Hemorheological in vitro action of propofol on erythrocytes from healthy donors and diabetic patients.

Drugs used during anesthesia might induce disturbance on microcirculation due to their systemic cardiovascular actions and to direct hemorheological effects. A comparative investigation of the hemorheological alterations related to in vitro propofol treatment of red blood cells (RBCs) from healthy and diabetic volunteers is presented here. Viscoelasticity and aggregation of RBCs from type 2 diabetic patients (DBT) and healthy donors (HD) were studied from RBCs incubated with propofol near steady-state concentration. 'S parameter', which measures the aggregation degree, was obtained using digital analysis of microscopic images. Erythrocyte viscoelasticity parameters were determined using an Erythrocyte Rheometer. Results obtained from DBT samples showed an increase of 10% or more in aggregation due to the propofol action. The phase shift between erythrocyte response and oscillating shear stress applied at 1 Hz was altered by propofol treatment of erythrocyte from HD and DBT. Propofol could produce slight alterations in the rheological behavior of erythrocyte from HD and DBT, at concentrations near those of steady state. Moreover, this anesthetic could induce an adverse effect in DBT, particularly on erythrocyte aggregation. The observed hemorheologic alteration would increase the possibility of microcapillary obstruction. Hence, this type of study [0] would prove relevant to avoid possible postoperative complications.

Preliminary characterization of erythrocytes deformability on the entropy-complexity plane.

We present an application of wavelet-based Information Theory quantifiers (Normalized Total Shannon Entropy, MPR-Statistical Complexity and Entropy-Complexity plane) on red blood cells membrane viscoelasticity characterization. These quantifiers exhibit important localization advantages provided by the Wavelet Theory. The present approach produces a clear characterization of this dynamical system, finding out an evident manifestation of a random process on the red cell samples of healthy individuals, and its sharp reduction of randomness on analyzing a human haematological disease, such as ß-thalassaemia minor.

[Serum sialic acid, cellular anionic charge and erythrocyte aggregation in diabetic and hypertensive patients]. / Acido siálico sérico, carga aniónica y agregación eritrocitaria en pacientes diabéticos e hipertensos.

The aim of this work was to study the relationship between serum sialic acid (SSA) and erythrocyte anionic charge (EAC) with erythrocyte aggregation in two groups: diabetic (DBT, n=20) and hypertensive (HT, n=21) patients, compared to a control group (n=20). We worked with anticoagulated blood with EDTA and serum. The erythrocyte aggregation was studied by microscopically observing and quantifying aggregates using an ASP (Aggregate Shape Parameter). The EAC was determined by binding an Alcian blue dye to the membrane sialic acid and SSA was determined by spectrophotometric method with an Erlich reactant. The values of ASP and SSA increased significantly in HT and DBT patients compared to the control group. The HT and DBT groups showed amorphous aggregates, evident in an alteration in the values of ASP, which were significantly higher ( p < 0.005) than in healthy patients. The EAC values were much lower in HT and DBT patients than in the control group (p < 0.0001). In this work, abnormalities in the erythrocyte aggregation could be detected by the values of ASP, EAC and SSA, which might be involved in vascular disorders of diseases such as hypertension and diabetes.

Ácido siálico sérico, carga aniónica y agregación eritrocitaria en pacientes diabéticos e hipertensos / Serum sialic acid, cellular anionic charge and erythrocyte aggregation in diabetic and hypertensive patients

El objetivo de este trabajo fue estudiar la relación del ácido siálico sérico (AS) y la carga aniónica eritrocitaria (CAE) con la agregación eritrocitaria en dos grupos de pacientes: diabéticos (DBT n= 20) e hipertensos (HTA n= 21), comparados con un grupo control (n= 20). Se trabajó con sangre anticoagulada con EDTA y suero. La agregación eritrocitaria se estudió por observación microscópica de los agregados y cuantificación a través de un parámetro de forma denominado ASP (Aggregation Shape Parameter). La CAE se determinó por unión a colorante alcian blue y el AS por método espectrofotométrico con reactivo de Erlich. Los valores de ASP y AS resultaron significativamente aumentados en los HTA y DBT respecto de los normales. Los HTA y DBT presentaron agregados amorfos, lo que se refleja en los valores alterados de ASP, significativamente mayores (p < 0.005) respecto de los individuos normales. Los valores de CAE resultaron significativamente inferiores en los HTA y DBT respecto del grupo control (p < 0.0001). En este trabajo se demostraron anormalidades en la agregación eritrocitaria, detectadas por los valores de ASP, CAE y AS que podrían estar involucradas en las complicaciones vasculares de vasculopatías como la hipertensión y la diabetes.

The aim of this work was to study the relationship between serum sialic acid (SSA) and erythrocyte anionic charge (EAC) with erythrocyte aggregation in two groups: diabetic (DBT, n=20) and hypertensive (HT, n=21) patients, compared to a control group (n=20). We worked with anticoagulated blood with EDTA and serum. The erythrocyte aggregation was studied by microscopically observing and quantifying aggregates using an ASP (Aggregate Shape Parameter). The EAC was determined by binding an Alcian blue dye to the membrane sialic acid and SSA was determined by spectrophotometric method with an Erlich reactant. The values of ASP and SSA increased significantly in HT and DBT patients compared to the control group. The HT and DBT groups showed amorphous aggregates, evident in an alteration in the values of ASP, which were significantly higher ( p< 0.005) than in healthy patients. The EAC values were much lower in HT and DBT patients than in the control group (p < 0.0001). In this work, abnormalities in the erythrocyte aggregation could be detected by the values of ASP, EAC and SSA, which might be involved in vascular disorders of diseases such as hypertension and diabetes.

Hemorheologic changes in type 2 diabetic patients with microangiopathic skin lesions. A linear discriminant categorizing analysis.

The development of diabetic microangiopathy may produce lesions in distinct organic territories (the skin, among others). With an intention of identifying hemorheologic variables for a better characterization of diabetic patients, we studied plasmatic and blood viscosities (P Visc at 2.30 s(-1) and B Visc at 4.60 and 230 s(-1)), fibrinogenemia, and erythrocytic aggregation in 40 type 2 diabetic patients (13 with microangiopathic skin lesions and 27 without) and in 30 healthy controls. Considering its alterations in diabetic patients and applying linear discriminant analysis, two models may be characterized: (a) discriminant function (Disc F)=0.58 aggregate shape parameter (ASP)-0.61 B Visc(230)+0.89 fibrinogenemia for discriminating healthy individuals from diabetic patients with microangiopathic skin lesions and (b) Disc F=6.325 ASP-0.347 B Visc(230)+0.013 fibrinogenemia for discriminating healthy controls from diabetic patients with and without microangiopathic skin lesions. Both models appear to be valid due to the following: (a) Model 1: a coefficient of canonic correlation of 0.924, a highly significant Mahalanobis distance (P<10(-3)), a correct percentage of classification (100%), and the centroids of each group (0.94 and 5.63); (b) Model 2: a coefficient of canonic correlation of 0.898, a highly significant Mahalanobis distance (P<10(-3)), a correct percentage of classification (85.7%), and the centroids of each group (-1.9, 1.9, and 2.4). Just as the alterations in the analyzed hemorheologic variables could be suggesting their possible involvement in the physiopathogenia of diabetic microangiopathic skin lesions, the proposed models could characterize a microcirculatory profile in diabetic patients for preventing irreversible damages.

Laser diffractometry technique: clinical applications to vascular pathologies.

Hypertension (HTA) and dyslipidemia (DLP) represent major risk factors for cardiovascular and cerebral-vascular ischemic disease. The mechanisms through which they can induce vascular damage are both metabolic and mechanical. Hemorheological alterations in HTA are result of changes affecting both red cell intrinsic structure and their interactions with the plasmatic components. Several hemorheological determinants (biochemical, ionic, metabolic and rheologic) could influence and produce an impaired erythrocyte deformability determining an increased flow resistance in the microcirculation. The "Erythrodeformeter" allows obtaining the stationary and dynamical linear parameters of erythrocyte membrane by laser diffractometry. Stationary and oscillatory shear-induced elongation of cells leads to an elliptical diffraction pattern, its geometric characteristics being directly related to those of deformed RBC. Erythrocyte stationary parameters (Deformability Index, surface viscosity and elastic modulus) were obtained in stationary regime. Complex viscoelastic parameters (dynamic elasticity, dynamic loss, viscous and elastic components of the complex viscosity) were obtained when operating in oscillating mode. The diffractometric method is sensitive to detect pathological or induced alterations on RBC membrane, which can affect blood flow in vivo. The rheological parameters obtained give important information about the erythrocyte membrane and allow to detect and characterize erythrocyte alterations in vascular pathologies.

Frecuencia alélica de apolipoproteina E en una población aborigen / Apolipoprotein E allelic frequency in a native population

El polimorfismo de apolipoproteína E (apoE) es originado por los alelos e2, e3 y e4. El origen étnico demostró ser un factor determinante del genotipo de apoE; existen pocos estudios acerca de su distribución. Realizamos un estudio explorativo para determinar la frecuencia alélica (FA) de apoE en una muestra de una población de origen aborigen (PA) nacidos en la provincia de Chaco (Rep. Argentina) y emigrados a Rosario y/o descendientes de los mismos nacidos en la ciudad, y compararla con la de una población caucásica argentina (PC), dato no reportado hasta el momento. Para comparar la FA en ambas poblaciones (PA n: 71,1 a 45 años y PC n: 56, 5 a 17 años), el tamaño muestral fue calculado para lograr una estimación representativa de la población total con una confianza del 95%. Las muestras fueron reclutadas en forma aleatoria de individuos que aceptaron participar previo consentimiento firmado. La caracterización molecular se realizó por ASA­PCR. Para comparar la FA de PA con PC, se realizó el ensayo de hipótesis de una proporción bajo teoría normal. Los resultados de FA fueron: PC: e3 0,786 (IC 95% 0,679­0,893), e4 0,178 (IC 95% 0,078­0,278), e2 0,036 (IC 95% 0,000­0,084), PA: e3 0,880 (IC 95% 0,804-0,956), e4 0,084 (IC 95% 0,021­0,147), e2 0,035 (IC 95% 0,000­0,075). Se encontró diferencia significativa en la FA de e3 y e4 entre las poblaciones estudiadas. El tamaño y esquema de muestreo, etnia, factores ambientales y protocolos utilizados, podrían contribuir a la diversidad de los resultados.

The polymorphism of apolipoprotein E (apoE) is originated by e2, e3 and e4 alleles. Ethnic origin has demonstrated to be a decisive factor for ApoE genotype. There are few studies about its distribution. We carried out this explorative study of the apoE genotype frequency (AF) in a native population (NP) born in the Chaco province and emigrated to Rosario (Argentina) and/or descendants in order to compare it with a Caucasian Argentinean population (CP), a fact that has not been reported yet. To compare the allelic frequency of both populations (NP n: 71. 1 to 45 yr and CP n: 56.5 to 17 yr), the sample size was calculated to achieve a representative estimation of total population with a confidence interval of 95%. Samples were randomly collected from individuals that accepted to participate and signed an informed consent. The molecular characterization was made by ASA­PCR. To compare the AF of both populations, the hypothesis assay of a proportion under a normal theory was carried out. The allelic frequencies (AF) in the PC were: e3 0.786 (IC 95% 0.679­0.893), e4 0.178 (IC 95% 0.078­0.278), e2 0.036 (IC 95% 0.000­0.084). While FA in PA were e3 0.880 (IC 95% 0.804­0.956), e4 0.084 (IC 95% 0.021­0.147) and e2 0.035 (IC 95% 0.000­0.075). Significant differences were observed in the AF of e3 and e4 among the different populations. The sample size and sampling procedure, ethnia, environmental factors, and lab protocols could have contributed to the diversity of the results.

[Hemorheological alterations in hypertensive patients]. / Evaluación de alteraciones hemorreológicas en pacientes hipertensos.

The aim of this study was to investigate the blood viscosity profile and to evaluate the influence of plasmatic (fibrinogen) and cellular (erythrocyte aggregation) factors in a group of hypertensive patients, compared with a normotensive group. We worked with anticoagulated blood of both non diabetic hypertensive patients (n=31), and healthy individuals (n=40). The plasmatic viscosity and whole blood determination were obtained with a cone-plate viscometer. Erythrocyte aggregation was studied by microscopical observation and quantified by an Aggregate Shape Parameter (ASP), defined as the relation projected area/perimeter. Fibrinogen was determined by the Clauss method with a coagulometer. A comparison between these groups led us to assert that whole blood viscosity was significantly higher in hypertensive patients than in the controls at all shear rates. Plasma viscosity values only showed significant differences between both groups at low shear rate (1.15 a 11.56 seg(-1)). The hypertensive patients showed irregular and amorphous aggregates so that ASP appeared significantly higher (p< 0.001) in patients with hypertension (0.69 +/- 0.11) than in healthy subjects (0.25 +/- 0.12). Fibrinogen appeared slightly higher (p<0.01) in the hypertensive group than in the normal group. Several hemorheological parameters play important roles in the pathogenesis of hypertension. Among these factors, several hemorheological parameters could be altered in hypertension (hematocrit, plasma fibrinogen level, erythrocyte deformability and aggregability, plasma and whole blood viscosity). An increased RBC aggregation has been identified as an important factor responsible for disturbing blood rheological behavior in the microcirculation. The present study demonstrates an abnormal erythrocyte aggregation, which was detected by increased ASP values that could be responsible for vascular complications in hypertension.

Perfil lipídico en niños y adolescentes de una población escolar / Lipid profile in a school population of children and adolescents

Introducción. La relación existente entre las alteraciones del metabolismo lipídico y el riesgo de enfermedades cardiovasculares, unida a otras condiciones como la obesidad, lleva a considerar la importancia del estudio del perfil lipídico desde edades tempranas. El objetivo de este trabajo fue estudiar el perfil lipídico de niños y adolescentes para aportar datos según edad y sexo comparándolos con los obtenidos por otros autores.Población, material y métodos. Se realizó un estudio descriptivo transversal de una muestra de 960 niños y adolescentes escolarizados, en distintas escuelas públicas de Rosario y alrededores, pertenecientes a una situación socioeconómica media o baja. Se incluyeron varones y mujeres de 5 a 18 años, sin antecedentes patológicos conocidos; se excluyeron aquellos con sobrepeso (6,6 por ciento).Resultados. Se determinaron parámetros antropométricos y bioquímicos. Los valores obtenidos fueron:colesterol: 164,9 más o menos 23,6 mg/dl; triglicéridos: 72,3 más menos 31,7 mg/dl; colesterol LDL: 96,1 más menos 23,6 mg/dl; colesterol HDL: 55,1 más menos 5,6 mg/dl; colesterol no HDL: 110,1 más menos 25,4mg/dl; colesterol/colesterol HDL: 3,03 más menos 0,59; colesterol LDL/colesterol HDL: 1,77 más menos 0,59. En la muestra estudiada, no se observaron diferencias estadísticamente significativas en los parámetros entre varones y mujeres ni entre los distintos grupos etarios, a excepción de los triglicéridos (significativamente mayores en mujeres de 5 a 11 años, p mayor 0,001).Conclusión. La comparación de nuestros resultados con los de otros autores nos permitió establecer diferencias con distinto grado de significación. El aporte del estudio del perfil lipídico en una población de niños y adolescentes podría ser de utilidad como referente para identificar factores de riesgo modificables y la necesidad de intervenciones conducentes a adoptar medidas de prevención desde edades tempranas.

Perfil lipídico en niños y adolescentes de una población escolar / Lipid profile in a school population of children and adolescents

Introducción. La relación existente entre las alteraciones del metabolismo lipídico y el riesgo de enfermedades cardiovasculares, unida a otras condiciones como la obesidad, lleva a considerar la importancia del estudio del perfil lipídico desde edades tempranas. El objetivo de este trabajo fue estudiar el perfil lipídico de niños y adolescentes para aportar datos según edad y sexo comparándolos con los obtenidos por otros autores.Población, material y métodos. Se realizó un estudio descriptivo transversal de una muestra de 960 niños y adolescentes escolarizados, en distintas escuelas públicas de Rosario y alrededores, pertenecientes a una situación socioeconómica media o baja. Se incluyeron varones y mujeres de 5 a 18 años, sin antecedentes patológicos conocidos; se excluyeron aquellos con sobrepeso (6,6 por ciento).Resultados. Se determinaron parámetros antropométricos y bioquímicos. Los valores obtenidos fueron:colesterol: 164,9 más o menos 23,6 mg/dl; triglicéridos: 72,3 más menos 31,7 mg/dl; colesterol LDL: 96,1 más menos 23,6 mg/dl; colesterol HDL: 55,1 más menos 5,6 mg/dl; colesterol no HDL: 110,1 más menos 25,4mg/dl; colesterol/colesterol HDL: 3,03 más menos 0,59; colesterol LDL/colesterol HDL: 1,77 más menos 0,59. En la muestra estudiada, no se observaron diferencias estadísticamente significativas en los parámetros entre varones y mujeres ni entre los distintos grupos etarios, a excepción de los triglicéridos (significativamente mayores en mujeres de 5 a 11 años, p mayor 0,001).Conclusión. La comparación de nuestros resultados con los de otros autores nos permitió establecer diferencias con distinto grado de significación. El aporte del estudio del perfil lipídico en una población de niños y adolescentes podría ser de utilidad como referente para identificar factores de riesgo modificables y la necesidad de intervenciones conducentes a adoptar medidas de prevención desde edades tempranas.(AU)

A dynamic and stationary rheological study of erythrocytes incubated in a glucose medium.

A higher than normal glucose concentration in a suspending medium may produce non-enzymatic glycosylation of erythrocyte proteins. This process can modify the viscoelastic properties of erythrocytes. In this paper, we studied the possible relationship between glucose concentration in a suspending medium and erythrocyte rheological parameters. Human venous blood was obtained from the antecubital veins of 10 healthy volunteers. Blood samples were anticoagulated with EDTA and centrifuged. Red blood cells (RBCs) were washed and subsequently divided in aliquots, which were incubated in vitro with glucose solutions of different concentrations. Dynamic and stationary viscoelastic parameters of RBCs were determined by laser diffractometry in an Erythrodeformeter. Aggregate shape parameter (ASP) of the RBCs was determined by digital image processing. Significant changes were observed both in ASP and in rheological parameters when the glucose concentration in the medium was increased, demonstrating that a glucose concentration as low as 1% induces alterations in the mechanical properties of RBCs.

Adhesión eritrocitaria: método aplicado a patologías asociadas con proteínas portadoras de grupos sanguíneos eritrocitarios / Red blood cell adhesion. A method to be applied to the pathologies associated with protein carring erythrocitic blood groups

El estudio de la agregación eritrocitaria cobra importancia en la medida que permita cuantificar anormalidades circulatorias en diversas patologías. En condiciones normales los glóbulos rojos (GR) se agregan en estructuras cilíndricas denominadas rouleaux, mientras que en condiciones anormales, los agregados adoptan formas irregulares con tendencia morfológica esferoidal. Estas formas anómalas pueden ser inducidas por alteraciones celulares (disminución del contenido de ácido siálico de las glicoproteínas), o por factores extracelulares. El objetivo de éste trabajo fue estudiar la adhesión eritrocitaria relacionada con patologías asociadas a glicoforina A portadora de los antígenos MN de grupos sanguíneos eritrocitarios mediante metodología no convencional. Se estudió la morfología de los agregados eritrocitarios de 36 pacientes diabéticos, 20 pacientes hipertensos, 40 individuos sanos y GR con tratamiento enzimático a distintos tiempos. La agregación se cuantificó con un parámetro de forma de los agregados, denominado ASP (Aggregate Shape Parameter), definido como la relación entre el área proyectada de los agregados y el cuadrado de su perímetro. Los datos fueron obtenidos con muestras de suspensiones de GR en plasma autálogo, al 2 por ciento de hematocrito, las cuales fueron observadas con una cámara CCD (Camera Coupled Digital) y procesadas numéricamente con un procesador digital de imágenes (DIP), ambos acoplados a un microscopio invertido. Las glicoforinas (GP) portadoras de los antígenos M y N, juegan un papel estructural en la preservación de la forma del GR. Esto está ligado a la gran cantidad de ácido siálico (AS) que contienen, el que confiere al eritrocito, una carga negativa. Al aumentar el tiempo de incubación de la tripsina con los GR se produce una desialización progresiva de las GP de la membrana. Como consecuencia de ello se observa la formación de clusters (agregados irregulares) que llevan a valores progresivamente aumentados del ASP. Los pacientes diabéticos (ASP = 0,65 ñ 0,18) e hipertensos (ASP = 0,69 ñ 0,19) presentan valores significativamente mayores (p<10-5) que los controles normales (ASP = 0,28 ñ 0,15). Un aumento de la agregación eritrocitaria representa un importante factor de riesgo en el desarrollo de patologías vasculares, con posible deterioro de la microcirculación. En éste sentido, el ASP provee una útil referencia para cuantificar alteraciones en la morfología de los agregados

Comparative analysis of aggregate shapes by digitized microscopic images. Application to hypertension.

The main objective of the present work was to study modifications in RBC aggregate morphology by analyzing digitized microscopic images and compare them between healthy subjects and patients suffering from essential hypertension. Blood samples were obtained from normal subjects (n=30) and patients suffering from essential hypertension (n=20). RBC aggregate morphology was quantified using direct microscopic observation and numerical analysis of images. ASP (Aggregation Shape Parameter) defined as the ratio of the area of the projected image to its square perimeter was calculated. Other rheological parameters have been determined in order to establish the hemorheological profile of the studied hypertension states. ASP appears significantly higher (p<0.001) in patients suffering essential hypertension (0.69+/-0.11) than in normal control subjects (0.25+/-0.12). RBC aggregation is known to be responsible for the high increase in apparent blood viscosity at low shear rates. By compare ASP values with whole blood viscosity at low rate (2.30 s(-1)) a high correlation was formed between both parameters (Spearman coefficient was 0.8835 and p<0.001). The applied method is simple, direct and quantitative and provides a useful tool for measuring deviations of RBC aggregate morphology.

Hemorreología comparativa: estudios en diabéticos e hipertensos / Comparative hemorheological: study on diabetics and hypertensive patients

La medición de viscosidad plasmática y de sangre entera, determinadas en un viscosímetro rotacional, fue utilizada para verificar la existencia de anormalidaes hemorreológicas en pacientes diabéticos e hipertensos. Dichas mediciones se realizaron a distintas velocidades de corte, con lo cual se trazaron los correspondientes reogramas. Con esos datos se calcularon las correspondientes viscosidades relativas. Los resultados obtenidos, comparados con valores de los mismos parámetros obtenidos en individuos normales, permitiernon detectar comportamientos anormales, característicos de esas patologías circulatorias. Las diferencias más significativas se obtuvieron a una velocidad de corte de 5,76 seg. Se concluye que, en los pacientes diabéticos, los factores plasmáticos tienen mayor influencia en la aparición de hiperviscosidad, mientras que en los pacientes hipertensos son más influyentes los factores globulares

Evaluation of red blood aggregation in diabetes by computarized image analisis

Red blood cell (RBC) aggregation has been widely studied and its importance is well established in the rheology of microcirculation. RBC aggregation is a major factor responsible for the flow properties of blood. Increased RBC aggregation has been observed in several pathological states. Therefore, the measurement of erythrocyte aggregation is rhealogically important for quantifying flow abnormality in pathological conditions. Normal RBC under low flow or at rest form rouleaux aggregates, while abnormal RBC aggregation may lead to the formation of irregular aggregate structures, which may be induced by cell-associated factors (reduced membrane sialic acid levels) but also by extracellular factors. The main objective of the present investigation was to study RBC aggregate morphology in diabetic patients, using direct microscopic observation and numerical processing of recorded digitized images. Blood samples were obtained from 20 diabetic patients and from 15 normal control subjects. The aggregate morphology was quantified by the so-called Aggregate Shape Parameter (ASP) defined as the ratio of the aggregate projected area to its square perimeter. ASP appeared higher (p<10 - 5) in diabetic patients (0.65 +/- 0.18) than in normal controls (0.28 +/- 0.15). This rheo-optical method based on the theoretical model for rouleaux aggregates provides a useful reference for measuring deviations of RBC aggregate morphology. Increased aggregation of RBC resulting from a decreased sialylation of glycophorins may be an important factor in the development of vascular diseases and in the microcirculation impairment.

Estudio de las propiedades reológicas de la sangre durante la conservación / The study of the blood rheologics properties during its storage

Por medio de los parámetros viscoelásticos in vitro se estudiaron las alteraciones reológicas producidas durante el almacenamiento de eritrocitos humanos. Se estudiaron durante 35 días alícuotas semanales de globulos rojos compactados (CG) y de sangre entera (SE) almacenadas en CPD-adenina. Las muestras fueron analizadas utilizando el eritrodefórmetro en régimen estacionario y en régimen oscilante. Se midió la viscosidad sanguínea y plasmática con un viscosímetro cono/plato. La viscosidad sanguínea y el índice de deformabilidad de los eritrocitos se ven alterados con el tiempo de conservación, mostrando un pico máximo a la segunda semana de conservación. Todos los parámetros de viscoelasticidad compleja se modifican también, siendo más notorias estas alteraciones para las mayores frecuencias de oscilación. Todas las determinaciones reológicas realizadas muestran alteraciones en las propiedades estructurales de los eritrocitos almacenados como concentrado globular. Estas alteraciones son menos importantes que las encontradas en la sangre entera almacenada. En consecuencia, es importante evaluar no sólo los componentes celulares sino también el plasma debido al papel predominante que tienen las proteínas plasmáticas an las alteraciones del comportamiento reológico de los eritrocitos durante su almacenamiento.