The management of heparin-induced thrombocytopenia

[Heparin-Induced Thrombocytopenia]

The extensive use of therapeutic doses of heparin to prevent thrombosis in critically ill patients with COVID-19 during the pandemic has led to an increased incidence of bleeding and heparin-induced thrombocytopenia (HIT). In addition, the introduction of the AstraZeneca and Johnson&Johnson vaccines against COVID-19 into clinical practice was associated with the development of a rare but very severe, adverse thrombotic complication, vaccine-induced immune thrombotic thrombocytopenia (VITT). Thrombotic complications of VITT turned out to be similar to HIT both clinically and pathophysiologically. HIT is a potentially fatal immune-mediated adverse drug response that results in emergence of antibodies that activate platelets in the presence of heparin. HIT is characterized by a high incidence of venous and arterial thromboses, often with fatal outcomes. Currently, there are clearly defined international guidelines for the diagnosis, treatment and prevention of HIT. In case of thrombotic complications, non-heparin anticoagulants should be used.

Vaccine-Induced Immune Thrombotic Thrombocytopenia: Clinicopathologic Features and New Perspectives on Anti-PF4 Antibody-Mediated Disorders

INTRODUCTION

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare yet severe adverse complication first identified during the global vaccination effort against SARS-CoV-2 infection, predominantly observed following administration of the ChAdOx1-S (Oxford-AstraZeneca) and Ad26.CoV2.S (Johnson & Johnson/Janssen) adenoviral vector-based vaccines. Unlike other anti-platelet factor 4 (PF4) antibody-mediated disorders, such as heparin-induced thrombocytopenia (HIT), VITT arises with the development of platelet-activating anti-PF4 antibodies 4-42 days post-vaccination, typically featuring thrombocytopenia and thrombosis at unusual sites.

AIM

To explore the unique properties, pathogenic mechanisms, and long-term persistence of VITT antibodies in patients, in comparison with other anti-PF4 antibody-mediated disorders.

DISCUSSION

This review highlights the complexity of VITT as it differs in antibody behavior and clinical presentation from other anti-PF4-mediated disorders, including the high incidence rate of cerebral venous sinus thrombosis (CVST) and the persistence of anti-PF4 antibodies, necessitating a re-evaluation of long-term patient care strategies. The nature of VITT antibodies and the underlying mechanisms triggering their production remain largely unknown.

CONCLUSION

The rise in awareness and subsequent prompt recognition of VITT is paramount in reducing mortality. As vaccination campaigns continue, understanding the role of adenoviral vector-based vaccines in VITT antibody production is crucial, not only for its immediate clinical implications, but also for developing safer vaccines in the future.

Bivalirudin as a Systemic Anticoagulant and Flush Solution Additive for Sequential Mitral and Tricuspid Valve Percutaneous Edge-to-Edge Repair in a Patient With Heparin-Induced Thrombocytopenia

Herein the case of a patient with a prior history of heparin-induced thrombocytopenia who underwent percutaneous mitral valve edge-to-edge repair that was followed by a tricuspid edge-to-edge repair two months later is presented. Recommendations exist for systemic anticoagulant alternatives for percutaneous mitral valve edge-to-edge repair with the MitraClip device (Abbott, Chicago, IL), but minimal guidance and experience are present regarding alternative systemic anticoagulation during the performance of right-sided interventions, including tricuspid edge-to-edge repair (TriClip; Abbott). Notably, there is no clear consensus regarding the use of an alternative anticoagulant in the catheter flush solution for the delivery systems used during these procedures, particularly for right-sided interventions.

Anticoagulation management strategies in heart transplantation

Anticoagulation before, during, and after heart transplantation (HT) presents unique challenges to clinicians. Bleeding and thrombotic morbidity continues to affect this patient population throughout all phases of the HT journey. Reversal is commonly required since patients are commonly bridged to HT with left ventricular assist devices, which require chronic anti platelet and anticoagulation. Caution must be exercised in patients requiring cardiopulmonary bypass during surgery who are at risk of complications from heparin induced thrombocytopenia. The reported incidence of venous thromboembolism following HT is high, particularly during the first post-HT year, most likely due to surgery, biopsies, specific immunosuppression (mTOR inhibitors) and immobilization. It is crucial to maintain long-term oral anticoagulation after the first venous thromboembolism event, especially when risk factors exist. A major issue, and one for which there remains considerable debate, is the optimal treatment of such complications, particularly upper extremity venous thrombosis. For both warfarin and the thrombin inhibitors or Factor Xa inhibitors, the clinician must determine potential drug interactions based on the HT drug regimen, and then develop a patient-specific management strategy.

Risk of Venous Thromboembolism in Patients With Keratinocyte Carcinoma

Importance

Although malignancy is an established risk factor for venous thromboembolism (VTE), the risk of VTE specifically in patients with keratinocyte carcinoma (KC) has not been previously studied.

Objective

To determine the risk of VTE in patients with KC compared with patients not diagnosed with cancer and with patients diagnosed with common malignant neoplasms associated with VTE.

Design, Setting, and Participants

Population-based retrospective analysis of patient insurance claims made between January 1, 2007, and December 31, 2014, from the Truven MarketScan Commercial and Medicare Supplemental Databases. Patients treated across the United States were divided into 3 cohorts: patients with KC, patients with pancreatic cancer or acute myelogenous leukemia who are thus at high risk for VTE, and patients without a history of common malignant neoplasms. Patients were excluded from the KC cohort if they had a history of another type of cancer. Data were analyzed between April 1, 2017, and January 15, 2018.

Main Outcomes and Measures

Diagnosis of VTE within 1 year following the index date (for the KC and high-risk cohorts, the date of the initial diagnosis of cancer; for the control cohort, the date following 365 days of continuous insurance enrollment). Logistic regression was used to assess the risk of VTE in the KC cohort compared with the high-risk and control cohorts before and after matching across patient characteristics and known risk factors for VTE.

Results

Of 5 753 613 potentially eligible patients, the final sample consisted of 740 246 patients (12.8%) across 3 cohorts. Of the 740 246 study participants, 417 839 were in the KC cohort (223 986 [53.6%] men, mean [SD] age, 64.2 [13.6] years); 314 736 were in the control cohort (135 203 [43.0%] men, 42.9 [15.2] years); and 7671 were in the high-risk cohort (3502 [45.7%] men, 59.4 [14.4] years) The risk of VTE in the KC cohort was lower compared with the high-risk cohort in univariable analysis (odds ratio [OR], 0.22; 95% CI, 0.20-0.23; P < .001), multivariable analysis (OR, 0.29; 95% CI, 0.26-0.32; P < .001), and after matching across patient characteristics and known risk factors (OR, 0.52; 95% CI, 0.35-0.78; P = .001). The risk of VTE in the KC cohort was higher in the univariable analysis (OR, 2.31; 95% CI, 2.23-2.41; P < .001), lower in the multivariable analysis (OR, 0.85; 95% CI, 0.80-0.90; P < .001), and not different after matching of patient characteristics and risk factors (OR, 0.95; 95% CI, 0.89-1.01; P = .08) than that of the control cohort.

Conclusions and Relevance

The results of this study provided no evidence supporting the increased risk of VTE in the KC cohort compared with the control cohort. Given the inherent risks of chemoprophylaxis, the need for prophylactic anticoagulation in patients with KC who are scheduled for surgery should be carefully considered.

Level of Evidence

NA.

Thrombocytopenia in the intensive care unit

Thrombocytopenia is a frequent finding in intensive care unit especially among adults and medical ICU patients. Thrombocytopenia is defined as a platelet count less than 100×10⁹/l in ICU setting. Platelets are made in the bone marrow from megakaryocytes. Although not fully understood, proplatelets transform into platelets in the lung. The body tries to maintain platelet count relatively constant throughout life. Pathophysiology of thrombocytopenia can be defined by hemodilution, elevated levels of platelet consumption, compromise of platelet production, increased platelet sequestration and increased platelet destruction. Unlike in other situations, absolute platelet count alone does not provide sufficient data in characterizing thrombocytopenia in ICU patients. In such cases, the time course of changes in platelet count is also pivotal. The dynamics of platelet count decrease vary considerably between different ICU patient populations including trauma, major surgery and minor surgery/medical conditions. There are strong evidences available that delay in platelet count restoration in ICU patients is an indicator of a bad outcome.

Heparin-induced thrombocytopaenia

Heparin-induced thrombocytopaenia (HIT) is a severe and potentially life-threatening adverse drug reaction. Patients become extremely hypercoagulable, and this can lead to life-threatening and limb-threatening thrombosis with a mortality of 5%-10%. HIT is an antibody-mediated process in which platelet activation occurs. Diagnosis requires a high index of suspicion along with a scoring system and laboratory testing. Patients suspected of having HIT must not receive any further heparin or low-molecular weight heparin and must be started on an alternative anticoagulant such as argatroban or danaparoid. Fondaparinux may also be considered but is not licenced for this indication.

Incidence of heparin-induced thrombocytopenia in lower-extremity free flap reconstruction correlates with the overall surgical population

BACKGROUND

Lower-extremity free flap reconstruction is a growing trend in the management of lower extremity wounds. Heparin-induced thrombocytopenia (HIT) is a significant risk to free flap reconstruction. The purpose of this study was to investigate the incidence of HIT in patients receiving lower-extremity free flap surgery.

METHODS

We conducted a retrospective, single center, IRB approved cohort study in which we reviewed all patients who received lower-extremity free flap surgeries between 2011 and 2016. The 4T and HIT Expert Probability (HEP) scores were calculated to assess the likelihood of HIT.

RESULTS

One hundred patient charts revealed three patients with HIT. One patient was excluded due to a prior diagnosis of HIT. HIT incidence in patients receiving lower-extremity free flaps was between 1% and 3%, which is consistent with the national average. 4T scores indicated that two of three HIT-positive patients had a high probability of HIT (approximately 64%), and one of three HIT-positive patients had an intermediate probability (approximately 14%). HEP scoring indicated that all the three (100%) patients had HIT.

CONCLUSIONS

These data suggest that the incidence of HIT in patients receiving lower-extremity free flaps correlates with the incidence of HIT nationally. The use of available scoring methods and other algorithms, combined with patient history helps to assess the immediate perioperative risks of HIT in the absence of rapid immunologic confirmatory tests. This knowledge can allow for successful free flap salvage or for performance of free flaps in patients with a history of HIT.

Pentasaccharides for the treatment of deep vein thrombosis

BACKGROUND

Standard treatment of deep vein thrombosis (DVT) is based on antithrombotic therapy, initially with parenteral administration of unfractionated heparin or low molecular weight heparins (LMWH) for five to seven days, then subsequent long-term therapy with oral vitamin K antagonists (e.g. warfarin). Pentasaccharides are novel anticoagulants that may be favourable over standard therapy due to their predictable effect, no need for frequent monitoring or re-dosing, and few known drug interactions. Heparin-induced thrombocytopenia, a harmful effect of heparins, appears to be rare during treatment with pentasaccharides.

OBJECTIVES

To assess the efficacy and harms of pentasaccharides for the treatment of deep vein thrombosis.

SEARCH METHODS

The Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (22 March 2017) and the Cochrane Central Register of Controlled Trials (CENTRAL) (2017, Issue 2) (searched 22 March 2017). We searched clinical trials databases for details of ongoing or unpublished studies and the reference lists of relevant articles for additional citations.

SELECTION CRITERIA

We included randomised controlled trials in which people 18 years of age or older with a DVT confirmed by standard imaging techniques were allocated to receive a pentasaccharide (fondaparinux, idraparinux, or idrabiotaparinux) for the treatment of DVT in comparison with standard therapy or other treatments.

DATA COLLECTION AND ANALYSIS

We extracted data characterising the included trials according to the methods, participants, interventions, and outcomes. We assessed risk of bias using Cochrane's 'Risk of bias' tool and employed the GRADE methodology to evaluate the quality of the evidence.The main primary outcome for efficacy was recurrent venous thromboembolism (VTE), and the main primary outcome for harm was major and clinically relevant bleeding. Since our outcomes were dichotomous, we calculated the risk ratio (RR) with a 95% confidence interval (CI). We combined the effects of different comparisons through a meta-analysis using a fixed-effect model.

MAIN RESULTS

We included five randomised controlled trials of 6981 participants comparing pentasaccharides with standard therapy or other pentasaccharides. The quality of the evidence varied depending on the outcome and was judged as of moderate to very low quality. We downgraded the quality of the evidence due to risk of bias or imprecision, or both.Two studies evaluated fondaparinux, at doses of 5.0 mg, 7.5 mg, and 10.0 mg, plus vitamin K antagonist in comparison with standard therapy. A meta-analysis of these two studies showed no clear difference in the risk of recurrent VTE (RR 0.80, 95% CI 0.43 to 1.47; 2658 participants); moderate-quality evidence. The frequencies of major bleeding were similar between interventions in the initial period of treatment (approximately five days) (RR 1.15, 95% CI 0.39 to 3.44; 2645 participants) and at three months' follow-up (RR 1.05, 95% CI 0.64 to 1.71; 2645 participants). We judged the quality of the evidence as moderate.One study (757 participants) compared idrabiotaparinux (3.0 mg) with idraparinux (2.5 mg) and demonstrated no clear difference in the risk of recurrent VTE at six months' follow-up (RR 0.72, 95% CI 0.31 to 1.69); low-quality evidence. Major bleeding during the initial treatment period was not reported. Major bleeding at six-month follow-up was less frequent in participants receiving idrabiotaparinux versus participants treated with idraparinux (RR 0.21, 95% CI 0.06 to 0.71); low-quality evidence.The effect of an initial treatment with LMWH followed by three months of idraparinux (10 mg) showed no clear difference from standard therapy for risk of recurrent VTE (RR 1.51, 95% CI 0.26 to 8.90; 263 participants); very low-quality evidence; one study. Major bleeding during the initial treatment period was not reported. The frequency of major and other clinically relevant bleeding at three months' follow-up ranged from 2% to 15% in participants receiving LMWH and increasing doses of idraparinux of 2.5 mg, 5 mg, 7.5 mg, or 10 mg. When dosage groups were combined, there was no clear difference in major plus other clinically relevant bleeding or in major bleeding alone between the idraparinux treatment group and the standard therapy group (RR 1.30, 95% CI 0.70 to 2.40; 659 participants; RR 3.76, 95% CI 0.50 to 28.19; 659 participants, respectively); very low-quality evidence.One study (2904 participants) compared idraparinux (2.5 mg) to standard therapy. There was no clear difference in the risk of recurrent VTE at three months' follow-up (RR 0.98, 95% CI 0.64 to 1.48); low-quality evidence. Major bleeding during the initial treatment period was not reported. Major bleeding at three months of follow-up appeared to be similar in the idraparinux group and the standard therapy group (RR 0.71, 95% CI 0.34 to 1.47); very low-quality evidence.

AUTHORS' CONCLUSIONS

We found moderate-quality evidence that the effects of fondaparinux at doses of 5.0 mg, 7.5 mg, and 10.0 mg plus vitamin K antagonist are similar in terms of recurrent VTE and risk of major bleeding compared with standard treatment for DVT.Low-quality evidence suggests equal efficacy of idraparinux at 2.5 mg and the equimolar dose of 3.0 mg of idrabiotaparinux with regard to recurrent VTE, but a higher frequency of major bleeding was observed in participants treated with idraparinux.We judged evidence on the effectiveness of idraparinux compared with standard therapy, with or without initial treatment with LMWH, and on associated bleeding risk to be low to very low quality, therefore we have very limited confidence in the estimated effects.The observed similar effectiveness in terms of recurrent DVT and harmful effects in terms of bleeding risk with fondaparinux plus vitamin K antagonist compared to standard treatment for DVT suggest that it may be an alternative to conventional anticoagulants for the treatment of DVT in certain circumstances.

Unfractionated heparin versus low molecular weight heparins for avoiding heparin-induced thrombocytopenia in postoperative patients

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction presenting as a prothrombotic disorder related to antibody-mediated platelet activation. It is a paradoxical immune reaction resulting in thrombin generation in vivo, which leads to a hypercoagulable state and the potential to initiate venous or arterial thrombosis. A number of factors are thought to influence the incidence of HIT including the type and preparation of heparin (unfractionated heparin (UFH) or low molecular weight heparin (LMWH)) and the heparin-exposed patient population, with the postoperative patient population at higher risk.Although LMWH has largely replaced UFH as a front-line therapy, there is evidence supporting a lack of superiority of LMWH compared with UFH regarding prevention of deep vein thrombosis and pulmonary embolism following surgery, and similar frequencies of bleeding have been described with LMWH and UFH. The decision as to which of these two preparations of heparin to use may thus be influenced by harmful effects such as HIT. We therefore sought to determine the relative impact of UFH and LMWH on HIT in postoperative patients receiving thromboembolism prophylaxis. This is an update of a review first published in 2012.

OBJECTIVES

The objective of this review was to compare the incidence of heparin-induced thrombocytopenia (HIT) and HIT complicated by venous thromboembolism in postoperative patients exposed to unfractionated heparin (UFH) versus low molecular weight heparin (LMWH).

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Specialised Register (May 2016), CENTRAL (2016, Issue 4) and trials registries. The authors searched Lilacs (June 2016) and additional trials were sought from reference lists of relevant publications.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in which participants were postoperative patients allocated to receive prophylaxis with UFH or LMWH, in a blinded or unblinded fashion. Studies were excluded if they did not use the accepted definition of HIT. This was defined as a relative reduction in the platelet count of 50% or greater from the postoperative peak (even if the platelet count at its lowest remained greater than 150 x 109/L) occurring within five to 14 days after the surgery, with or without a thrombotic event occurring in this timeframe. Additionally, we required circulating antibodies associated with the syndrome to have been investigated through laboratory assays.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias. Disagreements were resolved by consensus with participation of a third author.

MAIN RESULTS

In this update, we included three trials involving 1398 postoperative participants. Participants were submitted to general surgical procedures, minor and major, and the minimum mean age was 49 years. Pooled analysis showed a significant reduction in the risk of HIT with LMWH compared with UFH (risk ratio (RR) 0.23, 95% confidence interval (CI) 0.07 to 0.73); low-quality evidence. The number needed to treat for an additional beneficial outcome (NNTB) was 59. The risk of HIT was consistently reduced comparing participants undergoing major surgical procedures exposed to LMWH or UFH (RR 0.22, 95% CI 0.06 to 0.75); low-quality evidence. The occurrence of HIT complicated by venous thromboembolism was significantly lower in participants receiving LMWH compared with UFH (RR 0.22, 95% CI 0.06 to 0.84); low-quality evidence. The NNTB was 75. Arterial thrombosis occurred in only one participant who received UFH. There were no amputations or deaths documented. Although limited evidence is available, it appears that HIT induced by both types of heparins is common in people undergoing major surgical procedures (incidence greater than 1% and less than 10%).

AUTHORS' CONCLUSIONS

This updated review demonstrated low-quality evidence of a lower incidence of HIT, and HIT complicated by venous thromboembolism, in postoperative patients undergoing thromboprophylaxis with LMWH compared with UFH. Similarily, the risk of HIT in people undergoing major surgical procedures was lower when treated with LMWH compared to UFH (low-quality evidence). The quality of the evidence was downgraded due to concerns about the risk of bias in the included studies and imprecision of the study results. These findings may support current clinical use of LMWH over UFH as front-line heparin therapy. However, our conclusions are limited and there was an unexpected paucity of RCTs including HIT as an outcome. To address the scarcity of clinically-relevant information on HIT, HIT must be included as a core harmful outcome in future RCTs of heparin.

Heparin-induced thrombocytopenia in solid organ transplant recipients: The current scientific knowledge

Exposure to heparin is associated with a high incidence of immunization against platelet factor 4 (PF4)/heparin complexes. A subgroup of immunized patients is at risk of developing heparin-induced thrombocytopenia (HIT), an immune mediated prothrombotic adverse drug effect. Transplant recipients are frequently exposed to heparin either due to the underlying end-stage disease, which leads to listing and transplantation or during the transplant procedure and the perioperative period. To review the current scientific knowledge on anti-heparin/PF4 antibodies and HIT in transplant recipients a systematic PubMed literature search on articles in English language was performed. The definition of HIT is inconsistent amongst the publications. Overall, six studies and 15 case reports have been published on HIT before or after heart, liver, kidney, and lung transplantation, respectively. The frequency of seroconversion for anti-PF4/heparin antibodies ranged between 1.9% and 57.9%. However, different methods to detect anti-PF4/heparin antibodies were applied. In none of the studies HIT-associated thromboembolic events or fatalities were observed. More importantly, in patients with a history of HIT, reexposure to heparin during transplantation was not associated with thrombotic complications. Taken together, the overall incidence of HIT after solid organ transplantation seems to be very low. However, according to the current knowledge, cardiac transplant recipients may have the highest risk to develop HIT. Different alternative suggestions for heparin-free anticoagulation have been reported for recipients with suspected HIT albeit no official recommendations on management have been published for this special collective so far.

A comparison of enoxaparin with unfractionated heparins in patients with coronary heart disease in an emergency department in rural South Indian tertiary care teaching hospital

Aim:

Antithrombotic therapy with heparin plus antiplatelets reduces the rate of ischemic events in patients with coronary heart disease. Low molecular weight heparin has a more predictable anticoagulant effect than standard unfractionated heparin, is easier to administer, does not require monitoring and is associated with less ADRs. The purpose of the present study was to evaluate and compare the clinical and cost outcomes of Enoxaparin with a standard unfractionated heparin in patients with coronary heart disease.

Materials and Methods:

This was a noninvasive prospective observational descriptive study carried out at a multi-specialty tertiary care teaching hospital situated in rural Tamil Nadu, India. Male and female coronary heart disease (CHD) patients aged 35–75 years newly diagnosed or those having a history of CHD were included. The intervention group received enoxaparin for 5 days. A series of resting the electrocardiogram, prothrombin time and ADRs were measured in all patients during days 1 and 21 respectively.

Results:

Compared to unfractionated heparin group of patients, the average prothrombin time was significantly higher (P < 0.0001) whereas hypokalemia was significantly lower (P < 0.02) in enoxaparin group of patients. Even though recurrence of angina and ADRs such as bleeding, nausea, headache and sudden cough occurred less frequently in the enoxaparin group of patients compared to unfractionated heparin group of patients, the differences were not significant.

Conclusions:

Antithrombotic therapy with enoxaparin plus aspirin was safer and more effective than unfractionated heparin plus aspirin, in reducing the incidence of ischemic events in patients with unstable angina or myocardial infarction in the early phase.

Anticoagulation in Chronic Hemodialysis: Progress Toward an Optimal Approach

Appropriate anticoagulation for hemodialysis (HD) requires a subtle balance between under- and over-heparinization to prevent extracorporeal circuit (ECC) clotting and bleeding, respectively. We discuss five key issues relating to anticoagulation therapy for chronic HD in adults following a review of relevant literature published since 2002: (i) options for standardization of anticoagulation in HD settings. The major nephrology societies have issued low evidence level recommendations on this subject. Interventional studies have generally investigated novel low-molecular weight heparins and provided data on safety of dosing regimens that cannot readily be extrapolated to clinical practice; (ii) identification of clinical and biological parameters to aid individualization of anticoagulation treatment. We find that use of clinical and biological monitoring of anticoagulation during HD sessions is currently not clearly defined in routine clinical practice; (iii) role of ECC elements (dialysis membrane and blood lines), dialysis modalities, and blood flow in clotting development; (iv) options to reduce or suppress systemic heparinization during HD sessions. Alternative strategies have been investigated, especially when the routine mode of anticoagulation was not suitable in patients at high risk of bleeding or was contraindicated; (v) optimization of anticoagulation therapy for the individual patient. We conclude by proposing a standardized approach to deliver anticoagulation treatment for HD based on an individualized prescription prepared according to the patient's profile and needs.

Argatroban therapy in heparin-induced thrombocytopenia

Argatroban is a direct thrombin inhibitor approved for anticoagulation in heparin-induced thrombocytopenia (HIT; in several countries) and in patients with or at risk of HIT undergoing percutaneous coronary intervention (PCI; in the USA). HIT is a relatively common extreme prothrombotic condition. When HIT is reasonably suspected, an alternative anticoagulant should be promptly initiated. In historical controlled studies, argatroban reduced new thrombosis, mortality from thrombosis and the composite of death, amputation or thrombosis, without increasing bleeding. With intravenous infusion, advantages include short half-life, easy monitoring and elimination primarily by hepatobiliary (rather than renal) means. In patients undergoing PCI, argatroban with or without glycoprotein IIb/IIIa inhibition leads to high rates of procedural success with low bleeding risk. Herein we review argatroban therapy for HIT and for PCI.

Heparin-induced thrombocytopenia: a review of concepts regarding a dangerous adverse drug reaction

Heparin is a natural agent with antithrombotic action, commercially available for therapeutic use as unfractionated heparin and low molecular weight heparin. Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin that promotes antibody-mediated platelet activation. HIT is defined as a relative reduction in platelet count of 50% (even when the platelet count at its lowest level is above>150 x 10(9)/L) occurring within five to 14 days after initiation of the therapy. Thrombocytopenia is the main feature that directs the clinical suspicion of the reaction and the increased risk of thromboembolic complications is the most important and paradoxical consequence. The diagnosis is a delicate issue, and requires a combination of clinical probability and laboratory tests for the detection of platelet activation induced by HIT antibodies. The absolute risk of HIT has been estimated between 1% and 5% under treatment with unfractionated heparin, and less than 1% with low molecular weight heparin. However, high-quality evidence about the risk of HIT from randomized clinical trials is scarce. In addition, information on the frequency of HIT in developing countries is not widely available. This review aims to provide a better understanding of the key features of this reaction and updated information on its frequency to health professionals and other interested parties. Knowledge, familiarity, and access to therapeutic options for the treatment of this adverse reaction are mandatory to minimize the associated risks, improving patient safety.

Heparin-induced thrombocytopenia following hip and knee arthroplasty

Until recently, both the British Society for Haematology and American College of Chest Physicians recommended platelet monitoring in all surgical patients receiving prophylactic low molecular weight heparin (LMWH) for the early diagnosis of heparin-induced thrombocytopenia (HIT). These guidelines were reversed in 2012 based upon an analysis considering resource expenditure, assay result timeframes, and complications relating to HIT treatment. However, there are no large studies reviewing lower limb arthroplasty patients on an individual basis to determine the incidence of HIT in this patient group. This study investigated 10 797 patients who underwent primary hip or knee arthroplasty with LMWH prophylaxis over a 5 years period. 32·6% of patients (n = 3515) had platelet counts recorded up to 14 d postoperatively with 13 patients (0·37%) developing thrombocytopenia. Platelet counts recovered spontaneously in five patients, and two patients had other identifiable causes. Only one of the remaining six patients developed thrombosis indicating an incidence of HIT-related thrombosis of 0·03%. The potential for identifying HIT with platelet monitoring in patients receiving LMWH prophylaxis is low and therefore routine monitoring for HIT is not justified.

Livedoid vasculopathy: an intringuing cutaneous disease

Livedoid vasculopathy is a skin disease that occludes the blood vessels of the dermis. It has a pauciinflammatory or non-inflammatory nature. It is characterized by the presence of macular or papular, erythematous-purpuric lesions affecting the legs, especially the ankles and feet, and producing intensely painful ulcerations, which cause white atrophic scars called "atrophie blanche". This review includes studies and case reports found in the medical literature regarding the etiopathogenic associations of the disease, particularly those related to thrombophilia, their histopathological findings and the therapeutic approaches used in the difficult clinical management of these cases.

Unfractionated heparin versus low molecular weight heparin for avoiding heparin-induced thrombocytopenia in postoperative patients

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction presenting as a prothrombotic disorder related to antibody-mediated platelet activation. It is a poorly understood paradoxical immune reaction resulting in thrombin generation in vivo, which leads to a hypercoagulable state and the potential to initiate venous or arterial thrombosis. A number of factors are thought to influence the incidence of HIT including the type and preparation of heparin (unfractionated heparin (UFH) or low molecular weight heparin (LMWH)) and the heparin-exposed patient population, with the postoperative patient population presenting a higher risk.Although LMWH has largely replaced UFH as a front-line therapy, there is evidence supporting a lack of superiority of LMWH compared with UFH regarding prevention of deep vein thrombosis and pulmonary embolism following surgery, and similar frequencies of bleeding have been described with LMWH and UFH. The decision as to which of these two preparations of heparin to use may thus be influenced by adverse reactions such as HIT. We therefore sought to determine the relative impact of UFH and LMWH specifically on HIT in postoperative patients receiving thromboembolism prophylaxis.

OBJECTIVES

The objective of this review was to compare the incidence of HIT and HIT complicated by thrombosis in patients exposed to UFH versus LMWH in randomised controlled trials (RCTs) of postoperative heparin therapy.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (March 2012) and CENTRAL (2012, Issue 2). In addition, the authors searched LILACS (March 2012) and additional trials were sought from reference lists of relevant publications.

SELECTION CRITERIA

We were interested in comparing the incidence of HIT occurring during exposure to UFH or LMWH after any surgical intervention. Therefore, we studied RCTs in which participants were postoperative patients allocated to receive UFH or LMWH, in a blinded or unblinded fashion. Eligible studies were required to have as an outcome clinically diagnosed HIT, defined as a relative reduction in the platelet count of 50% or greater from the postoperative peak (even if the platelet count at its lowest remained > 150 x 10(9)/L) occurring within five to 14 days after the surgery, with or without a thrombotic event occurring in this timeframe. Additionally, circulating antibodies associated with the syndrome were required to have been investigated through laboratory assays.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias. Disagreements were resolved by consensus with participation of a third author.

MAIN RESULTS

In total two studies involving 923 participants met all the inclusion criteria and were included in the review. Pooled analysis showed a statistically significant reduction in the risk of HIT with LMWH compared with UFH (risk ratio (RR) 0.24, 95% confidence interval (CI) 0.07 to 0.82; P = 0.02). This result suggests that patients treated with LMWH would have a relative risk reduction (RRR) of 76% in the probability of developing HIT compared with patients treated with UFH.Venous thromboembolism (VTE) complicating HIT occurred in 12 of 17 patients who developed HIT. Pooled analysis showed a statistically significant reduction in HIT complicated by VTE with LMWH compared with UFH (RR 0.20, 95% CI 0.04 to 0.90; P = 0.04). This result indicates that patients using LMWH would have a RRR of 80% for developing HIT complicated by VTE compared with patients using UFH. Arterial thrombosis occurred in only one patient who received UFH and there were no amputations or deaths documented.

AUTHORS' CONCLUSIONS

There was a lower incidence of HIT and HIT complicated by VTE in postoperative patients undergoing thromboprophylaxis with LMWH compared with UFH. This is consistent with the current clinical use of LMWH over UFH as front-line heparin therapy. However, conclusions are limited by a scarcity of high quality evidence. We did not expect the paucity of RCTs including HIT as an outcome as heparin is one of the most commonly used drugs worldwide and HIT is a life-threatening adverse drug reaction. To address the scarcity of clinically-relevant information on the topic of HIT as a whole, HIT should be included as an outcome in future RCTs of heparin, and HIT as an adverse drug reaction should be considered in clinical recommendations regarding monitoring of the platelet count for HIT.

A case of ST elevation myocardial infarction secondary to heparin-induced thrombocytopaenia with thrombosis

A 54 year-old woman with Noonan Syndrome presented with an acute anterolateral ST elevation myocardial infarction two weeks post septal myectomy and heparin exposure, on the background of known normal coronary arteries. Coronary angiography revealed acute thrombosis of the left main, left anterior descending and left circumflex arteries, which was successfully treated by percutaneous coronary intervention with overlapping bare metal stents. A positive heparin induced platelet antibody test and dramatic fall in platelet count confirmed the diagnosis of heparin induced thrombocytopaenia with thrombosis (HITTS) as the underlying diagnosis. This represents the first documented case of HITTS induced left main coronary artery thrombosis and occlusion.

Pregnancy-associated venous thrombosis

Pregnant women are at an increased risk of venous thromboembolism (VTE) and the consequences of an acute event in pregnancy can be debilitating, long-lasting or fatal. Screening for risk factors early in pregnancy and the provision of thromboprophylaxis are useful ways of preventing VTE in some women, but even when performed diligently, acute events are likely to remain common for the foreseeable future. It is therefore important for obstetric and non-obstetric clinicians to recognize the symptoms and signs of deep vein thrombosis and pulmonary embolism in pregnancy, to understand how a diagnosis can be reached in an effective yet safe manner and to be aware of the available treatment modalities.

Thrombocytopenia in the Intensive Care Unit

Thrombocytopenia is a common laboratory finding in critically ill patients admitted to the intensive care unit. Potential etiologies of thrombocytopenia are myriad, ranging from acute disease processes and concomitant conditions to exposures and drugs. The mechanism of decreased platelet counts can also be varied: laboratory measurement may be spurious, platelet production may be decreased, or platelet destruction or sequestration may be increased. In addition to evaluation for the cause of thrombocytopenia, the clinician must also guard against spontaneous bleeding due to thrombocytopenia, prophylax against bleeding resulting from an invasive procedure performed in the setting of thrombocytopenia, and treat active bleeding related to thrombocytopenia.

Rapid exclusion or confirmation of heparin-induced thrombocytopenia: a single-center experience with 1,291 patients

BACKGROUND

The current gold-standard for diagnosing heparin-induced thrombocytopenia is the detection of platelet-activating antibodies by means of functional assays which, since they are time consuming and not widely available, are not suited to guiding acute treatment decisions. The objective of our study was to assess the ability of more rapid immunoassays to predict the presence of functionally relevant anti-platelet factor 4/heparin-antibodies.

DESIGN AND METHODS

We analyzed 1,291 of 1,383 (93.4%) patients consecutively evaluated for suspected heparin-induced thrombocytopenia at our institution. Clinical pre-test probability was defined by the 4T-score. Anti-platelet factor 4/heparin-antibodies were measured with three immunoassays (ID-H/PF4-PaGIA, Asserachrom-HPIA, and GTI-PF4) and their functional relevance was assessed by a two-point heparin-induced platelet aggregation test. Performance of the immunoassays was evaluated by receiver operating characteristic analysis.

RESULTS

Among 1,291 patients, 96 (7.4%) had a positive heparin-induced platelet aggregation-test: 7 of 859 (0.8%) with a low, 50 of 358 (14.0%) with an intermediate, and 39 of 74 (52.7%) with a high 4T-score. Receiver operating characteristics analysis indicated that best immunoassay thresholds for predicting a positive platelet aggregation test were: Titer of 4 or more (ID-H/PF4-PaGIA), optical density more than 0.943 (Asserachrom-HPIA) and more than 1.367 (GTI-PF4). A 100% negative predictive value was observed at the following thresholds: Titer of 1 or under (ID-H/PF4-PaGIA), optical density less than 0.300 (Asserachrom-HPIA) and less than 0.870 (GTI-PF4). A 100% positive predictive value was reached only by ID-H/PF4-PaGIA, at titers of 32 or over. Positive and negative likelihood ratios were calculated for results between the thresholds with 100% negative or positive predictive value.

CONCLUSIONS

We show that: i) negative and weak positive results of immunoassays detecting anti-platelet factor 4/heparin-antibodies exclude heparin-induced thrombocytopenia; ii) anti-platelet factor 4/heparin-antibody titers of 32 or over (ID-H/PF4-PaGIA) have a 100% positive predictive value for functionally relevant antibodies; iii) combining the clinical pre-test probability with the likelihood ratio of intermediate immunoassay results allows assessment of post-test probability for heparin-induced thrombocytopenia in individual patients.

Nafamostat Mesilate as an Anticoagulant during Continuous Veno-Venous Hemodialysis: A Three-Year Retrospective Cohort Study

Introduction

Although nafamostat mesilate, a synthetic serine protease inhibitor, has been commonly used in Japan as an anticoagulant during continuous renal replacement therapy (CRRT), its clinical utility has not been well determined. The aim of this study was to evaluate the efficacy (filter survival) and safety (bleeding complications) of nafamostat mesilate in CRRT for acute kidney injury (AKI) among critically ill patients.

Methods

We retrospectively studied consecutive patients with AKI treated with continuous veno-venous hemodialysis and nafamostat mesilate from April 2005 to March 2008. Demographic, clinical and laboratory data were extracted from the clinical chart.

Results

Fifty-eight patients were enrolled in this study (45 males with an average age of 66±15 years). The median filter survival was 21.8 h (range: 2.8–55.5 h), and the mean was 20.8±8.4 h. Only 38 out of 181 filters (21%) were interrupted because of filter failure within 24 hours and 89 filters (49%) were electively renewed within 24 hours. Activated partial thromboplastin time was elevated especially during the first 24 hours (46.7±13.1 s at baseline versus 73.9±24.3 s at day 1; ANOVA p<0.01). Hematocrit level was kept around 30% and did not change significantly (ANOVA p=0.69). No patients experienced major bleeding while treated with CRRT.

Conclusions

Nafamostat mesilate provided sufficient filter survival without causing major bleeding complications despite the prolongation of APTT.

Argatroban therapy in pediatric patients requiring nonheparin anticoagulation: an open-label, safety, efficacy, and pharmacokinetic study

BACKGROUND

An increasing number of pediatric patients suffer from thrombotic events necessitating anticoagulation therapy including heparins. Some such patients develop heparin-induced thrombocytopenia (HIT) and thus require alternative anticoagulation. As such, studies evaluating the safety, efficacy, and dosing of alternative anticoagulants are required.

PROCEDURE

In this multicenter, single arm, open-label study, 18 patients ≤ 16 years old received argatroban for either a suspicion of or being at risk for HIT, or other conditions requiring nonheparin anticoagulation. Endpoints included thrombosis, thromboembolic complications, and bleeding.

RESULTS

Patients (ages, 1.6 weeks to 16 years) received argatroban usually for continuous anticoagulation (n = 13) or cardiac catheterization (n = 4). One catheterization patient received a 250 µg/kg bolus only; 17 patients received argatroban continuous infusion (median (range)) 1.1 (0.3-12) µg/kg/min (of whom four received a bolus) for 3.0 (0.1-13.8) days. In patients without bolus dosing, typically argatroban 1 µg/kg/min was initiated, with therapeutic activated partial thromboplastin times (aPTTs) (1.5-3× baseline) achieved within 7 hr. Within 30 days, thrombosis occurred in five patients (two during therapy). No one required amputation or died due to thrombosis during therapy. Two patients had major bleeding. Pharmacometric analyses demonstrated the optimal initial argatroban dose to be 0.75 µg/kg/min (if normal hepatic function), with dose reduction necessary in hepatic impairment.

CONCLUSIONS

In pediatric patients requiring nonheparin anticoagulation, argatroban rapidly provides adequate levels of anticoagulation and is generally well tolerated. For continuous anticoagulation, argatroban 0.75 µg/kg/min (0.2 µg/kg/min in hepatic impairment), adjusted to achieve therapeutic aPTTs, is recommended.

Optimized alkylated cyclodextrin polysulphates with reduced risks on thromboembolic accidents improve osteoarthritic chondrocyte metabolism

OBJECTIVES

To compare the ability of different cyclodextrin polysulphate (CDPS) derivatives to affect human articular cartilage cell metabolism in vitro.

METHODS

OA chondrocytes were cultured in alginate and exposed to 5 µg/ml of 2,3,6-tri-O-methyl-β-cyclodextrin (ME-CD), 2,3-di-O-methyl-6-sulphate-β-cyclodextrin (ME-CD-6-S), 2,6-di-O-methyl-3-sulphate-β-cyclodextrin (ME-CD-3-S), (2-carboxyethyl)-β-CDPS (CE-CDPS), (2-hydroxypropyl)-β-CDPS (HP-CDPS), 6-monoamino-6-monodeoxy-β-CDPS (MA-CDPS) or β-CDPS for 5 days. Effects on IL-1-driven chondrocyte extracellular matrix (ECM) metabolism were assayed by analysis of the accumulation of aggrecan in the interterritorial matrix, IL-6 secretion and qPCR. MA-CDPS, HP-CDPS, CE-CDPS and CDPS were analysed for their in vitro effect on coagulation and their ability to activate platelets in an in vitro assay to detect possible cross-reactivity with heparin-induced thrombocytopenia (HIT) antibodies.

RESULTS

The monosulphated cyclodextrins ME-CD-6-S and -3-S failed to affect aggrecan synthesis and IL-6 secretion by the OA chondrocytes. Polysulphated cyclodextrins MA-CDPS, HP-CDPS, CE-CDPS and CDPS at 5 µg/ml concentrations, on the other hand, significantly induced aggrecan production and repressed IL-6 release by the chondrocytes in culture. aPTT and PT for all derivatives were lengthened for polysaccharide concentrations >50 µg/ml. Five micrograms per millilitre of β-CDPS concentrations that significantly modulated ECM ground substance production in vitro did not affect aPTT or PT. Furthermore, CE-CDPS, in contrast to MA-CDPS, HP-CDPS and CDPS, did not significantly activate platelets, suggesting a minimal potential to induce HIT thromboembolic accidents in vivo.

CONCLUSIONS

CE-CDPS is a new, structurally adjusted, sulphated β-cyclodextrin derivative with preserved chondroprotective capacity and a promising safety profile.

On the use of prothrombin complex concentrate in patients with coagulopathy requiring tooth extraction

In patients on high-level anticoagulant therapy (prothrombin time-international normalized ratio [PT-INR] ≥ 4.5), surgical procedures can be carried out with bridging therapy using heparin. However, surgical treatment options are severely limited in patients on high-level anticoagulant therapy and who have heparin-induced thrombocytopenia (HIT), as heparin use is contraindicated. We performed tooth extraction using prothrombin complex concentrate (PCC) in 2 HIT patients on high-level anticoagulation therapy (PT-INR ≥ 4.5). Five hundred units of PCC were administered intravenously, and after 15 minutes, it was confirmed that PT-INR was less than 2.0. Tooth extraction was then performed and sufficient local hemostasis was achieved. At 3 hours after tooth extraction, PT-INR was 2.0 or higher and later increased to 4.0 or higher, but postoperative bleeding was mostly absent. When performing tooth extraction in HIT patients on high-level anticoagulant therapy, favorable hemostatic management was achieved through sufficient local hemostasis and transient warfarin reversal using PCC.

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.