Treatment and prevention of heparin-induced thrombocytopenia: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

Oral factor Xa inhibitors for thromboprophylaxis in major orthopedic surgery: a review

Venous thromboembolism (VTE), which includes deep vein thrombosis and pulmonary embolism, is a major cause of morbidity and mortality in patients undergoing major orthopedic surgery. Routine thromboprophylaxis has been the standard of care over the last 20 years. Currently available options for the prevention of VTE in major orthopedic surgery include low molecular weight heparins, vitamin K antagonists, and, more recently, the synthetic pentasaccharide fondaparinux. Although effective, all these drugs have several limitations and new oral antithrombotics offering predictable, effective and safe anticoagulation are strongly needed. This overview focuses on the most advanced oral direct inhibitors to factor Xa rivaroxaban, apixaban, LY517717 and YM150; specifically, the results of phase II and III studies and the designs of ongoing clinical trials in patients undergoing elective hip and knee replacement are reviewed.

Preoperative evaluation and preparation of the patient for cardiac surgery

Cardiac surgery is associated with significant morbidity, mortality, and socioeconomic costs. Preoperative assessment assists the clinician in identifying potential complications and facilitates discussion of these risks with the patient. Careful patient selection and preparation during preoperative evaluation may minimize morbidity, mortality, and resource use. This article outlines a system-based approach to preoperative evaluation and preparation of the patient undergoing cardiac surgery.

Thrombin-inducible platelet adhesion and regulation of the platelet seven-transmembrane thrombin receptor-1 (PAR-1): effects of unfractionated heparin and lepirudin

Heparin may induce platelet activation and even heparin-induced thrombocytopenia. Lepirudin has been approved for HIT treatment. We speculated that lepirudin inhibits platelet function under high shear and the platelet thrombin receptor PAR-1 better than heparin. Thrombin-inducible platelet adherence under high shear conditions and the expression of PAR-1 were studied after samples from healthy donors were exposed in vitro to increasing concentrations of unfractionated heparin or lepirudin. Compared to baseline and to lepirudin, heparin induced platelet P-selectin expression (p = 0.04). Platelet adherence increased slightly in the presence of lepirudin, but not heparin (p = 0.04). Thrombin-inducible platelet aggregate formation and consecutive adherence under high shear conditions was inhibited by both anticoagulants (p = 0.004). Further, heparin and lepirudin inhibited thrombin-inducible cleavage and internalization of PAR-1 at a dosage of 1.0 U/ml and 1.6 microg/ml, respectively (p = 0.004). Thus, heparin and lepirudin inhibit thrombin-inducible platelet activation in vitro to a similar extent.

The severity of trauma determines the immune response to PF4/heparin and the frequency of heparin-induced thrombocytopenia

Heparin can induce heparin-induced thrombocytopenia (HIT). The combined effect of type of surgery (major vs minor) and heparin on this prothrombotic immune reaction to platelet factor 4 (PF4)/heparin was analyzed. In a randomized, double-blind study, trauma patients receiving low-molecular-weight (LMWH) or unfractionated heparin (UFH) for thrombosis prophylaxis were assessed for PF4/heparin-antibody seroconversion, HIT, and thrombosis according to type of surgery. The risk for seroconversion was higher than major versus minor surgery odds ratio, 7.98 [95% confidence interval, 2.06-31.00], P = .003, controlled for potential confounders, as was the risk for HIT (2.2% [95% confidence interval, 0.3%-4.1%] vs 0.0%, P = .010). During LMWH compared with UFH thromboprophylaxis, HIT (1 of 298 vs 4 of 316; P = .370) and PF4/heparin seroconversion (1.7% vs 6.6%; P = .002) were less frequent, driven by differences in patients undergoing major surgery (incidence of HIT: LMWH 0.8% vs UFH 4.0%; P = .180; seroconversion rates: 4.0% vs 17.0%; P = .001). After minor surgery, no case of HIT occurred. The severity of trauma and the need for major surgery strongly influence the risk of an anti-PF4/heparin immune response, which is then increased by UFH. In major trauma certoparin may be safer than UFH because it induces HIT-antibody seroconversion, and the corresponding risk of HIT, less frequently.

A review of 122 published outcomes of danaparoid anticoagulation for intermittent haemodialysis

One hundred and twenty-two case reports of treatment outcomes of danaparoid use for intermittent haemodialysis (HD) in severely ill patients with heparin intolerance (including 97 HIT patients) have been analysed. HD sessions of 4 - 6 hours were successfully conducted daily to 3 times/week for periods of up to 4 years (median 7 sessions/patient (range 1 - >650). In these patients danaparoid use was relatively safe (4 unprovoked non-fatal major bleeds) and efficacious in protecting the circuit (95% no clotting problem) or patient (6 thromboses: 4 fatal or leading to danaparoid discontinuation). HIT diagnosis was improved if recurrent platelet count reduction with each HD and circuit/AV graft clotting were included. Alternative reasons for and very low nadirs of the platelet count undermined the usefulness of the 4 T pre-test HIT predictability scores, but a positive functional serological test confirmed HIT in most patients. Deaths (15.6%) and thrombosis only occurred in HIT cases. Possible reasons are discussed. Replacing the standard intermittent pre-HD dose regimen with the therapeutic infusion regimen to provide continuous daily systemic antithrombotic protection, should further improve efficacy.

CONCLUSION

Danaparoid appears to be a useful alternative antithrombotic for patients with heparin intolerance and renal failure requiring haemodialysis.

Six-month follow-up of patients with in-hospital thrombocytopenia during heparin-based anticoagulation (from the Complications After Thrombocytopenia Caused by Heparin [CATCH] registry)

Thrombocytopenia is a predictor of adverse outcomes in patients with acute coronary syndromes and in critically ill patients. The Complications After Thrombocytopenia Caused by Heparin (CATCH) registry was designed to explore the incidence, management, and clinical consequences of in-hospital thrombocytopenia occurring during heparin-based anticoagulation in diverse clinical settings. We conducted a prospective observational study of 37 United States hospitals participating in the CATCH registry to assess the relation of in-hospital thrombocytopenia to long-term outcomes. A total of 2,104 patients at increased risk of developing in-hospital thrombocytopenia or thrombosis were identified, and the 6-month mortality and rehospitalization rates were determined. Thrombocytopenia was not a significant predictor of 6-month mortality. In an adjusted model for in-hospital death in this cohort, thrombocytopenia had an odds ratio of 3.59 (95% confidence interval 2.24 to 5.77). The postdischarge mortality rate at 6 months was 9.7%. No significant difference was observed in the long-term mortality between patients who developed thrombocytopenia and those who did not. Thrombocytopenia was a weak, but statistically significant, predictor of a composite of mortality and rehospitalization at 6 months (hazards ratio 0.80, 95% confidence interval 0.65 to 0.98, p = 0.03). In conclusion, the 6-month mortality rate among heparin-treated patients with thrombocytopenia is high, although the risk independently related to thrombocytopenia appears to be restricted to the acute hospital phase.

Platelet functions beyond hemostasis

Although their central role is in the prevention of bleeding, platelets probably contribute to diverse processes that extend beyond hemostasis and thrombosis. For example, platelets can recruit leukocytes and progenitor cells to sites of vascular injury and inflammation; they release proinflammatory and anti-inflammatory and angiogenic factors and microparticles into the circulation; and they spur thrombin generation. Data from animal models suggest that these functions may contribute to atherosclerosis, sepsis, hepatitis, vascular restenosis, acute lung injury, and transplant rejection. This article represents an integrated summary of presentations given at the Fourth Annual Platelet Colloquium in January 2009. The process of and factors mediating platelet-platelet and platelet-leukocyte interactions in inflammatory and immune responses are discussed, with the roles of P-selectin, chemokines and Src family kinases being highlighted. Also discussed are specific disorders characterized by local or systemic platelet activation, including coronary artery restenosis after percutaneous intervention, alloantibody-mediated transplant rejection, wound healing, and heparin-induced thrombocytopenia.

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.

Fondaparinux for the treatment of acute heparin-induced thrombocytopenia: a single-center experience

Heparin-induced thrombocytopenia (HIT) is a life-threatening immune response to heparin that is associated with a high risk of thromboembolic complications. The syndrome is caused by antibodies that are reactive against complexes of platelet factor 4/heparin (PF4/H). For patients with HIT, the discontinuation of heparin alone is not sufficient and the diagnosis necessitates the administration of an alternative anticoagulant. Fondaparinux is a synthetic pentasaccharide that binds to antithrombin and potentiates inhibition of factor Xa. Data have shown that fondaparinux is structurally too short to induce an antibody response and could be a useful agent to treat HIT. In our hospital, we retrospectively analyzed the use of fondaparinux in the treatment of 24 patients with acute HIT during unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) administration and compared the results to a similar population of 20 patients who were treated with lepirudin. The treated patients had a complete platelet count recovery, and none experienced a new thromboembolic complication or major bleeding. The development of limb gangrene (2 patients who received lepirudin and 1 who received fondaparinux) likely resulted from a delay in diagnosis and treatment initiation. Our data suggest that fondaparinux may be considered a safe and an effective alternative treatment in HIT complicated with or without thrombosis.

Anticoagulation in the Treatment of Established Venous Thromboembolism in Patients With Cancer

Cancer-associated thrombosis is a frequent and costly complication in patients with cancer. Significant morbidity and mortality not only result from thrombotic events, but may also occur as a result of the therapeutic interventions. The established treatment for cancer-associated thrombosis is anticoagulant therapy. Of the few options available, low molecular weight heparin (LMWH) is the preferred agent because of its efficacy, safety, and convenience. Alternatives to LMWH have undesirable limitations and have demonstrated poorer efficacy and safety in the oncology population. Treatment of recurrent thrombosis, patients with concurrent bleeding issues, role of vena cava filter insertion, and duration of therapy are all areas in need of urgent research. Treatment of cancer-associated thrombosis remains a challenging task and is limited by the paucity of evidence-based data. Research is urgently needed to advance current practice and improve patient care.

Argatroban: a review of its use in the management of heparin-induced thrombocytopenia

Argatroban, a highly selective direct thrombin inhibitor, is indicated for use as an anticoagulant for the treatment and prophylaxis of thrombosis in patients with heparin-induced thrombocytopenia (HIT), and in patients undergoing percutaneous coronary intervention (PCI) who have, or are at risk for, HIT. Intravenous argatroban improved clinical outcomes and was generally well tolerated in adults with HIT or HIT with thrombosis syndrome (HITTS). In two pivotal, open-label, historically controlled studies in adults with HIT, the incidence of the primary composite endpoint (all-cause death, all-cause amputation, or new thrombosis) was significantly lower in argatroban recipients than in historical controls, and more argatroban recipients than historical controls stayed event-free during the study according to a Kaplan-Meier analysis. In adults with HITTS in these trials, although the incidence of the primary composite endpoint did not differ significantly between argatroban recipients and historical controls, a Kaplan-Meier analysis showed that more patients receiving argatroban than historical controls remained event-free during the study. Major and minor bleeding rates in argatroban recipients were generally similar to those in historical controls in these studies. Argatroban was also an effective anticoagulant in patients with HIT undergoing PCI in three small, uncontrolled trials, pooled data from which showed that most (>or=95%) patients achieved a satisfactory outcome of the PCI procedure and adequate anticoagulation (coprimary endpoints). It was generally well tolerated in these patients, with the incidence of major bleeding being <or=1.1%. The efficacy and safety of argatroban in pediatric patients has not been established. However, a small uncontrolled, preliminary study suggests that it may be useful in seriously ill pediatric patients requiring nonheparin anticoagulation.

Cardiac transplantation and/or mechanical circulatory support device placement using heparin anti-coagulation in the presence of acute heparin-induced thrombocytopenia

BACKGROUND

Patients with congestive heart failure, decreased left ventricular function, and debilitation are frequently maintained on anti-coagulants, including heparin. As such, these patients are at high risk for developing heparin-induced thrombocytopenia (HIT). Some of these HIT-positive individuals will ultimately undergo urgent heart transplantation or placement of a mechanical circulatory support device (MCSD). Such procedures require cardiopulmonary bypass (CPB) and full anti-coagulation. The safety of re-exposure to heparin during CPB despite the presence of recent-onset thrombocytopenia and Hep/PF4 antibodies has not been studied in the transplant or MCSD populations.

METHODS

Over a 24-month period, 75 heart transplants and 55 MCSD implants were performed. Fourteen patients with acute HIT (thrombocytopenia and positive Hep/PF4 antibody by enzyme-linked immunosorbent assay [ELISA]) and 3 patients with a history of remote HIT underwent cardiac transplantation (n = 9) and/or MCSD placement (n = 8) using heparin as the anti-coagulant during CPB. The median time from diagnosis to CPB was 4.5 days in patients with acute HIT.

RESULTS

Thirty-day survival was 100% in transplant patients and 75% in MCSD patients. Post-transplant ELISA testing was found to be negative in 4 patients with acute HIT and 3 with remote HIT.

CONCLUSIONS

This series demonstrates that short-term re-exposure to heparin during urgent CPB for heart transplantation or MCSD placement is safe despite the presence of thrombocytopenia and Hep/PF4 antibodies. Moreover, the rapid clearance of Hep/PF4 antibodies in our transplant patients suggests a potential therapeutic role for immunosuppressive therapy in the management of HIT in the acute setting.

Variability of anti-PF4/heparin antibody results obtained by the rapid testing system ID-H/PF4-PaGIA

BACKGROUND

Recent studies have shown that a low clinical pretest probability may be adequate for excluding heparin-induced thrombocytopenia. However, for patients with intermediate or high pretest probability, laboratory testing is essential for confirming or refuting the diagnosis. Rapid assessment of anti-PF4/heparin-antibodies may assist clinical decision-making.

OBJECTIVES

To evaluate the performance of rapid ID-H/PF4-PaGIA. In particular, we verified reproducibility of results between plasma and serum specimens, between fresh and frozen samples, and between different ID-H/PF4-polymer lots (polystyrene beads coated with heparin/PF4-complexes).

PATIENTS/METHODS

The samples studied were 1376 plasma and 914 corresponding serum samples from patients investigated for suspected heparin-induced thrombocytopenia between January 2000 and October 2008. Anti-PF4/heparin-antibodies were assessed by ID-H/PF4-PaGIA, commercially available ELISAs and heparin-induced platelet aggregation test.

RESULTS

Among 914 paired plasma/serum samples we noted discordant results (negative vs. low-titre positive) in nine instances (1%; 95%CI, 0.4-1.6%). Overall, agreement between titres assessed in plasma vs. serum was highly significant (Spearman correlation coefficient, 0.975; P < 0.0001). Forty-seven samples tested both fresh and after freezing/thawing showed a good agreement, with one discordant positive/negative result (Spearman correlation coefficient, 0.970; P < 0.0001). Among 1376 plasma samples we noted a strikingly variable incidence of false negative results (none - 82%; 95%CI, 66-98%), depending on the employed ID-H/PF4-polymer lot. Faulty lots can be recognized by titrating commercial positive controls and stored samples of HIT-patients.

CONCLUSION

Laboratories performing the assay should implement stringent internal quality controls in order to recognize potentially faulty ID-H/PF4-polymer lots, thus avoiding false negative results.

[Treatment of postoperative thrombosis]

For the treatment of deep vein thrombosis (DVT), rapid diagnosis and prompt therapy are crucial to minimize the risk of fatal pulmonary embolism and long-term complications, including the postthrombotic syndrome and recurrent thromboembolism. The treatment of acute DVT remains controversial. In this review, treatment options in relation to exposing and predisposing risk factors are discussed. Evidence-based data and recommendations from official guidelines are presented.

The current role of anticoagulants in cardiovascular medicine

Thrombotic events in cardiovascular disease are a huge burden to healthcare budgets. Anticoagulant use is recommended for thrombotic event prevention in many cardiovascular diseases, including stroke prevention in atrial fibrillation, treatment and secondary prevention of acute coronary syndrome. Current parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins (LMWHs) and fondaparinux. Patients with acute coronary syndrome usually receive unfractionated heparin or a LMWH on hospital admission, both exhibit similar efficacy in reducing mortality and myocardial infarction rates; however, LMWHs may have a better safety profile and do not require routine coagulation monitoring. In acute coronary syndrome, fondaparinux use results in significantly lower mortality compared with LMWHs or unfractionated heparin. However, parenteral drugs are inconvenient for long-term outpatient use. Vitamin K antagonists are currently the only oral anticoagulants available for long-term use, but multiple drawbacks hinder their use. A large unmet need exists for new convenient and well-tolerated oral anticoagulants that do not require routine monitoring.

Fondaparinux and the management of heparin-induced thrombocytopenia: the journey continues

OBJECTIVE

To review the available literature addressing the role of fondaparinux in the management of heparin-induced thrombocytopenia (HIT).

DATA SOURCES

Primary articles were identified by a MEDLINE search (2004-June 2009) of English-language literature using the MeSH headings fondaparinux, heparin, low-molecular-weight heparin, and thrombocytopenia. Relevant consensus guidelines (2006-June 2009) were also identified.

STUDY SELECTION AND DATA EXTRACTION

All published studies and case reports, as well as relevant consensus guidelines, evaluating the use of fondaparinux for the management of HIT were included.

DATA SYNTHESIS

The role of fondaparinux in the management of HIT is a therapeutic controversy challenging clinicians today. An open-label, prospective pilot study of 7 patients with acute HIT supports fondaparinux as an alternative anticoagulant. Additionally, a total of 12 patients with HIT from a larger case study and retrospective cohort were successfully treated with fondaparinux. Much of the supporting data exists in the form of case reports, each demonstrating normalization of platelet counts without any evidence of new thrombosis. The differences in clinical scenarios as well as the role and dose of fondaparinux make interpretation of these reports difficult. Three case reports have been published raising concerns regarding fondaparinux causing or failing to manage HIT appropriately. However, common weaknesses such as small sample sizes and nonuniform definitions of HIT limit the usefulness of these findings. The updated American College of Chest Physicians consensus guidelines now recognize fondaparinux as an option in the management of HIT; however, the level of evidence supporting this is of low quality. The use of fondaparinux as a bridging agent between direct thrombin inhibitor and warfarin therapy has been proposed. A recently published case report gives support to this approach.

CONCLUSIONS

Controlled clinical trials evaluating the use of fondaparinux in the management of HIT need to be completed before this therapy can be routinely recommended.

How I treat the antiphospholipid syndrome

This article discusses how we approach medical decision making in the treatment of the various facets of the antiphospholipid syndrome (APS), including secondary prophylaxis in the setting of venous and arterial thrombosis, as well as treatment for the prevention of recurrent miscarriages and fetal death. The role of primary thromboprophylaxis is also discussed in depth. Great emphasis is given to incorporating the most up-to-date and relevant evidence base both from the APS literature, and from large, recent, randomized controlled trials (RCTs) of primary and secondary thrombotic prophylaxis in the general population setting (ie, the population that has not been specifically investigated for APS).

Thrombocytopenia and other hot topics

A frequent issue in the management of cancer patients with thrombosis is thrombocytopenia, whether related to chemotherapy, heparin, or other drugs. The oncologist will have multiple new anticoagulants to choose from in the future, but for now, the effect of these experimental agents on cancer thrombosis is unknown. Despite the effectiveness of anticoagulation in cancer patients, survival benefit remains controversial. Given the ongoing clinical questions and new drugs, anticoagulant therapy in patients with cancer promises to have an exciting future.

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.

Heparin induced thrombocytopenia and re-thrombosis associated with warfarin and fondaparinux in a child

An 11-year-old female developed heparin induced thrombocytopenia (HIT) with thrombosis during therapy for lower extremity deep vein thrombosis and pulmonary embolism. Transition from bivalirudin, a direct thrombin inhibitor (DTI), to warfarin resulted in extensive re-thrombosis, and fondaparinux therapy similarly failed. She was then treated with argatroban, and transitioned successfully to warfarin after 9 weeks. The risk of re-thrombosis was ultimately reduced by allowing time for the thrombogenic potential to abate. The argatroban/warfarin transition was monitored with chromogenic factor X levels. This case highlights several difficult problems in pediatric thrombosis.

Preoperative evaluation and preparation of the patient for cardiac surgery

Cardiac surgery is associated with significant morbidity, mortality, and socioeconomic costs. Preoperative assessment assists the clinician in identifying potential complications and facilitates discussion of these risks with the patient. Careful patient selection and preparation during preoperative evaluation may minimize morbidity, mortality, and resource use. This article outlines a system-based approach to preoperative evaluation and preparation of the patient undergoing cardiac surgery.

Evaluation of a clinical scoring scale to direct early appropriate therapy in heparin-induced thrombocytopenia

Background. Heparin-induced thrombocytopenia (HIT) is a serious adverse effect associated with heparin therapy. Current laboratory confirmation for immune mediated HIT often results in false positives and unnecessary treatment, exposing individuals to possible complications. As a result, clinical evaluation has been recommended in conjunction with laboratory testing. We hypothesize that utilization of a clinical scoring scale, the 4T’s, will result in the initial appropriate therapy for suspected HIT.

Methods. This is a retrospective chart review of 108 patients who underwent ELISA testing for HIT at a university hospital. The 4T’s scale was applied, stratifying individuals into low, intermediate, and high-risk categories. Each risk score was compared to the ELISA results to determine if the 4T’s can predict the diagnosis of HIT and result in appropriate management. ELISA optical density scores as well as incidence of adverse events were also compared among risk categories.

Study Results. Individuals with low risk correlate with a negative ELISA compared to intermediate and high-risk individuals (p = 0.01 and p<0.01) and also were significantly more likely to predict institution of appropriate therapy (p<0.01). Median optical density scores were 0.184 (0.046—2.116), 0.226 (0.067—1.887), and 0.476 (0.096—1.309) for low, intermediate, and high 4T scores. Major adverse events include thrombosis and bleeding.

Conclusions. Individuals with low risk were more likely to receive initial, appropriate therapy and were also significantly more likely to have a negative ELISA test result. Individuals with low risk determined by the 4T score therefore may have therapy and serologic testing for HIT withheld.

Compliance with platelet count monitoring recommendations and management of possible heparin-induced thrombocytopenia in hospitalized patients receiving low-molecular-weight heparin

BACKGROUND

Summaries of product characteristics (SPCs) and clinical guideline recommendations are available for monitoring the platelet count for heparin-induced thrombocytopenia (HIT) in patients receiving low-molecular-weight heparin (LMWH). Testing for the presence of heparin-platelet factor 4 antibodies (HPF4-Ab) and starting alternative anticoagulation is recommended when HIT is suspected.

OBJECTIVE

To investigate the frequency of compliance with recommendations for platelet count monitoring and management of possible HIT in hospitalized patients receiving prophylaxis and treatment dosing of LMWH for at least 5 consecutive days.

METHODS

A retrospective cohort study within the Utrecht Patient Oriented Database (UPOD) was conducted. For all inpatients, all episodes of exposure to dalteparin or nadroparin for at least 5 consecutive days in 2004-2005 were selected. In 4 different nonexclusive groups of patients (all pts. receiving dalteparin, all pts. receiving nadroparin, surgical pts. with a prophylactic dose of either dalteparin or nadroparin, and pts. exposed to unfractionated heparin [UFH] within 100 days before receiving either dalteparin or nadroparin), compliance with recommendations for platelet count monitoring from SPCs and a clinical guideline was studied. The frequency of compliance with these recommendations was determined. In addition, it was determined whether patient and treatment characteristics were associated with regular platelet count monitoring. Finally, the frequency of testing for HPF4-Ab and the initiation of danaparoid treatment in patients with a drop of at least 50% in platelet count were investigated.

RESULTS

A total of 6804 patients, with 7770 episodes of LMWH treatment, were included in the analysis. The frequency of compliance with platelet count monitoring recommendations was 26.3% for all patients receiving dalteparin, 35.6% for all patients receiving nadroparin, 23.0% for surgical patients receiving prophylactic dosing of either dalteparin or nadroparin, and 41.5% for patients exposed to UFH within 100 days before the start of either dalteparin or nadroparin treatment. Regular platelet count monitoring was strongly positively associated with medical patients (relative risk [RR] 2.33), surgical patients (RR 2.03), critically ill patients (RR 2.80), and those with recent exposure to UFH (RR 2.19). The frequency of testing for HPF4-Ab was 5.4% and the initiation of alternative anticoagulation with danaparoid in patients with a 50% drop in platelet count was 0%.

CONCLUSIONS

The results suggest that compliance with recommendations for platelet count monitoring and management of possible HIT is low at our institution. Policies and tools to improve compliance with recommended laboratory monitoring should be developed to secure the safe use of LMWH and other medications.

Rivaroxaban for the prevention of venous thromboembolism following major orthopedic surgery: the RECORD trials

Patients undergoing total hip or knee arthroplasty face an increased risk for venous thromboembolism in the days and weeks following surgery. Hence, the routine application of prophylactic strategies is currently recommended. These include parenteral anticoagulants such as the low-molecular-weight heparins or fondaparinux and oral anticoagulants such as warfarin. New anticoagulant drugs are rapidly becoming available, including drugs that are administered orally, at fixed doses and without laboratory monitoring. Rivaroxaban is the first of a new class of anticoagulants: the selective, direct Factor Xa inhibitors. It has completed clinical evaluation in the setting of major orthopedic surgery and is now approved in many countries for the prevention of venous thromboembolism in patients undergoing total knee and hip arthroplasty. In this paper, we will review the trial data now supporting the clinical use of rivaroxaban and will discuss the potential role of this agent in daily clinical practice.

Heparin-induced thrombocytopenia: a renal perspective

Heparin-induced thrombocytopenia (HIT) is a clinicopathologic syndrome in which one or more clinical events, usually thrombocytopenia or thrombosis, are temporally related to heparin administration and caused by HIT antibodies. Rapid and accurate diagnosis is essential given the high incidence of thrombosis at around the time of initial disease recognition. Discontinuation of heparin and initiation of alternative anticoagulants reduces HIT-associated morbidity and mortality. The clinical consequences of HIT in hemodialysis patients remain unclear, with several studies reporting no clinical sequelae and others describing complications such as thrombocytopenia or clotting of the extracorporeal circuit. Frequent clotting of the extracorporeal circuit has also been reported in HIT-antibody-positive patients on continuous veno-venous hemofiltration. Several recent findings are of particular interest to nephrologists. An acute systemic reaction has been described as a presentation of HIT in hemodialysis patients shortly after administration of an unfractionated heparin bolus. This syndrome is important to recognize as it might mimic a dialyzer reaction. More recently, the presence of a positive HIT-antibody test or increasing titers of HIT antibody were associated with increased mortality in hemodialysis patients, raising the question of whether these antibodies have a role in the increased cardiovascular mortality seen in these patients. HIT-antibody production is often transient and small numbers of hemodialysis patients with undetectable antibody levels have been rechallenged with heparin without adverse clinical consequences.

Severe bleeding secondary to misuse of fondaparinux: a case report

Venous thromboembolism (VTE) remains a great challenge because of its frequency and of its potential severity. However, VTE treatment can also lead to iatrogenic complications. We report a case of thigh haematoma by a 83-year-old woman under fondaparinux for a solear thrombosis. Then we discuss the indications of Unfractionated Heparin (UFH), Low-Molecular-Weight Heparins (LMWH) and Fondaparinux, which are the three classes of rapidly acting anticoagulant treatments nowadays available. As their efficacy is comparable, the choice between these classes relies on the risk of adverse effects, which depends on some patient's characteristics. LMWH and fondaparinux are contra-indicated by the patients with a renal clearance under 30 ml/min. Only UFH are authorized during the whole pregnancy even though LMWH are more and more used. Fondaparinux has proven its safety by patients over 100 kg. UFH requires a daily biological management whereas it is optional for LMWH and fondaparinux, as long as their contra-indications are taken into account. No Heparin-induced-thrombocytopenia Syndrome (HIT-Sd) has been proven yet under fondaparinux so that platelets management seems not necessary, contrary to UFH and LMWH which require a twice-weekly platelets count. The accuracy of the therapeutic indication should result in the best benefit/risk assessment.

Treatment of venous thromboembolism in cancer patients

Venous thromboembolism (VTE) is a major cause of morbidity and mortality in patients with cancer. Monotherapy with low-molecular-weight heparin is the recommended first-line approach in cancer patients with newly diagnosed VTE, and is usually continued for a minimum of 3-6 months. Other management issues that require further research include optimal duration of anticoagulant therapy, treatment of recurrent VTE, the role of vena cava filters, the effects of VTE and its treatment on quality of life, and the impact of anticoagulants on survival. Newer anticoagulants hold promise in providing more effective and convenient treatment of VTE for this high-risk population, but further studies are awaited.

Hematology pharmacology: anticoagulant, antiplatelet, and procoagulant agents in practice

Alterations in hemostasis and coagulation are common problems during critical illness. For that reason, it is essential that advanced practice and critical care nurses have an understanding of the medications used to treat these potentially deadly disorders. The antithrombotic drugs, including anticoagulants, antiplatelet agents, and fibrinolytics, are among the most frequently used drug therapies in the United States. These agents prevent and treat the thrombotic diseases, a leading cause of morbidity and mortality. Anticoagulants, the indirect and direct thrombin inhibitors as well as the vitamin K antagonists, are critical in treating venous thrombosis and preventing serious thrombotic complications with atrial fibrillation. The antiplatelet drugs work to decrease platelet aggregation and are especially effective in preventing and managing arterial thrombus. On the other end of the spectrum, the procoagulants are used to help prevent and control blood loss. These agents include human blood stimulators, human factor concentrates, including recombinant activated factor VIIa, and desmopressin.

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

Thrombocytopenia following heparin administration can be associated with an immune reaction, now referred to as heparin-induced thrombocytopenia (HIT). HIT is essentially a prothrombotic disorder mediated by an IgG antiplatelet factor 4/heparin antibody, which induces platelet, endothelial cell, monocyte, and other cellular activation, leading to thrombin generation and thrombotic complications. Indeed, HIT can also be regarded as a serious adverse drug effect. Importantly, HIT can be a life-threatening and limb-threatening condition frequently associated with characteristically severe and extensive thromboembolism (both venous and arterial) rather than with bleeding. This article provides an overview of HIT, with an emphasis on the clinical diagnosis and management.

False-positive tests for heparin-induced thrombocytopenia in patients with antiphospholipid syndrome and systemic lupus erythematosus

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a severe complication of heparin therapy that can be associated with arterial or venous thrombosis and is caused by antibodies against platelet factor 4 (PF4)-heparin complex. Patients with antiphospholipid syndrome (APS) have been reported with positive tests for PF4-heparin complex antibodies by antigen assay. Whether such patients can be treated with heparin is a dilemma.

OBJECTIVES

To determine the incidence and nature of the HIT immune reaction in patients with APS and/or systemic lupus erythematosus (SLE).

METHODS

Antibodies against PF4-heparin complex were assayed by particle gel immunoassay (PaGIA), or enzyme immunoassay (EIA) with or without an excess of heparin. EIA for PF4 alone was also performed. Functional assays for HIT, that is, heparin-induced platelet activation (HIPA) and heparin-induced platelet aggregation, were also performed.

RESULTS

In 32 of 42 patients (76.2%) with APS, APS and SLE, SLE, or SLE with antiphospholipid antibodies, EIA IgG or PaGIA for PF4-heparin complex antibodies were positive. Of these 32 samples, 26 (81.3%) tested positive for anti-PF4 antibodies. All 24 samples that were positive for PF4-heparin complex by EIA IgG were also positive for EIA IgG in the presence of heparin excess, and all were negative by the HIPA and heparin-induced platelet aggregation tests.

CONCLUSION

A large proportion of patients with APS and/or SLE give false-positive HIT antigen test results that are presumably related to autoantibodies against PF4, which can be distinguished from true HIT antibodies by EIA for PF4-heparin complexes tested with heparin excess, and by functional assays.

Clinical experience with argatroban for heparin-induced thrombocytopenia in a large teaching hospital

BACKGROUND

Argatroban is a direct thrombin inhibitor approved for the prophylaxis or treatment of thrombosis in patients with heparin-induced thrombocytopenia (HIT). The product monograph does not guide clinicians beyond specifying the initial dose of 2 μg/kg per minute (or 0.5 μg/kg per minute for patients with hepatic impairment). Some authors have suggested that in the intensive care unit (ICU) and for patients with acute cardiac disease and those with renal or hepatic dysfunction, this dose may result in a supratherapeutic activated partial thromboplastin time (aPTT).

OBJECTIVES

To evaluate the efficacy and safety of argatroban in adult patients with suspected HIT in a large teaching hospital, and to review dosing for patients in the ICU, patients with acute cardiac disease, and patients with renal or hepatic dysfunction.

METHODS

Charts of patients with suspected HIT who had received argatroban for at least 24 h between October 1, 2005, and October 1, 2007, at the Foothills Medical Centre, Calgary, Alberta, were examined retrospectively.

RESULTS

Thirty patients met the inclusion criteria, with charts available for review. Of these, 21 (70%) patients had an initial argatroban dose of 2 μg/kg per minute and 4 (13%) had an initial dose of 0.5 μg/kg per minute. The median duration of therapy was 6 days, and the mean dose was 2.14 μg/kg per minute. There were 122 dosage adjustments, the most common change being 0.5 μg/kg per minute, followed by adjustments of 1 and 0.1 μg/kg per minute. Six patients had supratherapeutic aPTT values (above 100 s), and none experienced major bleeding.

CONCLUSIONS

The results of this study suggest that an initial argatroban dose of 2 μg/kg per minute is appropriate for patients with no hepatic dysfunction. Patients with acute cardiac disease and critically ill patients may require lower doses of argatroban; however no dosage adjustments are required for patients with renal dysfunction.

Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT), typically occurring in the second week of heparin therapy, is an antibody-mediated adverse drug reaction associated with increased thrombotic risk. The most important antigens are located on platelet factor 4 (PF4)/heparin complexes. All HIT is caused by platelet-activating antibodies, but not all PF4/heparin-reactive antibodies cause HIT. Thus, tests have high negative, but only moderate, positive predictive value. Cessation of heparin requires substitution with an alternative anticoagulant, but as these drugs have increased bleeding risk, they should be used in therapeutic doses only if HIT is considered very likely. Avoiding/postponing coumarin is crucial in minimizing microthrombotic complications. Recent studies of HIT immunobiology suggest that HIT mimics immunity against repetitive antigens, as they are relevant in microbial defense. Thus, understanding HIT may help unravel why host defenses can trigger autoimmunity.

Therapeutic approaches to secondary immune thrombocytopenic purpura

Secondary thrombocytopenia is similar to primary or idiopathic thrombocytopenia (ITP) in that it is characterized by reduced platelet production or increased platelet destruction resulting in platelet levels<60,000/microL. Thrombocytopenia can occur from secondary causes associated with chronic disorders or with disturbed immune function due to chronic infections, lymphoproliferative and myeloproliferative disorders, pregnancy, or autoimmune disorders. Diagnosis of secondary ITP in some cases is complex, and the thrombocytopenia can often be resolved by treating the underlying disorder to the extent this is possible. In most cases, treatment is focused on reducing platelet destruction, but, in some cases, treatment may also be directed at stimulating platelet production. The most problematic cases of thrombocytopenia may be seen in pregnant women. This review will address various agents and their utility in treating ITP from secondary causes; in addition, thrombocytopenia in pregnancy, ITP in immunodeficiency conditions, and drug-induced thrombocytopenia will be discussed. Unlike primary ITP, treatment often must be tailored to the specific circumstance underlying the secondary ITP, even if the condition itself is incurable.

Reducing harm associated with anticoagulation: practical considerations of argatroban therapy in heparin-induced thrombocytopenia

Argatroban is a hepatically metabolized, direct thrombin inhibitor used for prophylaxis or treatment of thrombosis in heparin-induced thrombocytopenia (HIT) and for patients with or at risk of HIT undergoing percutaneous coronary intervention (PCI). The objective of this review is to summarize practical considerations of argatroban therapy in HIT. The US FDA-recommended argatroban dose in HIT is 2 microg/kg/min (reduced in patients with hepatic impairment and in paediatric patients), adjusted to achieve activated partial thromboplastin times (aPTTs) 1.5-3 times baseline (not >100 seconds). Contemporary experiences indicate that reduced doses are also needed in patients with conditions associated with hepatic hypoperfusion, e.g. heart failure, yet are unnecessary for renal dysfunction, adult age, sex, race/ethnicity or obesity. Argatroban 0.5-1.2 microg/kg/min typically supports therapeutic aPTTs. The FDA-recommended dose during PCI is 25 microg/kg/min (350 microg/kg initial bolus), adjusted to achieve activated clotting times (ACTs) of 300-450 sec. For PCI, argatroban has not been investigated in hepatically impaired patients; dose adjustment is unnecessary for adult age, sex, race/ethnicity or obesity, and lesser doses may be adequate with concurrent glycoprotein IIb/IIIa inhibition. Argatroban prolongs the International Normalized Ratio, and published approaches for monitoring the argatroban-to-warfarin transition should be followed. Major bleeding with argatroban is 0-10% in the non-interventional setting and 0-5.8% periprocedurally. Argatroban has no specific antidote, and if excessive anticoagulation occurs, argatroban infusion should be stopped or reduced. Improved familiarity of healthcare professionals with argatroban therapy in HIT, including in special populations and during PCI, may facilitate reduction of harm associated with HIT (e.g. fewer thromboses) or its treatment (e.g. fewer argatroban medication errors).

[Heparin resistance and antithrombin deficiency]

The phenomenon of heparin resistance (HR) is characterized by high doses of unfractionated heparin (UFH) being required to bring activated partial thromboplastin time (aPTT) and activated coagulation time (ACT) within therapeutically desired ranges, or by the impossibility of reaching these ranges. At UFH dosages > 35,000 IU/d, HR should be considered a factor. The most frequent cause of HR is deficiency of antithrombin (AT), the presence of which is essential for UFH to exert its anticoagulatory effect. AT in concentrate form may be applied to overcome AT-dependent HR. The main clinically relevant situations in which AT-dependent HR occurs, with possible indication of AT substitution, are congenital AT deficiency, asparaginase therapy, disseminated intravascular coagulation (DIC) and administration of high doses of heparin during extracorporeal circulation, where it is significant, due to the need to maintain a very high ACT (> 400 s), that use of heart-lung machines is associated with an HR incidence of approximately 20%. The following procedure is recommended when there is no DIC and when extracorporeal circulation is not used: if HR is suspected and AT activity is < or = 60%, UFH should first be reduced to 500 IU/h (to prevent bleeding complications), before AT is substituted. AT activity should then exceed 80%. Under normalized and stable AT activity, the UFH dose should be adjusted such that aPTT is within a range of 60-100 s. If anticoagulation over a longer term is indicated, then overlapping anticoagulation with a vitamin K antagonist should be started as quickly as possible.

Heparin-induced anaphylactic and anaphylactoid reactions: two distinct but overlapping syndromes

BACKGROUND

Heparin-induced anaphylactic and anaphylactoid reactions are of increasing clinical and scientific interest, particularly given the recent identification of a syndrome of heparin-induced anaphylaxis due to oversulfated chondroitin sulfate (OSCS), a contaminant in certain heparin preparations. However, heparin-induced anaphylactoid reactions also have been reported to be a consequence of immune-mediated heparin-induced thrombocytopenia (HIT).

OBJECTIVE

To summarize the clinical features and pathophysiology of two distinct disorders, HIT-associated anaphylactoid reactions as well as anaphylaxis resulting from OSCS-contaminated heparin.

METHODS

We review literature describing these two types of heparin-induced anaphylactic and anaphylactoid reactions, and seek potential pathophysiologic links between them.

RESULTS

Intravenous bolus heparin administered to patients with circulating 'HIT antibodies', usually as a result of recent heparin therapy, can produce anaphylactoid reactions, probably as a consequence of in vivo activation of platelets and, possibly, leukocytes. Affected patients often evince fever/chills, hypertension and/or acute respiratory compromise ('pseudo-pulmonary embolism'). In contrast, heparin-induced anaphylaxis is caused by activation of the contact system, with formation of vasoactive kinins (bradykinin, des-arg(9)-bradykinin). This latter syndrome has been linked in an epidemic form to administration of OSCS-contaminated heparin; these reactions feature prominent hypotension and laryngeal edema. Hemodialysis patients are at increased risk for both syndromes. There is evidence that OSCS-contaminated heparin itself increases the risk of HIT compared with non-contaminated heparin.

CONCLUSION

Two distinct syndromes of heparin-induced anaphylaxis and anaphylactoid reactions exist. These seem to share certain epidemiologic features, given that OSCS-contaminated heparin can produce anaphylaxis through contact system activation but also could increase risk of HIT and HIT-associated anaphylactoid reactions.

The new tyrosine-kinase inhibitor and anticancer drug dasatinib reversibly affects platelet activation in vitro and in vivo

Dasatinib is an oral potent adenosine triphosphate (ATP)-competitive inhibitor of BCR-ABL, cKIT, platelet-derived growth factor receptor, and SRC family kinases (SFKs), which has demonstrated high efficiency in patients with imatinib-resistant chronic myelogenous leukemia. Here, we show that dasatinib weakly affects platelet activation by thrombin or adenosine diphosphate but is a potent inhibitor of platelet signaling and functions initiated by collagen or FcgammaRIIA cross-linking, which require immunoreceptor tyrosine-based activation motif phosphorylation by SFKs. Accordingly, dasatinib treatment rapidly decreases the volume of thrombi formed under arterial flow conditions in whole blood from patients or mice perfused over a matrix of collagen. Moreover, treatment of mice with dasatinib increases the tail bleeding time in a dose-dependent manner. Interestingly, these effects are rapidly reversible after interruption of the treatment. Our data clearly demonstrate that, in contrast to imatinib, dasatinib affects platelet functions in vitro and in vivo, which has important implications in clinic and could explain increased risks of bleeding observed in patients. Moreover, dasatinib efficiently prevents platelet activation mediated by FcgammaRIIA cross-linking and by sera from patients with heparin-induced thrombocytopenia, suggesting that reversible antiplatelet agents acting as ATP-competitive inhibitors of SFKs may be of therapeutic interest in the treatment of this pathology.