Use of lepirudin in patients with heparin-induced thrombocytopenia and renal failure requiring hemodialysis

Dilemmas in the Choice of Adequate Therapeutic Treatment in Patients with Acute Pulmonary Embolism—From Modern Recommendations to Clinical Application

Pulmonary thromboembolism is a very common cardiovascular disease, with a high mortality rate. Despite the clear guidelines, this disease still represents a great challenge both in diagnosis and treatment. The heterogeneous clinical picture, often without pathognomonic signs and symptoms, represents a huge differential diagnostic problem even for experienced doctors. The decisions surrounding this therapeutic regimen also represent a major dilemma in the group of patients who are hemodynamically stable at initial presentation and have signs of right ventricular (RV) dysfunction proven by echocardiography and positive biomarker values (pulmonary embolism of intermediate–high risk). Studies have shown conflicting results about the benefit of using fibrinolytic therapy in this group of patients until hemodynamic decompensation, due to the risk of major bleeding. The latest recommendations give preference to new oral anticoagulants (NOACs) compared to vitamin K antagonists (VKA), except for certain categories of patients (patients with antiphospholipid syndrome, mechanical valves, pregnancy). When using oral anticoagulant therapy, special attention should be paid to drug–drug interactions, which can lead to many complications, even to the death of the patient. Special population groups such as pregnant women, obese patients, patients with antiphospholipid syndrome and the incidence of cancer represent a great therapeutic challenge in the application of anticoagulant therapy. In these patients, not only must the effectiveness of the drugs be taken into account, but great attention must be paid to their safety and possible side effects, which is why a multidisciplinary approach is emphasized in order to provide the best therapeutic option.

Direct thrombin inhibitors: pharmacology and application in intensive care medicine

PURPOSE

Anticoagulation is part of the daily routine of intensive care physicians. As the possibilities of pharmacological anticoagulation are becoming more numerous and diverse, intensive care physicians have to be familiar with indications, contraindications, dosing, and reversal of many different substances. This paper presents an overview of the substance group of direct thrombin inhibitors (DTI) indicated for alternative anticoagulation in intensive care medicine.

METHODS

The review is a synopsis of scientific evidence, expert opinion, open forum commentary, and clinical feasibility data.

RESULTS AND CONCLUSIONS

Due to their antithrombotic potential without direct activation of platelets, DTI could offer potential advantages over heparins and vitamin K antagonists in critically ill patients, especially regarding heparin-induced thrombocytopenia. Because of multiple organ dysfunction, organ failure, and comedications, simple extrapolation of results of medical to critically ill patients is not permissible. The fine line between thrombosis and bleeding in intensive care patients requires cautious dosing and close drug monitoring. Studies dealing with DTI in the intensive care setting are of utmost clinical interest.

Heparin-Induced Thrombocytopenia: Treatment Options and Special Considerations

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse effect that typically manifests several days after the start of heparin therapy, although both rapid- and delayed-onset HIT have been described. Its most serious complication is thrombosis. Although not all patients develop thrombosis, it can be life threatening. The risk of developing HIT is related to many factors, including the type of heparin product administered, route of administration, duration of therapy, patient population, and previous exposure to heparin. The diagnosis of HIT is typically based on clinical presentation, exposure to heparin, and presence of thrombocytopenia with or without thrombosis. Antigen and activation laboratory assays are available to support the diagnosis of HIT. However, because of the limited sensitivity and specificity of these assays, bedside probability scales for HIT were developed. When HIT is suspected, prompt cessation of all heparin therapy is necessary, along with initiation of alternative anticoagulant therapy. Two direct thrombin inhibitors--argatroban and lepirudin--are approved for the management of HIT in the United States, and bivalirudin is approved for use in patients with HIT who are undergoing percutaneous coronary intervention. Other agents, although not approved to manage HIT, have also been used; however, their role in therapy requires further evaluation. A comprehensive HIT management strategy involves the evaluation of numerous factors. Many patients, including those undergoing coronary artery bypass surgery, those with acute coronary syndromes, those with hepatic or renal insufficiency, and children, require special attention. Clinicians must become familiar with the available information on this serious adverse effect and its treatment so that optimum patient management strategies may be formulated.

Heparin-induced Thrombocytopenia, a Prothrombotic Disease

Heparin-induced thrombocytopenia (HIT) is a serious, yet treatable prothrombotic disease that develops in approximately 0.5% to 5% of heparin-treated patients and dramatically increases their risk of thrombosis (odds ratio, 37). The antibodies that mediate HIT (ie, heparin-platelet factor 4 antibodies) occur more frequently than the overt disease itself, and, even in the absence of thrombocytopenia, are associated with increased thrombotic morbidity and mortality. HIT should be suspected whenever the platelet count drops more than 50% from baseline (or to <150 x 10(9)/L) beginning 5 to 14 days after starting heparin (or sooner if there was prior heparin exposure) or new thrombosis occurs during, or soon after heparin treatment, with other causes excluded. When HIT is strongly suspected, with or without complicating thrombosis, heparins should be discontinued, and a fast-acting, nonheparin alternative anticoagulant such as argatroban should be initiated immediately. With prompt recognition, diagnosis, and treatment of HIT, the clinical outcomes and health economic burdens of this prothrombotic disease are improved significantly.

HEMATOLOGY: ISSUES IN THE DIALYSIS PATIENT: The Safety of Heparins in End-Stage Renal Disease

In patients on chronic dialysis, unfractionated heparin (UFH) is the most commonly used agent for anticoagulation of the hemodialysis extracorporeal circuit, for hemodialysis catheter "locking" between dialysis treatments, and for nondialysis indications such as venous thromboembolic disease, peripheral vascular disease, and acute coronary artery disease. Potentially serious complications of UFH, such as hemorrhage, osteoporosis, and thrombocytopenia, have led to consideration of other options for anticoagulation, including low molecular weight heparin (LMWH) and direct thrombin inhibitors (DTIs). LMWH can be used for anticoagulation of the hemodialysis circuit, but whether this has significant benefit compared to UFH remains to be proven. Because of the somewhat unpredictable risk of severe bleeding complications when LMWH is used for other indications in dialysis patients, UFH rather than LMWH is preferred for treatment of thromboembolic disease in these patients. DTIs have been used for anticoagulation in dialysis patients with heparin-induced thrombocytopenia (HIT), with argatroban being the preferred agent if heparin-free hemodialysis cannot be performed. UFH still remains the preferred anticoagulant in the vast majority of dialysis patients requiring systemic anticoagulation and for anticoagulation of the extracorporeal hemodialysis circuit.

HEMATOLOGY: ISSUES IN THE DIALYSIS PATIENT: When Heparin Causes Thrombosis: Significance, Recognition, and Management of Heparin-Induced Thrombocytopenia in Dialysis Patients

Heparin-induced thrombocytopenia (HIT) is characterized by thrombocytopenia and paradoxical hypercoagulability. HIT occurs when an antibody ("HIT antibody") produced against the complex of heparin and platelet factor 4 (PF4) causes systemic platelet consumption and activation. Nephrologists encounter HIT in the care of end-stage renal disease (ESRD) patients because heparin is a routine anticoagulant in hemodialysis. The incidence of HIT in ESRD appears to be lower than in other clinical settings. However, HIT is equally life threatening in ESRD patients and therefore demands the same prompt recognition and aggressive treatment. Diagnosing HIT requires the detection of HIT antibodies. A functional assay (e.g., [(14)C] serotonin release assay) relies on the patient's HIT antibodies to activate donor platelets at pharmacologic heparin concentrations. The more common antigen assay (e.g., enzyme-linked immunosorbent assay [ELISA]) detects the binding of the patient's HIT antibodies to antigens (e.g., heparin-PF4 complex) in a microtiter well and does not involve platelets. The moment HIT is suspected, heparin should be stopped and an alternative anticoagulant initiated immediately, even before the result of a serologic test becomes available. The advent of several new anticoagulants in the last decade, especially argatroban and bivalirudin, has expanded treatment options for HIT in dialysis patients. This review discusses the epidemiology, pathogenesis, clinical features, diagnosis, and treatment of HIT, with special emphasis on concepts relevant to the care of dialysis patients.

The Management of Patients With Heparin-Induced Thrombocytopenia Who Require Anticoagulant Therapy

For patients with heparin-induced thrombocytopenia (HIT), reexposure to heparin is generally not recommended. However, these patients are likely to require anticoagulation therapy at some point in the future. During acute HIT, when thrombocytopenia and anti-heparin-platelet factor 4 antibodies (or HIT antibodies) are present, therapy with heparin must be avoided. In patients with subacute HIT, when platelets have recovered but HIT antibodies are still present, therapy with heparin should be avoided. In patients with a remote history of HIT, when HIT antibodies have cleared, heparin reexposure may be safe, although recurrent HIT has been described in some patients. For all of these patients, the use of alternate anticoagulant agents, including direct thrombin inhibitors and anti-Xa agents, is preferable. There is an increasing amount of data supporting the use of these alternative agents in a wide variety of clinical circumstances, including thromboprophylaxis and treatment of acute thrombosis. Except for a few clinical situations, it is generally possible to avoid heparin reexposure in patients with a history of HIT.

Pharmacotherapy of heparin- induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a life-and-limb threatening condition that is associated with the development of antibodies that activate platelets and the coagulation system in the presence of unfractionated heparin or low molecular weight heparin. The binding of antibody to heparin-PF-4 complexes can activate platelets, leading to an acute, often catastrophic, thrombotic diathesis. The most common laboratory finding is the development of thrombocytopenia 5 or more days after beginning heparin treatment, which occur in up to 1 - 5% of patients exposed to heparin, depending on type of heparin and indication for anticoagulation. The onset of thrombocytopenia can be immediate or delayed for several weeks after the exposure to heparin. Approximately 50 - 60% of patients who develop HIT manifest acute venous or arterial thrombosis and a significant percentage of these patients die or develop vascular gangrene of a limb that requires amputation. Given the severe sequelae associated with HIT, recognition and immediate medical management is essential. Treatment of a patient with HIT is complex, as there are several different anticoagulants now available which have been shown to be useful. Optimal management depends on each patient's individual clinical manifestations, as well as the need for ongoing anticoagulation therapy. No single agent or treatment approach can be considered to be 'standard practice' as very few clinical trials have been completed, compare different treatment options. The use of warfarin alone in a patient with HIT, must be avoided in order to avoid the possibility of further activating coagulation, which may hasten the development of venous limb gangrene. There are several different tests available that detect HIT antibodies and each has different sensitivity and specificity for HIT. In this review we discuss the epidemiology and natural history of HIT, risk factors associated with the development of HIT and the clinical and laboratory tests that aid in the diagnosis and treatment. Special emphasis is given to addressing the management of HIT in special populations, particularly patients with renal or liver disease, acute coronary syndromes, pregnancy, paediatrics and patients who require cardiopulmonary bypass surgery.

Heparin-induced antiheparin-platelet antibody associated with retinal venous thrombosis

OBJECTIVE

To report a case of a 33-year-old white woman in whom retinal venous thromboses developed secondary to heparin-induced antiheparin-platelet antibodies.

DESIGN

Interventional case report.

METHODS

The patient underwent complete ophthalmic and medical examinations. Laser Doppler measurement of retinal blood circulation also was performed.

INTERVENTION

Prolonged anticoagulation with thrombin inhibitors and warfarin.

MAIN OUTCOME MEASURES

Visual symptoms, retinal appearance on clinical examination, and measurement of retinal blood flow by laser Doppler technique.

RESULTS

The patient experienced a scotoma in the visual field of the left eye, left retinal venous thrombosis, decreased venous blood flow in the left eye, and heparin-induced antiheparin-platelet antibodies in serum. After intervention, the visual symptoms and retinal appearance improved, and retinal blood flow normalized.

CONCLUSIONS

Heparin-induced antiheparin-platelet antibody can lead to thrombosis of the ocular circulation. This index case, which is the first one ever reported in association with antiheparin-platelet antibodies, further illustrates the potential side effects of heparin and widens the spectrum of complications of heparin-induced thrombocytopenia (HIT) and HIT thrombosis syndrome (HITTS).

Tackling the devastating effects of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia with associated thrombosis is a potentially catastrophic complication of heparin therapy. Heart failure patients often require heparin therapy in the setting of multiple comorbidities, particularly renal insufficiency. The authors report a case of heparin-induced thrombocytopenia with associated thrombosis in a patient with multisystem organ failure and discuss dosing regimens using lepirudin for the treatment of this disorder. The potential risk for excessive anticoagulation is highlighted and a conservative dosing strategy with frequent monitoring of this agent in the presence of renal failure is emphasized.

Current agents for the treatment of patients with heparin-induced thrombocytopenia

Several counterintuitive treatment paradoxes complicate the management of immune heparin-induced thrombocytopenia (HIT). For example, simple discontinuation of heparin often fails to prevent subsequent HIT-associated thrombosis. Thus, current treatment guidelines recommend substituting heparin with a rapidly acting alternative anticoagulant (eg, danaparoid, lepirudin, or argatroban) even when HIT is suspected on the basis of thrombocytopenia alone ("isolated HIT"). Another paradox-coumarin (warfarin) anticoagulation-can lead to venous limb gangrene in a patient with HIT-associated deep-vein thrombosis. Thus, warfarin is not recommended during acute thrombocytopenia secondary to HIT. However, warfarin can be given as overlapping therapy with an alternative anticoagulant, provided that (1) initiation of warfarin is delayed until substantial platelet count recovery has occurred (to at least above 100 x 10(9)/L); (2) low initial doses of warfarin are used; (3) at least 5 days of overlapping therapy are given; and (4) the alternative agent is maintained until the platelet count has normalized. It has recently been recognized that HIT antibodies are transient and usually do not recur upon subsequent re-exposure to heparin. This leads to a further paradox-patients with previous HIT can be considered for a brief re-exposure to heparin under exceptional circumstances; for example, heart surgery requiring cardiopulmonary bypass, if HIT antibodies are no longer detectable using sensitive assays. For patients with acute or recent HIT who require urgent heart surgery, other approaches include use of alternative anticoagulants (eg, lepirudin or danaparoid) for cardiopulmonary bypass or antiplatelet agents (eg, tirofiban or epoprostenol) to permit intraoperative use of heparin.

Treatment of heparin-induced thrombocytopenia

OBJECTIVE

To describe heparin-induced thrombocytopenia (HIT or HIT-2), an immune-mediated adverse reaction to heparin or low-molecular-weight heparin. Available treatment options and considerations in developing a therapy approach are discussed.

DATA SOURCES

A search of the National Library of Medicine (1992-June 2001) was done to identify pertinent literature. Additional references were reviewed from selected articles.

STUDY SELECTION

Articles related to laboratory recognition and treatment options of HIT, including the use of agents in selected clinical conditions, were reviewed and included.

CONCLUSIONS

HIT is a rare but potentially severe adverse reaction to heparin that was, until recently, poorly understood and had limited treatment options. Recent advances describing the recognition and clinical manifestations of immune-mediated HIT, including recently available antithrombotic treatment options, have dramatically changed outcomes for patients having this syndrome.