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Background: Atrial fibrillation is associated to a high risk of systemic embolism and to hypercoagulability. Aim: To evaluate the activation of the coagulation cascade through determinations of the thrombin-antithrombin complex in patients with atrial fibrillation and to correlate this data with the clinical and echocardiographic risk factors for systemic embolism. Patients and Methods: In 53 patients with atrial fibrillation plasma levels of the thrombin-antithrombin complex were determined on admission to a coronary care unit and 30 days later. Using a univariate and multiple regression analysis, the association basal thrombin-antithrombin with the duration of the arrhythmia, age over 70 years, previous use of antiplatelet agents, history of hypertension, mitral valve disease, diabetes, heart failure, previous systemic embolism, left atrial diameter and the presence of spontaneous contrast echo or thrombus in the left atrial appendage, was studied. Results: Basal thrombin-antithrombin values were 40.1ñ69 mg/L (Median 8.34 [3.0-47.5]) compared to 2.7ñ3.3 mg/L in healthy controls (p <0.001). No significant correlation was found between activation of the coagulation cascade and risk factors for systemic embolism. There were no significant differences in thrombin-antithrombin values between patients with chronic or paroxysmal atrial fibrillation (29.5ñ43 mg/L and 49.4ñ83 mg/L respectively). Mean thrombin-antithrombin values in patients under antiplatelet agents were lower than in those without treatment (17.3ñ43 vs 66.8ñ127 mg/L; p=0.018). Conclusions: The activation of the coagulation cascade in patients with atrial fibrillation was confirmed. However, no association of this activation with well known clinical and echocardiographic risk factors for systemic embolism, was found. Previous antiplatelet treatment prevented a higher activation of the coagulation cascade

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Objetivo: el transplante de médula ósea (TMO) es un procedimiento que constituye la única posibilidad de tratamiento para algunas enfermedades hematológicas y oncológicas de la infancia. Se describe un programa de trasplante de médula ósea implementado en nuestra institución, habilitando la infraestructura y personal necesarios. Pacientes: 60 pacientes pediátricos han recibido TMO, 37 niños, 23 niñas, edades entre 7 meses y 17 años. Los diagnósticos correspondieron a leucemia aguda 24, aplasia medular 5, leucemia mieloide crónica/mielodisplasia 6, tumores sólidos 17, enfermedades congénitas 7, histiocitosis 1. Fueron TMO autólogos 14 casos y alogeneicos 46. Donantes: hermanos idénticos: 34. Familiares no idénticos: 6. Cordón umbilical no relacionado: 6. Correspondieron a grupo de riesgo estándar 31 pacientes, y grupo de riesgo alto (leucemias o tumores refractarios, pacientes politransfundidos, donantes no hermano), 29. Resultados: sobrevida actuarial libre de eventos (a 3 años): grupo total: 36 por ciento, grupo riesgo estándar: 61 por ciento, grupo riesgo alto: 10 por ciento (p < 0,01). Conclusiones el TMO es un tratamiento efectivo para pacientes pediátricos sin otra alternativa terapéutica. Los resultados en pacientes con enfermedad muy avanzada son malos, apoyando la necesidad de realizar oportunamente el procedimiento

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Las células del sistema inmune que incluyen linfocitos, granulocitos y monocitos-macrófagos, se forman en la médula ósea a partir de células pluripotentes, a través de un proceso finamente regulado y el que participan varias citoquinas. Los granulocitos (neutrófilos, eosinófilos y basófilos) presentan particularidades morfológicas y funcionales. La principal función de los neutrófilos es su capacidad fagocítica. En el capítulo se explican los procesos de activación, quimiotaxis, fagocitosis y bacteriolisis. Las células del sistema fagocítico mononuclear (monocitos y macrófagos) tienen como función fagocitar; actividad más desarrollada en los macrófagos, que son células tisulares derivadas de los monocitos circulantes. Los linfocitos son las células que participan en la inmunidad adquirida o específica. Las células T participan en la inmunidad celular y las células B en la inmunidad humoral. Una tercera subpoblación de linfocitos, las células NK, participan en la inmunidad celular de tipo innata. Los órganos linfoides se pueden clasificar en primarios (timo y médula ósea) y secundarios (bazo, ganglios linfáticos y tejido linfoide asociado a mucosas). En el timo maduran los LT y en la médula ósea los LB. En los órganos linfoides secundarios los linfocitos y otras células del sistema inmune toman contacto con los antígenos y es en ellos donde se genera la respuesta inmune específica. En estos órganos existen zonas ricas en células T, y otras en que, principalmente, existen células B. La capacidad de los linfocitos de recircular entre los órganos linfoides secundarios, vasos linfáticos, conducto torácico y vasos sanguíneos le permiten tomar contacto con antígenos en diferentes lugares del organismo

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Backgrour: Neonatal alloimmune thrombocytopenia (NAIT) is a result of fetomaternal incompatibility. Platelet destruction is caused by a maternal alntibody directed against a fetal platelet antigen inherited from the father and lacking on the mother's platelets. The incidence and features of transplacental alloimmunization depend on the frequency of expression of platelet specific antigens, which are highly variable among different populations. Aim: To determine the prevalence and characteristics of transplacental alloimmunization in a large, group of pregnant women in Chile. Material and methods: We, studied 3,041 samples obtained during the third trimester of gestation. In all samples, anti platelet antibodies were screened by ELISA with platelet membranes fixed to a microtiter plate. Positive samples were further studied for antigenic specificity with the monoclonal antibody specific immobilization of platelet antigens (MAIPA) test. Results: Anti platelet antibodies were found in 261 samples (8.5 percent). The MAIPA test identified 6 samples with antibodies directed against major platelet membrane glycoproteins, 2 anti GPIb, 2 anti GPIIb/IIIa and 2 anti GPIa/IIIa. In four cases, anti HLA antibodies coexisted. Two cases corresponded to well defined platelet antigen systems: one anti HPA-1a and one anti HPA-5b. No clinical evidence of thrombocytopenia of the newborn was detected in all these cases with anti GP antibodies. Conclusions: A prevalence of platelet specific antibodies of 0.2 por ciento with only one anti HPA-1a was detected. These findings are in contrast with those of other populations but in accordance with the low frequency of the HPA-1b/b phenotype in the Chilean population. The very low incidence of platelet specific antibodies and the lack of association with clinical thrombocytopenia in the newborn, do not support the recommendation of routine antenatal screening to all women in Chile

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Background: Refractoriness continues to he a major complication of platelet transfusion therapy in patients with multiple transfusions: Despite most cases are secondary to non-immune causes, the most serious is that associated to alloimmunization. The incidence and consequences of HLA and non-HLA (platelet specific) antibodies are unknown in our country. Aim: To prospectively determinate the frequency and characteristic of post transfusion alloimmunization and the incidence of platelet specific antibodies. Patients and methods: Forty one adults and 24 children with a recently diagnosed malignancy and undergoing chemotherapy that required multiple transfusions were studied. Screening for antiplatelet antibodies (platelet membrane ELISA) was performed before the first transfusion, every four weeks or whenever the 1 hour corrected count increment for platelet transfusions was lower that 5000. Platelet specific antibodies werw identified with a monoclonal antibody-specific immobilization of platelet antigens (MAIPA), with anti-GPIIb, GPIIb/IIIa, GPIa/lia and anti-HLA class I. Results: Adult patients received an averafge of 10.2 ñ 5.5 units of red blood cells and 58.6 ñ 35.4 units of platelets. Children received 4.8 ñ 3.7 units of red blood cells and 9.6 ñ 6.7 units of platelets. HLA antibodies appeared in 7 of 41 adult patients (17 percent), platelet specific alloantibodies were found in two patients (one anti GP Ia/IIa and one anti GP ib). Platelet refractoriness appeared in three alloimmunized patients. No Child had detectable serum antibodies during follow up. Conclusions: Platel transfusion refractoriness of immune origin occurs infrequently in our population and the presence of platelet antibodies does not mean that it will appear. The use of leukocyte depleted blood components to prevent refractoriness cannot be justified at this time

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Patients and methods: Five hundred eighty nine patients whose main symptom was the presence of mucocutaneous hemorrhages were studied. Bleeding time, platelet count, coagulant activity of factor VIII (FVIII:C), FvW: Ag and FvW:CoRis and ABO blood group were measured in all patients in a first stage. According to the results of these tests, further studies were decided. Results: In patients younger than 13 years old, males predominated and, in older patients, females consulted with higher frequency. There was a higher proportion of individuals with O blood type than in the normal population. Bleeding time was abnormal in 330 patients (56 percent). One hundred ten patients (19 percent) had von Willebrand disease and, among them, one third had a normal bleeding time. Isolated reduction of factor VIII activity was found in 66 patients (11 percent, 51 males) and 32 of these had normal bleeding time. Eighty one patients (14 percent) were considered to have an hereditary platelet function defect. A precise diagnosis was not achieved in 332 patients (56 percent). Conclusions: Among patients consulting for mucocutaneous hemorrhages, 19 percent had von Willebrand disease, 11 had an isolated reduction of factor VIII activity, 14 percent had platelet function defects and in 56 percent, a precise diagnosis was not reached

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La hemorragia intracraneana ocurre entre 2 por ciento y 13 por ciento de los enfermos hemofílicos,pudiendo ser subaracnoidea, subdural o intracerebral (hematoma intracerebral). Es infrecuente como primera manifestación de la enfermedad, habiéndose demostrado en 5,9 por ciento de los pacientes con hemofilia A. En 54 por ciento de los casos hay antecedentes de traumatismo, pero en 38 por ciento no se identifica una causa desencadenante. La tomografía axial computadorizada suele permitir el diagnóstico sin dificultad, pero excepcionalmente las imágenes obtenidas pueden ser confundidadas con las de otras afecciones. Se describe un niño de tres meses de edad, en quien la primera manifestación de hemofilia fue un hematoma intracerebral, interpretado inicialmente como tumor, descubriéndose su verdadera naturaleza durante la intervención quirúrgica y su etiología hemofílica al estudiar la coagulación como consecuencia de nuevos sangramientos intracraneanos en el período postoperatorio

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