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PubMed2003

Potential uses of recombinant human factor VIIa in veterinary medicine.

In human beings, rFVIIa has been used successfully to promote hemostasis in patients with various bleeding disorders. Patients with hemophilia, thrombocytopenia, and thrombocytopathy have been effectively and safely treated as well as patients with severe trauma or surgery resulting in profuse bleeding and patients with impaired liver function. Given these successes, the possibility of using rFVIIa in veterinary medicine is appealing. The clinical indications and uses in veterinary medicine would be similar, but there are currently two major obstacles: immunogenicity and cost. If these problems can be addressed, rFVIIa may become a valuable and indispensable therapy, especially in the emergency and critical care settings. The use of rFVIIa could allow for successful treatment of otherwise intractable bleeding as well as decrease the number of blood transfusions needed.

Animals↗

PubMed1994

Coagulation defects in liver disease.

A normally functioning hemostasis system is closely related to liver function. The liver parenchymal cells produce most of the factors and inhibitors of the clotting and fibrinolytic systems, and the RES of the liver greatly aids in the clearance of activation products. Hemostasis defects thus depend on the extent of liver damage. A wide spectrum of defects is found in patients with liver cirrhosis. Owing to impaired protein synthesis, most factors and inhibitors of the clotting and the fibrinolytic systems are markedly reduced. Additionally, abnormal vitamin K-dependent factor and fibrinogen molecules have been encountered. Most patients have hyperfibrinolysis that could be DIC in nature. Thrombocytopenia and thrombocytopathy are also found. Acute or chronic hepatocellular disease may display decreased vitamin K-dependent factor levels, especially factor VII and protein C, with other factors still being normal. If patients go into hepatic failure, the abnormalities resemble those found in liver cirrhosis. Vitamin K deficiency is associated with the production of poorly functioning vitamin K-dependent factors. All other hemostasis parameters are normal. Disturbances associated with liver surgeries again depend on the underlying liver problem. Peritoneovenous shunts (LeVeen) may lead to DIC; bleeding from partially resected liver surfaces is usually a mechanical problem. Severe bleeding is encountered with orthotopic liver transplantation. It is greatly influenced by the activation of the fibrinolytic system. This occurs during the anhepatic phase and during the reperfusion phase. The hyperfibrinolysis is mediated by an intense release of t-PA. Antifibrinolytic drugs, if used cautiously, have markedly reduced bleeding and thus reduced need for blood and blood product substitution.

Blood Coagulation Disorders↗

PubMed1989

Laboratory evaluation of hemorrhagic coagulopathies in small animal practice.

Assessment of animals with a suspected hemorrhagic diathesis of unknown cause(s) should be methodical. Most acquired coagulopathies result from thrombocytopenia. A platelet estimate (from a blood smear) and/or a platelet count on a fresh blood sample therefore are useful first steps in case evaluation. If thrombocytopenia is present, the most likely causes are immune-mediated destruction of platelets, DIC, or megakaryocytic hypoplasia. These diagnoses can be pursued by further test, including antiplatelet antibody assays (for example, the platelet factor 3 tests or an ELISA test), measurement of FDP, and bone marrow biopsy, respectively. If the platelet count is normal, a buccal mucosa bleeding time test is a useful second step. If this is prolonged, most likely causes are vWD or a thrombocytopathy (functional platelet defect). von Willebrand's disease can be diagnosed by measurement of vWf concentration or activity. A normal bleeding time does not exclude a diagnosis of vWD, but suggests that the functional activity of vWf is not compromised markedly. If the bleeding time is normal, APTT and PT should be measured. A prolonged APTT with normal PT, in the clinical setting, implies a deficiency of factor XI, IX, or VIII. A prolonged PT with normal APTT indicates factor VII deficiency. Prolongation of both APTT and PT usually is caused by a deficiency of several factors and is seen most often in cases with vitamin K deficiency or antagonism. Obviously, if a particular cause is suspected from the case history or for other reasons, appropriate tests should be evaluated at the beginning. If these do not confirm the provisional diagnosis, the just-described protocol might be a useful one to follow.

Animals↗

PubMed1992

Potentiation of uremic bleeding by hereditary storage pool disease.

This study demonstrates that specific bleeding tests can separate the thrombocytopathy of uremia alone from the bleeding disorders caused by uremia superimposed on preexisting platelet dysfunction. The case history of a uremic patient with exaggerated bleeding tendencies is presented. The findings in this patient are compared with the clinical characteristics and platelet function studies of nine other patients with chronic renal failure. The index and other uremic patients were similar except for the clinical bleeding and results of platelet function studies. The patient's nonocclusive bleeding time and measured blood loss during bleeding time tests were increased compared with the other uremic controls. In addition, her platelet aggregation in response to collagen was lower than that of the other uremic subjects. Repeat studies following renal transplantation were consistent with hereditary storage pool disease. An underlying platelet disorder may potentiate the hemostatic defects of uremia. The diagnosis should be suspected in patients with frequent and severe bleeding manifestations. Renal transplantation led to control of clinical bleeding.

Adult↗

PubMed1993

Massive blood transfusion: the blood bank perspective.

The pathophysiology and support of the massively transfused patient from the vantage of a blood banker is reviewed. Hypothermia, acidosis and shock must be reversed if blood component therapy is to be effective. Algorithms which employ ratios of various blood components have not proved themselves, nor are screening coagulation tests of value until they are remarkably abnormal. Thrombocytopenia, thrombocytopathy, and hypofibrinogenemia appear to be the parameters which predispose to continued bleeding and microvascular hemorrhage in these patients. A large part of the impaired hemostasis is due to a consumption coagulopathy rather than the anecdotal assumption that dilution of the hemostatic elements is to blame. Hypocalcemia, hypomagnesemia and hyperkalemia are rarely observed nor do they pose a problem for this group of individuals. The logistics of blood supply to the clinical areas are addressed by describing one system that has proved itself.

Blood↗

PubMed2002

Flow cytometric findings in platelets of patients following allogeneic hematopoietic stem cell transplantation.

Following allogeneic hematopoietic stem cell transplantation (HSCT) patients may have an increased bleeding tendency in spite of a normal platelet count. Moreover, an association between chronic graft-versus-host disease (cGVHD) and a thrombophilic state has been observed. Platelet receptors and granules from 27 patients following HSCT (13 without cGVHD, 14 with cGVHD) were evaluated by flow cytometric analysis and compared to 62 healthy controls. Platelets from HSCT patients stained weakly with mepacrine indicating a reduced content of dense bodies, whereas no significant degranulation reaction of alpha granules and lysosomes was detectable. In addition, a lower surface expression of GP Ia/IIa was observed, indicating an acquired thrombocytopathy. The surface receptors are activated in HSCT patients, which could be seen by the lower surface expression of GP Ib internalized during the activation process and elevated levels of LIBS-1 and PAC-1 antibody binding. Patients with cGVHD had a seven-fold increased ratio of microparticles. This study demonstrates platelet receptor and granule defects in patients following HSCT. The key role of platelets in HSCT-associated hemostatic disorders is underscored by the high levels of circulating microparticles in cGvHD patients which might explain the thrombophilic state in these patients.

Adult↗

PubMed1999

Studies of platelet volume, chemistry and function in patients with essential thrombocythaemia treated with Anagrelide.

Anagrelide (imidazoquinazolin derivative) is a new compound proposed for the treatment of myeloproliferative disorders. In this study, Anagrelide was given to patients with essential thrombocythaemia (ET) in a compassionate-use protocol. The aim of this study was to test the effect of this drug not only on the platelet count but also on platelet volume, chemistry and function, which has not previously been reported. Thus, in ET, different functional or structural platelet abnormalities were reported: a shortening of the bleeding time, hypoaggregation to several agonists, and in particular a lack of response to adrenalin, an increase in the amount of total platelet glycoprotein IV (or CD36), and an abnormal migration of thrombospondin on electrophoresis. These different parameters were studied before and during therapy with Anagrelide. Although the platelet count was corrected, no functional or chemical abnormality was improved. Furthermore, platelet volume was shown to be constantly increased under Anagrelide. Thus, Anagrelide, in reducing the platelet count, may possibly decrease the risk of thrombosis and haemorrhage. Nevertheless, if the risk of thromboses and/or myelofibrosis is related not only to the platelet count but also to the platelet abnormalities, the persistence of a thrombocytopathy in patients treated with Anagrelide must be taken in consideration. Our data suggest that thromboses and myelofibrosis are clinical end-points which should be included in future large-scale use of Anagrelide.

Bleeding Time↗

PubMed2000

Platelet ultrastructural abnormalities in three patients with type 2B von Willebrand disease.

Several reports have described the presence of giant platelets in patients with type 2B von Willebrand disease (VWD). We have now characterized the ultrastructural changes in platelets from three unrelated patients with type 2B VWD and different mutations within exon 28 of the von Willebrand factor (VWF) gene. Electron microscopy showed that each of these subjects had an increased proportion of large platelets when compared with those of a patient with type 2A VWD or control subjects. Immunogold labelling for VWF was performed. Large masses detected by anti-VWF antibody were seen not only on the platelet surface, but also inside the platelet surface-connected canalicular system (SCCS) when ultrathin sections were labelled. This suggested translocation of the abnormally bound VWF from the platelet surface. Labelling of the alpha-granules was eccentric as for normal platelets. Labelling for glycoprotein (GP) Ib was seen on the surface and within the SCCS, suggesting co-localization with the bound VWF. However, there was no evidence for VWF in endosomes or other endocytic vesicles. The presence of platelet-bound VWF was not accompanied by high levels of platelet activation, as detected by electron microscopy, or by using monoclonal antibodies against P-selectin or activation-dependent determinants on GP IIb-IIIa in flow cytometry. Intriguingly, platelet ultrastructure often resembled that seen in patients with congenital thrombocytopathies characteristic of giant platelet syndromes.

Adult↗

PubMed1998

Bernard-Soulier syndrome in pregnancy: case report and review of the literature.

Bernard-Soulier Syndrome is a rare hereditary thrombocytopathy that manifests clinically by excessive bleeding out of proportion to the degree of thrombocytopenia. Only eight reports of Bernard-Soulier Syndrome in pregnancy have been previously described. In some patients the pregnancy course was smooth while in others post-partum haemorrhage was the most common complication. We present a primiparous female who had immediate and delayed post-partum haemorrhage that was managed conservatively. Review of the literature is also included.

Adult↗

PubMed1998

Heart disease in diabetes mellitus: a challenge for early diagnosis and intervention.

Most people with diabetes die from thrombotic complications superimposed to degenerative arterial vascular lesions, mostly myocardial infarction. Diabetes is a risk factor per se for such complications, but often clusters with dyslipoproteinemia, hypertension and obesity. In NIDDM (Type-II) patients this is referred to as "metabolic syndrome" and often operates on a genetically programmed susceptibility which accelerates the pathogenesis of coronary artery disease in front of a much wider diabetes specific cardiopathy. From a pathophysiological point of view none of these associated risk factors explains the pathogenetic series of events leading to the precipitation of an occlusive thrombus at sites of complicated coronary plaques. In patients with diabetes the coagulation system is switched towards a prethrombotic state, involving increased plasmatic coagulation, diminished fibrinolysis, decreased endothelial thromboresistance and predominantly platelet hyperreactivity ("diabetic thrombocytopathy"). Some of these factors are associated with an increased coronary risk (e.g. fibrinogen, PAI-1, platelets), but are also directly linked to the pathogenesis of "atherothrombosis". Altered cardiac remodelling together with adhesion and coagulation mechanisms appears suitable to explain decreased functional performance of infarcted organs, decreased success of acute (reduced fibrinolytic response, reperfusion injury) and longterm intervention strategies (PTCA, CABG) in diabetes. Glucose adjustment alone will not adequately neutralize these complex mechanisms. Particularly in diabetes a multidimensional interventional repertoire is required including antihypertensive, antidyslipoproteinemic and antithrombotic drugs, customized according to the individual patients needs as assessed by early diagnostic measures ("early secondary prevention").

Diabetes Complications↗

PubMed1998

The bleeding time in pediatrics.

When performed with standardized methods and techniques, the bleeding time (BT) depends on variables that physiologically alter primary hemostasis. These variables include number of platelets and platelet function, white and red blood cell counts, vascular factors, hormones, and temperature. Variations within normal limits reflect the in vivo situation and are of no clinical relevance. If the BT is prolonged far above the upper normal limit, however, defects of primary hemostasis have to be anticipated. These include thrombocytopenia or thrombocytopathy, anemia, leukopenia, and deficiencies of plasmatic factors such as von Willebrand factor (vWF), fibrinogen, the lupus anticoagulant, and factor V. The BT can be used as screening test for patients with bleeding symptoms. As a single test, the BT gives the best information in pediatrics, in which defects of primary hemostasis are more common than coagulopathies. In addition, BT can guide the therapy of these patients, because it reflects clinical improvement. When used as a preoperative screening test, BT should be combined with the activated partial thromboplastin time (aPTT) because BT usually does not recognize patients with coagulopathies. With standardized techniques and the knowledge of its merits and limitations, BT is a useful test for diagnosing hemostatic disorders, guiding their therapy, and warning of unexpected bleeding complications during surgery. The BT is especially suited for use in pediatrics for the following reasons: (1) It does not require a venipuncture and is similar to capillary blood sampling if performed with standardized devices adapted for pediatric use; (2) it is an in vivo test informing mostly on defects of primary hemostasis, which are the most common bleeding diatheses in childhood; (3) the results are immediately available; (4) it requires only minimal amounts of blood; and (5) it does not require unphysiological reagents and preparation of the sample. The test requires a highly motivated and experienced operator who knows of the many variables influencing the BT. The interpretation cannot be done without knowledge of the history and physical status of the patient and of the limitations of the BT.

Bleeding Time↗

PubMed1989

Modulation of mild bleeding disorder during remissions and exacerbations of Graves' disease.

A patient with Graves' disease had a symptomatic thrombocytopathy during periods of remission. When euthyroid, she noticed bruising, petechiae, and epistaxis. Hemostatic abnormalities included prolongation of the bleeding time by aspirin, reduced platelet retention (a second-phase defect), and abnormal thrombin-induced aggregation and serotonin release. When hyperthyroid, bleeding symptoms resolved, and platelet function returned to normal. These observations suggest that mild bleeding disorders may be influenced either directly or indirectly by thyroid hormone levels.

Adult↗

PubMed1976

Platelet dysfunction in vincristine treated patients.

Recent revival of interest in the use of vincristine (VCR) for the treatment of idiopathic thrombocytopenic purpura prompted us to evaluate the platelet function of our patients on VCR. Eighteen patients with acute lymphoblastic leukaemia (ALL) in remission, and nine children with solid tumours were studied on 80 occasions at different time intervals after their last VCR dose. A mildly elevated threshold for epinephrine-induced second phase aggregation and a delay in the onset of collagen-induced aggregation was found in patients with ALL not on VCR. Vincristine induced unobtainable second phase aggregation to epinephrine in 67%, 38%, 30% and to ADP in 53%, 13%, 33% of the patients 1 week, 2-3 weeks and 4 weeks respectively after administration. The thrombocytopathy was relative, not absolute, since collagen induced aggregation at all times. Platelet counts, uptake and release of serotonin, bleeding times, clot retractions and release of platelet factor 3 were normal. Platelet adhesion was abnormal in five of 12 patients tested. In vitro platelets are a hundred-fold less sensitive to VCR than in vivo. Cyclic adenosine monophosphate, cyclic guanosine monophosphate and dimethylsulfoxide do not protect platelets from VCR. The exact mechanism by which VCR abolishes second phase aggregation in patients is uncertain. Because of VCR's narrow therapeutic index between thrombocytopenia and thrombocythaemia, the use of VCR should be reserved for life-threatening haematologic disorders when treating non-malignant conditions.

Adenosine Diphosphate↗

PubMed1994

A case of severe neonatal thrombocytopenia with schizencephaly associated with anti-HPA-1b and anti-HPA-2a.

We report a family with a neonate who was severely damaged by intracranial haemorrhages. These probably occurred before the 20th week of gestation. The neonate had a moderate thrombocytopenia. In the maternal serum anti-HPA-1b and anti-HPA-2a alloantibodies were detected. Third-generation assays were applied to identify the alloantibodies. No other cause for the bleeding was found. Probably the combination of anti-HPA-1b and anti-HPA-2a alloantibodies, directed against the platelet fibrinogen receptor and the von Willebrand receptor, respectively, induced a thrombocytopenia and a thrombocytopathy.

Antigens, Human Platelet↗

PubMed1992

Thrombocytopenia due to platelet glycoprotein IIb/IIIa-reactive autoantibodies non-reactive with platelets from EDTA blood.

We describe 2 patients with thrombocytopenia and autoantibodies in the blood against platelet membrane glycoprotein (GP) IIb/IIIa, in whom reactivity of the antibodies with their antigen was greatly diminished in the presence of sodium EDTA. One patient also showed a marked thrombocytopathy, suggesting a functional blocking of GP IIb/IIIa by these autoantibodies. These observations show that some immunologically important autoantibodies can easily be missed in routine serological investigations in which EDTA blood is used, obscuring the autoimmune nature of a thrombocytopenia and possibly of a thrombopathy as well.

Adult↗

PubMed2005

Recombinant factor VIIa (NovoSeven) as a hemostatic agent after surgery for congenital heart disease.

BACKGROUND: Postoperative bleeding and blood product requirements can be substantial in children undergoing open-heart surgery, and reexploration is required in 1% of cases. Recombinant activated factor VII (rFVIIa, NovoSeven, NovoNordisk, Denmark) is a hemostatic agent approved for the treatment of hemophilic patients with inhibitors to factor VIII or factor IX. It has also been used with success in other conditions. We present our experience with rFVIIa treatment for uncontrolled bleeding after open-heart surgery in five pediatric patients. METHODS: The study group consisted of five patients after open-heart surgery with excessive blood loss. The patients were treated with rFVIIa after failure of conventional treatment to control the bleeding. Blood loss, blood product consumption, and coagulation test results were recorded before and after rFVIIa administration. RESULTS: In all cases, blood loss decreased considerably after rFVIIa administration (mean 7.8 ml x kg(-1) x h(-1)), almost eliminating the need for additional blood products, and the prolonged prothrombin time normalized. In two patients with thrombocytopathy, rFVIIa helped to discriminate surgical bleeding from bleeding caused by a defect in hemostasis. No side effects of rFVIIa treatment were noted. CONCLUSIONS: These cases support the impression that RFVIIa is efficient and safe in correcting hemostasis in children after cardiopulmonary bypass when other means fail. However, the data are still limited, and more extensive research is needed.

Adolescent↗

PubMed1975

Pseudothrombocytopenia due to platelet aggregation and degranulation in blood collected in EDTA.

Three patients are described in whom platelet aggregation and/or degranulation occurred in blood collected into EDTA. These changes resulted in spurious thrombocytopenia and morphological changes similar to those observed in some thrombocytopathies. The abnormalities were dependent on the presence of EDTA and did not occur in citrate, oxalate or heparin anticoagulants. In two patients the abnormality was shown to be due to a plasma factor which was not IgG, IgM, fibrinogen or albumin. The most likely explanation is that these patients have an unidentified abnormal plasma component which, on exposure to EDTA, develops 'anti-platelet activity'. Althought relatively uncommon a prospective study of the incidence of these phenomena indicates that they are probably more common than either platelet cold agglutinins or platelet satellitism. They have practical significance with respect to the diagnosis of thrombocytopenia and also to the interpretation of abnormal platelet morphology.

Adenosine Diphosphate↗

PubMed1986

Thrombocytopenia and pseudothrombocytopenia: a clinical and laboratory problem.

During a 4-month period, the patients with thrombocytopenia (N = 14) at a haematological outpatient clinic were subjected to a special laboratory investigation. Evidence of pseudothrombocytopenia was found in 5 of the patients. 1 patient with a giant platelet syndrome associated with deficient platelet function was also found. It is concluded that pseudothrombocytopenia and various thrombocytopathies provide a significant confounding factor in the management of patients with alleged thrombocytopenia. It is therefore suggested that the initial diagnostic work-up of alleged thrombocytopenia patients should include an assessment of platelet morphology in addition to an overall haemostatic test (bleeding time) and platelet function tests.

Bleeding Time↗