[Potentials risks in drug prevention of thrombosis--low-molecular-weight heparin versus standard heparin]

Methods and Guidelines for Venous Thromboembolism Prevention in Polytrauma Patients with Pelvic and Acetabular Fractures

Sequential compression devices and chemical prophylaxis are the standard venous thromboembolism (VTE) prevention for trauma patients with acetabular and pelvic fractures. Current chemical pharmacological contemplates the use of heparins or fondaparinux. Other anticoagulants include coumarins and aspirin, however these oral agents can be challenging to administer and may need monitoring. When contraindications to anticoagulation in high-risk patients are present, prophylactic inferior vena cava filters can be an option to prevent pulmonary emboli. Unfortunately strong evidence about the most effective method, and the timing of their commencement, in patients with pelvic and acetabular fractures remains controversial.

Deep vein thrombosis prophylaxis in trauma patients

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are known collectively as venous thromboembolism (VTE). Venous thromboembolic events are common and potentially life-threatening complications following trauma with an incidence of 5 to 63%. DVT prophylaxis is essential in the management of trauma patients. Currently, the optimal VTE prophylaxis strategy for trauma patients is unknown. Traditionally, pelvic and lower extremity fractures, head injury, and prolonged immobilization have been considered risk factors for VTE; however it is unclear which combination of risk factors defines a high-risk group. Modalities available for trauma patient thromboprophylaxis are classified into pharmacologic anticoagulation, mechanical prophylaxis, and inferior vena cava (IVC) filters. The available pharmacologic agents include low-dose heparin (LDH), low molecular weight heparin (LMWH), and factor Xa inhibitors. Mechanical prophylaxis methods include graduated compression stockings (GCSs), pneumatic compression devices (PCDs), and A-V foot pumps. IVCs are traditionally used in high risk patients in whom pharmacological prophylaxis is contraindicated. Both EAST and ACCP guidelines recommend primary use of LMWHs in trauma patients; however there are still controversies regarding the definitive VTE prophylaxis in trauma patients. Large randomized prospective clinical studies would be required to provide level I evidence to define the optimal VTE prophylaxis in trauma patients.

Coronary arterial bypass surgery with beating heart in a patient with heparin-induced thrombocytopenia: Usage of thrombin inhibitor (Lepirudin; r-hirudin)

One of the most important adverse drug reactions that physicians encounter is the life-threatening prothrombotic syndrome known as heparin-induced thrombocytopenia (HIT). In patients with a history of heparin-induced thrombocytopenia and coronary arterial disease, alternative anticoagulatory regimens are needed during cardiac surgery for prevention of thrombosis. Treatment options for such patients now generally include the use of alternative anticoagulants such as lepirudin, bivalirudin, argatroban or danaparoid. In this article, we present a case where heparin-induced thrombocytopenia was properly performed coronary arterial bypass grafting by using lepirudin. (This sentence is confusing)

Incidence of thrombocytopenia in hospitalized patients with venous thromboembolism

PURPOSE

To determine the incidence of heparin-associated thrombocytopenia in patients receiving prophylaxis or treatment for venous thromboembolism.

METHODS

We assessed the database of the National Hospital Discharge Survey from 1979 through 2005 and complemented this with a meta-analysis of published literature.

RESULT

Among 10,554,000 patients discharged from short-stay hospitals throughout the US with venous thromboembolism during the 27 years of study, secondary thrombocytopenia was coded in 38,000 patients (0.36%). From 1979 through 1992, secondary thrombocytopenia was coded in only 0.15% of hospitalized patients with venous thromboembolism. The frequency increased sharply to 0.54% from 1993 through 2005. Secondary thrombocytopenia was rarely diagnosed among 1,446,000 patients aged <40 years and among 77,000 women who had venous thromboembolism with deliveries. Meta-analysis of published literature showed a higher incidence among patients who received unfractionated heparin (UFH) for prophylaxis than those who received low-molecular-weight heparin (LMWH) for prophylaxis. Treatment resulted in smaller differences of the incidence between UFH and LMWH.

CONCLUSION

Heparin-associated thrombocytopenia is rare among patients aged <40 years and women following delivery. The risk of heparin-associated thrombocytopenia is more duration-related than dose-related, and higher with UFH when used for an extended duration. Our findings and those of the literature suggest that although heparin-associated thrombocytopenia is uncommon, the incidence can be minimized by use of LMWH, particularly if extended prophylaxis or extended treatment is required.

Evaluating the effectiveness of a deep-vein thrombosis prophylaxis protocol in orthopaedics and traumatology

RATIONALE, AIMS AND OBJECTIVES

To evaluate the effectiveness of the deep-vein thrombosis (DVT) prophylaxis protocol for adult patients in a general orthopaedics and traumatology clinic.

METHOD

We followed the DVT prophylaxis protocol in 1326 (776 female, 550 male) of 2114 adult patients admitted to the Department of Orthopaedics and Traumatology in Goztepe Research and Training Hospital. They were followed for symptomatic DVT and possible complications of low-molecular-weight heparin (LMWH) therapy. A Doppler ultrasonography (US) was performed when DVT was suspected. The medical information treatment protocols of DVT patients were recorded.

RESULTS

Doppler US was performed in 58 patients with suspected DVT. Six of these patients were diagnosed with DVT. The side effects of LMWH were upper gastrointestinal bleeding (0.5%), widespread ecchymosis of the extremities (1.9%) and heparin-induced thrombocytopenia (0.16%).

CONCLUSION

Symptomatic DVT occurrences were similar to those in medical literature; however, there were fewer side effects of LMWH than reported in literature.

The incidence of heparin-induced thrombocytopenia Type II in patients with subarachnoid hemorrhage treated with heparin versus enoxaparin

Object

Heparin-induced thrombocytopenia Type II (HIT II) is a serious complication that occurs in 0.2–3% of patients treated with heparin and is associated with a high risk of thrombotic events. One center recently reported an incidence of HIT II of 15% in a population of patients with aneurysmal subarachnoid hemorrhage (aSAH). Because these patients are typically exposed to heparin during angiography, controversy exists regarding whether prophylaxis with enoxaparin rather than heparin affords any reduction in the risk of developing HIT II. In this study, the authors investigated the effect of heparin compared with enoxaparin on the incidence of HIT II in patients with aSAH.

Methods

The authors reviewed the medical records of 300 patients treated for aSAH who received thromboprophylaxis with either heparin or enoxaparin, and identified patients who developed HIT II. The incidences of HIT II in the 2 treatment groups were then compared.

Results

One hundred sixty-six patients with aSAH were treated with heparin, and 134 patients were treated with enoxaparin. Sixteen (5.3%) of 300 patients met the diagnostic criteria for HIT II. Of those treated with heparin, 8 (4.8%) of 166 developed HIT II, compared with 8 (6%) of 134 treated with enoxaparin (difference not significant).

Conclusions

The authors report a lower incidence of HIT II in patients with aSAH than has previously been reported. The data also suggest that patients with aSAH who receive heparin are at no greater risk of developing HIT II than those who receive enoxaparin. This finding challenges the merit of choosing enoxaparin rather than heparin for thromboprophylaxis in patients with a SAH.

Gender imbalance and risk factor interactions in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is caused by antibodies against a "self" protein-platelet factor 4-bound to heparin. We observed an overrepresentation of the female gender in 290 patients who developed HIT after cardiac or orthopedic surgery compared with the representation found in national databases (study 1). Therefore, we investigated gender imbalance in HIT by logistic regression analysis of a randomized controlled trial of unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) (study 2), and we analyzed individual patient data from 7 prospective studies comparing HIT frequency between UFH and LMWH, evaluating effects of gender, heparin (UFH vs LMWH), and patient type (surgical vs medical) (study 3). All 3 studies showed female overrepresentation, which for study 3 was a common odds ratio (OR) of 2.37 (95% confidence interval [95% CI], 1.37-4.09; P = .0015). Study 3 also showed an interaction between gender, heparin, and patient type. Although UFH was more likely than LMWH to cause HIT (P < .0001), this effect was predominantly seen in women compared with men (common OR, 9.22 vs 1.83; P = .020) and in surgical patients compared with medical patients (common OR, 13.93 vs 1.75; P = .005). We conclude that females are at greater risk for HIT and that using LMWH to prevent HIT may have greatest absolute benefit in females undergoing surgical thromboprophylaxis.

Risk for heparin-induced thrombocytopenia with unfractionated and low-molecular-weight heparin thromboprophylaxis: a meta-analysis

Heparin-induced thrombocytopenia (HIT) is an uncommon but potentially devastating complication of anticoagulation with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). Our objective was to determine and compare the incidences of HIT in surgical and medical patients receiving thromboprophylaxis with either UFH or LMWH. All relevant studies identified in the MEDLINE database (1984-2004), not limited by language, and from reference lists of key articles were evaluated. Randomized and nonrandomized controlled trials comparing prophylaxis with UFH and LMWH and measuring HIT or thrombocytopenia as outcomes were included. Two reviewers independently extracted data on thromboprophylaxis (type, dose, frequency, and duration), definition of thrombocytopenia, HIT assay, and rates of the following outcomes: HIT, thrombocytopenia, and thromboembolic events. HIT was defined as a decrease in platelets to less than 50% or to less than 100 x 10(9)/L and positive laboratory HIT assay. Fifteen studies (7287 patients) were eligible: 2 randomized controlled trials (RCTs) measuring HIT (1014 patients), 3 prospective studies (1464 patients) with nonrandomized comparison groups in which HIT was appropriately measured in both groups, and 10 RCTs (4809 patients) measuring thrombocytopenia but not HIT. Three analyses were performed using a random effects model and favored the use of LMWH: (1) RCTs measuring HIT showed an odds ratio (OR) of 0.10 (95% confidence interval [CI], 0.01-0.2; P = .03); (2) prospective studies measuring HIT showed an OR of 0.10 (95% CI, 0.03-0.33; P < .001); (3) all 15 studies measured thrombocytopenia. The OR was 0.47 (95% CI, 0.22-1.02; P = .06). The inverse variance-weighted average that determined the absolute risk for HIT with LMWH was 0.2%, and with UFH the risk was 2.6%. Most studies were of patients after orthopedic surgery.

New Developments in Diagnosis and Treatment of Heparin-induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a drug induced immune mediated thrombocytopenia that affects up to 3% of patients treated with unfractionated heparin (UFH). It is less frequent when low molecular weight heparins (LMWH) are used. Fondaparinux does not seem to induce HIT. A functional and an antigen assay should be performed to confirm the clinical diagnosis of HIT. Immediate cessation of heparin and start of compatible anticoagulant is mandatory when HIT is suspected clinically. Danaparoid (a heparinoid)and the direct thrombin inhibitors lepirudin and argatroban are available for this purpose. Short-term reexposure with heparin, for example during cardiopulmonary bypass, is possible in patients with history of HIT, provided HIT antiodies are no longer detectable. In children systematic data on treatment of HIT are lacking.

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

Most patients with heparin-induced thrombocytopenia (HIT), a serious adverse effect of heparin mediated by platelet-activating heparin-dependent antibodies, require alternative anticoagulation. This is because HIT is highly prothrombotic and is characterized by markedly increased thrombin generation. Unfractionated heparins seem to induce HIT more often than low molecular weight heparins. There are three anticoagulants for which there is an emerging consensus for their efficacy in management of HIT, and which are currently approved for treatment of HIT in several countries: the recombinant hirudin, lepirudin, a direct thrombin inhibitor; the synthetic direct thrombin inhibitor, argatroban; and the heparinoid, danaparoid sodium, mainly exhibiting antifactor-Xa activity. Recommendations for optimal use of these drugs in HIT are given in this review stressing the need for immediate treatment of patients with HIT without awaiting laboratory diagnosis. Hirudin, the drug for which most data from prospective trials exists, can be safely and effectively used in patients with HIT, its dramatically increased elimination half-life in patients with renal failure being the most important drawback. Argatroban, which is mainly eliminated by the liver, could be used preferentially in such patients with renal impairment. Interference with the international normalized ratio makes oral anticoagulation, which is necessary in many patients with HIT, problematic. Activated partial thromboplastin time is sufficient to monitor lepirudin and argatroban treatment in most cases. Danaparoid sodium, with an antifactor-X activity half-life of about 24 hours seems to be best suited for thrombosis prophylaxis in patients with HIT. In some patients monitoring by determining antifactor-Xa activity is necessary. No antidote is available for any of the drugs discussed, and bleeding complications are the most important adverse effects. In situations such as hemodialysis or cardiopulmonary bypass, not only the characteristics of the drug in use itself, but also availability of monitoring methods play an important role. Adjunctive treatments have not been systematically evaluated and should be used cautiously. Recent data suggest that re-exposure of patients with a history of HIT with heparin, for example during cardiopulmonary bypass, can be well tolerated provided no circulating HIT antibodies are detectable at the time of re-exposure, and heparin is strictly avoided pre- and postoperatively.

Severe enoxaparin-induced thrombocytopenia complicated by pulmonary emboli

Low molecular weight heparins (LMWH) have been widely used in the last decade, especially for prophylaxis of deep venous thrombophlebitis. Enoxaparin-induced thrombocytopenia is rarely encountered, in contrast to its high prevalence among patients treated with unfractionated heparin. We report a case of a patient who was admitted because of a pulmonary embolus due to proximal deep vein thrombophlebitis 2 weeks after surgery, despite prophylaxis with low-dose enoxaparin after prostatectomy. The patient's original normal platelet count (255,000/microl) dropped to 30,000/microl while on enoxaparin therapy. Testing for antibodies against heparin was positive. Warfarin was initiated and an inferior vena caval filter was inserted. Within a few days, platelet count increased to 100,000/microl, pulmonary status improved, and the patient was released in good clinical condition. Heparin-induced thrombocytopenia (HIT) is discussed, as are alternative treatments for unfractionated heparins and LMWH.

Drug-induced and drug-dependent immune thrombocytopenias

Thrombocytopenia is a frequent comorbid condition in many in hospital patients. In some patients, drugs are the cause of low platelet counts. While cytotoxic effects of anti-tumor therapy are the most frequent cause, immune mechanisms should also be considered. This review addresses thrombocytopenias in four groups. Heparin-dependent thrombocytopenia (HIT), by far the most frequent drug-induced immune-mediated type of thrombocytopenia, has a unique pathogenesis and clinical consequences. HIT is a clinicopathological syndrome in which antibodies mostly directed against a multimolecular complex of platelet factor 4 and heparin cause paradoxical thromboembolic complications. The mechanisms through which heparin can enhance thrombin generation are discussed and treatment alternatives for affected patients are presented in detail. It is of primary importance to recognize these patients as early as possible and to substitute heparin with a compatible anticoagulatory drug, such as hirudin, danaparoid or argatroban. Patients seem to benefit from therapeutic doses of alternative treatment rather than from low-dose prophylactic doses. With the increasing use of glycoprotein (GP) IIb/IIIa inhibitors in patients with acute coronary syndromes, thrombocytopenias are increasingly recognized as an adverse effect of these drugs. Up to 4% of treated patients are affected. Most important, pseudothrombocytopenia, a laboratory artefact, is as frequent as real drug-induced thrombocytopenia and must be excluded before changes in treatment are considered. The pathogenesis of these thrombocytopenias is still debated; an immune mechanism involving preformed antibodies is likely. However, since these antibodies are also detectable in a high percentage of normal controls and of patients not developing thrombocytopenia, their impact is still unclear. Patients with real thrombocytopenia are at an increased risk of bleeding; treatment consists of cessation of the GP IIb/IIIa inhibitor and platelet transfusions in cases of severe hemorrhage. Classic immune thrombocytopenia can be induced by some drugs, e.g. gold, which trigger anti-platelet antibodies indistinguishable from platelet autoantibodies found in autoimmune thrombocytopenia. Drug-induced and drug-dependent immune thrombocytopenia is induced by antibodies recognizing an epitope on platelet GP formed after binding of a drug to a platelet glycoprotein. Still unresolved is whether antibody binding is the consequence of a conformational change of the antigen, the antibody, or both. These antibodies typically react with monomorphic epitopes on platelet GP, but only in the presence of the drug or a metabolite. Although several platelet GP have been identified as antibody target (GPIb/IX, GPV, GP IIb/IIIa), antibodies in an individual patient are highly specific for a single GP. Clinically, these patients present with very low platelet counts and acute, sometimes severe, hemorrhage. Treatment is restricted to withdrawal of the drug and symptomatic treatment of bleeding.