydrolysis of a tripeptide chromogenic substrate indicating a mixed inhibition mechanism. Together, it appears that SBCD is a potent and selective inhibitor of human FXIa with substantial anticoagulant activity in human plasma. Overall, this study introduces SBCD as a promising lead for further development as a safer anticoagulant.

Novel Antithrombotic Agents in Pregnancy Anticoagulants and Antiplatelet Agents

Increasing rates of thromboembolic complications have required increasing use of anticoagulant and antiplatelet agents during and after pregnancy. Furthermore, thromboembolism is both a cause and a complication of severe maternal morbidity requiring intensive care. As a consequence, almost all patients admitted to intensive care units receive an anticoagulant or an antiplatelet agent (or both) for either treatment or prevention of thromboembolism. In this review, we summarize commonly used anticoagulants and antiplatelet agents and outline the potential role of newly developed (novel) antithrombotic agents for pregnant and postpartum patients.

A Historical Perspective on the Reversal of Anticoagulants

There has been a landmark shift in the last several decades in the management and prevention of thromboembolic events. From the discovery of parenteral and oral agents requiring frequent monitoring as early as 1914, to the development of direct oral anticoagulants (DOACs) that do not require monitoring or dose adjustment in the late 20th century, great advances have been achieved. Despite the advent of these newer agents, bleeding continues to be a key complication, affecting 2 to 4% of DOAC-treated patients per year. Bleeding is associated with substantial morbidity and mortality. Although specific reversal agents for DOACs have lagged the release of these agents, idarucizumab and andexanet alfa are now available as antagonists. However, the efficacy of these reversal agents is uncertain, and complications, including thrombosis, have not been adequately explored. As such, guidelines continue to advise the use of nonspecific prohemostatic agents for patients requiring reversal of the anticoagulant effect of these drugs. As the indications for DOACs and the overall prevalence of their use expand, there is an unmet need for further studies to determine the efficacy of specific compared with nonspecific pro-hemostatic reversal agents. In this review, we will discuss the evidence behind specific and nonspecific reversal agents for both parenteral and oral anticoagulants.

Porous Polymers as Universal Reversal Agents for Heparin Anticoagulants through an Inclusion-Sequestration Mechanism

Heparins are widely used anticoagulants for surgical procedures and extracorporeal therapies. However, all of them have bleeding risks. Protamine sulfate, the only clinically approved antidote for unfractionated heparin (UFH), has adverse effects. Moreover, protamine can only partially neutralize low-molecular-weight heparins (LMWHs) and is not effective for fondaparinux. Here, an inclusion-sequestration strategy for efficient neutralization of heparin anticoagulants by cationic porous supramolecular organic frameworks (SOFs) and porous organic polymers (POPs) is reported. Isothermal titration calorimetric and fluorescence experiments show strong binding affinities of these porous polymers toward heparins, whereas dynamic light scattering and zeta potential analysis confirm that the heparin sequences are adsorbed into the interior of the porous hosts. Activated partial thromboplastin time, anti-FXa, and thromboelastography assays indicate that their neutralization efficacies are higher than or as high as that of protamine for UFH and generally superior to protamine for LMWHs and fondaparinux, which is further confirmed by tail-transection model in mice and ex vivo aPTT or anti-FXa analysis in rats. Acute toxicity evaluations reveal that one of the SOFs displays outstanding biocompatibility. This work suggests that porous polymers can supply safe and rapid reversal of clinically used heparins, as protamine surrogates, providing an improved approach for their neutralization.

Porous dynamic covalent polymers as promising reversal agents for heparin anticoagulants

Heparins are natural and partially degraded polyelectrolytes that consist of sulfated polysaccharide backbones. However, as clinically used anticoagulants, heparins are associated with clinical bleeding risks and thus require rapid neutralization. Protamine sulfate is the only clinically approved antidote for unfractionated heparin (UFH), which not only may cause severe adverse reactions in patients, but also is only partially effective against low molecular weight heparins (LMWHs). We here present the facile synthesis of four porous multicationic dynamic covalent polymers (DCPs) from the condensation of tritopic aldehyde and acylhydrazine precursors. We show that, as new water-soluble polymeric antidotes, the new DCPs can effectively include both UFH and LMWHs and thus reverse their anticoagulating activity, which is confirmed by the activated partial thromboplastin time and thromboelastographic assays as well as mouse tail transection assay (bleeding model). The neutralization activities of two of the DCPs were found to be overall superior to that of protamine and have wider concentration windows and good biocompatibility. This pore-inclusion neutralization strategy paves the way for the development of water-soluble polymers as universal heparin binding agents.

Venous Thromboembolism and Pulmonary Embolism: Strategies for Prevention and Management

Perioperative venous thromboembolism (VTE) is a common complication within the surgical patient population. Perioperative mechanical and chemoprophylaxis have been shown to reduce the incidence of both deep venous thrombosis and pulmonary embolism. Prophylactic regimen must be tailored to the patient's individual risk factors as well as the nature of the procedure. In the event of VTE, treatment most commonly includes long-term anticoagulation, whereas more severe cases may require lytic or mechanical interventions.

Optimization of Heparin Monitoring with Anti-FXa Assays and the Impact of Dextran Sulfate for Measuring All Drug Activity

Heparins, unfractionated or low molecular weight, are permanently in the spotlight of both clinical indications and laboratory monitoring. An accurate drug dosage is necessary for an efficient and safe therapy. The one-stage kinetic anti-FXa assays are the most widely and universally used with full automation for large series, without needing exogenous antithrombin. The WHO International Standards are available for UFH and LMWH, but external quality assessment surveys still report a high inter-assay variability. This heterogeneity results from the following: assay formulation, designed without or with dextran sulfate to measure all heparin in blood circulation; calibrators for testing UFH or LMWH with the same curve; and automation parameters. In this study, various factors which impact heparin measurements are reviewed, and we share our experience to optimize assays for testing all heparin anticoagulant activities in plasma. Evidence is provided on the usefulness of low molecular weight dextran sulfate to completely mobilize all of the drug present in blood circulation. Other key factors concern the adjustment of assay conditions to obtain fully superimposable calibration curves for UFH and LMWH, calibrators' formulations, and automation parameters. In this study, we illustrate the performances of different anti-FXa assays used for testing heparin on UFH or LMWH treated patients' plasmas and obtained using citrate or CTAD anticoagulants. Comparable results are obtained only when the CTAD anticoagulant is used. Using citrate as an anticoagulant, UFH is underestimated in the absence of dextran sulfate. Heparin calibrators, adjustment of automation parameters, and data treatment contribute to other smaller differences.

Updates in Anticoagulation Therapy Monitoring

In the past six decades, heparin and warfarin were the primary anticoagulants prescribed for treatment and prophylaxis of venous thromboembolism worldwide. This has been accompanied by extensive clinical knowledge regarding dosing, monitoring, and reversal of these anticoagulants, and the resources required to do so have largely been readily available at small and large centers alike. However, with the advent of newer oral and parenteral anticoagulants such as low molecular weight heparins, factor Xa inhibitors, and direct thrombin inhibitors in recent years, new corresponding practice guidelines have also emerged. A notable shift in the need for monitoring and reversal agents has evolved as well. While this has perhaps streamlined the process for physicians and is often desirable for patients, it has also left a knowledge and resource gap in clinical scenarios for which urgent reversal and monitoring is necessary. An overview of the currently available anticoagulants with a focus on the guidelines and available tests for anticoagulant monitoring will be discussed in this article.

Unfractionated Heparin Versus Subcutaneous Nadroparin in Adults Supported With Venovenous Extracorporeal Membrane Oxygenation: a Retrospective, Multicenter Study

Extracorporeal membrane oxygenation (ECMO) requires constant management of coagulation. Whereas unfractionated heparin remains the anticoagulant of choice, experienced centers report high bleeding rates. Biocompatibility of the extracorporeal circuit enables management of anticoagulation with subcutaneous low-molecular-weight heparins only. The aim of this study was to evaluate the safety and feasibility of anticoagulation with subcutaneous nadroparin compared with unfractionated heparin during respiratory ECMO in patients. We assessed for thrombotic complications and number of bleeding and life-threatening bleeding events. Additionally, we evaluated the change in resistance to flow in the oxygenator and the number of transfused blood products. Nadroparin and unfractionated heparin were comparable in terms of number of bleeding (34 vs. 53%; p = 0.12), life-threatening bleeding (2.8 vs. 9.3%; p = 0.26) events, and daily red blood cell transfusion rates (0.79 units/patient/day vs. 0.71 units/patient/day in nadroparin group; p = 0.87) during respiratory ECMO. The relative change in resistance to flow in the oxygenator was similar between groups (8.03 vs. 11.6%; p = 0.27). Nadroparin seemed equivalent to unfractionated heparin in the number of thrombotic and hemorrhagic events as well as in the daily red blood cell transfusion rates during venovenus-ECMO.

Intravenous thrombolysis for the management of acute ischemic stroke in patients therapeutically anticoagulated with heparin: A review

BACKGROUND

Intravenous thrombolysis (IVT) with alteplase is effective in acute ischemic stroke (AIS). However, its use rate remains low due to the many exclusion criteria. Recent guidelines recommend excluding patients suffering AIS with an elevated aPTT secondary to heparin exposure from receiving IVT. The purpose of this review is to explore the safety and efficacy of IVT in patients therapeutically anticoagulated with heparin. We also propose a treatment algorithm for IVT in patients with AIS that are therapeutically anticoagulated with heparin.

METHODS

We performed a systematic review of PubMed and Embase through March 2020 to identify the literature regarding AIS in patients exposed to heparin, followed by IVT treatment, emphasizing safety, efficacy, and clinical outcome using PRISMA guidelines.

RESULTS

We included thirteen articles in the final analysis, including three retrospective studies, two observational studies, one randomized trial, five case reports, and two case series.

CONCLUSION

There is limited information about the off-label use of IVT in patients with elevated aPTT. Patients with AIS are excluded from IVT if they have recent exposure to heparin. Our review indicates that this population of patients may benefit from IVT as the cases of active bleeding after IVT are few, and functional outcomes are favorable in the long term suggesting that IVT in therapeutically anticoagulated patients may be safe and efficacious.

A review of anticoagulation in patients with central nervous system malignancy: between a rock and a hard place

The incidence and prevalence of patients who develop primary and secondary metastatic central nervous system cancer (CNS) is increasing. This is a consequence of advancements in the sensitivity and availability of diagnostic imaging, and improved therapeutic options, leading to increased detection of CNS malignancies and improved survival. These patients are at very high risk of thrombosis as well as haemorrhage, and the optimum management of anticoagulation can be challenging for treating clinicians, particularly as robust prospective evidence is sparse. In this focused review, we discuss (1) risk factors for thrombosis and bleeding in these patients, (2) management of acute venous thromboembolism (VTE) including evidence for direct oral anticoagulants, and how to approach patients with contraindications to anticoagulation, (3) ambulatory VTE prophylaxis, (4) VTE prophylaxis in patients who have undergone craniotomy for cancer, and (5) management of anticoagulation-related intracranial haemorrhage. Based on review of the available literature and author opinion, we propose practical management algorithms to aid clinicians faced with treating CNS cancer patients with thrombosis or CNS haemorrhage.

<p>The Challenge of Hemorrhagic Shock Management During Low-Molecular-Weight Heparin Treatment</p>

The reversal of low-molecular-weight heparin (LMWH) and the management of bleeding patients on LMWH remain highly challenging. Even if LMWH is very extensively administered in the prophylaxis and treatment of venous thrombosis, specific antidotes are lacking, and reversal strategies have very weak grade of evidences on clinical effectiveness. We here describe a reversal strategy with protamine and FVIIa in a patient presenting with hemorrhagic shock and cardiocirculatory arrest.

Treatment of venous thromboembolism in pediatric patients

Venous thromboembolism (VTE) is rare in healthy children, but is an increasing problem in children with underlying medical conditions. Pediatric VTE encompasses a highly heterogenous population, with variation in age, thrombosis location, and underlying medical comorbidities. Evidence from pediatric clinical trials to guide treatment of VTE is lacking so treatment is often extrapolated from adult trials and expert consensus opinion. Aspects unique to children include developmental hemostasis and the major role of central venous access devices. There is an absence of information regarding the optimal target levels of anticoagulation for neonates and infants and lack of suitable drug formulations. Anticoagulants, primarily low-molecular-weight heparin and warfarin, are used to treat children with symptomatic VTE. These drugs have significant limitations, including the need for subcutaneous injections and frequent monitoring. Randomized clinical trials of direct oral anticoagulants in pediatric VTE are ongoing, with results anticipated soon. These trials will provide new evidence and options for therapy that have the potential to improve care. International collaborative registries offer the ability to study outcomes of rare subgroups of pediatric VTE (eg, renal vein thrombosis), and will be important to ultimately guide therapy in a more disease-specific manner.

Perioperative management of antithrombotic treatment

End-stage liver disease is characterized by multiple and complex alterations of hemostasis that are associated with an increased risk of both bleeding and thrombosis. Liver transplantation further challenges the feeble hemostatic balance of patients with decompensated cirrhosis, and the management of antithrombotic treatment during and after transplant surgery, which is particularly difficult. Bleeding was traditionally considered the major concern during and early after surgery, but it is increasingly recognized that transplant recipients may also develop thrombotic complications. Pathophysiology of hemostatic complications during and after transplantation is multifactorial and includes pre-, intra-, and postoperative risk factors. Risk stratification is important, as it helps the identification of high-risk recipients in whom antithrombotic prophylaxis should be considered. In recipients who develop thrombosis during or after surgery, prompt treatment is indicated to prevent graft failure, retransplantation, and death.

Heparin-Binding Copolymer as a Complete Antidote for Low-Molecular-Weight Heparins in Rats

Bleeding resulting from the application of low-molecular-weight heparins (LMWHs) may be treated with protamine sulfate, but this treatment lacks efficiency; its action against antifactor Xa activity is limited to ∼60%. Moreover, protamine sulfate can cause life-threatening hypersensitivity reactions. We developed diblock heparin-binding copolymer (HBC), which can neutralize the anticoagulant activity of parenteral anticoagulants. In the present study, we explored the safety profile of HBC and its potential to reverse enoxaparin, nadroparin, dalteparin, and tinzaparin in human plasma and at in vivo conditions. HBC-LMWH complexes were characterized using zeta potential, isothermal titration calorimetry, and dynamic light scattering. The rat cardiomyocytes and human endothelial cells were used for the assessment of in vitro toxicity. Male Wistar rats were observed for up to 4 days after HBC administration for clinical evaluation, gross necropsy, and biochemistry and histopathological analysis. Rats were treated with LMWHs alone or followed by short-time intravenous infusion of HBC, and bleeding time and antifactor Xa activity were measured. HBC completely reversed antifactor Xa activity prolonged in vitro by all LMWHs with an optimal weight ratio of 2.5:1. The complexes of HBC-LMWHs were below 5 µm. We observed no effects on the viability of cardiovascular cells treated with HBC at concentrations up to 0.05 mg/ml. Single doses up to 20 mg/kg of HBC were well tolerated by rats. HBC completely reversed the effects of LMWHs on bleeding time and antifactor Xa activity in vivo after 20 minutes and retained ∼80% and ∼60% of reversal activity after 1 and 2 hours, respectively. Well-documented efficacy and safety of HBC both in vitro and in vivo make this polymer a promising candidate for LMWHs reversal. SIGNIFICANCE STATEMENT: Over the last decade, there has been significant progress in developing antidotes for the reversal of anticoagulants. Until now, there has been no effective and safe treatment for patients with severe bleeding under low-molecular-weight heparin therapy. Based on our in vitro and in vivo studies, heparin-binding copolymer seems to be a promising candidate for neutralizing all clinically relevant low-molecular-weight heparins.

Analysis of the Action of Quaternized Chitosans with Different Molecular Weight on Anticoagulant Activity of Heparins In Vitro

Quaternized derivatives of chitosan with a substitution degree of 85-98% (highly substituted) synthesized from chitosans with a molecular weight of 5, 10, 20 kDa, with a degree of deacetylation of 89-98%, and the code numbers of QChit 5, QChit 10, QChit 20, respectively, completely neutralize antithrombin activity of unfractionated heparin and partially neutralize aXa activity of low-molecular-weight heparin (clexane), similar to protamine sulfate. The advantages of QChit 5 and QChit 10 over QChit 20 and protamine sulphate are the follows: the effect is achieved at lower concentrations and in greater concentration range; they do not promote platelet aggregation; in a concentration of 0.0072 mg/ml they do not destroy the erythrocyte membranes.

Reversing anticoagulation in the hemorrhaging patient

PURPOSE OF REVIEW

Anticoagulants in general, but especially the relatively new direct oral anticoagulants and platelet inhibitors, pose a great challenge for physicians in the hemorrhaging patient. The aim of the present review is to provide an overview on recent studies dealing with the reversal of anticoagulation in the hemorrhaging patient and to describe our therapeutic emergency strategy for those patients.

RECENT FINDINGS

A specific antidote for dabigatran is already on the market and antidotes for the direct and indirect factor Xa inhibitors are in development. Moreover, bleeding under platelet inhibitors remains critical with very little evidence on effective reversal strategies.

SUMMARY

To reverse anticoagulation in the hemorrhaging patient, specific antidotes should be the first option if available, followed by four-factor prothrombin complex concentrate (PCC), activated PCC and recombinant activated factor seven as the emergency strategy. Fibrinogen concentrate, antifibrinolytics and oral charcoal, respectively, can be considered as an additional measure. Massive blood loss and thrombocytopenia should be treated independently according to the respective, local guidelines for (massive) transfusion of blood and blood products.

Reversal of Anticoagulants in Critical Care

There has seen an increase in anticoagulant consumption worldwide over the past few decades. With this widespread utilization of anticoagulants, clinicians are increasingly likely to encounter situations where anticoagulants would need to be withheld. This includes emergency and elective procedures or surgeries as well as major or minor bleeding as a direct result of over anticoagulation or consequent to other intercurrent illnesses such as sepsis or trauma with multiorgan failure, where the anticoagulant may contribute to coagulation abnormalities. Clinicians are required to have a thorough understanding of the indications for anticoagulant prescription, drug interactions and monitoring, indications and options of reversal of anticoagulation and management of bleeding in the situations described above. Once the acute process is managed, the ongoing need and timing of reinitiation of anticoagulation is also crucial. This article provides an overview on the indications for reversal of anticoagulation, the agents used for reversal and the timing of reinitiation of anticoagulants.

Treatment of bleeding complications in patients on anticoagulant therapy

Anticoagulant therapy is often refrained from out of fear of hemorrhagic complications. The most frequent type of major bleeding is gastrointestinal, but intracranial hemorrhage has the worst prognosis. Management of these complications in patients on anticoagulants should follow the same routines as for nonanticoagulated patients, as described here with the previously mentioned bleeds as examples. In addition, for life-threatening or massive hemorrhages, reversal of the anticoagulant effect is also crucial. Adequate reversal requires information on which anticoagulant the patient has taken and when the last dose was ingested. Laboratory data can be of some help, but not for all anticoagulants in the emergency setting. This is reviewed here for the different types of anticoagulants: vitamin K antagonists, heparins, fondaparinux, thrombin inhibitors and factor Xa inhibitors. Specific antidotes for the latter are becoming available, but supportive care and nonspecific support for hemostasis with antifibrinolytic agents or prothrombin complex concentrates, which are widely available, should be kept in mind.

Protamine sulfate for the reversal of enoxaparin associated hemorrhage beyond 12 h

Clinical practice guidelines recommend protamine sulfate for reversal of enoxaparin associated bleeds dependent on the time from last administration and dose of enoxaparin. We present a case of a hemodynamically unstable patient with an enoxaparin induced abdominal wall hematoma/hemorrhage and the previous enoxaparin administration 21.5 h prior to presentation with a therapeutic anti-Xa assay (0.8 IU/mL) upon assessment in the emergency department. Along with resuscitative efforts, an interdisciplinary team collaborated to administer protamine sulfate 50 mg intravenous once (0.5 mg per 1 mg of enoxaparin) to reverse the therapeutic anticoagulation. Our case demonstrates the importance of monitoring renal function and the potential for accumulation of enoxaparin in patients with renal dysfunction leading to prolonged therapeutic anti-Xa assays. With the availability of anti-Xa assays, future reversal recommendations of enoxaparin associated bleeds using protamine sulfate should include the initial anti-Xa assay as a guide for the dosing regimen.

The reversal of anticoagulation in clinical practice

Widespread use of anticoagulant drugs for treatment and -prevention of thromboembolic events means it is common to encounter patients requiring reversal of anticoagulation for management of bleeding or invasive procedures. While supportive and general measures apply for patients on all agents, recent diversification in the number of licensed agents makes an understanding of drug-specific reversal strategies essential. Recognising effects upon, and limitations of, laboratory measures of coagulation also plays an important role. An understanding of reversal strategies alone is insufficient to competently care for patients who may require anticoagulation reversal. It is also necessary to reduce the need for reversal through correct prescribing and by employing appropriate periprocedural bridging strategies for elective and semi-elective procedures. Finally, consideration of whether and when to reintroduce an anticoagulant drug following reversal is important not only to balance bleeding and thrombotic risks for individual patients but also for timely management of discharge.

Evidence based diagnosis and management of chronic subdural hematoma: A review of the literature

Chronic subdural hematomas are encapsulated blood collections within the dural border cells with characteristic outer "neomembranes". Affected patients are more often male and typically above the age of 70. Imaging shows crescentic layering of fluid in the subdural space on a non-contrast computed tomography (CT) scan, best appreciated on sagittal or coronal reformats. Initial medical management involves reversing anticoagulant/antiplatelet therapies, and often initiation of anti-epileptic drugs (AEDs). Operative interventions, such as twist-drill craniostomy (TDC), burr-hole craniostomy (BHC), and craniotomy are indicated if imaging implies compression (maximum fluid collection thickness >1 cm) or the patient is symptomatic. The effectiveness of various surgical techniques remains poorly characterized, with sparse level 1 evidence, variable outcome measures, and various surgical techniques. Postoperatively, subdural drains can decrease recurrence and sequential compression devices can decrease embolic complications, while measures such as early mobilization and re-initiation of anticoagulation need further study. Non-operative management, including steroid therapy, etizolam, tranexamic acid, and angiotensin converting enzyme inhibitors (ACEI) also remain poorly studied. Recurrent hemorrhages are a major complication affecting around 10-20% of patients, and therefore close follow-up is essential.

Major publications in the critical care pharmacotherapy literature: January-December 2016

PURPOSE

To summarize select critical care pharmacotherapy guidelines and studies published in 2016.

SUMMARY

The Critical Care Pharmacotherapy Literature Update (CCPLU) Group screened 31 journals monthly for relevant pharmacotherapy articles and selected 107 articles for review over the course of 2016. Of those included in the monthly CCPLU, three guidelines and seven primary literature studies are reviewed here. The guideline updates included are as follows: hospital-acquired pneumonia and ventilator-associated pneumonia management, sustained neuromuscular blocking agent use, and reversal of antithrombotics in intracranial hemorrhage (ICH). The primary literature summaries evaluate the following: dexmedetomidine for delirium prevention in post-cardiac surgery, dexmedetomidine for delirium management in mechanically ventilated patients, high-dose epoetin alfa after out-of-hospital cardiac arrest, ideal blood pressure targets in ICH, hydrocortisone in severe sepsis, procalcitonin-guided antibiotic de-escalation, and empiric micafungin therapy.

CONCLUSION

The review provides a synopsis of select pharmacotherapy publications in 2016 applicable to clinical practice.

Targeting heparin and heparan sulfate protein interactions

Heparin and heparan sulfate glycosaminoglycans are long, linear polysaccharides that are made up of alternating dissacharide sequences of sulfated uronic acid and amino sugars. Unlike heparin, which is only found in mast cells, heparan sulfate is ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These negatively-charged glycans play essential roles in important cellular functions such as cell growth, adhesion, angiogenesis, and blood coagulation. These biomolecules are also involved in pathophysiological conditions such as pathogen infection and human disease. This review discusses past and current methods for targeting these complex biomolecules as a novel therapeutic strategy to treating disorders such as cancer, neurodegenerative diseases, and infection.

Perioperative Considerations and Management of Patients Receiving Anticoagulants

Anticoagulants remain the primary strategy for the prevention and treatment of thrombosis. Unfractionated heparin, low molecular weight heparin (LMWH), fondaparinux, and warfarin have been studied and employed extensively with direct thrombin inhibitors typically reserved for patients with complications or those requiring interventions. Novel oral anticoagulants have emerged from clinical development and are expected to replace older agents with their ease to use and more favorable pharmacodynamic profiles. Increasingly, anesthesiologists are being requested to anesthetize patients who are on some form of anticoagulants and hence it is important to have sound understanding of pharmacology, dosing, monitoring, and toxicity of anticoagulants. We searched the online databases including PubMed Central, Cochrane, and Google Scholar using anticoagulants, perioperative management, anesthetic considerations, and LMWH as keywords for the articles published between 1994 and 2015 while writing this review. In this article, we will review the different classes of anticoagulants and how to manage them in the perioperative settings.

Heparin-binding copolymer reverses effects of unfractionated heparin, enoxaparin, and fondaparinux in rats and mice

The parenteral anticoagulants may cause uncontrolled and life-threatening bleeding. Protamine, the only registered heparin antidote, is partially effective against low-molecular weight heparins, completely ineffective against fondaparinux and may cause unacceptable toxicity. Therefore, we aimed to develop a synthetic compound for safe and efficient neutralization of all parenteral anticoagulants. We synthesized pegylated PMAPTAC block copolymers, and then, we selected a lead heparin-binding copolymer (HBC). We assessed the effectiveness of HBC in the model of arterial thrombosis electrically induced in the carotid artery of rats by measuring thrombus weight, bleeding time, activated partial thromboplastin time, activated clotting time, and anti-factor Xa activity. The intravital tissue distribution, the cardiorespiratory, and organ toxicity were monitored. HBC diminished antithrombotic and anticoagulant effects of unfractionated heparin. Moreover, it stopped bleeding and completely reversed the enhancement of clotting times and anti-factor Xa activity caused by enoxaparin or fondaparinux. We observed slight pulmonary congestion and cell infiltration, but the cardiorespiratory parameters remained unchanged. We found a strong signal of fluorescently-labeled HBC in the urine, and a weaker in the liver and in the kidney. No signs of hepatic or nephrotoxicity were observed in the blood biochemistry or histopathologic examination. We developed a copolymer efficiently neutralizing effects of heparins in the living organism, which shows a very promising efficacy/safety profile and may help in the management of uncontrolled bleeding resulting from an anticoagulant injection. HBC could enable the safe replacement of unfractionated heparin with low-molecular weight heparins in patients undergoing cardiac surgery and complex vascular procedures.

Reliable low-molecular-weight heparin reversal in a child undergoing emergency surgery: a case report

Low-molecular-weight heparin neutralization using protamine alone can be unreliable, especially in cases of immediate reversal for emergency surgery. Here, we describe a unique case of a 17-month-old girl with a history of glioneuronal tumor and corresponding hydrocephalus status post debulking and ventriculoperitoneal shunt placement, who was placed on enoxaparin after the development of a sagittal sinus thrombosis. Patient presented for emergency craniectomy and evacuation of subdural bleed after a fall while on therapeutic dose of enoxaparin. Protamine and fresh frozen plasma were used in the patient's perioperative course providing a reliable reversal of enoxaparin.

Inactivated antithrombins as fondaparinux antidotes: a promising alternative to haemostatic agents as assessed in vitro in a thrombin-generation assay

In the absence of specific antidote to fondaparinux, two modified forms of antithrombin (AT), one recombinant inactive (ri-AT) and the other chemically inactivated (chi-AT), were designed to antagonise AT-mediated anticoagulants, e. g. heparins or fondaparinux. These inactive ATs were previously proven to effectively neutralise anticoagulant activity associated with heparin derivatives in vitro and in vivo, as assessed by direct measurement of anti-FXa activity. This study was undertaken to evaluate in vitro the effectivity of inactive ATs to reverse anticoagulation by heparin derivatives and to compare them with non-specific fondaparinux reversal agents, like recombinant-activated factor VII (rFVIIa) or activated prothrombin-complex concentrate (aPCC), in a thrombin-generation assay (TGA). Addition of fondaparinux (3 µg/ml) to normal plasma inhibited thrombin generation by prolonging lag time (LT) as much as 244 % and lowering endogenous thrombin potential (ETP) to 17 % of their control (normal plasma) values. Fondaparinux-anticoagulant activity was reversed by ri-AT and chi-AT, as reflected by the corrections of LT up to 117 % and 114 % of its control value, and ETP recovery to 78 % and 63 %, respectively. Unlike ri-AT that had no effect on thrombin generation in normal plasma, chi-AT retained anticoagulant activity that minimises its reversal capacity. However, both ATs were more effective than rFVIIa or aPCC at neutralising fondaparinux and, unlike non-specific antidotes, inactive ATs specifically reversed AT-mediated anticoagulant activities, as suggested by their absence of procoagulant activity in anticoagulant-free plasma.

Inadvertent Overdose of Low-Molecular-Weight Heparin in an Elderly Patient with Deep Vein Thrombosis and Acute Kidney Injury

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An Algorithmic Approach to Management of Venous Thromboembolism

Venous thromboembolism (VTE) is associated with significant morbidity and mortality. Factors such as the presence of transient risk factors for VTE, risk of bleeding, and location of deep vein thrombosis (DVT) determine the duration of anticoagulation. Extended anticoagulation is offered to patients with unprovoked pulmonary embolism (PE) or proximal DVT and a low risk of bleeding. Anticoagulation for 3 months is advised in patients with provoked DVT or PE, high risk of bleeding, and isolated distal or upper extremity DVT. In patients with unprovoked PE or proximal DVT and a low risk of bleeding, who want to stop anticoagulation after 3 months, further risk stratification is necessary. Clinical scoring system, and thrombophilia testing otherwise not routinely performed, may be considered to measure risk of annual recurrence in such cases. Short-term anticoagulation may be considered in subsegmental PE and superficial vein thrombosis, particularly if patients are at low risk of bleeding and have persistent risk factors for recurrent VTE. In cases of catheter-associated thrombosis, the catheter need not be removed routinely, and the patient may be anticoagulated for 3 months or longer if the catheter is maintained in patients with cancer. Extensive screening for occult cancer in cases of unprovoked VTE is not beneficial. New oral anticoagulants such as apixaban, rivaroxaban, or dabigatran may be preferred to vitamin K antagonists in patients without cancer or renal failure, more so after the development of reversal agents such as idarucizumab and andexanet alfa.

The design and synthesis of new synthetic low-molecular-weight heparins

Low-molecular-weight heparin (LMWH) has remained the most favorable form of heparin in clinics since the 1990s owing to its predictable pharmacokinetic properties. However, LMWH is mainly eliminated through the kidney, which limits its use in renal-impaired patients. In addition, the anticoagulant activity of LMWH is only partially neutralized by protamine. LMWH is obtained from a full-length, highly sulfated polysaccharide harvested from porcine mucosal tissue. The depolymerization involved in LMWH production generates a broad distribution of LMWH fragments (6-22 sugar residues). This, combined with the various methods used to produce commercial LMWHs, results in variable pharmacological and pharmacokinetic properties. An alternative chemoenzymatic approach offers a method for the synthesis of LMWH that has the potential to overcome the limitations of current LMWHs. This review summarizes the application of a chemoenzymatic approach to generate LMWH and the rationale for development of a synthetic LMWH.

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux.