Heparin-induced thrombocytopenia: recognition, treatment, and prevention: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

Peripartum pulmonary embolism

Pregnancy is an example of Virchow's triad predisposing to the development of venous thromboembolism (VTE). Specific risk factors for antepartum and postpartum VTE have been identified. The diagnosis of pulmonary embolism in pregnancy is complicated by the physiologic changes of pregnancy as well as physicians' apprehension about ordering radiologic studies during pregnancy because of concerns with fetal well-being. Therapy for VTE is complicated by pregnancy physiology affecting medication pharmacokinetics and bioavailability, and the unpredictable occurrence of labor during therapeutic anticoagulation.

Acute bioprosthetic mitral valve stenosis in a patient with HITS

Acute thrombosis involving the left atrium and a bioprosthetic valve during the early postoperative period is an extremely rare complication of heparin-induced thrombocytopenia syndrome (HITS). We present a patient with early bioprosthetic mitral valve stenosis complicated by HITS in a patient with severe mitral regurgitation, atrial fibrillation, and severe left ventricular dysfunction.

Old and new anticoagulant drugs: a minireview

Abstract The limits of traditional anticoagulants, such as heparin and warfarin, have prompted the search for new agents for prophylaxis and treatment of arterial and venous thromboembolism, including factor Xa and thrombin inhibitors. These agents can be given orally, and their most significant advantage is that no laboratory monitoring is needed. The anti-Xa inhibitor rivaroxaban and the direct thrombin inhibitor dabigatran etexilate are licensed for prophylaxis of venous thromboembolism (VTE) in high-risk orthopedic surgery. They are at least as safe and effective as heparins but much more expensive. Dabigatran, rivaroxaban, and other agents currently in the pipeline of clinical development have the potential to replace warfarin in the two most frequent indications for anticoagulation, i.e. secondary prophylaxis of VTE and atrial fibrillation. Prevention and treatment of coronary artery thrombosis in patients with ischemic heart disease is another area of investigation for the role of new anticoagulants. These drugs have the potential to meet some currently unmet needs of traditional anticoagulants, but available clinical data warrant confirmation and expansion. Lack of specific antidotes for anticoagulation reversal and the high cost are important limitations of their use.

Drug allergy: an updated practice parameter

Adverse drug reactions (ADRs) result in major health problems in the United States in both the inpatient and outpatient setting. ADRs are broadly categorized into predictable (type A and unpredictable (type B) reactions. Predictable reactions are usually dose dependent, are related to the known pharmacologic actions of the drug, and occur in otherwise healthy individuals, They are estimated to comprise approximately 80% of all ADRs. Unpredictable are generally dose independent, are unrelated to the pharmacologic actions of the drug, and occur only in susceptible individuals. Unpredictable reactions are subdivided into drug intolerance, drug idiosyncrasy, drug allergy, and pseudoallergic reactions. Both type A and B reactions may be influenced by genetic predisposition of the patient

IgG-class anti-PF4/heparin antibodies and symptomatic DVT in orthopedic surgery patients receiving different anti-thromboembolic prophylaxis therapeutics

Background

Heparin-induced thrombocytopenia (HIT) is a thromboembolic complication that can occur with unfractionated heparin (UFH) or low molecular weight heparin (LMWH). Our objective was to determine and compare the incidence of IgG-class HIT antibodies in patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA) with different antithrombotic prophylaxis therapies and their contributions to the occurrence of venous thromboembolism (VTE).

Methods

A prospective observational study was performed for 374 Japanese patients undergoing THA or TKA to determine the incidence of VTE. IgG-class anti-PF4/heparin antibodies were measured using IgG-specific EIA before and after the operation.

Results

In the clinical outcome, the incidence of symptomatic deep vein thrombosis (DVT) was 15.0% (56/374, TKA; 35, THA; 21) and pulmonary emboli (PE) were not observed. The total seroconversion incidence of IgG-class PF4/heparin antibodies was 19.8% (74/374). The seroconversion incidence of IgG-class PF4/heparin antibodies was higher in patients receiving UFH (32.7%) compared to those receiving LMWH (9.5%) or fondaparinux (14.8%). Furthermore, the seroconversion incidence was significantly higher in patients undergoing TKA compared to those undergoing THA. Based on multivariate analysis, seroconversion of the IgG-class PF4/heparin antibodies was independent a risk factor for symptomatic DVT.

Conclusion

Our findings show that the seroconversion of IgG-class anti-PF4/heparin antibodies differed with various anti-thrombotic prophylaxis therapeutics and was associated with the risk of DVT in a subset of patients undergoing total joint arthroplasty (TKA and THA).

Venous thromboembolic prophylaxis for hip fractures

Patients with hip fractures are at very high risk for the development of venous thromboembolism (VTE). To provide an overview of cause, risk factors, current treatment strategies, and complications associated with VTE prophylaxis, we reviewed the most current, best available evidence on VTE prophylaxis for patients with hip fractures. We comprehensively reviewed the literature to assess the efficacy of VTE prophylaxis in patients with hip fractures, including the most recent published guidelines by national medical and surgical health organizations from the UK, USA, and Canada. Mechanical devices are effective in reducing the risk of VTE for hip fracture, but poor patient compliance is common and the devices are not recommended for sole VTE prophylaxis. Aspirin reduces the risk of VTE but does not provide optimal protection compared with other chemical agents; therefore, it is not recommended for sole VTE prophylaxis. Fondaparinux, warfarin, low-molecular-weight heparin, and unfractionated heparin reduce the risk of venographic deep vein thrombosis, but there is insufficient evidence that they reduce fatal pulmonary embolism or all-cause mortality. Fondaparinux is considered to be cost effective and more efficacious than low-molecular-weight heparin. At present, most major health organizations advocate at least 28 days of postoperative chemical prophylaxis. Chemical VTE prophylaxis should be administered to all patients with hip fractures unless contraindicated. Additional research is required to establish an agent that has a significant impact on fatal pulmonary embolism and all-cause mortality, without increasing bleeding complications, in this group of patients.

Trombocitopenia induzida por heparina e necrose cutânea por varfarina: relato de caso

É relatado um caso de trombocitopenia induzida por heparina complicada, com necrose cutânea induzida por varfarina em paciente de 74 anos, sexo feminino, internada com diagnóstico de fratura do colo do fêmur, trombose venosa profunda e tromboembolismo pulmonar. A necrose cutânea induzida por varfarina é uma complicação rara da terapia anticoagulante, com alta morbidade e mortalidade, que pode estar associada à trombocitopenia induzida por heparina.

Choosing the right heparin prophylaxis strategy in medical patients at risk for developing VTE: an evidence-based approach

Many acutely ill medical patients are at significant risk for developing venous thromboembolism (VTE) during hospitalization. Venous thromboembolism risk arises from both the presenting clinical condition as well as predisposing risk factors, such as advanced age. Thromboprophylaxis is underprescribed in these patients. Thrombotic risk assessment could encourage the prescribing of thromboprophylaxis and, therefore, improve patient protection against VTE. Current guidelines from the American College of Chest Physicians and the International Union of Angiology (IUA) recommend thromboprophylaxis with low-dose unfractionated heparin (UFH), a low-molecular-weight heparin (LMWH), or fondaparinux for acutely ill medical patients with VTE risk factors. However, the optimal dose regimen for UFH is unclear. The 2006 evidence-based guidelines from the IUA recommend a 3-times-daily dose regimen for UFH. However, UFH is usually administered twice daily despite a lack of evidence for the superiority of this regimen. Both heparin-induced thrombocytopenia and bleeding are associated with UFH, and to a lesser degree with alternative anticoagulants, such as the LMWHs. If utilized, an appropriate prophylaxis regimen in medical patients can reduce the risk of VTE and its burden.

Guidelines for the prevention of stroke in patients with stroke or transient ischemic attack: a guideline for healthcare professionals from the american heart association/american stroke association

The aim of this updated statement is to provide comprehensive and timely evidence-based recommendations on the prevention of ischemic stroke among survivors of ischemic stroke or transient ischemic attack. Evidence-based recommendations are included for the control of risk factors, interventional approaches for atherosclerotic disease, antithrombotic treatments for cardioembolism, and the use of antiplatelet agents for noncardioembolic stroke. Further recommendations are provided for the prevention of recurrent stroke in a variety of other specific circumstances, including arterial dissections; patent foramen ovale; hyperhomocysteinemia; hypercoagulable states; sickle cell disease; cerebral venous sinus thrombosis; stroke among women, particularly with regard to pregnancy and the use of postmenopausal hormones; the use of anticoagulation after cerebral hemorrhage; and special approaches to the implementation of guidelines and their use in high-risk populations.

Laboratory methods and management of patients with heparin-induced thrombocytopenia

The clinical effects of heparin are meritorious and heparin remains the anticoagulant of choice for most clinical needs. However, as with any drug, adverse effects exist. Heparin-induced thrombocytopenia (HIT) is an important adverse effect of heparin associated with amputation and death due to thrombosis. Although the diagnosis and treatment of HIT can be difficult and complex, it is critical that patients with HIT be identified as soon as possible to initiate early treatment to avoid thrombosis.

The influence of poly-N-[(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide on fibrin polymerization, cross-linking and clot structure

Poly-N-[(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide (PDMDOMA) is a neutral synthetic water-soluble polymer. In this report, we evaluated the influence of PDMDOMA on blood hemostasis by studying the fibrin polymerization process, the three-dimensional clot structure, and the mechanical properties and fibrinolysis. PDMDOMA altered the normal fibrin polymerization by changing the rate of protofibril aggregation and resulting in a 5-fold increase in the overall turbidity. Fibrin clots formed in presence of PDMDOMA exhibited thinner fibers with less branching which resulted in a more porous and heterogeneous clot structure in scanning electron micrographs. The overall strength and rigidity of the whole blood clot also decreased up to 10-fold. When a combination of plasminogen and tissue-plasminogen activators were included in clotting reactions, fibrin clots formed in the presence of PDMDOMA exhibited highly shortened clot lysis times and was supported by the enhanced clot lysis measured by thromboelastography in whole blood. Further evidence of the altered clot structure and clot cross-linking was obtained from the significant decrease in d-dimer levels measured from degraded plasma clot. Thus, PDMDOMA may play an important role as an antithrombotic agent useful in prophylactic treatments for thrombosis by modulating fibrin clot structure to enhance fibrinolysis.

Pharmacist-Managed Direct Thrombin Inhibitor Protocol Improves Care of Patients with Heparin-Induced Thrombocytopenia

Use of direct-thrombin inhibitors (DTIs) for the management of patients with heparin-induced thrombocytopenia (HIT) is challenging. A pharmacist-managed DTI protocol was implemented to standardize and improve the care of patients with HIT. A background study that compared DTI protocol–treated patients to those who did not receive treatment with the DTI protocol found that significantly more of the DTI protocol–treated patients received care that was consistent with level 1 guidelines from the American College of Chest Physicians (41% vs 0%). Because outcomes were poor regardless of whether the DTI protocol was used, the protocol was revised to require pharmacist implementation and oversight. A follow-up study compared DTI protocol patients from the background study (non-pharmacist-managed) to the pharmacist-managed DTI protocol group. There were significantly fewer dosing errors, improved nursing documentation, and less reexposure to heparin when the pharmacist was responsible for managing the DTI protocol. A trend toward reduced bleeding was noted. The management of patients with HIT is complex, and there are a number of pitfalls that may lead to poor outcomes. DTIs are high-risk medications that require careful dosing and monitoring to minimize risk for adverse drug events. A DTI protocol may improve care of patients with HIT, and pharmacist oversight of DTI use can help to reduce risk for errors and adverse medication events.

Warfarin-induced penile necrosis in a patient with heparin-induced thrombocytopenia

A 56-yr-old man with lung adenocarcinoma presented with subsegmental pulmonary thrombosis. Platelet count on presentation was 531 x 10(9)/L. The patient was anticoagulated with subcutaneous low molecular weight heparin (LMWH). Next day, oral anticoagulation was initiated with 5 mg of warfarin once daily with LMWH and LMWH was discontinued at third hospital day. On the third day of oral anticoagulation therapy, he complained of left leg swelling and prolonged painful penile erection of 24 hr-duration. His platelet count reached a nadir 164 x 10(9)/L at that time, and the patient had a deficiency of protein C and S, with an activity level of 16% and 20% of normal value. Warfarin was stopped and he underwent penile aspiration. The next day, left leg edema and penile erection was disappeared, but penile and glans penis necrosis was started. This case illustrates that processes underlying heparin-induced thrombocytopenia (HIT) may also underlie warfarin-induced skin necrosis.

HEPARIN IN HUMAN PLACENTAL DEVELOPMENT AND THE PREVENTION OF PLACENTAL COMPLICATIONS OF PREGNANCY

The development of effective anticoagulant drugs available for use in pregnancy has resulted in dramatic improvements for a number of potentially life-threatening conditions. These include the treatment and prevention of venous thromboembolism and the thrombotic complications of antiphospholipid antibody syndrome, as well as the management of pregnant women with mechanical heart valves. The most commonly used class of drug includes heparin, a highly-charged macro-molecule that does not cross the placenta, in contrast to the potentially teratogenic and fetotoxic oral drug warfarin. This review will focus on our current lack of understanding of the wider actions of heparin and examines the possibility that large numbers of pregnant women are presently being treated inappropriately with heparin.

Aptamers: the emerging class of future anticoagulation for vascular disease

Anticoagulation is an important therapeutic strategy to treat and prevent recurrent thrombotic events in patients after acute myocardial infarction and ischemic stroke. However, available anticoagulants have numerous shortcomings including hemorrhage risks, limited clinical application including heparin-induced thrombocytopenia and modest therapeutic benefit. Each component of the coagulation cascade is a potential target for new drug developments. Representing an attractive new therapeutic class, aptamers are nucleic acid ligand with a high affinity and specificity for proteins involved in the clot growth. Potential antidote control of aptamer activity offers an important advance in anticoagulant safety. Aptamers are a promising class of compounds, both for target validation and therapy. As designer drugs, they exhibit high specificity, high affinity and modifiable bioavailability. The ability to generate inhibitors with such properties against a variety of target proteins will be valuable as the human genome and proteome are deciphered. This article summarizes current knowledge of aptamers developed against coagulation proteins, focusing on the biology, pharmacology, preclinical and early clinical experience with this novel class of anticoagulants.

Heparin-induced non-necrotizing skin lesions: rarely associated with heparin-induced thrombocytopenia

SUMMARY BACKGROUND

Recently, there has been an increasing number of reports regarding adverse skin reactions to subcutaneous heparin administration. Case series have implied that heparin-induced skin lesions are predominantly associated with life-threatening heparin-induced thrombocytopenia (HIT) in at least 22% of patients. Skin lesions, therefore, have been included in clinical scores for HIT.

OBJECTIVES

To determine the association of heparin-induced skin lesions with HIT. This would have a pivotal impact on further anticoagulatory management in patients with heparin-induced skin lesions.

PATIENTS/METHODS

In our observational cohort study, 87 consecutive patients with heparin-induced skin lesions (85 occurring during low-molecular-weight heparin administration) were evaluated using a standardized internal protocol, including HIT diagnostics (heparin-platelet factor 4-ELISA, heparin-induced platelet activation assay), platelet count monitoring, clinical/sonographical screening for thrombosis, skin allergy testing and, if necessary, histology.

RESULTS

None of the observed heparin-induced skin lesions was due to HIT; all lesions were caused by delayed-type IV-hypersensitivity reactions (DTH) instead. Even the cutaneous reaction in one patient with concomitant HIT could be classified histologically as DTH reaction, amounting to an association of heparin-induced skin lesions and HIT in 1.2% (1/87; 95% confidence interval, 0.00-0.06).

CONCLUSION

Heparin-induced skin lesions associated with use of low-molecular-weight heparins do not seem to be strongly associated with a systemic immunologic reaction in terms of HIT and might rather be due to DTH reactions than due to microvascular thrombosis. Hence, we propose refining existing pretest probability scores for HIT, unless underlying causes have been clarified.

The complex clinical picture of side effects to anticoagulation

Inflammatory plaques at injection sites are frequent side effects of heparin treatment and a clinical symptom of delayed-type hypersensitivity (DTH) to heparin. In most cases, changing the subcutaneous therapy from unfractionated to low-molecular-weight heparin or treatment with heparinoids does not provide improvement because of extensive cross-reactivity. Because of their completely different chemical structure, hirudins are a safe alternative for anticoagulation. Despite DTH to subcutaneously injected heparins, patients tolerate heparin intravenously. Therefore, in case of therapeutic necessity and DTH to heparins, the simple shift from subcutaneous to intravenous heparin administration is justified. Skin necrosis is a rare complication of anticoagulation. Heparin-induced skin necrosis is 1 of the symptoms of immune-mediated heparin-induced thrombocytopenia and should result in the immediate cessation of heparin therapy to prevent potentially fatal thrombotic events. This is in contrast to coumarin-induced skin necrosis, where therapy may be continued or restarted at a lower dose.

Validation of the high-dose heparin confirmatory step for the diagnosis of heparin-induced thrombocytopenia

The diagnosis of heparin-induced thrombocytopenia (HIT) requires detection of antibodies to the heparin/platelet factor 4 (PF4) complexes via enzyme-linked immunosorbent assay. Addition of excess heparin to the sample decreases the optical density by 50% or more and confirms the presence of these antibodies. One hundred fifteen patients with anti-heparin/PF4 antibodies detected by enzyme-linked immunosorbent assay were classified as clinically HIT-positive or HIT-negative, followed by confirmation with excess heparin. A multivariate logistic regression model was fitted to estimate relationships between patient characteristics, laboratory findings, and clinical HIT status. This model was validated on an independent sample of 97 patients with anti-heparin/PF4 antibodies. No relationship between age, race, or sex and clinical HIT status was found. Maximal optical density and confirmatory positive status independently predicted HIT in multivariate analysis. Predictive accuracy on the training set (c-index 0.78, Brier score 0.17) was maintained when the algorithm was applied to the independent validation population (c-index 0.80, Brier score 0.20). This study quantifies the clinical utility of the confirmatory test to diagnose HIT. On the basis of data from the heparin/PF4 enzyme-linked immunosorbent assay and confirmatory assays, a predictive computer algorithm could distinguish patients likely to have HIT from those who do not.

Post-operative thromboprophylaxis: new oral thrombin and factor X inhibitors and their place in clinical practice

Thromboprophylaxis can reduce the incidence of postoperative thromboembolic events by two-thirds. Traditionally, unfractionated heparin, low-molecular-weight heparins, vitamin K antagonists, and mechanical methods have been used. Recently, thrombin and factor Xa (FXa) antagonists have been introduced in clinical practice. Advantages are oral administration, potentially higher efficacy in reducing thromboembolic events without increasing major bleeding, and no need for monitoring of the anticoagulatory effect. So far these drugs have mainly been tested after total hip and knee arthroplasties. However, data after most other orthopedic and surgical procedures are sparse. In special populations - for example, patients with renal failure - these drugs have not been sufficiently tested yet. Accordingly, the clinical use of these promising new drugs should be restricted to situations where efficacy has been proven with clear evidence from controlled clinical trials.

Argatroban therapy for heparin-induced thrombocytopenia in ICU patients with multiple organ dysfunction syndrome: a retrospective study

Introduction

Heparin-induced thrombocytopenia (HIT) is a serious, prothrombotic, immune-mediated adverse reaction triggered by heparin therapy. When HIT is diagnosed or suspected, heparins should be discontinued, and an alternative, fast-acting, parenteral, nonheparin anticoagulation such as argatroban should be initiated. Limited and inconsistent data exist about dosing of argatroban in intensive care unit (ICU) patients with critical illnesses.

Methods

Retrospective analysis of 12 ICU patients with multiple organ dysfunction syndrome (MODS) treated with argatroban for suspected or diagnosed HIT.

Results

The 12 ICU patients with a mean platelet count of 46,000 ± 30,310 had a mean APACHE II score of 26.7 ± 7.8 on ICU admission and a mean SAPS II score of 61.5 ± 16.3 on the first day of argatroban administration. A mean argatroban starting dose of 0.32 ± 0.25 μg/kg/min (min, 0.04; max, 0.83) was used to achieve activated partial thromboplastin times (aPTTs) >60 sec or aPTTs of 1.5 to 3 times the baseline aPTT. Adjustment to aPTT required dose reduction in six (50%) patients. Patients were treated for a mean of 5.5 ± 3.3 days. The final mean dose in these critically ill patients was 0.24 ± 0.16 μg/kg/min, which is about one eighth of the usually recommended dose and even markedly lower than the previously suggested dose for critically ill ICU patients. In all patients, desired levels of anticoagulation were achieved. The mean argatroban dose was significantly lower in patients with hepatic insufficiency compared with patients without hepatic impairment (0.10 ± 0.06 μg/kg/min versus 0.31 ± 0.14 μg/kg/min; P = 0.026). The mean argatroban dose was significantly correlated with serum bilirubin (r = -0.739; P = 0.006).

Conclusions

ICU Patients with MODS and HIT can be effectively treated with argatroban. A decrease in the initial dosage is mandatory in this patient population. Further studies are needed to investigate argatroban elimination and dosage adjustments for critically ill patients.

Acute myocardial infarction during thrombolysis of mechanical aortic valve thrombosis associated with heparin-induced thrombocytopenia

We report a case of a 60-year-old man with obstructive aortic prosthetic valve thrombosis (APVT). He was treated with low-dose (25 mg) slow infusion (6 hours) of intravenous tissue plasminogen activator (t-PA), and he suffered acute anterior myocardial infarction (MI) at the fourth hour of t-PA infusion. Infusion was kept on, and coronary reperfusion and successful lysis of APVT were achieved. Intravenous unfractionated heparin (UFH) was then started, however, on the third day following heparin treatment, heparin-induced thrombocytopenia (HIT) was recognized by a drop in the platelet count and rethrombosis of the prosthetic valve. Although no nonheparin anticoagulant was available, intravenous continuous infusion of streptokinase (SKZ) 250,000 U per day was administered for 5 days followed by transition to warfarin therapy. Successful lysis of the APVT was again achieved with this regimen and the patient was discharged after uneventful recovery. The patient remained well at 6 months and 1 year follow-up.

Primary prevention of venous thromboembolism in medical and surgical oncology patients

Recent data suggest that patients with a malignancy have a seven-fold increased risk for venous thromboembolism (VTE) compared with those without cancer, suggesting that these patients may benefit from thromboprophylaxis. Mechanisms for the prevention of thromboembolism can be divided into two broad categories: mechanical and pharmacological. Although generally used in combination with pharmacotherapy, little evidence exists for the efficacy of mechanical modalities either in the broader population of patients at risk for VTE or for patients with cancer specifically. A recent study using graduated compression stockings (GCS) for thromboprophylaxis showed no support for the use of stockings in acute stroke patients. Established pharmacological modalities, including warfarin, unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), and the factor Xa inhibitor fondaparinux, have been shown to reduce risk for VTE in general medical and surgical populations. In medical cancer patients, only limited data are available for the efficacy of thromboprophylaxis. In contrast, considerable evidence indicates that thromboprophylaxis is warranted in patients undergoing cancer surgery. The most recent evidence suggests that catheter-related thrombosis is not prevented by current pharmacological modalities. On 22 May 2009, a group of clinicians based in the United Kingdom (UK) met in London, UK, to evaluate recent data on cancer thrombosis. This article (the second of four) briefly reviews key data on the prevention of VTE in medical and surgical oncology patients, providing context for a brief transcript of the surrounding discussion and a consensus statement, developed by meeting attendees, on the implications of this information for UK clinical practice.

Fondaparinux (Arixtra®), a Safe Alternative for the Treatment of Patients With Heparin-Induced Thrombocytopenia?

Fondaparinux, a pentasaccharide which selectively binds to antithrombin III, has negligible to no cross-reactivity with heparin-induced thrombocytopenia (HIT) antibodies in in vitro studies. The lack of cross-reactivity suggests a potential role in the management of HIT, and indeed, there are several such case reports and small studies. These published data have used both the prophylactic and weight-based treatment doses. However, due to the small possibility of developing HIT with thromboembolic complications while receiving fondaparinux, it is suggested that the appropriate weight-based treatment dose be used. In all these reports, fondaparinux provided adequate anticoagulation, prevented further thromboembolic events, and platelet counts returned to normal. However, there have been a couple of case reports on possible HIT or HIT-like syndrome secondary to fondaparinux use. Conclusion: Fondaparinux is an attractive anticoagulant therapy in patients with HIT. There is still the need for larger randomized trials evaluating the true efficacy, appropriate dose, safe duration of treatment, and the true incidence of HIT associated with fondaparinux.

Controversies of Anticoagulation Reversal in Life-Threatening Bleeds

Therapeutic anticoagulation with heparins, warfarin, and anti-Xa inhibitors carry an inherent risk of complications due to their multifaceted pharmacokinetic and pharmacodynamic properties as well as narrow therapeutic ranges. When an anticoagulated patient presents with a major or life-threatening bleed, immediate and effective therapy may be necessary to reverse the effects of the anticoagulant, minimize blood loss, and reduce patient morbidity and mortality. Optimal agents and strategies for anticoagulant reversal are limited, particularly for newer anticoagulants. The literature describing such strategies available to reverse the effects of anticoagulants in the setting of a bleed is limited, and therefore many controversies exist. Thus, as new anticoagulants become available, without a specific agent for reversal, the concerns and controversies related to this topic must be addressed. The purpose of this review is to discuss the management of major or life-threatening bleeds by addressing the following controversies: (1) the use of recombinant factor VIIa for rapid reversal of warfarin in patients with intracerebral hemorrhage, (2) the role of prothrombin complex concentrate in emergent warfarin reversal, and (3) the optimal approach to reverse newer anticoagulants such as low molecular weight heparins, fondaparinux, and direct thrombin inhibitors.

Venous thromboembolism: a clinical review

Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism, represents a significant source of morbidity and mortality. It is readily diagnosed with noninvasive modalities when there is a clinical suspicion. Most patients presenting with signs and symptoms of DVT have well-known risk factors, such as a history of VTE, malignancy, recent illness, or immobilization. A subset of individuals with idiopathic VTE have no readily identifiable risk factors. Therapeutic anticoagulation is the cornerstone of management in all patients with VTE. Adjunctive measures, such as thrombolysis and the use of vena cava filters, are indicated in select cases. The ideal duration of anticoagulation is unknown, but is often maintained long-term in patients with acquired or inherited thrombophilia. Warfarin is the only oral anticoagulant approved by the US Food and Drug Administration. Warfarin carries a substantial annual risk of bleeding complications, requires ongoing monitoring, and has extensive drug-drug interactions, which are causes for concern in patients requiring long-term anticoagulation. Alternative oral anticoagulants, such as direct thrombin inhibitors and factor Xa inhibitors, are subjects of active research in alternative agents for oral anticoagulation, and have been recently approved for prophylaxis in Canada and the European Union.

Pulmonary embolism in pregnancy

Pulmonary embolism (PE) is the leading cause of maternal mortality in the developed world. Mortality from PE in pregnancy might be related to challenges in targeting the right population for prevention, ensuring that diagnosis is suspected and adequately investigated, and initiating timely and best possible treatment of this disease. Pregnancy is an example of Virchow's triad: hypercoagulability, venous stasis, and vascular damage; together these factors lead to an increased incidence of venous thromboembolism. This disorder is often suspected in pregnant women because some of the physiological changes of pregnancy mimic its signs and symptoms. Despite concerns for fetal teratogenicity and oncogenicity associated with diagnostic testing, and potential adverse effects of pharmacological treatment, an accurate diagnosis of PE and a timely therapeutic intervention are crucial. Appropriate prophylaxis should be weighed against the risk of complications and offered according to risk stratification.

[Postoperative period in cardiac surgery: don't forget heparin induced thrombocytopenia!]

Type II heparin-induced thrombocytopenia (HIT) has a low incidence in cardiac surgery, but its mortality once declared is high. Its clinical recognition can be difficult with these patients who usually have thrombocytopenia in postoperative period and who are predisposed to develop HIT prematurely. Thromboses in this context must be specific, and treatment, which is nowadays well codified, must be begun without waiting for biologic results. Besides, specificity of Elisa's test is weakened in this population since there is a high rate of serum conversion; yet, its preoperative realization associated with pre-test probability scoring for HIT, can turn out useful.

Heparin-induced thrombocytopenia associated with pulmonary embolism

Type II heparin-induced thrombocytopenia (HIT) is a potentially severe adverse effect of heparin treatment triggered by an immune response. Although most cases occur in patients receiving unfractioned heparin, HIT can also arise after low-molecular-weight heparin (LMWH). We report a case of HIT in a postoperative orthopedic 75-year-old woman in treatment with LMWH (nadroparin) complicated by pulmonary embolism and treated successfully with recombinant hirudin. Early recognition and proper treatment are fundamental for the management of this life-threatening disorder.

An evaluation of monitoring possibilities of argatroban using rotational thromboelastometry and activated partial thromboplastin time

BACKGROUND

Rotational thrombelastometry/thrombelastography with ROTEM and TEG is becoming available bedside in an increasing number of intensive care units, where many patients with heparin-induced thrombocytopenia (HIT) are treated. The study has been performed in an effort to find out whether ROTEM could be an alternative to activated partial thromboplastin time (aPTT) when argatroban is used for anticoagulation.

METHODS

Argatroban was added in vitro to a series of citrated whole-blood samples from 10 healthy volunteers to obtain whole-blood concentrations of 0, 0.125, 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 mg/l. ROTEM and whole-blood aPTT analyses were performed at each argatroban concentration. Correlation analyses were performed using the Spearman correlation analysis.

RESULTS

There was a significant and strong correlation between argatroban concentrations and clotting time (CT in ROTEM analysis with INTEM) (P<0.0001 and r=0.98). Also, the ROTEM time to maximum clot formation velocity (MAXV-t) appeared to have a very strong and highly significant correlation to argatroban concentrations (P<0.0001 and r=0.95). When we studied the correlation between aPTT and CT, we found a highly significant and strong correlation between these two analyses (P<0.0001 and r=0.97), especially so in the clinically relevant therapeutic range up to 100 s aPTT prolongation for HIT patients.

CONCLUSION

A significant and strong correlation was found between argatroban concentrations and several ROTEM parameters. Rotational thrombelastometry/thrombelastography has a potential role in increasing the safety of argatroban anticoagulation in critically ill patients.

Profound thrombocytopenia after primary exposure to eptifibatide

Eptifibatide is a glycoprotein IIb/IIIa receptor antagonist used to reduce the incidence of ischemic events in patients with acute coronary syndromes and those undergoing percutaneous coronary intervention. A minority of patients given eptifibatide develop acute, profound thrombocytopenia (<20,000 cells/mm(3)) within a few hours of receiving the drug. This case report discusses a patient who developed profound thrombocytopenia within hours of receiving eptifibatide for the first time. The Naranjo algorithm classified the likelihood that this patient's thrombocytopenia was related to eptifibatide as probable. Profound thrombocytopenia is an uncommon but clinically important complication of eptifibatide. This case report emphasizes the importance of monitoring platelet counts routinely at baseline and within 2-6 hours of eptifibatide administration.

[Heparin-induced thrombocytopenia occurring after surgical treatment of atrial myxoma--a case report]

INTRODUCTION

Heparin-induced thrombocytopenia (HIT) is an acquired, prothrombotic disorder, caused by antibodies to a complex of heparin and platelet factor 4 (PF4) that activates platelets, resulting in the release of procoagulant microparticles, thrombocytopenia occurrence, generation of thrombin, and frequent thromboses.

CASE OUTLINE

We present a case of severe HIT in a 68-year-old female, which occurred after cardiosurgery of the left atrial myxoma with the aim to point out the importance of differential diagnosis of thrombocytopenia in patients recently exposed to heparin. Platelet count dropped on the eleventh postoperative day, six days after unfractioned heparin and enoxaparine threatment, to 4x10(9)/I.The correct diagnosis failed to be made at first. Since thrombocytopenia remained refractory to a corticosteroid treatment and platelet transfusion, the patient was hospitalized on the 13th postoperative day at the Institute of Haematology. The diagnosis of HIT was confirmed with the high-probability clinical score (4T's) and strongly positive anti-heparin-PF4 (PaGIA) test as well as positive platelet aggregation test. The treatment started with a smaller therapeutic doses of danaparoid than recommended of 750 U intravenous bolus and was followed by continuous infusions of 100 U per 1 h and intravenous gammaglobulins in full dosage for four days. The platelet count started to rise on the third day and it was completely normalized on the 5th day of the therapy.

CONCLUSION

Treatment of severe HIT with small doses of danaparoid supplemented by intravenous gamma globulin was successful. Additional awareness of heparin-induced thrombocytopenia is needed, especially of HIT in differential diagnosis of thrombocytopenia in patients recently exposed to heparin.

Heparin-induced thrombocytopenia and endovascular procedures: report of two cases

Heparin-induced thrombocytopenia (HIT) is a transient disorder caused by platelet-activating antibodies against platelet factor 4 (PF4)-heparin complexes. Clinically it translates into arterial or venous thrombosis and carries high morbidity and mortality. The use of large doses of heparin during endovascular repair of abdominal aortic aneurysm could increase the incidence of HIT. We report two cases associating the use of heparin during endovascular repair of abdominal aortic aneurysm with the development of HIT.

Pharmacogenetics in cardiovascular antithrombotic therapy

Thrombosis is the most important underlying mechanism of coronary artery disease and embolic stroke. Hence, antithrombotic therapy is widely used in these scenarios. However, not all patients achieve the same degree of benefit from antithrombotic agents, and a considerable number of treated patients will continue to experience a new thrombotic event. Such lack of clinical benefit may be related to a wide variability of responses to antithrombotic treatment among individuals (i.e., interindividual heterogeneity). Several factors have been identified in this interindividual heterogeneity in response to antithrombotic treatment. Pharmacogenetics has emerged as a field that identifies specific gene variants able to explain the variability in patient response to a given drug. Polymorphisms affecting the disposition, metabolism, transporters, or targets of a drug all can be implicated in the modification of an individual's antithrombotic drug response and therefore the safety and efficacy of the aforementioned drug. The present paper reviews the modulating role of different polymorphisms on individuals' responses to antithrombotic drugs commonly used in clinical practice.

A Benchmark for Platelet Count Monitoring with Low-Molecular-Weight Heparin: Expanding Implementation of National Patient Safety Goals

Practitioners in US hospitals are implementing anticoagulation dosing and monitoring protocols to improve the safety of anticoagulation, consistent with National Patient Safety Goal 03.05.01. An audit of the Utrecht Patient Oriented Database of patients treated with low-molecular-weight heparin (LMWH) at the University Medical Center Utrecht revealed low compliance with platelet count monitoring as well as initial management of suspected heparin-induced thrombocytopenia (HIT). Limitations to this work included the inability to exclude other drug-induced causes of thrombocytopenia and their definition of the frequency of platelet count monitoring for compliance in patients given venous thromboembolism prophylaxis. Despite these limitations, the authors’ work represents the first published report on extending the quality of heparin anticoagulation management to platelet count monitoring and evaluation for HIT in a large patient population. Clinicians should include evaluations of compliance with platelet count monitoring with unfractionated heparin and LMWH, as well as appropriateness of the initial management strategies for HIT, and direct thrombin inhibitor protocols in their patient safety practice assessments.

Hypothermic cardiopulmonary bypass as a determinant of late thrombocytopenia following cardiac operations in pediatric patients

BACKGROUND

Thrombocytopenia after cardiac operations is a common event in both adult and pediatric patients. Late thrombocytopenia (LTCP) is a less common event that is still without a well-recognized cause. This study explores the role of heparin-induced thrombocytopenia (HIT) and other factors (complexity of the operation, temperature management, and drug use) in determining LTCP.

METHODS

We conducted an observational study of 63 consecutive patients aged <36 months operated with or without cardiopulmonary bypass (CPB). LTCP was defined as a platelet count <100,000 cells/microl or <50% of the pre-operative count at any point in time between post-operative days 5 and 10. A diagnostic test for heparin-platelet factor 4 (PF4) antibodies was performed in patients with LTCP. Other pre- and post-operative factors were investigated for their association with LTCP.

RESULTS

LTCP occurred in 15 (24%) patients. No patient had positive heparin-PF4 antibodies. The lowest temperature on CPB was an independent predictor of LTCP, with a cut-off value at 29 degrees C (sensitivity 80%, specificity 70%). Other factors associated with LTCP were prolonged post-operative use of unfractionated heparin and milrinone. LTCP was associated with increased post-operative morbidity.

CONCLUSION

LTCP was related to a combination of factors (operation severity, degree of hypothermia during CPB, prolonged use of unfractionated heparin, and milrinone). The individual contribution of each factor seems difficult to establish. However, the degree of hypothermia during CPB and drug-associated effects were identified. HIT could be excluded in all cases.