Heparin-induced thrombocytopenia--recognition and treatment

Heparin, an important agent for the prophylaxis and treatment of venous and arterial thromboembolism, also can cause heparin-induced thrombocytopenia (HIT). This medication-induced immune-mediated syndrome is characterized by thrombocytopenia and life- or limb-threatening thrombotic events. The initial presentation of HIT is a decrease in platelet count with or without thrombosis. Heparin-induced thrombocytopenia frequently is overlooked in hospital settings, and it must be distinguished from other causes of thrombocytopenia. New therapies include the use of direct thrombin inhibitors argatroban and hirudin.

Generalized vasculitis, thrombocytopenia, and transient lymphoproliferative disorder caused by idiopathic mixed cryoglobulinemia

We present a 75-year-old patient with recurrent palpable purpura and multiorgan involvement by leukocytoclastic vasculitis caused by mixed-type cryoglobulinemia. The disease spanned 40 years, with many flare-ups, each associated with thrombocytopenia, and finally culminated in widespread involvement of not only the skin and the kidneys but also the lungs and spleen. Despite extensive investigation, no association with hepatitis C virus or with any malignant or connective tissue disorder was found.

Long-term effectiveness of danazol corticosteroids and cytotoxic drugs in the treatment of hematologic manifestations of systemic lupus erythematosus

The purpose of this study was to compare the long-term effectiveness among danazol, corticosteroids, cytotoxics, and dapsone in the treatment of hematological manifestations of systemic lupus erythematosus (SLE). Medical charts of all patients seen at the Rheumatic Disease Unit from January to December of 1998 were reviewed. Patient characteristics, disease and treatment information were collected. The main outcome measures were the cause of and time to discontinuation of drugs used to treat hematological manifestations of SLE resulting from all causes, mainly toxicity and inefficacy or both. Bivariate analysis including one-way ANOVA and chi2 tests were used to compare differences between means and proportions, respectively. Survival curves among the different drugs were evaluated using the Kaplan-Meier method. Multivariate analysis (Cox-regression) was used to adjust for potential confounders. After all medical records were reviewed 41 cases were eligible. Two cases had hemolytic anemia, 34 had thrombocytopenia, and five had both. These cases had received a total of 121 cycles of treatment at different times and they represent the study population (corticosteroids n = 37, danazol n = 51, citotoxic drugs n = 29, and dapsone n = 4). Crude rates of discontinuations due to any cause, toxicity and inefficacy werenot statistically significant among the drugs. However, the Kaplan-Meier curves showed statistically significant difference for discontinuations due to all causes as well as inefficacy. Prednisone and cytotoxic drugs had the lowest probability of continuation. In contrast, there were not statistically significant differences among the drugs with respect to first relapse. This is the first study examining the long-term termination rates of several drugs used to treat hematological manifestations of SLE. Using rates of discontinuation adjusted for time there were statistically significant differences among the drugs. Danazol had the highest probability of continuation.

Treatment of bleeding in patients with platelet disorders: is there a place for recombinant factor VIIa?

The mechanism of action of recombinant factor VIIa (rFVIIa), i.e. increased thrombin generation on the membrane of activated platelets, as well as the results from in vitro and ex vivo models of thrombocytopenia or inherited thrombocytopathia may support some potential of rFVIIa in thrombocytopenia/thrombocytopathia. rFVIIa was reported as effective to stop or to decrease bleeding in few patients with severe thrombocytopenia resistant to platelet transfusions; however data are still scarce and clinical studies are really needed to define efficacy/safety ratio as well as optimal treatment regimen in this potential indication. Some data in patients with Glanzmann thrombasthenia (GT) may support the use of rFVIIa outside its primary indication in the cases in which there is no real treatment alternative (GT patients with antibodies to GP IIb-IIIa or with platelet refractoriness).

A case of Evans' syndrome in a patient with ulcerative colitis

The case of a 37-year-old male diagnosed 16 years previously with ulcerative colitis, admitted on account of hemolytic anaemia and thrombocytopaenia that responded to immunosuppressive therapy, is reported. Despite various peculiarities discussed, this may be the first reported case of Evans' syndrome associated with ulcerative colitis.

Pharmacotherapy of heparin- induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a life-and-limb threatening condition that is associated with the development of antibodies that activate platelets and the coagulation system in the presence of unfractionated heparin or low molecular weight heparin. The binding of antibody to heparin-PF-4 complexes can activate platelets, leading to an acute, often catastrophic, thrombotic diathesis. The most common laboratory finding is the development of thrombocytopenia 5 or more days after beginning heparin treatment, which occur in up to 1 - 5% of patients exposed to heparin, depending on type of heparin and indication for anticoagulation. The onset of thrombocytopenia can be immediate or delayed for several weeks after the exposure to heparin. Approximately 50 - 60% of patients who develop HIT manifest acute venous or arterial thrombosis and a significant percentage of these patients die or develop vascular gangrene of a limb that requires amputation. Given the severe sequelae associated with HIT, recognition and immediate medical management is essential. Treatment of a patient with HIT is complex, as there are several different anticoagulants now available which have been shown to be useful. Optimal management depends on each patient's individual clinical manifestations, as well as the need for ongoing anticoagulation therapy. No single agent or treatment approach can be considered to be 'standard practice' as very few clinical trials have been completed, compare different treatment options. The use of warfarin alone in a patient with HIT, must be avoided in order to avoid the possibility of further activating coagulation, which may hasten the development of venous limb gangrene. There are several different tests available that detect HIT antibodies and each has different sensitivity and specificity for HIT. In this review we discuss the epidemiology and natural history of HIT, risk factors associated with the development of HIT and the clinical and laboratory tests that aid in the diagnosis and treatment. Special emphasis is given to addressing the management of HIT in special populations, particularly patients with renal or liver disease, acute coronary syndromes, pregnancy, paediatrics and patients who require cardiopulmonary bypass surgery.

Influence of tiapride on platelet counts in healthy volunteers and patients with movement disorders

BACKGROUND

The selective D2 antagonist tiapride is administered in various movement disorders. Furthermore, there are indications that tiapride increases platelet counts.

AIM

To characterize tiapride's potential to increase platelet counts in healthy subjects and patients with movement disorders.

METHODS

In Part A, 10 healthy volunteers received tiapride (300 mg/day) for 21 days in a longitudinal, prospective, open trial. One hundred healthy subjects served as controls. Part B was a retrospective analysis of 15 patients with movement disorders on tiapride [Huntington's disease (n=6), Morbus Little (n=3), hyperkinetic syndromes of undetermined etiology (n=3), blepharospasm (n=1), cervical dystonia (n=1), perioral dyskinesia (n=1)] and 15 age- and sex-matched controls.

RESULTS

Part A: Although serum prolactin levels increased by 526+/-14%, confirming good drug compliance, tiapride elicited only minor changes in platelet counts. Part B: Platelet counts correlated positively with the dose of tiapride (100-800 mg/day; r=.67; P=.007). Platelet counts were significantly higher in patients on tiapride compared to healthy age-matched controls (P<.001). Four patients responded to an increase in the tiapride dosage with an increase in platelet count by 97-173 cells/nl.

CONCLUSION

Three weeks of treatment with tiapride (300 mg/day) is insufficient to elevate platelet counts to a clinically relevant extent in young healthy volunteers. However, in elderly patients with movement disorders tiapride treatment is associated with markedly increased platelet counts.

Heparin-induced thrombocytopenia: clinical presentations and therapeutic management

With increasing indications for heparin usage, an understanding of heparin-induced thrombocytopenia (HIT) as a complication of heparin therapy is more essential than ever. Complications of HIT can result in significant morbidity and mortality. We review the clinical presentations of HIT, laboratory and diagnostic workup, and treatment agents available or being evaluated.

The interaction between platelets and factor VII/VIIa

Blood coagulation normally occurs when factor VII interacts with its specific cellular receptor, tissue factor, which is exposed when a blood vessel is severed. The factor VII/tissue factor complex then initiates a cascade of proteolytic reactions involving factors IX, X, prothrombin and fibrinogen, culminating in the formation of a fibrin clot. The role of platelets in the initiation phase of blood coagulation is still unclear. It has been postulated that platelets bind activated factor VIIa independently of tissue factor, and that this interaction forms the basis of the usefulness of high-dose recombinant factor VIIa in treating hemophiliacs with inhibitory antibodies, and other thrombocytopenia-like syndromes. In this review, we will examine the evidence for and against such an hypothesis, as well as discuss an alternative mechanism for the efficacy of high-dose factor VIIa in treating hemophilic patients with inhibitors.

Management of heparin-induced thrombocytopenia: a critical comparison of lepirudin and argatroban

Heparin-induced thrombocytopenia (HIT) is a transient hypercoagulability state initiated, paradoxically, by the anticoagulant, heparin. It is characterized by antibody-induced activation of platelets, leading to thrombin generation. Many patients with HIT develop thrombosis; even when heparin is stopped because of "isolated HIT" detected during routine platelet count monitoring, 25-50% of patients subsequently develop symptomatic thrombosis. Thus, an alternative anticoagulant should be substituted for heparin when HIT is strongly suspected. Two direct thrombin inhibitors (DTIs), lepirudin and argatroban, have been studied for prevention and treatment of thrombosis in HIT patients. Lepirudin is a polypeptide that binds irreversibly to the fibrin-binding and catalytic sites on thrombin (bivalent inhibitor). In contrast, argatroban is a synthetic, small-molecule DTI that binds reversibly to the catalytic site alone (univalent inhibitor). Results of historically controlled clinical trials suggest both agents are effective for preventing and treating thrombosis in HIT. However, these agents have not been compared directly, and important differences in study design limit conclusions from indirect comparison. For example, lepirudin was given for 12-14 days (mean) in treatment studies of thrombosis complicating HIT, whereas argatroban was given only for 6-7 days, a difference that could explain apparent lower thrombosis rates (and greater bleeding) with lepirudin. Recently, the transition from DTI therapy to oral anticoagulation in patients with deep venous thrombosis (DVT) complicating HIT has been identified as a risk period for coumarin-induced venous limb gangrene. Thus, the DTI should be given alone during acute HIT, with oral anticoagulants deferred until substantial resolution of the thrombocytopenia has occurred.

Autoimmunity in Wiskott-Aldrich syndrome: risk factors, clinical features, and outcome in a single-center cohort of 55 patients

OBJECTIVES

To evaluate the occurrence of autoimmune and inflammatory complications in Wiskott-Aldrich syndrome (WAS) and to determine risk factors and the prognosis of such complications with the aim of improving the definition of treatment options.

METHODS

We reviewed the records of 55 patients with WAS evaluated at Necker-Enfants Malades Hospital (Paris) from 1980 to 2000.

RESULTS

Forty patients (72%) had at least 1 autoimmune or inflammatory complication. Autoimmune hemolytic anemia was detected in 20 cases (36%); in all cases, onset occurred before the age of 5 years. Other complications included neutropenia (25%), arthritis (29%), skin vasculitis (22%), cerebral vasculitis (7%), inflammatory bowel disease (9%), and renal disease (3%). The median survival of the entire population was 14.5 years. Two autoimmune complications and 1 biological factor were predictive of a poor prognosis in this population: autoimmune hemolytic anemia, severe thrombocytopenia recurring after splenectomy, and high serum immunoglobulin M (IgM) levels before splenectomy. Autoimmune hemolytic anemia was significantly more observed in patients with high serum IgM level.

CONCLUSIONS

High serum IgM concentration before splenectomy was identified as a risk factor for autoimmune hemolytic anemia; however, it must be confirmed. Autoimmune hemolytic anemia and severe thrombocytopenia recurring after splenectomy were 2 indicators of a poor prognosis. Those results suggest that patients with WAS and IgM levels more than mean + 2 standard deviations before splenectomy should be placed under strict surveillance. Furthermore, severe autoimmune complications should lead, as early as possible, to hematopoietic stem cell transplantation using the best available donor.

Cutaneous dalteparin reactions associated with antibodies of heparin-induced thrombocytopenia

OBJECTIVE

To report widespread cutaneous lesions due to low-molecular-weight heparin therapy associated with heparin-induced thrombocytopenia (HIT), but without evidence of thrombocytopenia, and to review previously reported cases of skin reactions related to heparin therapy.

CASE SUMMARY

A 59-year-old white man with a subtotally resected glioblastoma developed febrile neutropenia and pneumonia secondary to chemotherapy. The development of an upper extremity thrombosis, following insertion of a peripherally inserted central venous catheter, was treated with subcutaneous dalteparin. Cutaneous lesions developed distant from the site of injection. The diagnosis of HIT was confirmed despite stable platelet counts. Dalteparin therapy was discontinued immediately, and anticoagulation was maintained with warfarin. The skin lesions resolved without further complications.

DISCUSSION

Numerous cases of heparin-induced cutaneous reactions have been reported. The majority of these describe a local reaction at the heparin injection site with or without associated thrombocytopenia. The case presented here is unique in that the observed skin reaction was distant to the injection site and occurred without thrombocytopenia, but with detectable heparin-dependent antibodies.

CONCLUSIONS

Although a skin reaction is a rare complication of heparin therapy, it can be a clinical indicator of HIT despite normal platelet counts. Patients who develop skin lesions should have their heparin therapy discontinued and a diagnosis of HIT investigated.

Recombinant human interleukin-11 improves thrombocytopenia in patients with cirrhosis

To elucidate the hematopoietic activity of recombinant human interleukin-11 (rhIL-11, [Neumega, Cambridge, MA]) in patients with cirrhosis and thrombocytopenia, we administered rhIL-11 at 50 microg/kg/d subcutaneously to 10 patients for 10 days with a 30-day follow-up period. All treated patients (n = 9) experienced a gradual, yet significant increase in their platelet count above the baseline value (P < or =.01) reaching the peak value (median, 93,000/microL; range, 60,000-206,000/microL) at a median of 13 days (range, 6-23 days). Eight patients (89%) had a significant increase of > or =50% over the baseline value (P <.05). Moreover, further increases to > or =60,000/microL, > or =80,000/microL, and > or =100,000/microL were observed in 100%, 78%, and 33% of the patients, respectively. A subsequent decline in platelet count was observed at a median of 19 days (range, 7-26 days) after the occurrence of peak concentration. A significant increase in neutrophil count was also demonstrated starting on the third day of treatment (P < or =.01). Concurrent with an increase in the serum level of fibrinogen, transaminase levels declined significantly during treatment period, while bilirubin levels continued to drop for up to 20 days after the initiation of treatment (P <.05). The most frequent effects were due to plasma volume expansion, including conjunctival redness and edema. In conclusion, rhIL-11 can improve platelet counts in patients with early cirrhosis and these patients could benefit from rhIL-11 treatment. However, given the high frequency of regimen-related toxicity, the use of rhIL-11 in patients with cirrhosis should be administered with caution.

Danaparoid: a review of its use in thromboembolic and coagulation disorders

Danaparoid (danaparoid sodium) is a low molecular weight heparinoid which has undergone clinical study for use as continued anticoagulant therapy in patients with heparin-induced thrombocytopenia (HIT), for the prophylaxis and treatment of deep vein thrombosis (DVT), and for the treatment of disseminated intravascular coagulation (DIC). A nonblind study in patients with HIT has reported that complete clinical resolution is significantly more likely in patients receiving danaparoid than in patients receiving dextran 70. In addition, retrospective analyses and noncomparative data support the use of danaparoid for continued anticoagulant therapy in patients with HIT. Studies in patients undergoing hip surgery have shown that danaparoid significantly reduces the incidence of postoperative DVT compared with aspirin, warfarin, dextran 70 and heparin-dihydroergotamine, while additional data suggest no difference between danaparoid, enoxaparin and dalteparin. In patients undergoing abdominal or thoracic surgery for removal of a malignancy, danaparoid reduced the incidence of postoperative DVT compared with placebo, but showed no significant difference when compared with unfractionated heparin (UFH). Two studies have compared danaparoid with UFH in the prophylaxis of DVT following acute ischaemic stroke; twice daily danaparoid was significantly superior to UFH whereas there was no significant difference between a once-daily dosage and UFH. Danaparoid did not differ from UFH in terms of efficacy in the treatment of existing DVT. In all comparative studies examining the efficacy of danaparoid in the prophylaxis or treatment of DVT (versus warfarin, dextran 70, enoxaparin, dalteparin, aspirin, heparin-dihydroergotamine, UFH and placebo), the incidence of haemorrhagic complications did not differ between treatment groups. In patients with DIC, 61.9% of those patients receiving danaparoid experienced either disappearance or reduction of symptoms of DIC whereas 62% of those receiving UFH showed either no change or aggravation of their symptoms. There was no significant difference between treatment groups in tolerability or overall improvement of DIC.

CONCLUSIONS

Danaparoid is an effective anticoagulant agent which has undergone clinical evaluation in a wide range of disease indications. Current guidelines support the use of danaparoid in prophylaxis of DVT following ischaemic stroke, and in patients who develop HIT. Danaparoid has shown efficacy in DIC, and for DVT prophylaxis in patients undergoing hip surgery although further data are required to establish the role of danaparoid in these indications. In particular, double-blind trials comparing danaparoid with such recommended therapies as the low molecular weight heparins will provide more definitive data on the place of danaparoid in the clinical management of these conditions and ultimately lead to improved patient outcomes.

Co-administration of Flt-3 ligand counteracts the actions of thrombopoietin in myelosuppressed rhesus monkeys

This placebo-controlled study evaluated the efficacy of Flt-3 ligand (FL) combined with TPO in myelosuppressed rhesus monkeys. The monkeys were subjected to 5 Gy total body irradiation (TBI), resulting in 3 weeks of profound pancytopenia, and received either 5 microg/kg of rhesus TPO i.v. on d 1 (n = 4) and 100 microg/kg/d s.c. human FL (n = 4) or FL alone (n = 4) for 14 consecutive days and were compared with results from a concomitant study involving the administration of TPO alone (n = 4) or placebo (carrier; n = 4). The TPO/FL combination was considerably less effective than TPO alone, with a more profound nadir and a slower recovery to thrombocyte counts > 100 x 109/l, approaching recovery patterns of placebo controls. Leucocyte regeneration was similar in all animals. Monkeys treated with FL alone displayed a regeneration of reticulocytes and thrombocytes in the lower range of those of the placebo controls. Recovery of bone marrow (BM) cellularity was slightly accelerated in the TPO/FL-treated monkeys, but was not reflected by an increase in progenitor cells, in contrast to TPO alone. Monkeys treated with FL alone showed a BM reconstitution similar to placebo-treated controls. FL by itself was not effective as a therapeutic agent in this model for myelosuppression. As FL also suppressed BM CD34+ cell reconstitution, we concluded that FL competed with TPO at the level of immature cell differentiation.

Thrombocytopenia, low molecular weight heparin, and obstetric anesthesia

The parturient with coagulation defects, whether related to thrombocytopenia or to anticoagulation therapy, presents a unique challenge to the anesthesiologist. The risk of spinal or epidural hematoma in these patients has not been quantified fully but is a factor that one must consider on a case-by-case basis in determining whether neuraxial anesthesia is appropriate for the parturient. Following the guidelines set forth in this article should help reduce the risk of spinal or epidural hematoma without sacrificing the quality of care provided to patients.

Evans syndrome in a patient with chromosome 22q11.2 deletion syndrome: a case report

One patient with a chromosome 22q11.2 deletion and Evans syndrome is reported in this paper. Microdeletions of 22q11.2 are the main etiology for DiGeorge syndrome, a disorder characterized by heart defects, immune deficiencies due to aplasia or hypoplasia of the thymus, and hypocalcemia. Evans syndrome refers to a hematological autoimmune disorder with autoimmune hemolytic anemia accompanied by immune thrombocytopenia. A wide range of autoimmune disorders have been described in DiGeorge syndrome and velocardiofacial syndrome, including one prior report of autoimmune hemolytic anemia and immune thrombocytopenia. The patient reported herein strengthens the association between the 22q11.2 deletion spectrum and Evans syndrome.

Platelet substitutes in the management of thrombocytopenia

A variety of agents can improve hemostasis and reduce blood loss caused or exacerbated by congenital or acquired defects in platelet number of function. This review discusses several available approaches for the practicing clinician to reduce bleeding (diffuse or localized) in this clinical setting.

Diagnosis and treatment of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a major side effect secondary to the administration of heparin. This syndrome is serious and potentially life threatening. This response is the result of antibodies formed against the platelet factor 4 (PF4)/heparin complex. The incidence of this immune-mediated syndrome has been estimated to be 1-3% of all patients receiving heparin therapy. The occurrence of HIT in patients requiring full anticoagulation for cardiopulmonary bypass (CPB), therefore, presents a serious challenge to the cardiac surgery team. The diagnosis of HIT should be based on both clinical and laboratory evidence. While functional assays, platelet aggregation tests, and the serotonin release assay can be used to support the diagnosis, the negative predictive value of these tests is generally less than 50%. In contrast, although non-functional antibody detection assays are more sensitive, they have a low specificity. HIT can be treated in several ways, including cessation of all heparin and giving an alternative thrombin inhibitor, platelet inhibition followed by heparin infusion, and the use of low molecular weight heparins. In this presentation, the pathology and current diagnostic tests, as well as the successful management of patients with HIT undergoing CPB at New York Presbyterian Hospital, are reviewed.

Severe autoimmune cytopenias in treatment-naive hepatitis C virus infection: clinical description of 35 cases

To determine the clinical characteristics and outcome of patients with chronic hepatitis C virus (HCV) infection presenting severe autoimmune cytopenia unrelated to interferon alpha therapy, we analyzed characteristics and outcomes of 35 patients with HCV (16 from our departments and 19 from the literature). We considered active autoimmune hemolytic anemia (AHA) as a decrease of at least 2 g/dL in hemoglobin levels, an increase of at least 0.6 mg/dL in the serum unconjugated bilirubin level, a reticulocyte count >5%, and a positive direct Coombs test. Severe neutropenia was defined as a neutrophil count <0.5 x 10(9)/L, and severe thrombocytopenia as a platelet count <30 x 10(9)/L. We identified the following cytopenias: AHA (17 cases), severe thrombocytopenia (16 cases), aplastic anemia (2 cases), severe neutropenia (1 case), refractory sideroblastic anemia (1 case), and pure red cell aplasia (1 case). Three patients simultaneously presented 2 types of severe cytopenias. Twenty-seven patients (77%) were female and 8 (23%) male, with a mean age at diagnosis of cytopenia of 51.7 years (range, 18-84 yr). Immunologic markers were detected in 19 (68%) of 28 patients, the most frequent being hypocomplementemia in 16 (57%), cryoglobulins in 15 (54%), antinuclear antibodies in 12 (43%), and rheumatoid factor in 5 (18%). Other associated processes were autoimmune diseases in 14 (50%) of 28 and human immunodeficiency virus (HIV) coinfection in 3 (9%) of 32. We found clinical and immunologic differences between HCV patients with AHA and those with severe thrombocytopenia. Patients with HCV-related AHA showed a higher prevalence of associated autoimmune diseases (71%), cryoglobulins (67%), and cirrhosis (59%). All had a good response to corticosteroids, but a poor prognosis (47% mortality). In contrast, patients with HCV-related severe thrombocytopenia had a lower prevalence of associated autoimmune diseases (11%), a poorer response to corticosteroids (55%), and lower mortality (6%), with HIV/HBV coinfections in some patients. The 35 cases presented demonstrate that different types of immune-mediated cytopenias may be severe and clinically significant in patients with HCV infection. Hemolytic anemia and severe thrombocytopenia were the most frequent cytopenias observed. Most patients responded well to corticosteroids, although a higher rate of mortality was observed in those with liver cirrhosis.

Recombinant factor VIIa reduces bleeding in severely thrombocytopenic rabbits

Severe thrombocytopenia is a common complication to intensive chemotherapeutic regimens. For bleeding episodes associated with severe thrombocytopenia, the current standard treatment is platelet transfusion. However, due to several transfusion complications such as transfusion-transmitted diseases, platelet refractoriness and immunomodulation, as well as increasing problems with sufficient supply of platelet products, it is imperative to search for alternatives to platelet transfusion. To test the efficacy of recombinant activated human coagulation factor VII (rFVIIa, NovoSeven) in thrombocytopenia, a preclinical study was conducted in thrombocytopenic rabbits. Thrombocytopenia was induced by a combination of gamma-irradiation and the use of platelet antibodies, and the effect of rFVIIa on nail cuticle bleeding was determined. Administration of rFVIIa at 2 mg/kg significantly shortened the prolonged bleeding time in thrombocytopenic animals (rFVIIa vs. control, median 23 min 41 s vs. 60 min, p=0.016) as well as significantly reducing the blood loss (rFVIIa vs. control, median: 8.8 vs. 12.2 nmol hemoglobin/ml, p=0.016). This effect was also reflected by a significant reduction of the prothrombin time, activated partial thromboplastin time, as well as improvement in clotting parameters in an in vitro thromboelastography thrombocytopenia model. Histopathological evaluation of kidney biopsies for the presence of micro thrombi did not reveal evidence of prothrombotic effects of rFVIIa in this model. These data demonstrate the haemostatic efficacy of rFVIIa in a rabbit model of severe thrombocytopenia. Clinical trials will be needed to further explore the potential of NovoSeven as a haemostatic agent in thrombocytopenic patients.