Plasma viscosity and cerebral blood flow

2000 ◽  
Vol 279 (4) ◽  
pp. H1949-H1954 ◽  
Author(s):  
Yoshinobu Tomiyama ◽  
Johnny E. Brian ◽  
Michael M. Todd
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Viscosity ◽  
Blood Cells ◽  
Exchange Transfusion ◽  
Ringer Solution ◽  
Plasma Viscosity ◽  
High Flow ◽  
Flow Conditions ◽  
Whole Blood Viscosity

We hypothesized that the response of cerebral blood flow (CBF) to changing viscosity would be dependent on “baseline” CBF, with a greater influence of viscosity during high-flow conditions. Plasma viscosity was adjusted to 1.0 or 3.0 cP in rats by exchange transfusion with red blood cells diluted in lactated Ringer solution or with dextran. Cortical CBF was measured by H2 clearance. Two groups of animals remained normoxic and normocarbic and served as controls. Other groups were made anemic, hypercapnic, or hypoxic to increase CBF. Under baseline conditions before intervention, CBF did not differ between groups and averaged 49.4 ± 10.2 ml · 100 g−1 · min−1 (±SD). In control animals, changing plasma viscosity to 1.0 or 3.0 cP resulted in CBF of 55.9 ± 8.6 and 42.5 ± 12.7 ml · 100 g−1 · min−1, respectively (not significant). During hemodilution, hypercapnia, and hypoxia with a plasma viscosity of 1.0 cP, CBF varied from 98 to 115 ml · 100 g−1 · min−1. When plasma viscosity was 3.0 cP during hemodilution, hypercapnia, and hypoxia, CBF ranged from 56 to 58 ml · 100 g−1 · min−1 and was significantly reduced in each case ( P < 0.05). These results support the hypothesis that viscosity has a greater role in regulation of CBF when CBF is increased. In addition, because CBF more closely followed changes in plasma viscosity (rather than whole blood viscosity), we believe that plasma viscosity may be the more important factor in controlling CBF.

scholarly journals Whole blood viscosity parameters and cerebral blood flow.

Stroke ◽  
1982 ◽  
Vol 13 (3) ◽  
pp. 296-301 ◽  
Author(s):  
J Grotta ◽  
R Ackerman ◽  
J Correia ◽  
G Fallick ◽  
J Chang
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Whole Blood Viscosity

Effect of increased whole blood viscosity on regional blood flows in chronically hypoxemic lambs

1994 ◽  
Vol 267 (2) ◽  
pp. H471-H476
Author(s):  
M. Dalinghaus ◽  
H. Knoester ◽  
J. W. Gratama ◽  
J. Van der Meer ◽  
W. G. Zijlstra ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Oxygen Supply ◽  
Arterial Oxygen ◽  
Organ Blood Flow ◽  
Whole Blood Viscosity ◽  
Blood Flows ◽  
Chronic Hypoxemia

In chronic hypoxemia blood flow and oxygen supply to vital organs are maintained, but to nonvital organs they are decreased. We measured organ blood flows (microspheres) and whole blood viscosity in 10 chronically hypoxemic lambs, with an atrial septal defect and pulmonary stenosis, and in 8 control lambs. Vascular hindrance (resistance/viscosity) was calculated to determine to what extent the effect of increased blood viscosity on organ blood flow was compensated for by a decrease in vascular tone. Arterial oxygen saturation was decreased (68 +/- 10 vs. 91 +/- 3%, P < 0.001), and both hemoglobin concentration (145 +/- 10 vs. 109 +/- 9 g/l, P < 0.05) and blood viscosity (4.4 +/- 0.6 vs. 3.6 +/- 0.6 mPa.s, P < 0.05) were increased in hypoxemic lambs. Systemic blood flow, oxygen supply, oxygen uptake, and blood pressures were not significantly different between hypoxemic and control lambs. Myocardial and cerebral blood flow was maintained in hypoxemic lambs, whereas renal, gastrointestinal, splenic, and thyroidal blood flows were at least 30% lower. Vascular hindrance was significantly decreased in the myocardium and tended to be lower in the brain of hypoxemic lambs, but in all other organs it was similar to that in control lambs. It is concluded that blood flow is redistributed in chronic hypoxemia in lambs; myocardial and cerebral blood flow is maintained, whereas blood flow to splanchnic organs, the kidneys, and the thyroids is decreased. The decreased blood flow to organs is a consequence of the increased whole blood viscosity.

Whole blood viscosity and cerebral blood flow velocities in obese hypertensive or obese normotensive adolescents

2018 ◽  
Vol 31 (3) ◽  
pp. 275-281 ◽  
Author(s):  
Meltem Akcaboy ◽  
Bijen Nazliel ◽  
Tayfun Goktas ◽  
Serdar Kula ◽  
Bülent Celik ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebral Artery ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Artery Blood Flow ◽  
Whole Blood Viscosity ◽  
Blood Flow Velocities ◽  
Flow Velocities

AbstractBackground:Obesity affects all major organ systems and leads to increased morbidity and mortality. Whole blood viscosity is an important independent regulator of cerebral blood flow. The aim of the present study was to evaluate the effect of whole blood viscosity on cerebral artery blood flow velocities using transcranial Doppler ultrasound in pediatric patients with obesity compared to healthy controls and analyze the effect of whole blood viscosity and blood pressure status to the cerebral artery blood flow velocities.Methods:Sixty patients with obesity diagnosed according to their body mass index (BMI) percentiles aged 13–18 years old were prospectively enrolled. They were grouped as hypertensive or normotensive according to their ambulatory blood pressure monitoring. Whole blood viscosity and middle cerebral artery velocities by transcranial Doppler ultrasound were studied and compared to 20 healthy same aged controls.Results:Whole blood viscosity values in hypertensive (0.0619±0.0077 poise) and normotensive (0.0607±0.0071 poise) groups were higher than controls (0.0616±0.0064 poise), with no significance. Middle cerebral artery blood flow velocities were higher in the obese hypertensive (73.9±15.0 cm/s) and obese normotensive groups (75.2±13.5 cm/s) than controls (66.4±11.5 cm/s), but with no statistical significance.Conclusions:Physiological changes in blood viscosity and changes in blood pressure did not seem to have any direct effect on cerebral blood flow velocities, the reason might be that the cerebral circulation is capable of adaptively modulating itself to changes to maintain a uniform cerebral blood flow.

Role of O2-hemoglobin affinity in the regulation of cerebral blood flow in fetal sheep

1986 ◽  
Vol 251 (1) ◽  
pp. H56-H62 ◽  
Author(s):  
A. A. Rosenberg ◽  
A. P. Harris ◽  
R. C. Koehler ◽  
M. L. Hudak ◽  
R. J. Traystman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Cells ◽  
Exchange Transfusion ◽  
Fetal Sheep ◽  
Sagittal Sinus ◽  
Cerebral O2 Consumption ◽  
O2 Transport ◽  
The Difference

Cerebral blood flow (CBF) and cerebral O2 transport (CBF X arterial O2 content) in the fetal sheep are nearly twice that in the adult, despite similar rates of cerebral O2 utilization. We tested the hypothesis that the difference depends on the increased oxyhemoglobin affinity in the fetus, using P50 (PO2 at which hemoglobin is 50% saturated) as the index of oxyhemoglobin affinity. We studied 18 unanesthetized fetal sheep in utero. In six animals the P50 was raised from 16.6 +/- 1.2 (SD) mmHg to 31.7 +/- 4.7 mmHg by exchange transfusing the fetus with adult sheep red blood cells. We measured CBF (with radioactive microspheres) and the PO2, PCO2, pH, and O2 content in carotid artery and sagittal sinus blood twice at the original P50 and twice after exchange transfusion. Arterial O2 content fell significantly at the higher P50. Since the fall in O2 content was not accompanied by a corresponding rise in CBF, O2 transport fell by 45%. Cerebral O2 consumption (CMRO2) did not change and cannot be implicated in the fall of O2 transport. E (the ratio CMRO2/O2 transport) rose by 77%. Sham exchange transfusions in six fetuses showed that the exchange transfusion procedure itself was not responsible for this alteration. To determine whether the fall in O2 transport and the rise in E was reproducible over a range of arterial O2 contents, a third group of six fetuses was studied. Fetal arterial O2 content varied from 4 to 12 vol%, first at P50 = 17 +/- 1.8 mmHg and again after exchange transfusion at P50 = 29.6 +/- 3.9 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Modeling the Effect of Red Blood Cells Deformability on Blood Flow Conditions in Human Carotid Artery Bifurcation

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Janez Urevc ◽  
Iztok Žun ◽  
Milan Brumen ◽  
Boris Štok
Keyword(s):  
Blood Flow ◽  
Carotid Artery ◽  
Red Blood Cells ◽  
Blood Viscosity ◽  
Blood Cells ◽  
Viscosity Model ◽  
Flow Conditions ◽  
Geometrical Properties ◽  
Carotid Artery Bifurcation ◽  
Human Carotid

The purpose of this work is to predict the effect of impaired red blood cells (RBCs) deformability on blood flow conditions in human carotid artery bifurcation. First, a blood viscosity model is developed that predicts the steady-state blood viscosity as a function of shear rate, plasma viscosity, and mechanical (and geometrical) properties of RBC's. Viscosity model is developed by modifying the well-known Krieger and Dougherty equation for monodisperse suspensions by using the dimensional analysis approach. With the approach, we manage to account for the microscopic properties of RBC's, such as their deformability, in the macroscopic behavior of blood via blood viscosity. In the second part of the paper, the deduced viscosity model is used to numerically predict blood flow conditions in human carotid artery bifurcation. Simulations are performed for different values of RBC's deformability and analyzed by investigating parameters, such as the temporal mean wall shear stress (WSS), oscillatory shear index (OSI), and mean temporal gradient of WSS. The analyses show that the decrease of RBC's deformability decrease the regions of low WSS (i.e., sites known to be prevalent at atherosclerosis-prone regions); increase, in average, the value of WSS along the artery; and decrease the areas of high OSI. These observations provide an insight into the influence of blood's microscopic properties, such as the deformability of RBC's, on hemodynamics in larger arteries and their influence on parameters that are known to play a role in the initiation and progression of atherosclerosis.

scholarly journals Effect of Normalization of Hematocrit on Brain Circulation and Metabolism in Hemodialysis Patients

1999 ◽  
Vol 10 (4) ◽  
pp. 854-863
Author(s):  
GEORGE METRY ◽  
BJÖRN WIKSTRÖM ◽  
SVEN VALIND ◽  
BO SANDHAGEN ◽  
TORBJÖRN LINDE ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Blood Flow ◽  
Brain Tissue ◽  
Blood Viscosity ◽  
Plasma Viscosity ◽  
Emission Tomography ◽  
Whole Blood Viscosity ◽  
Positron Emission ◽  
Healthy Control ◽  
The Brain

Abstract. Full correction of anemia with recombinant human erythropoietin (rhEPO) has been reported to reduce the risk of cardiovascular morbidity and mortality and improve the quality of life in hemodialysis (HD) patients. Effects of normalization of hematocrit on cerebral blood flow and oxygen metabolism were investigated by positron emission tomography. Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction ratio (rOER), and metabolic rate for oxygen (rCMRO2) were measured in seven HD patients before and after correction of anemia and compared with those in six healthy control subjects. In addition, blood rheology before and on rhEPO therapy was measured in HD patients, which included blood viscosity, plasma viscosity, erythrocyte fluidity, and erythrocyte aggregability. The results showed that plasma viscosity was high (1.51 ± 0.19 mPa · s) and erythrocyte fluidity was low (85.8 ± 4.8 Pa-1 · s-1), while whole blood viscosity was within the normal range (3.72 ± 0.38 mPa · s) before rhEPO therapy. After treatment, the hematocrit rose significantly from 29.3 ± 3.3 to 42.4 ± 2.2% (P < 0.001), accompanied by a significant increase in the whole blood viscosity to 4.57 ± 0.16 mPa · s, nonsignificant decrease in erythrocyte fluidity to 79.9 ± 7.4 mPa-1 · s-1 and nonsignificant change in plasma viscosity (1.46 ± 1.3 mPa · s). Positron emission tomography measurements revealed that by normalization of hematocrit, rCBF significantly decreased from 65 ± 11 to 48 ± 12 ml/min per 100 cm3 (P < 0.05). However, arterial oxygen content (caO2) significantly increased from 5.7 ± 0.7 to 8.0 ± 0.4 mmol/L (P < 0.0001), rOER of the hemispheres significantly increased from 44 ± 3 to 51 ± 6% (P < 0.05) and became significantly higher than healthy control subjects (P < 0.05). In addition, rCBV significantly increased from 3.5 ± 0.5 to 4.6 ± 0.6 ml/100 cc brain tissue. The results showed that oxygen supply to the brain tissue increased with normalization of hematocrit, but it was accompanied by increased oxygen extraction in the brain tissue. This may be assumed to be related to the decrease of erythrocyte velocity in the cerebral capillaries as a result of the decreased blood deformability and the increased plasma viscosity.

Viscosity and Red Cell Deformity in Arterial Disease

1979 ◽  
Author(s):  
G Cella ◽  
H de Haas ◽  
M Rampling ◽  
V Kakkar
Keyword(s):  
Vascular Disease ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Arterial Disease ◽  
Plasma Viscosity ◽  
Control Group ◽  
Fibrinogen Concentration ◽  
Red Cell ◽  
Whole Blood Viscosity ◽  
Significant Difference

Haemorrheological factors have been shown to be affected in many kings of vascular disease. The present study was undertaken to correlate these factors in normal subjects and patients suffering from peripheral arterial disease. Twenty-two patients were investigated; they had moderate or severe intermittent claudication, extent of disease being confirmed by aorto-arteriography and ankle-systolic pressure studies. Twenty-five controls with no symptoms or signs of arterial disease were selected with comparable age and sex distribution. Whole blood viscosity was measured at shear rates of 230 secs-1 and 23 secs-lat 37°c using a Wells Brookfield cone plate microvisco meter. Plasma viscosity was also measured in an identical manner. Erythrocyte flexibility was measured by centrifuge technique and fibrinogen concentration as well as haematocrit by standard techniques. The fibrinogen concentration appeared to be the only significant parameter; the mean concentration in patients with peripheral vascular disease of 463 ± 73mg/l00ml in the control group ( < 0.05). Although whole blood viscosity was high in patients, when corrected to a common haematocrit, there was no significant difference between patients and controls. The same megative correlation was found for plasma viscosity. The red cell flexibility was found to be increased in patients as compared to the control group, but this effect appeared to be simply proportional to the fibrinogen concentration.

Sign in / Sign up

Export Citation Format

Share Document