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Microcirculation (New York, N.Y. : 1994) Nov 2010Blood is modeled as a suspension of red blood cells using the dissipative particle dynamics method. The red blood cell membrane is coarse-grained for efficient...
Blood is modeled as a suspension of red blood cells using the dissipative particle dynamics method. The red blood cell membrane is coarse-grained for efficient simulations of multiple cells, yet accurately describes its viscoelastic properties. Blood flow in microtubes ranging from 10 to 40 μm in diameter is simulated in three dimensions for values of hematocrit in the range of 0.15-0.45 and carefully compared with available experimental data. Velocity profiles for different hematocrit values show an increase in bluntness with an increase in hematocrit. Red blood cell center-of-mass distributions demonstrate cell migration away from the wall to the tube center. This results in the formation of a cell-free layer next to the tube wall corresponding to the experimentally observed Fahraeus and Fahraeus-Lindqvist effects. The predicted cell-free layer widths are in agreement with those found in in vitro experiments; the results are also in qualitative agreement with in vivo experiments. However, additional features have to be taken into account for simulating microvascular flow, e.g., the endothelial glycocalyx. The developed model is able to capture blood flow properties and provides a computational framework at the mesoscopic level for obtaining realistic predictions of blood flow in microcirculation under normal and pathological conditions.
Topics: Blood Flow Velocity; Blood Viscosity; Elasticity; Erythrocyte Membrane; Erythrocytes; Hematocrit; Humans; In Vitro Techniques; Microcirculation; Microvessels; Models, Cardiovascular; Plasma
PubMed: 21044216
DOI: 10.1111/j.1549-8719.2010.00056.x -
Journal of the American College of... May 2019
Topics: Blood Pressure; Blood Viscosity; Disease Management; Female; Humans; Hypertension, Pulmonary; Male; Middle Aged; Vascular Resistance
PubMed: 31118156
DOI: 10.1016/j.jacc.2019.02.066 -
Annals of Oncology : Official Journal... Jan 2007
Review
Topics: Blood Viscosity; Brain Neoplasms; Disseminated Intravascular Coagulation; Emergencies; Hematologic Diseases; Hemorrhage; Humans; Hypercalcemia; Lymphoma; Renal Insufficiency; Spinal Cord Compression; Superior Vena Cava Syndrome; Tumor Lysis Syndrome
PubMed: 17311822
DOI: 10.1093/annonc/mdl450 -
Sensors (Basel, Switzerland) Dec 2022The biomechanical properties of blood have been used to detect haematological diseases and disorders. The simultaneous measurement of multiple haemorheological...
The biomechanical properties of blood have been used to detect haematological diseases and disorders. The simultaneous measurement of multiple haemorheological properties has been considered an important aspect for separating the individual contributions of red blood cells (RBCs) and plasma. In this study, three haemorheological properties (viscosity, time constant, and RBC aggregation) were obtained by analysing blood flow, which was set to a square-wave profile (steady and transient flow). Based on a simplified differential equation derived using a discrete circuit model, the time constant for viscoelasticity was obtained by solving the governing equation rather than using the curve-fitting technique. The time constant (λ) varies linearly with respect to the interface in the coflowing channel (β). Two parameters (i.e., average value: <λ>, linear slope: dλdβ) were newly suggested to effectively represent linearly varying time constant. <λ> exhibited more consistent results than dλdβ. To detect variations in the haematocrit in blood, we observed that the blood viscosity (i.e., steady flow) is better than the time constant (i.e., transient flow). The blood viscosity and time constant exhibited significant differences for the hardened RBCs. The present method was then successfully employed to detect continuously varying haematocrit resulting from RBC sedimentation in a driving syringe. The present method can consistently detect variations in blood in terms of the three haemorheological properties.
Topics: Blood Viscosity; Erythrocyte Aggregation; Hematocrit; Erythrocytes; Hemodynamics
PubMed: 36617006
DOI: 10.3390/s23010408 -
Journal of Clinical Pathology May 1980
Review
Topics: Anticoagulants; Blood Sedimentation; Blood Viscosity; Capillaries; Erythrocyte Membrane; Hematocrit; Hematologic Diseases; Hemodilution; Humans; Plasmapheresis; Rheology; Temperature; Vascular Diseases
PubMed: 6995492
DOI: 10.1136/jcp.33.5.417 -
Clinical Hemorheology and... 2016We investigated to what extent a prediction of the 'ideal' hematocrit based on individual hemorheological profile with an equation of viscosity is relevant in trained...
We investigated to what extent a prediction of the 'ideal' hematocrit based on individual hemorheological profile with an equation of viscosity is relevant in trained athletes, and how the agreement between theoretical and actual values is modified by changes in training volume and performance. Elite soccer players (national level: 18-32 yr, weight 61-83 kg, body mass index 20.9-25.8 kg/m2) were seen twice at one year interval. Hemorheologic parameters were measured with the MT90 viscometer and the Myrenne aggregometer the theoretical bell-shaped curve of hematocrit/viscosity ratio as a function of hematocrit was reconstructed with Quemada's equation using actual plasma viscosity and red cell rigidity to predict hematocrit/viscosity at various hematocrit levels. RBC aggregation is correlated at baseline with fat mass (M1 = 0.552 p < 0.02) and changes in aggregation are related to changes in fat mass (M = 0.652, p < 0.05; M1 = 0.647, p < 0.05). Predicted and actual hematocrit are correlated (r = 0.644, p < 0.05) but exhibit discrepancies (mean difference -1% range [3.24 to 1.24]) and those discrepancies are inversely correlated to the level of predicted hematocrit (r = -0.912, p < 0.01), to systolic blood pressure (r = -0.626, p < 0.05), and to the overtraining score (r = -0.693, p < 0.05). After one year changes in hematocrit are a close reflect of the change in training volume (r = -0.877, p < 0.01) but are not correlated to fitness changes. Therefore in these athletes i) systemic hematocrit is close to its predicted 'ideal value", suggesting the accuracy of the prediction; ii) red cell aggregation is correlated to fat mass even in nonobese subjects; iii) hematocrit is lower than predicted by the model when markers of sympathetic tone (systolic blood pressure, overtraining score) are increased; iv) weekly training volume appears the main determinant of the reduction of hematocrit.
Topics: Adolescent; Adult; Athletes; Blood Viscosity; Erythrocyte Aggregation; Female; Follow-Up Studies; Hematocrit; Hemorheology; Humans; Male; Soccer
PubMed: 27767967
DOI: 10.3233/CH-168014 -
Clinical Hemorheology and... 2015Renal failure is a disease with accelerated atherosclerosis beginning with endothelial cell dysfunction. Factors affecting endothelial cell dysfunction include whole...
BACKGROUND
Renal failure is a disease with accelerated atherosclerosis beginning with endothelial cell dysfunction. Factors affecting endothelial cell dysfunction include whole blood viscosity (WBV) and asymmetric dimethylarginine (ADMA). The relationship in controls and renal failure was determined.
METHODS
51 subjects, 20 controls, 11 renal transplant recipients, 10 chronic kidney disease and 10 end-stage renal disease patients had blood samples drawn for WBV, Hematocrit, and ADMA. WBV was measured at various shear rates from 10 s(-1) to 780 s(-1) at 37 °C. Hematocrit using CritSpin, and ADMA was assayed using an ELISA method. The significance between groups was compared by boxplots and analysis of variance. Linear relationships were shown by regression lines and correlation coefficients.
RESULTS
ADMA was elevated in all groups with renal failure when compared to controls (p < 0.05). Control subjects showed a positive correlation between ADMA and WBV, while those who received a renal transplant had a negative correlation (p < 0.05). The difference in ADMA comparing pre-dialysis to post-dialysis conditions was positive (p < 0.05).
CONCLUSIONS
The positive relationship between WBV and ADMA in controls is a novel finding and allows for comparison with other groups. This relationship is dramatically altered in renal failure.
Topics: Adult; Arginine; Blood Viscosity; Female; Humans; Kidney Failure, Chronic; Male; Risk Factors; Young Adult
PubMed: 24840340
DOI: 10.3233/CH-141843 -
Archives of Disease in Childhood Apr 1970
Topics: Acid-Base Equilibrium; Blood Viscosity; Hematocrit; Humans; Infant, Newborn; Infant, Newborn, Diseases; Polycythemia; Umbilical Cord
PubMed: 5419999
DOI: 10.1136/adc.45.240.273-a -
Transfusion Sep 2017Higher hematocrit increases the oxygen-carrying capacity of blood but also increases blood viscosity, thus decreasing blood flow through the microvasculature and...
BACKGROUND
Higher hematocrit increases the oxygen-carrying capacity of blood but also increases blood viscosity, thus decreasing blood flow through the microvasculature and reducing the oxygen delivery to tissues. Therefore, an optimal value of hematocrit that maximizes tissue oxygenation must exist.
STUDY DESIGN AND METHODS
We used viscometry and an artificial microvascular network device to determine the optimal hematocrit in vitro. Suspensions of fresh red blood cells (RBCs) in plasma, normal saline, or a protein-containing buffer and suspensions of stored red blood cells (at Week 6 of standard hypothermic storage) in plasma with hematocrits ranging from 10 to 80% were evaluated.
RESULTS
For viscometry, optimal hematocrits were 10, 25.2, 31.9, 37.1, and 37.5% for fresh RBCs in plasma at shear rates of 3.2 or less, 11.0, 27.7, 69.5, and 128.5 inverse seconds. For the artificial microvascular network, optimal hematocrits were 51.1, 55.6, 59.2, 60.9, 62.3, and 64.6% for fresh RBCs in plasma and 46.4, 48.1, 54.8, 61.4, 65.7, and 66.5% for stored RBCs in plasma at pressures of 2.5, 5, 10, 20, 40, and 60 cm H O.
CONCLUSION
Although exact optimal hematocrit values may depend on specific microvascular architecture, our results suggest that the optimal hematocrit for oxygen delivery in the microvasculature depends on perfusion pressure. Therefore, anemia in chronic disorders may represent a beneficial physiological response to reduced perfusion pressure resulting from decreased heart function and/or vascular stenosis. Our results may help explain why a therapeutically increasing hematocrit in such conditions with RBC transfusion frequently leads to worse clinical outcomes.
Topics: Anemia; Blood Pressure; Blood Viscosity; Hematocrit; Humans; Microvessels; Models, Cardiovascular; Oxygen; Oxygen Consumption
PubMed: 28681482
DOI: 10.1111/trf.14213 -
Clinical and Applied... 2024The pathogenesis of venous thromboembolism in multiple myeloma is still poorly understood because multiple factors are involved. In particular, the increase in whole... (Observational Study)
Observational Study
The pathogenesis of venous thromboembolism in multiple myeloma is still poorly understood because multiple factors are involved. In particular, the increase in whole blood viscosity has a key role and, therefore, we performed an evaluation of some hemorheological determinants in multiple myeloma patients, putting them in relation to the thrombotic risk, with the aim to evaluate if an alteration of the hemorheological pattern was associated with a higher thrombotic risk. We performed an observational retrospective cohort study with data collected from January 2017 to September 2022. In a group of 190 patients with newly diagnosed multiple myeloma, we have examined the trend of calculated blood viscosity according to the Merrill formula, and we stratified the patients for the thrombotic risk in accordance with the IMWG/NCCN guidelines and with IMPEDE VTE score. Using the thrombotic risk stratification proposed by IMWG/NCCN any variation in calculated blood viscosity is evident, while, with the IMPEDE VTE score, we observed an increase in calculated blood viscosity in patients with "intermediate + high" risk. The calculated blood viscosity is higher in subjects presenting an "intermediate + high" thrombotic risk according to the IMPEDE VTE score. This association could therefore lay the groundwork for further research with the aim to confirm the role of hemorheological pattern in MM-related thrombotic risk.
Topics: Humans; Blood Viscosity; Multiple Myeloma; Retrospective Studies; Risk Factors; Thrombosis; Venous Thromboembolism
PubMed: 38173275
DOI: 10.1177/10760296231222477