Heparininduced thrombocytopenia is a complication of treatment with the bloodthinner anticoagulant heparin that can cause low platelets in the blood and an increased risk of blood clotting. Guideline for anticoagulation and prophylaxis using low molecular weight heparin lmwh in adult inpatients. Despite their widespread use, reports about adverse effects from lmwhs are very scarce. Venous thromboembolism prophylaxis adult inpatient. Furthermore, with lower affinity for pf4 than heparin, lmwh is less likely to induce the conformational changes in pf4 that trigger the. Unfractionated heparin low molecular weight heparins warfarin stephanie inverso polli, pharm. Heparininduced thrombocytopenia hit is a lifethreatening complication of exposure to heparin eg, unfractionated heparin, low molecular weight lmw heparin that occurs in a small percentage of patients exposed, regardless of. All hospitalized patients should be evaluated for both bleeding and vte risk within 24 hours of admission, upon transferring level of care, and periodically during the. When a diagnosis of hit is suspected immediate cessation of all forms of heparin, including unfractionated heparin ufh, low molecular weight heparin lmwh and heparin flushes, is imperative. Heparininduced thrombocytopenia hit is an immune complication of heparin therapy caused by antibodies to complexes of platelet factor 4 pf4 and heparin. An enzymelinked immunosorbent assay elisa is usually performed to assist in the diagnosis of hit.
Been receiving low molecular weight heparin 40k daily since admission. Heparins, including unfractionated heparin and a variety of low molecular weight lmw heparin products, are used extensively as anticoagulants. Heparin infusion is higher risk than dvt prophylactic doses of heparin. Lowmolecularweight heparin binds less avidly to platelets and causes less pf4 release.
Heparininduced thrombocytopenia hit is a complication of heparin therapy and is characterized by two types. Hit predisposes to thrombosis the abnormal formation of blood clots inside a blood vessel because platelets release microparticles that activate thrombin, thereby leading to thrombosis. The first, hit type i also called heparinassociated thrombocytopenia in the past, is a benign form not associated with an increased risk of thrombosis. Low molecular weight heparins lmwhs have a favorably high antifactor xatoantifactor iia activity ratio, which implies an improved antithrombotic potential with fewer bleeding side effects. Heparininduced thrombocytopenia, or hit, occurs in some patients who have been taking the anticoagulant blood thinner heparin.
Heparininduced thrombocytopenia in a nonthrombocytopenic. Comparison of lowmolecularweight heparin and unfractionated heparin. Guideline for anticoagulation and prophylaxis using low. Platelet factor 4 heparin antibody testing has a high negative. Heparininduced thrombocytopenia in patients treated with lowmolecularweight heparin or unfractionated heparin article pdf available in new england journal of medicine 33220.
Treatment of hit should be initiated based on clinical suspicion and must never be delayed pending laboratory confirmation of hit. Pf4 without need for heparin, causing platelet activation non heparin polyanions causing activation of pf4. A systematic approach to the patient who is critically ill who has. Heparin induced thrombocytopenia is an antibodymediated drug reaction that may be complicated not by just low platelets but arterial or venous thrombosis heparin induced thrombocytopenia heparin induced thrombocytopenia occurs in up to 5 % of patients receiving unfractionated heparin and in 0. Heparin complexes pf4 and stimulates the formation of antibodies that cause heparininduced thrombocytopenia hit.
Is the incidence trend of heparininduced thrombocytopenia. The incidence of heparin induced thrombocytopenia hit is greater for unfractionated heparin ufh than low molecular weight heparin lmwh. After you stop using this medicine, it may still produce some side effects that need attention. This test detects and measures antibodies that are produced by some people when or after they are treated with heparin. Unfractionated heparin is higher risk than low molecularweight heparin. Heparin binds to the enzyme inhibitor antithrombin iii at, causing a conformational change.
Heparin and low molecular weight heparin are blood thinners that are injected under the skin. Use of low molecular weight heparin in patients with. Within ufh formulations, bovine origin heparin has a greater incidence of causing hit than porcine origin heparin products, which is why most use porcine origin. Hit is more common in surgical than medical patients.
Pdf heparininduced thrombocytopenia in patients treated. This guideline provides recommendations regarding best practice for anticoagulation treatment and prophylaxis of venous thromboembolism for adult inpatients in queensland health facilities using low molecular weight heparins. Heparin does not cross the placental barrier due to its high molecular weight and its negative charge. Cough up or vomit blood bright red or looks like coffee grounds. Low molecularweight heparins lmwhs are increasingly preferred to unfractioned heparin uh for thromboprophylaxis, as well as for the treatment of vte, and in the pregnant patient. Heparininduced thrombocytopenia hit natalie s evans. A case of unsuccessful treatment of heparininduced. Severe thrombocytopenia platelets low molecular weight heparin enoxaparin fondaparinux. They are used in the prevention of blood clots and treatment of venous thromboembolism deep vein thrombosis and pulmonary embolism and in the treatment of myocardial infarction heparin is a naturally occurring polysaccharide that inhibits coagulation, the process that leads to thrombosis.
Triggered by the immune system in response to heparin, hit causes a low platelet count thrombocytopenia. Heparininduced thrombocytopenia hit is associated with clinically significant morbidity and mortality. These antibodies trigger a highly prothrombotic state by causing intravascular. Heparin binds to platelets, causing activation 8 and release of pf4. Heparininduced skin necrosis at the injection site is a rare adverse effect, more commonly associated with unfractionated heparin ufh rather than with lmwh, while its mechanism remains unclear. Hit is characterised by immunoglobulin g igg antibodies that recognize an antigen complex of platelet factor 4 pf4 bound to heparin.
Riia on platelets and monocytes to propagate a hypercoagulable state culminating in lifethreatening thrombosis. Hit is characterised by immunoglobulin g igg antibodies. Heparin induced thrombocytopenia thrombosis hitt is associated with a high morbidity and mortality. Heparininduced thrombocytopenia hit ranges from an asymptomatic reaction to heparin with a transient mild thrombocytopenia hit i to a life and limbthreatening immunological reaction, heparininduced thrombocytopenia with thrombosis hitt or hit ii.
However, there have been three reported isolated cases of fondaparinux. Pf4 antibodies and thus has a very low likelihood of causing, or exacerbating, hit. Heparininduced thrombocytopenia is defined as a decrease in platelet count during or shortly following exposure to heparin 8. These short strands make lmwh last longer and act more predictably in the body than ufh. Randomized trial of a lowmolecularweight heparin kabi 2165 versus adjusteddose subcutaneous standard heparin in the prophylaxis of deepvein thrombosis after elective hip surgery.
Low molecular weight heparin 10mg galen laboratory supplies. Heparininduced thrombocytopenia hit is an antibodymediated adverse effect of heparin that is associated with devastating arterial and venous thrombotic complications occurring with an incidence between 1. The adoption of low molecular weight heparins is one reason for the reduced incidence of. Because the platelet count normalizes even with continued heparin therapy, it is not associated with increased thrombotic risk. The incidence is up to 10 times as high among patients receiving unfractionated heparin as it is among those receiving lowmolecularweight heparin, 25 and hit occurs more frequently among patients who have had major surgery than among those who. A free powerpoint ppt presentation displayed as a flash slide show on id. Heparin induced thrombocytopenia kettering health network. Hit occurs in up to 5% of patients receiving unfractionated heparin ufh and in pdf. The thrombocytopenia of hit is typically of moderate severity, with median platelet counts ranging between 5080. Pathogenic antibodies to pf4heparin bind and activate cellular fc. We sought to use a new cutoff to define a positive hit elisa.
Heparininduced thrombocytopenia hit is considered the most common form of druginduced thrombocytopenia as well as one of the common causes of thrombocytopenia in hospitalized patients. Diagnosis is essentially clinical and negative results of laboratory assays do not exclude the diagnosis. Although hit should be considered, it is not usually the cause of thrombocytopenia in the medicalsurgical icu population. Hit occurs in up to 5% of patients receiving unfractionated heparin ufh and in low molecular weight heparin lmwh. Patients who are critically ill are commonly thrombocytopenic and exposed to heparin. Heparininduced thrombocytopenia in the critically ill. How do lowmolecular weight heparins lmwh cause less.
Hit is characterized by a plateletcount fall of more than 50% at 5 to 10 days after the start of heparin and hypercoagulability. The increasing trend of using lowmolecularweightheparin lmwh versus unfractionated heparin ufh in hospitalized adult patients is raising concerns about the incidence of heparininduced thrombocytopenia hit. Heparininduced thrombocytopenia hit is a serious complication of heparin utilization. Low molecular weight heparin drug information, professional. Treatment involves stopping all heparin immediately and giving an alternative thrombin inhibitor. Heparininduced thrombocytopenia hit is a rare immunemediated complication associated with unfractionated heparin and to a lesser extent with lowmolecular weight heparins.
High quality polysaccharides including heparin and low molecular weight heparin, heparan sulphate, dermatan sulphate, lowincalcium heparin and hyaluronic acid polymers. The incidence is 10 times higher with unfractionated versus low molecular weight heparin. Less commonly, drugs related to heparin called lowmolecularweight heparins lmwhs can cause hit. Low molecular weight heparin, polydisperse molecular weight range from 1800 to. Lowmolecularweight heparin lmwh is a class of anticoagulant medications. Heparininduced thrombocytopenia hit is the development of thrombocytopenia a low platelet count, due to the administration of various forms of heparin, an anticoagulant. The american college of chest physicians recommends treating patients with suspected hit with a nonheparin product regardless if thrombosis is present.
The risk of hit is about fivefold lower with lmwh than with heparin. Ordinarily, heparin prevents clotting and does not affect the platelets, components of the blood that help form blood clots. Heparininduced thrombocytopenia is a profoundly dangerous, potentially lethal, immunologically mediated adverse drug reaction to unfractionated heparin or, less commonly, to low molecular weight heparin. During this period of time, check with your doctor immediately if you notice the following side effects. Two clinical forms of hit are generally recognized. Heparininduced thrombocytopenia pf4 antibody labcorp. Heparininduced thrombocytopenia hit is a lifethreatening immune response to heparin and its derivatives that is associated with a high risk of thromboembolic complications. A brief overview of the pathophysiology, diagnosis, and treatment of heparininduced thrombocytopenia hit is discussed. Low molecular weight heparins lmwhs are the standard agents used for antithrombotic therapy and prophylaxis. Heparin binds to the enzyme inhibitor antithrombin iii at iii, causing a conformational change that markedly increases its activation. In contrast, lowmolecularweight heparin lmwh has undergone fractionation for the purpose of making its pharmacodynamics more predictable. In patients with hit who are candidates for cea, a substitute for unfractionated heparin ufh should be used.
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