Search

Background: Previously, hemorheology studies using Rheoscan mainly focused on chronic kidney disease, cardiovascular disease, and endocrine disease in adults. The study using LORCA focused on erythrocyte disease. There were no studies using Rheoscan in children., Objective: We aimed to investigate erythrocyte deformability among various hematologic diseases occurring in children, namely, iron deficiency anemia (IDA), hereditary spherocytosis (HS), immune thrombocytopenia (ITP), and aplastic anemia (AA)., Methods: Differences between those with HS, IDA, ITP, AA and healthy controls were compared among 43 patients, comprising 7 patients with HS, 8 patients with IDA, 6 patients with AA, 9 patients with ITP, and 13 healthy controls. Erythrocyte deformability was measured using a microfluidic ektacytometer (RheoScan-D, RheoMeditech, Seoul, Korea). The erythrocyte elongation index (EI) was defined as (L - W)/(L + W), where L and W are the major and minor axes of the ellipse, respectively., Results: The EI values of IDA, HS and AA were significantly decreased compared with healthy controls, but those of ITP were similar to healthy controls., Conclusions: This study showed that erythrocyte deformability differed among various hematologic diseases. Further study concerning correlation in relation to the diagnostic and prognostic significance of erythrocyte deformability in hematologic disease is needed.

Background and Objective: Hemorheologic alterations have been suggested to play a role in the pathogenesis of diabetic microvascular complications. We measured various hemorheologic parameters and assessed their possible role as a diagnostic tool for diabetic nephropathy (DN)., Methods: 248 subjects with type 2 diabetes and 222 subjects with prediabetes were included in this study. Hemorheologic parameters, including erythrocyte sedimentation rate (ESR), elongation index at 3 Pa (EI) were measured using microfluidic hemorheometer. Various metabolic parameters were measured from fasting blood samples. The subjects were stratified into three groups according to classification of DN by urinary albumin to creatinine ratio (ACR) and four groups by estimated glomerular filtration rate (GFR), than analyzed., Results: Significant differences were observed in metabolic and hemorheologic parameters according to progression of DN. Among them, (Fibrinogen×ESR)/ EI differed in all three groups of urinary ACR. In multiple regression analysis, (Fibrinogen×ESR)/ EI was an independent predictor of urine ACR after adjusted with confounding factors (ß  = 0.010, p < 0.001). (Fibrinogen×ESR)/ EI also showed significant difference no or minimal CKD stage, moderate CKD and severe CKD classified by GFR. This parameter showed area under curve (AUC) of the receiver operating characteristic (ROC) curve of 0.762, and moderate sensitivity and specificity to predict prevalence of microalbuminuria., Conclusions: (Fibrinogen×ESR)/ EI is a sensitive parameter for screening diabetic nephropathy.

Background: Ozone is used intensively worldwide in treatment and research of various pathologies due to its healing effects., Objective: The aim of this study is to investigate the effect of major ozone autohemotherapy on erythrocyte deformability and aggregation., Methods: 10 and 50μg/ml doses of ozone was applied for 20 minute to venous blood samples obtained from 10 healthy male volunteers. Erythrocyte aggregation, deformability were measured by an ektacytometer. Total oxidant status, total antioxidant status were measured via a commercial kit. The oxidative stress index was calculated., Results: Ozone at 10 and 50μg/ml doses did not alter erythrocyte aggregation. 50μg/ml ozone increased red blood cell (RBC) deformability measured at 0.53 Pa. Compared with the Control value, there was a significant increase in TOS, TAS for the doses of 10 and 50μg/ml. The increase in TAS was found to be more significant at 10μg/ml dose. The most obvious increase in OSI value was observed at 50μg/ml., Conclusion: Our results demonstrate that although 10μg/ml ozone has no effect on hemorheology, 50μg/ml ozone concentration has positive effects on RBC deformability, thus circulation at 0.53 Pa corresponding to the shear stress encountered during venous circulation.

Background: The Nordic hamstring exercise (NHE) has been proven to be an effective preventive technique for hamstring injuries. Hemorheological parameters (erythrocyte deformability and aggregation) play a critical role in exercise influencing oxygenation. Although previous studies presented hemorheological alterations induced by different types of exercise, changes in red blood cell (RBC) deformability and aggregation following NHE remain unknown. Present study was designed to explore possible alterations in hemorheological and oxidative parameters after an acute bout of NHE., Methods: 10 healthy, male, active students (mean age 19.9±0.23, BMI: 21.56±0.54) participated to the study. They performed a single session of seven-repetitions of NHE followed by a familiarisation period. Blood samples were obtained before and immediately after the exercise from the antecubital vein. Hemorheological parameters were measured by an ektacytometer., Results: NHE did not change deformability, hematocrit and oxidative stress but, increased RBC aggregation index (AI, p = 0.011) and decreased RBC aggregation half time (t½, p = 0.009)., Conclusions: Our results suggest that, increased RBC aggregation following an acute bout of NHE may result in increased plasma skimming and thus ease the flow of blood.

In a number of human diseases such as diabetes mellitus and sickle cell anemia, variations in mechanical properties of red blood cells (RBCs) occur and cause reduced deformability. Investigating the behavior of such abnormal, hardened RBCs in microcapillary flow is of prime importance because of their effects on oxygen transport process. In the present paper, dynamic response of a RBC to a microcapillary flow is numerically studied at steady and transient conditions, considering the effect of essential parameters including RBC deformability, its initial orientation, velocity, and flow pressure gradient. Simulations are performed using a three-dimensional hybrid method, combining lattice Boltzmann method for plasma flow, finite element method for RBC membrane analysis, and immersed boundary method for their interaction. Quantitative and qualitative validations with the experimental data for different RBC velocities verify the accuracy of applied numerical method. Apart from the initial orientation, RBC experiences a complex shape deformation in which the biconcave discoid shape changes to a parachute-like shape. While deformation index of RBC does not change considerably with RBC deformability at steady state condition, it plays an important role in its shape evolution under transient condition. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

Even though exercise hemorheology at hypoxic condition has been considered as a good tool to understand clinical hemorheology, there have been limited studies reported. Previous researches showed that hemorheological variables are closely correlated with oxygen delivery capacity during exercise. The present study investigated hypoxic responses including RBC deformability and aggregation, metabolic parameters and complete blood cell counts at various hypoxic conditions during cycling exercise and recovery. Eleven Korean healthy male subjects performed submaximal bike exercise at sea level (20.9% O2) and under various hypoxic conditions (16.5% O2, 14.5% O2, 12.8% O2, and 11.2% O2) in a random order. The submaximal bike exercise intensity of the subjects was 70% maximum heart rate at sea level. All variables were measured at rest, during exercise and recovery 30-minute, respectively. As oxygen partial pressure decreased, arterial blood oxygen saturation decreased but oxygen uptake did not change much. Heart rate and lactate concentration during exercise increased when oxygen partial pressure is less than or equal to 14.5% O2 condition. Red blood cell (RBC) counts, hemoglobin counts, and hematocrit level were not apparently altered with hypoxic conditions. RBC deformability showed significant alterations at 11.2% O2 conditions compared with other hypoxic conditions during exercise or recovery, except at 10 minutes recovery. However, decreases in oxygen partial pressure did not affect red blood cell aggregation. Therefore, we conclude that alterations in RBC deformability may reduce aerobic capabilities at hypoxic condition.

Background: Postmenopausal women often develop hemorheological disorders which may affect the systemic blood circulation and present a cardiovascular risk factor., Objective: We evaluated effects of secoisolariciresinol (SECO), a phytoestrogen, on hemorheological parameters and lipid peroxidation in a model of the age-related and/or surgical menopause induced by ovariectomy in rats., Methods: Arterial blood was sampled from sham-operated female rats, ovariectomized rats (OVX), and OVX treated with SECO (OVXSECO) (20 mg/kg/day intragastrically for two weeks). Plasma estrogen concentration and the following hemorheological parameters were measured: RBC aggregation (half-time of aggregation, T1/2; amplitude of aggregation, AMP; aggregation index, AI), RBC deformability (elongation index, EI), whole blood viscosity at the shear rate of 3-300 s-1, plasma viscosity, hematocrit, plasma fibrinogen. Lipid peroxidation was evaluated by measuring conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in plasma., Results: Ovariectomy in rats caused a 60% decrease in plasma estrogen level and triggered the development of macro- and microhemorheological abnormalities. Blood viscosity increased by 12-31%, RBC elongation index reduced by 16-28%, and T1/2 and AI increased by 35% and 29% respectively. The increase in blood viscosity correlated predominantly with reduced RBC deformability. Plasma CD and TBARS were elevated by 47% and 104% respectively. SECO therapy for OVX rats reduced blood viscosity by 9-18% and T1/2 by 32%, and increased EI by 4-17%. SECO therapy disrupted the correlation between blood viscosity and RBC deformability. Lipid peroxidation was significantly inhibited, as shown by the reduction in CD and TBARS plasma concentrations by 89% and 70% respectively. SECO did not affect plasma viscosity, estrogen or fibrinogen levels., Conclusions: SECO treatment for OVX rats improves blood macro- and microrheological parameters, possibly through antioxidant protection of RBC.

Microvascular circulation plays a vital role in regulating physiological functions, such as vascular resistance, and maintaining organ health. Pathologies such as hypertension, diabetes, or hematologic diseases affect the microcirculation posing a significant risk to human health. The retinal vasculature provides a unique window for non-invasive visualisation of the human circulation in vivo and retinal vascular image analysis has been established to predict the development of both clinical and subclinical cardiovascular, metabolic, renal and retinal disease in epidemiologic studies. Blood viscosity which was otherwise thought to play a negligible role in determining blood flow based on Poiseuille's law up to the 1970s has now been shown to play an equally if not a more important role in controlling microcirculation and quantifying blood flow. Understanding the hemodynamics/rheology of the microcirculation and its changes in diseased states remains a challenging task; this is due to the particulate nature of blood, the mechanical properties of the cells (such as deformability and aggregability) and the complex architecture of the microvasculature. In our review, we have tried to postulate a possible role of red blood cell (RBC) biomechanical properties and laid down future framework for research related to hemorrheological aspects of blood in patients with retinal vascular disorders., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Simple Summary: SARS-CoV-2 alters the properties of oxygen-carrying red blood cells (RBCs) through a possible deterioration of hemorheological properties, such as aggregation and deformability. However, long-term changes in these properties and a possible association with morphological abnormalities remain unknown. Therefore, this study aims to investigate changes in the above-mentioned RBC properties in Long-COVID (LC). Venous blood was collected from n = 30 diagnosed LC and n = 30 non-Long-COVID controls (non-LC). Hematological parameters were measured, as well as the aggregation, deformability, and morphology of the RBCs and the mechanical sensitivity index (MS), which reflects the functional capacity of RBCs to deform. The results indicate that hematological parameters were not altered in LC. However, LC showed higher overall aggregation parameters. RBC deformability was higher in LC compared to non-LC; however, MS was limited in this group. LC showed a higher percentage of RBCs with abnormal shapes, which was related to MS and to fatigue, which is considered the leading symptom of LC. It is concluded that the symptoms of LC and changes in the blood flow determining the properties of RBCs are related to the morphological changes in RBCs. Future studies should investigate the underlying causes in order to develop appropriate therapies for this relatively new disease. Background: SARS-CoV-2 infection adversely affects rheological parameters, particularly red blood cell (RBC) aggregation and deformability, but whether these changes persist in patients suffering from Long-COVID (LC) and whether these changes are related to RBC morphology remain unknown. Methods: Venous blood was collected from n = 30 diagnosed LC patients and n = 30 non-LC controls and RBC deformability, RBC aggregation, and hematological parameters were measured. In addition, RBCs were examined microscopically for morphological abnormalities. The mechanical sensitivity index (MS) was assessed in n = 15 LC and n = 15 non-LC samples. Results: Hematological parameters did not differ between the groups. However, LC showed higher aggregation-related parameters. Although RBC deformability was higher in LC, MS, reflecting the functional capacity to deform, was limited in this group. RBCs from LC showed significantly more morphological abnormalities. The extent of morphological abnormalities correlated with MS and the FACIT-Fatigue score of the LC patients. Conclusion: RBCs from LC show a high degree of morphological abnormalities, which might limit the blood flow determining RBC properties and also be related to fatigue symptomatology in LC. Approaches are now needed to understand the underlying cause of these alterations and to ameliorate these permanent changes. [ABSTRACT FROM AUTHOR]

Background: This study investigated the effects of 12-week resistance training on body composition, blood pressure, blood lipid levels, muscle cross-sectional area (CSA), isokinetic muscle function, and hemorheological properties in middle-aged obese women. Methods: Twenty-eight obese women with a mean age of 50.79 ± 5.80 years were randomly assigned to the control (CON, n = 13) or experimental (EXP, n = 15) group. The EXP group underwent a resistance training program composed of warm-up, main resistance exercise (deadlift, barbell squat, seated leg extension, and lying leg curl, bench press, preacher bench biceps curl, barbell rowing, and dumbbell shoulder press), and cool-down. The resistance exercise consisted of three sets of 8-10 repetitions (reps) performed with 70-80% of 1-rep maximum, and reps and sets were increased every 3 weeks. The training frequency was 80 min, 3 days per week for 12 weeks. The CON group maintained their daily lifestyle without training. All participants underwent measurements of body composition (weight, body mass index, lean body mass, fat mass, and % body fat), blood pressure (systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse pressure), blood lipid levels (triglycerides, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol), CSA of the muscles (quadriceps, hamstring, and total thigh muscle), isokinetic muscle function (peak torque [PT], relative PT, mean power, and total work [TW]), and hemorheological properties (erythrocyte deformability and aggregation) before and after 12 weeks of training. Results: The EXP group showed a significant improved muscle function, including PT (p < 0.001), relative PT (p < 0.001) in extension 60°/s, TW (p < 0.001) in extension 180°/s, and TW (p = 0.018) in flexion 180°/s. Regarding hemorheological properties, the EXP group showed significant improvement in erythrocyte aggregation (p < 0.001) and deformability (p < 0.001). Conclusions: The present study verified that our resistance training program resulted in greater muscle function, decreased fat mass, and improved hemorheological properties. Clinical Trial Registration: This study was registered with cris.nih.go.kr (No. KCT0007412). [ABSTRACT FROM AUTHOR]

Hematological and hemorheological parameters are known to be altered in COVID-19; however, the value of combined monitoring in order to deduce disease severity is only scarcely examined. A total of 44 acute SARS-CoV-2-infected patients (aCOV) and 44 age-matched healthy controls (Con) were included. Blood of aCOV was sampled at admission (T0), and at day 2 (T2), day 5 (T5), day 10 (T10), and day 30 (T30) while blood of Con was only sampled once. Inter- and intra-group differences were calculated for hematological and hemorheological parameters. Except for mean cellular volume and mean cellular hemoglobin, all blood cell parameters were significantly different between aCOV and Con. During the acute disease state (T0–T5), hematological and hemorheological parameters were highly altered in aCOV; in particular, anemic conditions and increased immune cell response/inflammation, oxidative/nitrosative stress, decreased deformability, as well as increased aggregation, were observed. During treatment and convalescence until T30, almost all abnormal values of aCOV improved towards Con values. During the acute state of the COVID-19 disease, the hematological, as well as the hemorheological system, show fast and potentially pathological changes that might contribute to the progression of the disease, but changes appear to be largely reversible after four weeks. Measuring RBC deformability and aggregation, as well as oxidative stress induction, may be helpful in monitoring critically ill COVID-19 patients. [ABSTRACT FROM AUTHOR]

Patients with Fontan circulation are particularly dependent on low pulmonary vascular resistance because their lungs are passively perfused. Hypoxia drives pulmonary vasoconstriction; thus, red blood cell (RBC) deformability and stability of hematological parameters might be of particular importance, because alterations during hypoxia might further influence circulation. This study aimed to measure respective parameters in patients with Fontan circulation exposed to normobaric hypoxia. A total of 18 patients with Fontan circulation (16 to 38 years) were exposed to normobaric hypoxia (15.2% ambient oxygen). Blood samples were taken in normoxia, after 24 h in hypoxia, and 60 min after return to normoxia. Blood count, RBC age distribution, EPO, RBC deformability, marker of RBC nitric oxide, oxidative state, and RBC ATP were measured. Hypoxia increased oxidative stress in RBC, but without affecting RBC deformability. RBC age distribution remained unaffected, although EPO concentrations increased, followed by a rise in reticulocyte count at an already high hematocrit. NO metabolism was not affected by hypoxia. Modest normobaric hypoxia for 24 h did not impair RBC deformability in patients with Fontan circulation; however, the oxidative system seemed to be stressed. Given the high baseline Hct in these patients, hypoxia-induced erythropoiesis could adversely affect rheology with more prolonged hypoxia exposure. [ABSTRACT FROM AUTHOR]

Patients with Fontan circulation are particularly dependent on low pulmonary vascular resistance because their lungs are passively perfused. Hypoxia drives pulmonary vasoconstriction; thus, red blood cell (RBC) deformability and stability of hematological parameters might be of particular importance, because alterations during hypoxia might further influence circulation. This study aimed to measure respective parameters in patients with Fontan circulation exposed to normobaric hypoxia. A total of 18 patients with Fontan circulation (16 to 38 years) were exposed to normobaric hypoxia (15.2% ambient oxygen). Blood samples were taken in normoxia, after 24 h in hypoxia, and 60 min after return to normoxia. Blood count, RBC age distribution, EPO, RBC deformability, marker of RBC nitric oxide, oxidative state, and RBC ATP were measured. Hypoxia increased oxidative stress in RBC, but without affecting RBC deformability. RBC age distribution remained unaffected, although EPO concentrations increased, followed by a rise in reticulocyte count at an already high hematocrit. NO metabolism was not affected by hypoxia. Modest normobaric hypoxia for 24 h did not impair RBC deformability in patients with Fontan circulation; however, the oxidative system seemed to be stressed. Given the high baseline Hct in these patients, hypoxia-induced erythropoiesis could adversely affect rheology with more prolonged hypoxia exposure.

Background: Individuals with hereditary hemochromatosis (HH) receive frequent blood withdrawals (ie, venesections) as part of their primary treatment to assist in normalizing blood iron levels. It remains unclear whether this source of blood is suitable for use in blood product development, as current data indicate that red blood cell (RBC) deformability, both before and after shear stress exposure, is impaired in individuals with HH, relative to healthy controls. Given that venesection therapy is known to significantly reduce circulating iron levels in individuals with HH, the current study examined whether venesection therapy is effective at improving RBC mechanical properties, both before and after shear stress exposure, in individuals with HH. Study Design and Methods: Blood samples were initially collected from untreated HH patients (age, 61 ± 9 years; 14% female) undergoing their first venesection, and then again during their second (approx. 9 weeks later) and third (approx. 16 weeks later) venesections. RBC deformability was measured at each time point with a commercial ektacytometer. Moreover, to determine cell responses to mechanical stimuli, the mechanical sensitivity of blood samples was determined at each time point. Results: The salient findings indicate that venesection therapy used for managing plasma ferritin concentration significantly improves the cellular deformability of RBC in individuals with HH. Further, the sensitivity of RBC to supraphysiological mechanical stress is decreased (ie, improved) in a dose‐response fashion with routine venesection. Conclusion: While cellular mechanics of RBC from individuals with HH are impaired when untreated, venesection therapy significantly improves cellular properties of RBC, supporting the use of venesections in blood product development from individuals with well‐managed HH. [ABSTRACT FROM AUTHOR]

Blood exposure to supraphysiological shear stress within mechanical circulatory support is suspected of reducing red blood cell (RBC) deformability and being primal in the pathogenesis of several secondary complications. No prior works have explored RBC dynamics with the resolution required to determine shear elastic modulus, and/or cell capillary velocity, following exposure to mechanical stresses. Healthy RBCs were exposed to 0, 5, 50, and 100 Pa in a Couette shearing system. For comparison, blood was also exposed to heat treatment—a method that predictably increases RBC rigidity. Shear modulus assessment required aspiration of single RBCs through narrow micropipettes at known suction force. Cell transit velocities were measured within microchannels in regions of fully developed flow. Supraphysiological shear stress increased the elastic shear modulus by 39% and 69% following exposure to 50 and 100Pa, respectively. Cell transit velocity, however, did not change following shear, with concurrent decreases in cell volume likely nullifying increased shear modulus‐friction interactions. Differences observed were consistent with our internal control (heat treatment), supporting that cell mechanics are significantly impaired following supraphysiological‐sublethal shear exposure. Given mechanical circulatory support operates at shear stresses consistent with the present study, it is plausible that these devices induce fundamental impairment to the material properties of RBCs. [ABSTRACT FROM AUTHOR]

Red blood cells (RBC), the primary component of whole blood, play an essential role in maintaining blood fluidity and mass transport throughout the human body. RBC deformability is an important property that indicates RBC quality and diseases. Among the techniques for RBC deformability measurements, the hydrodynamic image-based approach represents the most advanced method. However, RBC have a complex shape and high deformability, they display a wide range of shapes during the transition in microvessels, making it a challenge for deformation measurement. Therefore, we propose an i mage-based R BC deformab i lity assessment via a s hape-classification approach (IRIS) to solve this issue, where six shapes are identified by deep learning technique. Then, the deformations of RBC stiffened by different glutaraldehyde (GA) concentrations are measured and compared. The results elucidate that IRIS is able to sensitively distinguish 0.001% GA treated RBC from the control. Moreover, it is superior to two-shape classification or zero-shape classification in terms of sensitivity for deformability quantification. IRIS demonstrates an improved sensitivity for deformability analysis, high automaticity and unprecedented large data volume by applying deep learning method, it has a vast potential to benefit the hemorheology field as a powerful tool for early detection and diagnosis of RBC related diseases. • Image-based deformability assessment of red blood cells (RBC) in microfluidics. • Identification of six RBC deformation shapes by deep learning. • Significant improvement of deformability quantification via shape-classification approach. • A scoring scheme proposed for the evaluation of RBC deformability in potential clinical applications. [ABSTRACT FROM AUTHOR]

Even though exercise hemorheology at hypoxic condition has been considered as a good tool to understand clinical hemorheology, there have been limited studies reported. Previous researches showed that hemorheological variables are closely correlated with oxygen delivery capacity during exercise. The present study investigated hypoxic responses including RBC deformability and aggregation, metabolic parameters and complete blood cell counts at various hypoxic conditions during cycling exercise and recovery. Eleven Korean healthy male subjects performed submaximal bike exercise at sea level (20.9% O2) and under various hypoxic conditions (16.5% O2, 14.5% O2, 12.8% O2, and 11.2% O2) in a random order. The submaximal bike exercise intensity of the subjects was 70% maximum heart rate at sea level. All variables were measured at rest, during exercise and recovery 30-minute, respectively. As oxygen partial pressure decreased, arterial blood oxygen saturation decreased but oxygen uptake did not change much. Heart rate and lactate concentration during exercise increased when oxygen partial pressure is less than or equal to 14.5% O2 condition. Red blood cell (RBC) counts, hemoglobin counts, and hematocrit level were not apparently altered with hypoxic conditions. RBC deformability showed significant alterations at 11.2% O2 conditions compared with other hypoxic conditions during exercise or recovery, except at 10 minutes recovery. However, decreases in oxygen partial pressure did not affect red blood cell aggregation. Therefore, we conclude that alterations in RBC deformability may reduce aerobic capabilities at hypoxic condition. [ABSTRACT FROM AUTHOR]

Significant progress has been made over the years on the topic of hemorheology, not only in terms of the development of more accurate and sophisticated techniques, but also in terms of understanding the phenomena associated with blood components, their interactions and impact upon blood properties. The rheological properties of blood are strongly dependent on the interactions and mechanical properties of red blood cells, and a variation of these properties can bring further insight into the human health state and can be an important parameter in clinical diagnosis. In this article, we provide both a reference for hemorheological research and a resource regarding the fundamental concepts in hemorheology. This review is aimed at those starting in the field of hemodynamics, where blood rheology plays a significant role, but also at those in search of the most up-to-date findings (both qualitative and quantitative) in hemorheological measurements and novel techniques used in this context, including technical advances under more extreme conditions such as in large amplitude oscillatory shear flow or under extensional flow, which impose large deformations comparable to those found in the microcirculatory system and in diseased vessels. Given the impressive rate of increase in the available knowledge on blood flow, this review is also intended to identify areas where current knowledge is still incomplete, and which have the potential for new, exciting and useful research. We also discuss the most important parameters that can lead to an alteration of blood rheology, and which as a consequence can have a significant impact on the normal physiological behavior of blood. [ABSTRACT FROM AUTHOR]

Rheohaemapheresis aims to normalize major rheological parameters and is used to treat patients with dry age-related macular degeneration (AMD). While effective, this approach is invasive and requires specially trained personnel. Therefore, the search for novel effective compounds with hemorheological properties that can be taken orally to treat AMD is justified. The use of a robust rodent model of AMD with high blood viscosity is crucial to test the efficacy of potential hemorheological drugs to treat this disease. The objective of this study was to investigate whether OXYS rats, generally used as an animal model of AMD, have hyperviscosity syndrome. The results of this study show that blood viscosity in OXYS rats at low (3-10 s-1) and high (45-300 s-1) shear rates were 14-20% and 7-10% higher than in Wistar rats, while hematocrit and plasma viscosity were not different. Red blood cells (RBCs) in OXYS rats were more prone to aggregation as shown by 39% shorter half-time than in Wistar rats. RBCs were also more rigid in OXYS than in Wistar rats as shown by 21-33% lower index of elongation at the shear stress of 1-7 Pa. These data indicate that OXYS rats have hyperviscosity syndrome as the result of abnormal RBC deformability and aggregation. We propose to use OXYS rats as an animal model for preclinical studies to test compounds with hemorheological properties aimed to treat AMD. [ABSTRACT FROM AUTHOR]

• Blood microflows in a micropillar array are studied. • Healthy and hardened red blood cell (RBCs) suspensions are examined and their flows compared. • The velocity field is resolved by micro Particle Image Velocimetry techniques. • RBC distributions are inferred from image intensity. • Impact of RBC deformability more evident on haematocrit distributions rather than velocity field. Red blood cell (RBC) deformability is an important haemorheological factor; it is impaired in many pathologies leading to microvascular complications. Several microfluidic platforms have been utilized to examine the role of deformability in RBC flows but their geometries tend to be simplified. In the present study, we extend our previous work on healthy RBC flows in micropillar arrays [1] to probe the effect of impaired RBC deformability on the velocity and haematocrit distributions in microscale RBC flows. Healthy and artificially hardened RBC suspensions at 25% haematocrit were perfused through the micropillar array at various flow rates and imaged. RBC velocities were determined by Particle Image Velocimetry (PIV) and haematocrit distributions were inferred from the image intensity distributions. The pillars divide the flow into two distinct RBC streams separated by a cell-depleted region along the centreline and in the rear/front stagnation points. RBC deformability was not found to significantly affect the velocity distributions; the shape of the velocity profiles in the interstitial space remained the same for healthy and hardened RBCs. Time-averaged and spatiotemporal intensity distributions, however, reveal differences in the dynamics and local distributions of healthy and hardened cells; hardened cells appear to enter the cell-depleted regions more frequently and their interstitial distributions are more uniform. The study highlights the importance of local RBC distributions and the impact of RBC deformability on cell transport in complex microscale flows. [ABSTRACT FROM AUTHOR]

Altitude training is frequently used by athletes to improve sea-level performance. However, the objective benefits of altitude training are controversial. This study aimed to investigate the possible alterations in hemorheological parameters in response to altitude training. Sprague Dawley rats, were divided into 6 groups: live low-train low (LLTL), live high-train high (LHTH), live high-train low (LHTL) and their controls live high and low (LHALC), live high (LHC), live low (LLC). LHC and LHTH groups were exposed to hypoxia (15% O2, altitudes of 3000 m), 4 weeks. LHALC and LHTL were exposed to 12 hours hypoxia/normoxia per day, 4 weeks. Hypoxia was maintained by a hypoxic tent. The training protocol corresponded to 60-70% of maximal exercise capacity. Rats of training groups ran on treadmill for 20-30 min/day, 4 days/week, 4 weeks. Erythrocyte deformability of LHC group was increased compared to LHALC and LLC. Deformability of LHTH group was higher than LHALC and LLTL groups. No statistically significant alteration in erythrocyte aggregation parameters was observed. There were no significant relationships between RBC deformability and exercise performance. The results of this study show that, living (LHC) and training at altitude (LHTH) seems more advantageous in hemorheological point of view. [ABSTRACT FROM AUTHOR]

Abstract: Background: Hemorrhagic shock is associated with severe rheological abnormalities. We hypothesized that in the setting of hemorrhagic shock, resuscitation can alter hemorheological characteristics dramatically, and different fluids cause different effects. The aim of this study was to investigate whether the type of fluid administered has an impact on hemorheological characteristics at the early stage of resuscitation in a rodent model of hemorrhagic shock. Methods: Animals were randomized into five groups: (1) sham hemorrhage (SHAM); (2) shock and sham resuscitation (SHOCK); (3) shock and resuscitation with normal saline 32ml/kg (NS); (4) shock and resuscitation with 7.5% hypertonic saline 4ml/kg (HS); (5) shock and resuscitation with 7.5% hypertonic saline/6% Dextran 70 4ml/kg (HSD). Hemorheological characteristics were measured at 60min after resuscitation. Results: Results showed that NS resuscitation deteriorated red blood cell (RBC) deformability compared with the SHOCK group. The HS group showed improved RBC deformability compared with the NS group, although the differences were not statistically significant. There were significant improvements of RBC deformability at all shear rates in the HSD group compared with the NS group. Whole blood and plasma viscosities decreased significantly in the SHOCK group compared with the SHAM group. At shear rates of 60 and 150s−1, the NS group decreased whole blood viscosity compared with the SHOCK group. The HSD group showed elevated plasma viscosity compared with the SHOCK, NS and HS groups. Conclusion: These results suggested that at the early stage of hemorrhagic shock resuscitation, hypertonic–hyperoncotic resuscitation could improve RBC deformability compared with isotonic crystalloid resuscitation. Dextran 70 could elevate plasma viscosity to nearly baseline level. These effects of hypertonic–hyperoncotic resuscitation could be beneficial to maintain microcirculation. [Copyright &y& Elsevier]

The hemorheological behavior pre‐ and post‐freezing and tissue survival area (TSA) of frostbitten hind feet in cold‐acclimated rats (group CA) and the control (group C) were observed in order to go further into the mechanism of cold acclimation. The results indicated that blood viscosity and RBC aggregation tendency were lowered and RBC deformability improved obviously in CA rats as compared with those in group C (p<0.01). After the rats' hind feet were frozen, the hemorheological behavior in both group CA and C rats was changed abnormally and the changes were less serious in CA rats than those in C rats. The TSA of CA rats was much larger than that of C rats (p<0.01). The aforesaid results revealed that after rats were acclimated to cold, their resistance to freezing increased and their adaptive changes in hemorheological behavior occurred. The extent of abnormal changes in hemorheological behavior caused by freezing was reduced in CA rats, therefore the disorder microcirculation could be improved. These changes were beneficial to the frostbitten tissue to recovering and healing. So it is considered that in CA rats, the adaptive change in hemorheological behavior is one of the cause enhancing resistance to frostbite. [ABSTRACT FROM AUTHOR]