Heparin-induced thrombocytopenia. A contemporary clinical approach to diagnosis and management

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Antifungal lock therapy: an eternal promise or an effective alternative therapeutic approach?

Each year, millions of central venous catheter insertions are performed in intensive care units worldwide. The usage of these indwelling devices is associated with a high risk of bacterial and fungal colonization, leading to the development of microbial consortia, namely biofilms. These sessile structures provide fungal cells with resistance to the majority of antifungals, environmental stress and host immune responses. Based on different guidelines, colonized/infected catheters should be removed and changed immediately in the case of Candida‐related central line infections. However, catheter replacement is not feasible for all patient populations. An alternative therapeutic approach may be antifungal lock therapy, which has received high interest, especially in the last decade. This review summarizes the published Candida‐related in vitro, in vivo data and case studies in terms of antifungal lock therapy. The number of clinical studies remains limited and further studies are needed for safe implementation of the antifungal lock therapy into clinical practice.

Heparin-induced thrombocytopenia in patients readmitted after open cardiac surgical procedures: A case series

Objectives

Heparin-induced thrombocytopenia (HIT) is an immune-mediated complication that occurs in a small percentage of patients exposed to heparin. Concerns of HIT are particularly high in patients undergoing cardiac procedures requiring cardiopulmonary bypass, as they are exposed to high doses of heparin intraoperatively. Our aim was to identify and assess the hospital courses of patients who were diagnosed with HIT during readmission following cardiac surgery.

Methods

A retrospective review of patients who underwent open cardiac surgical procedures from June 2017 through October 2019 was performed. Of these, we identified patients who were newly diagnosed with HIT upon readmission. HIT positivity was defined as a positive anti-PF4 antibody screening test, plus a positive serotonin release assay.

Results

Of the 2496 patients identified, 13 patients were HIT positive on index admission and were excluded. Of the remaining 2483 patients, 351 were readmitted within 30 days. Six were newly diagnosed with HIT during readmission, 5 of whom presented with thrombotic complications. One patient was readmitted with thrombocytopenia and was started on argatroban; the remaining 5 did not have a significantly lower platelet count on readmission. Of the 12 patients readmitted for venous thromboembolism, 4 tested positive for HIT.

Conclusions

HIT can have a delayed appearance following open heart surgery. Venous thromboembolism appears to be a significant indicator for HIT during readmission, even in the absence of thrombocytopenia. This may support the use of non-heparin anticoagulation for cardiac surgery patients readmitted with thromboembolism until HIT status is determined.

Neutrophil activation and NETosis are the major drivers of thrombosis in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia/thrombosis (HIT) is a serious immune reaction to heparins, characterized by thrombocytopenia and often severe thrombosis with high morbidity and mortality. HIT is mediated by IgG antibodies against heparin/platelet factor 4 antigenic complexes. These complexes are thought to activate platelets leading to thrombocytopenia and thrombosis. Here we show that HIT immune complexes induce NETosis via interaction with FcγRIIa on neutrophils and through neutrophil-platelet association. HIT immune complexes induce formation of thrombi containing neutrophils, extracellular DNA, citrullinated histone H3 and platelets in a microfluidics system and in vivo, while neutrophil depletion abolishes thrombus formation. Absence of PAD4 or PAD4 inhibition with GSK484 abrogates thrombus formation but not thrombocytopenia, suggesting they are induced by separate mechanisms. NETs markers and neutrophils undergoing NETosis are present in HIT patients. Our findings demonstrating the involvement of NETosis in thrombosis will modify the current concept of HIT pathogenesis and may lead to new therapeutic strategies.

The pathogenesis of heparin-induced thrombocytopenia and thrombosis (HIT) is mediated by heparin-reactive autoantibodies binding to platelets (thrombocytes). Here the authors show neutrophil activation and NETosis are elevated in patients with HIT, and are essential for thrombosis in HIT mouse models.

Clinical importance of thrombocytopenia in patients with acute coronary syndromes: a systematic review and meta-analysis

Thrombocytopenia (TP) is common in hospitalized patients. In the context of acute coronary syndromes (ACS), TP has been linked to adverse clinical outcomes. We present a systematic review and meta-analysis of the evidence on the clinical importance of preexisting and in-hospital acquired TP in the context of ACS. Specifically, we address (a) the prevalence and associated factors with TP in the context of ACS; and (b) the association between TP and all-cause mortality, major adverse cardiovascular events (MACEs), and major bleeding. We conducted systematic literature searches in MEDLINE and Web of Science. For the meta-analysis, we fit linear mixed models with a random study-specific intercept for the aggregate outcomes. A total of 16 studies and 190 915 patients were included in this study. Of these patients, 8.8% ± 1.2% presented with preexisting TP while 5.8% ± 1.0% developed TP after hospital admission. Preexisting TP was not statistically significantly associated with adverse outcomes. Acquired TP was associated with greater risk of all-cause mortality (risk difference [RD]: 4.3%; 95% confidence interval [CI]: 2-6%; p = 0.04), MACE (RD: 8.5%; 95% CI: 1-16.0%; p = 0.037), and major bleeding (RD: 11.9%; 95% CI: 5-19%; p = 0.005). In conclusion, TP is a prevalent condition in patients admitted for an ACS and identifies a high-risk patient population more likely to experience ischemic and bleeding complications, as well as higher mortality.

A Patient With Remote Heparin-Induced Thrombocytopenia and Antiphospholipid Syndrome Requiring Cardiopulmonary Bypass: Do Current Guidelines Apply?

Anticoagulation for cardiopulmonary bypass (CPB) is required to prevent acute disseminated intravascular coagulation and clot formation within the bypass circuit. Unfractionated heparin is the standard anticoagulant for CPB due to its many advantages and long history of successful use. However, heparin has the unique drawback of triggering Heparin-PF4 (PF4) antibodies potentially leading to heparin-induced thrombocytopenia (HIT). We have limited data regarding reformation of antibodies if a patient has had a prior (remote) antibody production or full HIT. Patients with antiphospholipid antibodies undergoing CPB with unfractionated heparin have a high complication rate, even in the absence of HIT. Antiphospholipid antibodies have a multifaceted, cumulatively inhibitory effect on the normal anticoagulation armamentarium in vivo. Even more concerning is the possibility that antiphospholipid syndrome and HIT may be synergistic. We report a patient with risk factors for both thromboembolic (remote history of HIT and antiphospholipid syndrome) and hemorrhagic complications who underwent an aortic valve replacement and coronary artery bypass grafting on CPB using bivalirudin. We discuss the complex decision making regarding anticoagulant for CPB, particularly with regard to American College of Chest Physicians guidelines.

Thrombotic Microangiopathies (TTP, HUS, HELLP)

Thrombocytopenia, strictly defined as a platelet count less than 150,000, is common in the emergency department. Recognition, diagnostic investigation, and proper disposition of a thrombocytopenic patient are imperative. One group of disorders leading to thrombocytopenia is the thrombotic microangiopathies, hallmarked by platelet destruction. These thrombotic microangiopathies include thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS) and hemolysis, elevated liver enzyme levels, low platelet count (HELLP), which should be distinguished from similar disease processes such as immune thrombocytopenia (ITP), disseminated intravascular coagulation (DIC) and heparin induced thrombocytopenia (HIT). In this article, clinical presentations, pathophysiology, diagnostic workup, management plans, complications, and dispositions are addressed for this complex group of platelet disorders.

Heparin-Induced Thrombocytopenia: A Comprehensive Clinical Review

Heparin-induced thrombocytopenia is a profoundly dangerous, potentially lethal, immunologically mediated adverse drug reaction to unfractionated heparin or, less commonly, to low-molecular weight heparin. In this comprehensive review, the authors highlight heparin-induced thrombocytopenia's risk factors, clinical presentation, pathophysiology, diagnostic principles, and treatment. The authors place special emphasis on the management of patients requiring procedures using cardiopulmonary bypass or interventions in the catheterization laboratory. Clinical vigilance of this disease process is important to ensure its recognition, diagnosis, and treatment. Misdiagnosis of the syndrome, as well as misunderstanding of the disease process, continues to contribute to its morbidity and mortality.

Anticoagulation Therapy during Extracorporeal Membrane Oxygenator Support in Pediatric Patients

Extracorporeal membrane oxygenation (ECMO) is a salvage therapy for critically ill patients. Although ECMO is becoming more common, hemorrhagic and thromboembolic complications remain the major causes of death in patients undergoing ECMO treatments. These complications commence upon blood contact with artificial surfaces of the circuit, blood pump, and oxygenator system. Therefore, anticoagulation therapy is required in most cases to prevent these problems. Anticoagulation is more complicated in pediatric patients than in adults, and the foreign surface of ECMO only increases the complexity of systemic anticoagulation. In this review, we discuss the pathophysiology of coagulation, anticoagulants, and monitoring tools in pediatric patients receiving ECMO.

Drug eluting antimicrobial vascular catheters: Progress and promise

Vascular catheters are critical tools in modern healthcare yet present substantial risks of serious bloodstream infections that exact significant health and economic burdens. Drug-eluting antimicrobial vascular catheters have become important tools in preventing catheter-related bloodstream infections and their importance is expected to increase as significant initiatives are expanded to eliminate and make the occurrence of these infections unacceptable. Here we review clinically significant and emerging drug-eluting antimicrobial catheters within the categories of antibiotic, antiseptic, novel bioactive agents and energy-enhanced drug eluting antimicrobial catheters. Important representatives of each category are reviewed from the standpoints of mechanisms of action, physical-chemical properties, safety, in vitro and clinical effectiveness.

Cardiopulmonary Bypass Without Heparin

Due to familiarity, short half-life, ease of monitoring, and the availability of a reversal agent, heparin remains the anticoagulant of choice for cardiac operations requiring cardiopulmonary bypass (CPB). However, occasionally patients require CPB but should not receive heparin, most often because of acute or subacute heparin-induced thrombocytopenia (HIT). In these cases, if it is not feasible to wait for the disappearance of HIT antibodies, an alternative anticoagulant must be selected. A number of non-heparin anticoagulant options have been explored. However, current recommendations suggest the use of a direct thrombin inhibitor such as bivalirudin. This review describes the use of heparin alternatives for the conduct of CPB with a focus on the direct thrombin inhibitors.

In Vitro Assessment of the Antimicrobial Efficacy of Optimized Nitroglycerin-Citrate-Ethanol as a Nonantibiotic, Antimicrobial Catheter Lock Solution for Prevention of Central Line-Associated Bloodstream Infections

The rapid, broad-spectrum, biofilm-eradicating activity of the combination of 0.01% nitroglycerin, 7% citrate, and 20% ethanol and its potential as a nonantibiotic, antimicrobial catheter lock solution (ACLS) were previously reported. Here, a nitroglycerin-citrate-ethanol (NiCE) ACLS optimized for clinical assessment was developed by reducing the nitroglycerin and citrate concentrations and increasing the ethanol concentration. Biofilm-eradicating activity was sustained when the ethanol concentration was increased from 20 to 22% which fully compensated for reducing the citrate concentration from 7% to 4% as well as the nitroglycerin concentration from 0.01% to 0.0015% or 0.003%. The optimized formulations demonstrated complete and rapid (2 h) eradication of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate Staphylococcus aureus (VISA), methicillin-resistant Staphylococcus epidermidis (MRSE), vancomycin-resistant enterococci (VRE), multidrug-resistant (MDR) Pseudomonas aeruginosa, MDR Klebsiella pneumoniae, MDR Enterobacter cloacae, MDR Acinetobacter baumannii, MDR Escherichia coli, MDR Stenotrophomonas maltophilia, Candida albicans, and Candida glabrata biofilms. The optimized NiCE lock solutions demonstrated anticoagulant activities comparable to those of heparin lock solutions. NiCE lock solution was significantly more effective than taurolidine-citrate-heparin lock solution in eradicating biofilms of Staphylococcus aureus and Candida glabrata The optimized, nonantibiotic, heparin-free NiCE lock solution demonstrates rapid broad-spectrum biofilm eradication as well as effective anticoagulant activity, making NiCE a high-quality ACLS candidate for clinical assessment.

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Protein-directed synthesis of highly monodispersed, spherical gold nanoparticles and their applications in multidimensional sensing

An in-situ reduction method has been reported to prepare gold nanoparticles (GNPs) of 40–110 nm by using the green reducing agents of proteins, which are activated by H₂O₂ and the superoxide anion (). The protein of collagen turns HAuCl₄ to the aqueous Au(I) ainions, which are further reduced by other proteins to be highly monodispersed and spherical GNPs of different sizes. The GNPs reduced by different proteins are found to be with the exposed {100} facets, the distinctive UV-vis absorption spectra and various colors (See Fig. 1). By means of extracting the color responses, such as red, green and blue (RGB) alterations, an in-situ reduction method-based multidimensional sensing platform is fabricated in the process of GNPs synthesis. Without further modification of GNPs, nine common proteins are found to be well detected and discriminated at different concentrations. Moreover, this sensing platform also demonstrates great potentials in qualitative and semiquantitative analysis on the individuals of these proteins with high sensitivity. Furthermore, the validation of this multidimensional sensing platform has been carried out by analysis on the spiked proteins in human urine and the target proteins in complex matrix (e.g. lysozyme in human tear).

A Novel PF4-Dependent Platelet Activation Assay Identifies Patients Likely to Have Heparin-Induced Thrombocytopenia/Thrombosis

BACKGROUND

Almost without exception, patients with heparin-induced thrombocytopenia/thrombosis (HIT) have antibodies that recognize platelet factor 4 (PF4) in a complex with heparin; however, many heparin-treated patients without HIT are also antibody-positive. A platelet activation test, the serotonin release assay (SRA), is useful for identifying a subset of antibodies that are platelet-activating and most likely to cause HIT. However, this "gold standard" assay for HIT diagnosis is technically demanding and is routinely available only through referral laboratories, limiting its availability for timely diagnosis and management.

METHODS

We compared the diagnostic performance of the SRA with that of a technically simple platelet activation assay, the PF4-dependent P-selectin expression assay (PEA), which uses platelets pretreated with PF4 as targets for antibody detection. Archived serum samples from 91 patients for whom clinical information (HIT 4Ts [thrombocytopenia, timing of platelet count fall, thrombosis, and other causes of thrombocytopenia] score) was available were used. Patients with an intermediate 4Ts score and a PF4 ELISA (enzyme-linked immunosorbent assay) optical density ≥ 2.0, or a high 4Ts score and a PF4 ELISA optical density ≥ 1.0, were considered HIT positive; others were designated HIT negative.

RESULTS

The PEA had higher diagnostic accuracy (area under the curve, 0.92 vs 0.82; P = .02) than the SRA, using this definition of HIT. Eleven of 16 serum samples that were PEA positive and SRA negative were HIT positive. Studies done with identical target platelets and serially diluted samples from patients with HIT showed that the PEA is inherently more sensitive than the SRA for the detection of platelet-activating antibodies.

CONCLUSIONS

The PEA is technically less demanding than the SRA and may be more accurate for the diagnosis of HIT.

Current Clinical Trials on the Use of Direct Oral Anticoagulants in the Pediatric Population

Common treatment options for deep vein thrombosis and venous thromboembolism in the pediatric population include unfractionated heparin, low molecular weight heparin, and warfarin. Other alternatives are bivalirudin, argatroban, and fondaparinux. Warfarin is the only approved oral option, but an oral agent without frequent monitoring would be optimal for pediatric patients. Thus, there is an increasing need for new anticoagulation options in this population. None of the current direct oral anticoagulants have FDA-approved indications and dosing in children. The two classes of DOACs and the drugs they are comprised of are factor Xa inhibitors (rivaroxaban, apixaban, edoxaban) and direct thrombin inhibitor (dabigatran). Off-label usage of these agents is largely based on adult doses. By far, rivaroxaban and dabigatran have the most published data and ongoing trials in pediatric patients compared to edoxaban and apixaban. After evaluating the current literature available on these agents, it is, however, still too early to make any definitive recommendations on their usage in this special population.

The epidemiology of venous thromboembolism

Venous thromboembolism (VTE) is categorized by the U.S. Surgeon General as a major public health problem. VTE is relatively common and associated with reduced survival and substantial health-care costs, and recurs frequently. VTE is a complex (multifactorial) disease, involving interactions between acquired or inherited predispositions to thrombosis and VTE risk factors, including increasing patient age and obesity, hospitalization for surgery or acute illness, nursing-home confinement, active cancer, trauma or fracture, immobility or leg paresis, superficial vein thrombosis, and, in women, pregnancy and puerperium, oral contraception, and hormone therapy. Although independent VTE risk factors and predictors of VTE recurrence have been identified, and effective primary and secondary prophylaxis is available, the occurrence of VTE seems to be relatively constant, or even increasing.

Why "R" HIT patients predisposed to thrombosis?

In this issue of Blood, Rollin et al demonstrate that heparin-induced thrombocytopenia and thrombosis (HIT) patients homozygous for arginine (R) at position 131 in the immunoglobulin (Ig)G receptor FcγRIIA have a significantly higher incidence of thrombosis, and show that plasma IgG may play a key role in modulating the thrombotic process.

Epidemiology of venous thromboembolism

Thrombosis can affect any venous circulation. Venous thromboembolism (VTE) includes deep-vein thrombosis of the leg or pelvis, and its complication, pulmonary embolism. VTE is a fairly common disease, particularly in older age, and is associated with reduced survival, substantial health-care costs, and a high rate of recurrence. VTE is a complex (multifactorial) disease, involving interactions between acquired or inherited predispositions to thrombosis and various risk factors. Major risk factors for incident VTE include hospitalization for surgery or acute illness, active cancer, neurological disease with leg paresis, nursing-home confinement, trauma or fracture, superficial vein thrombosis, and-in women-pregnancy and puerperium, oral contraception, and hormone therapy. Although independent risk factors for incident VTE and predictors of VTE recurrence have been identified, and effective primary and secondary prophylaxis is available, the occurrence of VTE seems to be fairly constant, or even increasing.

Active and passive surveillance of enoxaparin generics: a case study relevant to biosimilars

OBJECTIVE

This retrospective analysis assessed the capability of active and passive safety surveillance systems to track product-specific safety events in the USA for branded and generic enoxaparin, a complex injectable subject to immune-related and other adverse events (AEs).

METHODS

Analysis of heparin-induced thrombocytopenia (HIT) incidence was performed on benefit claims for commercial and Medicare supplemental-insured individuals newly treated with enoxaparin under pharmacy benefit (1 January 2009 - 30 June 2012). Additionally, spontaneous reports from the FDA AE Reporting System were reviewed to identify incidence and attribution of enoxaparin-related reports to specific manufacturers.

RESULTS

Specific, dispensed products were identifiable from National Drug Codes only in pharmacy-benefit databases, permitting sensitive comparison of HIT incidence in nearly a third of patients treated with brand or generic enoxaparin. After originator medicine's loss of exclusivity, only 5% of spontaneous reports were processed by generic manufacturers; reports attributable to specific generics were approximately ninefold lower than expected based on market share.

CONCLUSIONS

Claims data were useful for active surveillance of enoxaparin generics dispensed under pharmacy benefits but not for products administered under medical benefits. These findings suggest that the current spontaneous reporting system will not distinguish product-specific safety signals for products distributed by multiple manufacturers, including biosimilars.

Heparin-independent, PF4-dependent binding of HIT antibodies to platelets: implications for HIT pathogenesis

Antibodies specific for platelet factor 4 (PF4)/heparin complexes are the hallmark of heparin-induced thrombocytopenia and thrombosis (HIT), but many antibody-positive patients have normal platelet counts. The basis for this is not fully understood, but it is believed that antibodies testing positive in the serotonin release assay (SRA) are the most likely to cause disease. We addressed this issue by characterizing PF4-dependent binding of HIT antibodies to intact platelets and found that most antibodies testing positive in the SRA, but none of those testing negative, bind to and activate platelets when PF4 is present without any requirement for heparin (P < .0001). Binding of SRA-positive antibodies to platelets was inhibited by chondroitinase ABC digestion (P < .05) and by the addition of chondroitin-4-sulfate (CS) or heparin in excess quantities. The findings suggest that although all HIT antibodies recognize PF4 in a complex with heparin, only a subset of these antibodies recognize more subtle epitopes induced in PF4 when it binds to CS, the major platelet glycosaminoglycan. Antibodies having this property could explain "delayed HIT" seen in some individuals after discontinuation of heparin and the high risk for thrombosis that persists for weeks in patients recovered from HIT.

Array-based sensing of proteins and bacteria by using multiple luminescent nanodots as fluorescent probes

Luminescent nanodots for protein sensing and discrimination of bacteria: Luminescent nanodots are applied as novel fluorescent probes in a sensing array. The sensing strategy uses graphene oxide (GO) for protein recognition, with displacement of fluorescent probes to generate the output. This sensing platform is a powerful tool to detect protein targets and discriminate bacteria.

Drug-Induced Immune Thrombocytopenia

Thrombocytopenia is commonly seen in laboratory findings, especially in critically ill patients. Although the incidence is rare, drug-induced immune thrombocytopenia (DITP) is a serious complication that is often overlooked as a cause of thrombocytopenia. Over the last century, extensive research and data collection have been done in an attempt to better characterize DITP. Heparin-induced thrombocytopenia is the most common DITP and has distinct pathogenesis, diagnosis, and treatment options. However, other offending medications are less well known and have triggered many questions and constant search for answers. This review will discuss both drug-induced immune-mediated and nonimmune-mediated thrombocytopenias, with a focus on immune-mediated processes. Thrombocytopenia caused by chemotherapy will not be discussed in this article.

Anticoagulant therapy in pediatrics

Thromboembolic episodes are disorders encountered in both children and adults, but relatively more common in adults. However, the occurrence of venous thromboembolism and use of anticoagulants in pediatrics are increasing. Unfractionated Heparin (UH) is used as a treatment and prevention of thrombosis in adults and critically ill children. Heparin utilization in pediatric is limited by many factors and the most important ones are Heparin Induced Thrombocytopenia (HIT) and anaphylaxis. However, Low Molecular Weight Heparin (LMWH) appears to be an effective and safe alternative treatment. Hence, it is preferred over than UH due to favorable pharmacokinetic and side effect profile. Direct Thrombin Inhibitors (DTI) is a promising class over the other anticoagulants since it offers potential advantages. The aim of this review is to discuss the differences between adult and pediatric thromboembolism and to review the current anticoagulants in terms of pharmacological action, doses, drug reactions, pharmacokinetics, interactions, and parameters. This review also highlights the differences between old and new anticoagulant therapy in pediatrics.

[Thrombocytopenia]

Thrombocytopenia means low platelet count. This is the most frequent cause of bleeding abnormalities. Petechias, purpuras, mucosal bleeding are typical clinical findings. Severe, even life threatening gastrointestinal or intracranial bleeding may also occur. Diagnostic laboratory finding is the prolonged bleeding time. There are several causes of thrombocytopenia. The major mechanisms for a reduced platelet count are decreased production and increased destruction of platelets, or both. The major task is to reveal the underlying cause. Examination of the bone marrow and the peripheral blood smear can be helpful as well as special diagnostics of the assumed disease. Therapy targets the underlying disease, and also involves platelet transfusion. However, in case of diseases with increased platelet activation and consumption, platelet transfusion is contraindicated because it may lead to aggravation of the pathologic process.

Prognostic significance of post percutaneous coronary intervention thrombocytopenia

Several definitions of post percutaneous coronary intervention (PCI) thrombocytopenia (TC) were formulated. Recent studies demonstrated that a relative drop in platelet count ≥ 25% is the most appropriate criterion. By this definition a population is detected that is exposed not only to increased risk of hemorrhagic complications but also to increased risk of ischemic events, which may appear a paradox. In patients with acute coronary syndromes undergoing PCI, several conditions might be associated with TC: cardiopulmonary by-pass and the presence of extra corporeal membrane oxygenators, intra aortic balloon pump (IABP), cardiogenic shock, thrombolytic drugs and anticoagulant or antiplatelet drugs. Several studies demonstrated that TC and ischemic outcomes are related although it is unclear whether this is a direct relationship or TC is just a secondary effect of another cryptic protagonist. It is suggested that further investigations determine whether there is a real link between TC, a probably well defined covariate, and ischemic outcomes or whether IABP is the joining link between these two variables and whose presence needs in any case be considered in multivariable statistics. Post-PCI TC could be only a secondary effect of IABP use. On turn, the prolonged use of heparin necessarily accompanying the use of IABP, and producing a paradoxical pro-thrombotic TC, might also be implicated.

Contemporary anticoagulation therapy in patients undergoing percutaneous intervention

The proper use of anticoagulants is crucial for ensuring optimal patient outcomes post percutaneous interventions in the cardiac catheterization laboratory. Anticoagulant agents such as unfractionated heparin, a thrombin inhibitor; low-molecular weight heparins, predominantly Factor Xa inhibitors; fondaparinux, a Factor Xa inhibitor and bivalirudin, a direct thrombin inhibitor have been developed to target various steps in the coagulation cascade to prevent formation of thrombin. Optimal anticoagulation achieves the correct balance between thrombosis and bleeding and is related to optimal outcomes with minimal complications. This review will discuss the mechanisms and appropriate use of current and emerging anticoagulant therapies used during percutaneous interventions.

Unexpected hematologic effects of biotherapeutics in nonclinical species and in humans

Biotherapeutics are expanding the arsenal of therapeutics available for treating and preventing disease. Although initially thought to have limited side effects due to the specificity of their binding, these drugs have now been shown to have potential for adverse drug reactions including effects on peripheral blood cell counts or function. Hematotoxicity caused by a biotherapeutic can be directly related to the activity of the biotherapeutic or can be indirect and due to autoimmunity, biological cascades, antidrug antibodies, or other immune system responses. Biotherapeutics can cause hematotoxicity primarily as a result of cellular activation, cytotoxicity, drug-dependent and independent immune responses, and sequelae from initiating cytokine and complement cascades.  The underlying pathogenesis of biotherapeutic-induced hematotoxicity often is poorly understood. Nonclinical studies have generally predicted clinical hematotoxicity for recombinant cytokines and growth factors.  However, most hematologic liabilities of biotherapeutics are not based on drug class but are species specific, immune-mediated, and of low incidence. Despite the potential for unexpected hematologic toxicity, the risk-benefit profile of most biotherapeutics is favorable; hematologic effects are readily monitorable and managed by dose modification, drug withdrawal, and/or therapeutic intervention.  This article reviews examples of biotherapeutics that have unexpected hematotoxicity in nonclinical or clinical studies. 

Clinical and biologic features of patients suspected or confirmed to have heparin-induced thrombocytopenia in a cardiothoracic surgical ICU

BACKGROUND

The diagnosis of heparin-induced thrombocytopenia (HIT) is problematic in the surgical ICU, as there are multiple potential explanations for thrombocytopenia. We conducted a study to assess the incidence, clinical presentation, and outcome of HIT in a cardiothoracic surgical ICU.

METHODS

From January 2005 to December 2010, all patients with suspicion of HIT were prospectively identified, and data were collected retrospectively. Detection of anti-PF4/heparin antibodies and functional assays were systematically performed.

RESULTS

During the study period, 5,949 patients were admitted to the ICU (2,751 after cardiac surgery and 3,198 after thoracic surgery), of whom 101 were suspected to have HIT(1.7% [95% CI, 1.4%-2.0%]). Suspicion of HIT occurred at a median of 5 (4-9) days after ICU admission. Diagnosis was confirmed in 28 of 5,949 patients (0.47% [95% CI, 0.33%-0.68%]).Thrombosis was detected in 14 patients with HIT (50%) and in 12 patients without HIT (16%)( P 5 .0006). After receiver operating characteristic analysis (area under curve 5 0.78 0.06),a 4Ts score ≥ 5 had a sensitivity of 86% and a specificity of 70%. Course of platelet count was similar between the two groups. Six patients (21%) with HIT and 20 (27%) without died( P 5 .77).

CONCLUSIONS

Even with a prospective platelet monitoring protocol, suspicion for HIT arose in <2% of patients in a cardiothoracic ICU. Most were found to have other causes of thrombocytopenia,with HIT confirmed in 28 of 101 suspected cases (0.47% of all patients in the ICU). The 4Ts score may have value by identifying patients who should have laboratory testing performed.The mortality of patients with HIT was not different from other very ill thrombocytopenic patients in the ICU.

Drug-induced immune thrombocytopenia

Thrombocytopenia is caused by immune reactions elicited by diverse drugs in clinical practice. The activity of the drug-dependent antibodies produces a marked decrease in blood platelets and a risk of serious bleeding. Understanding of the cellular mechanisms that drive drug-induced thrombocytopenia has advanced recently but there is still a need for improved laboratory tests and treatment options. This article provides an overview of the different types of drug-induced thrombocytopenia, discusses potential pathologic mechanisms, and considers diagnostic methods and treatment options.

Antithrombotic therapy in heparin-induced thrombocytopenia: guidelines translated for the clinician

Heparin-induced thrombocytopenia (HIT) is a clinicopathologic syndrome initiated by heparin exposure and characterized by thrombocytopenia and paradoxical thrombophilia. HIT is mediated by the formation of antibodies against the platelet factor 4/heparin complex, which leads to platelet activation, thrombin generation, and potentially fatal thrombotic sequelae. The clinical presentation of HIT is variable and can be easily overlooked. Although a number of functional and antigen-based immunoassays have been developed to detect the presence of HIT antibodies, initial diagnosis is often based on recognition of thrombocytopenia in the appropriate clinical context and later confirmed with immunologic testing. Given the serious clinical consequences of HIT, immediate cessation of heparin products and administration of non-heparin anticoagulants are crucial components of treatment. We provide a review of the clinical syndrome and practical summary of treatment recommendations from the most recent 2012 American College of Chest Physicians evidence-based guidelines for the treatment and prevention of HIT.

Systemic infusion and local irrigation with argatroban effective in preventing clot formation during carotid endarterectomy in a patient with heparin-induced thrombocytopenia

BACKGROUND

A therapeutic dilemma exists when patients with symptomatic carotid stenosis and concomitant heparin-induced thrombocytopenia (HIT) are advised to urgently undergo carotid endarterectomy (CEA) with heparin therapy.

METHODS

After a 63-year-old man with HIT and multiple medical comorbidities underwent emergent coronary artery bypass grafting, postoperative imaging revealed plaque at the origin of the left internal carotid artery with 80%-99% stenosis and minimal contralateral internal carotid artery disease. During the patient's evaluation to undergo CEA for symptomatic high-grade carotid stenosis, enzyme-linked immunosorbent assay revealed persistent platelet factor 4 antibodies.

RESULTS

The endarterectomy was successfully performed while the patient received argatroban, both as a continuous infusion and intermittent irrigation during dissection of the plaque. Postoperatively, the drip was continued for 24 hours, and the patient was discharged day 2 on a daily dose of 325 mg of aspirin. At the 6-month examination, Doppler ultrasound revealed normal anterograde velocities with no evidence of stenosis, and the patient noted no subsequent ischemic events.

CONCLUSIONS

We now recommend systemic intravenous and local argatroban irrigation to prevent thromboembolic complications in CEA cases with HIT and renal insufficiency. Bivalirudin for both systemic intravenous use and local irrigation may be safer in patients without renal insufficiency because of its shorter half-life.

Updates in thrombosis in pediatrics: where are we after 20 years?

The incidence of venous thromboembolism (VTE) in the pediatric population is increasing. Technological advances in medicine and imaging techniques, improved awareness of the disease, and longer survival of life-threatening or chronic medical conditions all contribute to the increase in VTE rates. There is a paucity of data on management of VTE based on properly designed clinical trials, but there is significant advancement in the last 2 decades. This review summarizes the progress made in pediatric thrombosis, including epidemiological changes, advances in anticoagulant agents, and outcomes of VTE.

Safety and effectiveness outcomes of an inpatient collaborative drug therapy management service for direct thrombin inhibitors

PURPOSE

The impact of a collaborative drug therapy management (CDTM) agreement enabling pharmacist-managed direct thrombin inhibitor (DTI) therapy was evaluated.

METHODS

A retrospective chart review was conducted to compare selected outcome measures between cohorts of adults who received argatroban or bivalirudin therapy for suspected heparin-induced thrombocytopenia (HIT) before (n = 25) and after (n = 25) the implementation of an institutional DTI protocol under which properly trained and credentialed pharmacists have a primary role in dosing and monitoring DTI infusions. The primary endpoints were the mean time to attainment of activated partial thromboplastin time (aPTT) values in a specified therapeutic range and the proportion of total inpatient treatment time during which aPTT values were in that range. Secondary endpoints included the incidence of major and minor bleeding and the incidence of medication errors.

RESULTS

After implementation of the DTI protocol, therapeutic aPTT values were achieved more rapidly (a mean of 3.4 hours in the postimplementation cohort versus a mean of 7.7 hours in the preimplementation cohort, p = 0.009) and maintained more consistently. Rates of bleeding and overall mortality were similar in the two groups; the frequencies of documented medication errors were 12% and 40% in the postimplementation and preimplementation cohorts, respectively (p = 0.05).

CONCLUSION

A pharmacist-driven DTI program resulted in improved effectiveness and safety outcomes, as demonstrated by improved attainment of target aPTT values and a decreased frequency of medication errors.

Argatroban dose reductions for suspected heparin-induced thrombocytopenia complicated by child-pugh class C liver disease

OBJECTIVE

To report our experience of reduced-dose argatroban in a patient with suspected heparin-induced thrombocytopenia (HIT) and Child-Pugh class C liver disease and review the relevant literature to summarize current recommendations on argatroban use in patients with severe liver disease.

CASE SUMMARY

A 58-year-old male with Child-Pugh class C liver disease (Model for End-Stage Liver Disease [MELD] score = 31, total bilirubin 4.5 mg/dL) and hemodialysis-dependent renal failure was hospitalized with acute deep vein thrombosis (DVT). Three days after heparin initiation for DVT, he developed thrombocytopenia. Given his heparin exposure (both for treatment of DVT and ongoing hemodialysis), HIT was suspected and all heparinoids were immediately discontinued. Argatroban was initiated for the treatment of HIT while laboratory testing for HIT antibodies and the serotonin release assay were completed. Because of the patient's advanced liver disease, the starting dose of argatroban was reduced to 0.2 μg/kg/min, with frequent monitoring of the activated partial thromboplastin time (aPTT) (goal 60-85 seconds). Despite this dose reduction, the aPTT was supratherapeutic. Following further dose reductions, a final argatroban maintenance dose of 0.05 μg/kg/min was necessary for the attainment of goal aPTTs.

DISCUSSION

Reducing the starting dose of argatroban to 0.5 μg/kg/min is recommended in patients with liver disease. Nevertheless, this recommended dose is largely based on data from patients with more moderate liver disease (eg, Child-Pugh class A or B), and dosing in more advanced liver disease remains largely unexplored. Patients with more advanced liver disease may require additional dose reductions to avoid supratherapeutic concentrations of anticoagulation agents and to minimize bleeding risk.

CONCLUSIONS

This report illustrates the importance of careful selection of argatroban dosing and appropriate aPTT monitoring in patients with severe liver disease. Excessive anticoagulation may precipitate major bleeding complications, placing patients with this complicated disease at undue risk.

Efficacy of a Nurse-Managed Argatroban Dose-Adjustment Protocol in a University Teaching Hospital

Background

Argatroban is a direct thrombin inhibitor used in the treatment of heparin-induced thrombocytopenia (HIT). No study has evaluated the safety and efficacy of a nurse-managed argatroban dosing protocol.

Methods

We performed a retrospective analysis of 151 total admissions (129 patients) in which argatroban infusions were administered before and after protocol implementation. The preprotocol and postprotocol groups consisted of 69 and 68 admissions, respectively. Patients were eligible for inclusion if they were ≥18 years old and received an argatroban drip for any reason in the 2 years prior to or following protocol implementation.

Results

There were no statistically significant differences in the incidence of clinically overt bleeding (primary study safety endpoint) between groups. There was no difference between groups in the primary efficacy endpoints, the mean number of partial thromboplastin time (aPTT) assessments per day, and dose adjustments. The mean number of sub- and supratherapeutic aPTTs during treatment was higher in the preprotocol group when utilizing the specified range in the preprotocol group and the protocol's aPTT range (45–90 s); the preprotocol and postprotocol groups had an average of 3.4 and 1.04 subtherapeutic aPTTs, respectively ( P = .008). Similarly, the preprotocol group had an average of 4.98 supratherapeutic aPTTs, while the postprotocol group had 1.84 ( P < .001). There was no difference in duration of argatroban infusion in the preprotocol group compared to the postprotocol group with regard to duration of infusion or final infusion rate.

Conclusions

This nurse-managed argatroban adjustment protocol provides similar safety and efficacy outcomes and decreased monitoring when pre and post implementation were compared.

A multi-center, prospective, open-label, 8-week study of certoparin for anticoagulation during maintenance hemodialysis--the membrane study

Background

Adequate anticoagulation is prerequisite for effective hemodialysis to prevent clotting in the extracorporeal circuit. We aimed providing first data on the efficacy and safety of the low-molecular-weight heparin certoparin in this setting.

Methods

Multicenter, open-label, 8-week trial. Patients received a single dose of 3,000 IU certoparin i.v. with additional titration steps of 600 IU and/or continuous infusion if necessary.

Results

120 patients were screened, 109 enrolled (median age 71; range 26–90 years) and 106 available for efficacy analyses. The percentage of unsatisfactory dialysis results at 8 weeks due to clotting or bleeding, was 1.9% (n = 2/106; 95% confidence interval [CI] 0.23–6.65%); no major bleeding. 1.9% had moderate/severe clotting in the lines/bubble catcher and 2.8% in the dialyser at week 8. 15.7 ± 14.3% of the dialysis filters’ visual surface area was showing redness. In subgroups of patients receiving median doses of 3000 ± 0, 3000 (2400–6000) and 4200 (3000–6600) IU, plasma aXa levels at baseline, 4 and 8 weeks were 0.24 [95%CI 0.21–0.27], 0.33 [0.27–0.40] and 0.38 [0.33–0.45] aXa IU/ml at 2 h. C_48h was 0.01 [0.01–0.02] aXa IU at all visits. At baseline and 4 weeks AUC_0-48h was 2.66 [2.19–3.24] and 3.66 [3.00–4.45] aXa IU*h/ml. In 3.0% of dialyses (n = 83/2724) prolonged fistula compression times were documented. Eight patients (7.34%) had at least one episode of minor bleeding. 4) 85.3% of patients had any adverse event, 9.2% were serious without suspected drug relation; and in 32 patients a drug-relation was suspected.

Conclusions

Certoparin appears effective and safe for anticoagulation in patients undergoing maintenance hemodialysis.