Drugs for the prevention and treatment of thrombosis in patients with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia complicating extracorporeal membrane oxygenation support: Review of the literature and alternative anticoagulants

Heparin-induced thrombocytopenia (HIT) is a life-threatening prothrombotic, immune-mediated complication of unfractionated heparin and low molecular weight heparin therapy. HIT is characterized by moderate thrombocytopenia 5-10 days after initial heparin exposure, detection of platelet-activating anti-platelet factor 4/heparin antibodies and an increased risk of venous and arterial thrombosis. Extracorporeal membrane oxygenation (ECMO) is a form of mechanical circulatory support used in critically ill patients with respiratory or cardiac failure. Systemic anticoagulation is used to alleviate the thrombotic complications that may occur when blood is exposed to artificial surfaces within the ECMO circuit. Therefore, when HIT complicates patients on ECMO support, it is associated with a high thrombotic morbidity and mortality. The risk for HIT correlates with the accumulative dosage of heparin exposure. In ECMO patients receiving continuous infusion of heparin for circuit patency, the risk for HIT is not neglected and must be thought of in the differential diagnosis of the appropriate clinical and laboratory circumstances. The following article reviews the current knowledge in HIT complicating ECMO patients and the alternative anticoagulation options in the presence of HIT.

Heparin-induced thrombocytopenia complicating extracorporeal membrane oxygenation support in pediatric patients: review of the literature and alternative anticoagulants

Heparin-induced thrombocytopenia (HIT) is a prothrombotic, immune-mediated complication of unfractionated heparin (UFH) and low molecular weight heparin therapy. HIT is characterized by moderate thrombocytopenia 5-10 days after initial heparin exposure, detection of platelet-activating anti-platelet factor 4/heparin antibodies and an increased risk of venous and arterial thrombosis. Extracorporeal membrane oxygenation (ECMO) is a form of mechanical circulatory support used in critically ill patients with respiratory or cardiac failure. Systemic anticoagulation is used to alleviate the thrombotic complications that may occur when blood is exposed to artificial surfaces within the ECMO circuit. Therefore, when HIT complicates patients on ECMO support, it is associated with a high thrombotic morbidity and mortality. The following article reviews the current knowledge in pediatric HIT, especially in ECMO patients, and the alternative anticoagulation options in the presence of HIT.

Heparin-induced thrombocytopenia associated with acute liver graft failure

An orthotopic liver transplantation (OLT) is of a proven benefit in an acute liver failure (ALF). Heparin-induced thrombocytopenia (HIT) is strongly associated with thromboembolic complications. We present the case of a 56-year-old patient who underwent an OLT owing to an ALF of unknown aetiology. HIT type II with consecutive hepatic and portal vein thrombosis caused progressive graft failure. Total hepatectomy and porto-caval shunt were performed to reduce the toxic effects of liver cell necrosis such as multiorgan failure involving the respiratory, renal and cardiovascular systems. A suitable liver graft was allocated after an anhepatic bridging period of 56 h. Specific complications due to end-stage liver failure-such as acidosis, coagulopathy, decrease of vascular resistance, cerebral oedema, myocardial infarction and right heart failure-were treated. Following a re-OLT, the patient made a complete recovery. We present a rare case of HIT-associated early liver graft failure followed by a prolonged anhepatic phase and finally a successful re-OLT.

Prospective evaluation of the '4Ts' score and particle gel immunoassay specific to heparin/PF4 for the diagnosis of heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a severe disease that is often difficult to diagnose. A clinical scoring system, the '4Ts' score, has been proposed to estimate its probability before laboratory testing, and a particle gel immunoassay (H/PF4 PaGIA) has also been developed for rapid detection of HIT antibodies.

AIM

To evaluate the performance of both methods when HIT is suspected clinically.

METHODS

Two hundred thirteen consecutive patients were included in four centers. The probability of HIT was evaluated using the 4Ts score blind to antibody test results. HIT was confirmed only when the serotonin release assay (SRA) was positive.

RESULTS

The risk of HIT was evaluated by the 4Ts score as low (LowR), intermediate (IR) or high (HR) in 34.7%, 60.6% and 4.7% of patients, respectively. The negative predictive value (NPV) of the 4Ts score was 100%, as the SRA was negative in all LowR patients. PaGIA was negative in 176 patients without HIT (99.4%, NPV) and the negative likelihood ratio (LR-) was 0.05. PaGIA was positive in 37 patients, including 21 with HIT (positive predictive value = 56.8%), with a positive LR of 11.4. A negative PaGIA result decreased the probability of HIT in IR patients from 10.9% before assay to 0.6%, whereas a positive result did not substantially increase the likelihood for HIT.

CONCLUSION

The use of the 4Ts score with PaGIA appears to be a reliable strategy to rule out HIT.

Argatroban for anticoagulation in pediatric patients with heparin-induced thrombocytopenia requiring extracorporeal life support

Heparin-induced thrombocytopenia (HIT) is a well recognized and described immune phenomenon in adults. However, pediatric data on the incidence, treatment, and complications of HIT are limited. Despite the widespread use of heparin in pediatric patients and the repeated and sustained exposures to heparin in neonates and children with congenital heart disease, HIT has been infrequently recognized and under-reported in this population. HIT is an intensely procoagulant disorder and carries significant morbidity and mortality. In this case series, we describe HIT management with argatroban as alternative anticoagulation in 3 children requiring extracorporeal life support.

Haemodialysis-associated anaphylactic and anaphylactoid reactions

Anaphylactic and anaphylactoid reactions related to haemodialysis have been increasingly described for almost 3 decades. The majority of these cases used to occur with ethylene oxide sterilized, and complement-activating cellulose membranes. However, a considerable number of publications have focused on polyacrylonitrile AN69 high flux membranes, angiotensin converting enzyme inhibitors and iron as other important causes of potentially severe haemodialysis-related anaphylactoid reactions. Clinical manifestations vary considerably and generally do not allow differentiation between IgE-mediated anaphylaxis and anaphylactoid reactions (e.g. from nonspecific mediator release). Successful management of these patients requires multidisciplinary approach and involves prompt recognition and treatment by the attending physician, and identification of the offending agent(s) with subsequent avoidance of the incriminated compound(s). This review focuses on some major causes of anaphylactoid and anaphylactic reactions during haemodialysis. Special consideration is given to the therapeutic and diagnostic approach.

[Does antiaggregant therapy have a place in type II heparin-induced thrombocytopenia?]

We report a case of type II heparin-induced thrombocytopenia, which occurred after heart surgery in a 71-year-old female patient with several cardiovascular risk factors. The diagnosis of heparin-induced thrombopenia was suspected because association of multifocal arterial and venous thrombosis and detection of antiplatelet-factor 4 antibodies with a drop of more than 50% in the platelet count. Until diagnostic of heparin-induced thrombocytopenia was made, clopidogrel was introduced because of well-documented ischemia in middle-cerebral artery territory. The platelets subsequently increased by near 30%. The diagnosis of heparin-induced thrombocytopenia was finally confirmed a few days later by detection of antiplatelet-factor 4 antibodies associated with a positive platelet aggregation test for unfractionated heparin. Heparin was replaced by sodium danaparoid. These measures did not change the unfavorable outcome and death of the patient. The increase in the platelet count after fortuitous clopidogrel introduction raises the question of the role of antiaggregant agents in association with anticoagulants for the treatment of type II heparin-induced thrombocytopenia.