Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BLOOD VISCOSITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2001

Molecular biology and self-regulatory mechanisms of blood viscosity: a review.

Blood viscosity is determined by plasma viscosity, hematocrit, erythrocyte deformability and aggregation. Plasma viscosity and hematocrit are directly regulated by the organism. The molecular biology of the principal determinants of plasma viscosity, i.e., fibrinogen, immunoglobulins, albumin, and lipoproteins is outlined in this work. Hematocrit is regulated by erythropoietin, which is primarily induced by tissue hypoxia. Evidence begins to emerge that autoregulatory mechanisms may be involved in blood viscosity. Viscosity modulates gene transcription for albumin and apolipoproteins in cultured hepatocytes and the erythropoietin response to anemia in rats. Further investigations into these self-regulatory mechanisms in biorheology are, however, needed for a better understanding of blood viscosity regulation in health and disease.

Blood Viscosity↗
PubMed1978

Raynaud's disease: reduced hand blood flows with normal blood viscosity.

Hand blood flows and the blood and plasma viscosities were measured in patients with Raynaud's disease in an attempt to identify the mechanism of the episodic vascular insufficiency. Using venous occlusion plethysmography the following observations were made: (1) the hand blood flows were significantly less than in normals at 32 degrees, 27 degrees and 20 degrees C; (2) the percentage decrease in flow with cooling was greater in normals and (3) cooling of one hand from 32 degrees to 27 degrees C caused an abnormal decrease in flow through the contralateral hand. Using a rotational viscometer the blood and plasma viscosities were found to be normal at both high and low shear rates. The percentage increase in the blood viscosity with cooling from 35 degrees to 25 degrees was also normal. These studies demonstrate an increased constrictive response of the cutaneous vasculature of the hand to both local and reflex stimulation, and exclude a rheological abnormality, under conditions similar to those of the present study.

Adolescent↗
PubMed2000

On-line dynamic measurement of blood viscosity, hematocrit and change of blood volume.

OBJECTIVE: To develop an on-line system for the measurement of blood viscosity and hematocrit. The dynamic changes of the macrovascular blood volumes, microvascular blood volumes and the total blood volume were observed by means of calculating from the testing result. METHODS: Applying traditional viscosity measurement principle and specific wavelength optic density measurement method, an on-line system for the measurement of blood viscosity and hematocrit was developed, and the A/D multifunctional board and the testing circuit were designed by ourselves. The system was validated by experiments both in vitro and in vivo. Therapeutic effects of hypertonic saline dextran solution (HSD) and Lactatic Ringer's solution at the early stage after burn-blast combined injury were compared by this method. RESULTS: The results showed that the system has attained the goal of the design. The changes of the blood viscosity and hematocrit could be detected effectively and continuously. The changes of macrovascular, microvascular and total blood volume could be calculated approximately. CONCLUSIONS: The system and the method can continuously on-line test the blood viscosity and hematocrit, and reveal the change and distribution of blood volumes more accurately and clearly in the therapy process by estimating changes of the macrovascular, microvascular and total blood volumes, respectively. It has confirmed that HSD treatment could increase blood pressure and attenuate tissue edema by significantly increasing total blood volume, improving macrocirculatory and microcirculatory blood volumes. This study suggested that it could be desirable to develop an experiment technique based on the method mentioned above.

Journal Article↗
PubMed2002

Endothelium-dependent arterial wall tone elasticity modulated by blood viscosity.

The role of blood viscosity on arterial wall elasticity before and after deendothelization (DE) was studied. Seven ovine brachiocephalic arteries were studied in vitro under physiological pulsatile flow conditions achieved by a mock circulation loop. Instantaneous pressure and diameter signals were assessed in each arterial segment. Incremental elastic modulus (E(inc)) was calculated using the slope of the pure elastic stress-strain relationship. There was no significant difference between E(inc) values before and after DE (3.11 vs. 3.16 10(7) dyn/cm(2)) at a blood viscosity of 2.00 mPa. s. Increases in blood viscosity (2.50, 3.00, 3.50, and 4.00 mPa. s) always resulted in decreases of E(inc) before DE; inversely, increases in blood viscosity resulted in increases of E(inc) after DE. These values of E(inc), for identical levels of blood viscosity, were always significantly lower (P < 0.05) before DE than those obtained after DE. Arterial wall elasticity assessed through E(inc) was strongly influenced by blood viscosity, probably due to presence or absence of endothelium relaxing factors or to direct shear smooth muscle activation when endothelial cells are removed.

Animals↗
PubMed1994

Sex differences in susceptibility to etiologic factors for peripheral atherosclerosis. Importance of plasma fibrinogen and blood viscosity.

Cardiovascular risk factors in men, such as cigarette smoking, hypercholesterolemia, and hypertension, also increase risk in women, but the relative susceptibility to risk factors between the sexes is not established. Our aim was to investigate a wide range of possible etiologic factors in a single population study and identify those that were more strongly related to peripheral atherosclerosis in men or women. We studied personal factors (age and social class), lifestyle factors (smoking, exercise, alcohol intake, and dietary nutrients), and intermediary factors (obesity, diabetes, serum lipids, coagulation, and rheological factors). In the Edinburgh Artery Study in 1988 we measured cardiovascular risk factors in a random population sample of 1592 men and women aged 55 to 74 years. The ankle-brachial pressure index (ABPI), which is inversely related to the degree of peripheral atherosclerosis, was assessed in each subject. Lifetime cigarette smoking was correlated with a lower ABPI equally in men and women (r = -.27, P < .001). Dietary nutrients and alcohol intake were not related differently between the sexes with ABPI. However, recall of strenuous and moderate leisure time exercise during the age range of 35 to 45 years was related more strongly to a higher ABPI in men than in women (P < .05). Plasma fibrinogen, plasma viscosity, and blood viscosity were the only intermediary factors that had stronger univariate correlations with lower ABPI in men than in women. On multivariate analysis, the sex differences persisted for plasma fibrinogen (P < .05) and blood viscosity (P < .001); high-density lipoprotein cholesterol was related to ABPI in men only (sex difference, P < .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Blood viscosity and peripheral vascular resistance in patients with untreated essential hypertension.

OBJECTIVES: The viscosity of blood is increased in patients with essential hypertension. The aim of the present study was to investigate the importance of the different variables of blood rheology to total peripheral resistance, and to elucidate whether inappropriate regulation of the formation of erythropoietin could be important. DESIGN: Nineteen consecutive patients with untreated essential hypertension were examined and compared with a group of matched healthy volunteers. METHODS: The haemorheologic variables were assessed by rotational viscometry and the haemodynamic variables by bioimpedance cardiography. The serum concentrations of erythropoietin were determined by radioimmunoassay. RESULTS: The whole blood viscosity and peripheral resistance index were elevated in the hypertensive group. The two variables were positively correlated with each other (r = 0.68, P = 0.0015). The plasma viscosity and erythrocyte aggregation tendency were increased and the erythrocyte deformability, measured as fluidity, was decreased in the hypertensive patients. In the male subpopulation (n = 12) the aggregation tendency was positively, and the deformability negatively, correlated with body mass index. The serum concentrations of erythropoietin were equal in the two groups. CONCLUSIONS: The increased total peripheral resistance in patients with essential hypertension may in part be explained by an increased blood viscosity, but the possibility of an opposite cause-effect relationship must also be taken into consideration. The haemorheological abnormalities observed in the present patients cannot be explained by high serum levels of erythropoietin.

Adult↗
PubMed1981

Filterability and vascular disease--I. Red cell filterability in diabetes mellitus: its relation to other methods of measuring deformability and to blood viscosity.

Erythrocyte deformability, blood viscosity and other rheological variables were measured in 30 diabetics and 28 normal control subjects. Measurements of red cell rheology were made simultaneously by filtration of whole blood, centrifugation and viscometry of packed red cells. The diabetics showed a significant reduction of erythrocyte deformability measured by filtration, an increase in flexibility measured by centrifugation and values similar to normals for viscometry of packed red cells. Plasma viscosity but not whole blood viscosity (shear rates 23 and 230 s-1) was increased in the diabetics. Erythrocyte flexibility as measured by centrifugation was significantly related to blood viscosity and plasma fibrinogen and glucose in the diabetics, however, neither filtration nor viscometry of packed red cells correlated with other rheological variables. It seems likely that multiple rheological abnormalities are present in diabetes mellitus. Conclusions about erythrocyte rheology in particular will depend critically on the methodology used.

Adult↗
PubMed1991

The effects of diet and insulin therapy on coagulation factor VII, blood viscosity, and platelet release proteins in diabetic patients with secondary sulphonylurea failure.

The effect of intensified dietary measures and subsequently insulin therapy upon haemorheological measures were studied in Type 2 diabetic patients with secondary sulphonylurea failure. Coagulation factors VIIc and VIIIc, fibrinogen, plasma viscosity, whole blood viscosity, beta-thromboglobulin, platelet factor 4, von Willebrand factor, and euglobulin clot lysis time were measured at baseline, after 3 months intensified dietary therapy and after 4 months insulin therapy. During intensified dietary therapy there was a significant fall in serum cholesterol (p less than 0.05) and a small decrease in weight, but no significant change in blood glucose control. Factor VIIc levels fell significantly (1.22 (SE 0.07) vs 1.42 (0.08) u ml-1, p less than 0.01), and plasma viscosity and whole blood viscosity (23 s-1) also improved (both p less than 0.05). Insulin therapy was instituted with either continuous subcutaneous insulin therapy or twice daily injections of soluble and isophane (NPH) insulin. During this period glycosylated haemoglobin improved (mean (SE) 49.5 (1.4) vs 65.0 (2.1) mmol-HMF mol-Hb-1, p less than 0.001; normal range 29-39 mmol-HMF mol-Hb-1) as did serum triglyceride (p less than 0.01), but weight increased (p less than 0.001). The only haemorheological changes with insulin were increased levels of the platelet release proteins beta-thromboglobulin (37 (3) vs 28 (2) micrograms l-1, p less than 0.01) and platelet factor 4 (median 7.5 (range 3.0-18.0) vs 4.5 (2.0-10.5) micrograms l-1, p less than 0.01).

Adult↗
PubMed1988

Diabetic hypertension--the importance of fibrinogen and blood viscosity.

Fibrinogen and blood viscosity were measured in 72 stable non-insulin dependent diabetic subjects, 31 without hypertension, and 41 who had treated hypertension. The hypertensive group had higher plasma fibrinogen levels and blood viscosity. As both these rheological variables have been associated with micro- and macro-vascular disease, these findings may provide a possible explanation for the mechanism of the increased vascular disease seen in hypertensive compared with normotensive diabetic subjects.

Blood Viscosity↗
PubMed1980

Plasma and whole blood viscosity in treated primary polycythaemia.

Whole blood viscosity at a range of shear rates (230--0.77 s-1) and plasma viscosity have been measured in 39 patients with treated primary polycythaemia (idiopathic erythrocytosis and primary proliferative polycythaemia) and 30 age-matched normal individuals. There was a wider range of plasma viscosity and whole blood viscosity values at the same haematocrit (0.46), particularly at the lower shear rates, in the 'polycythaemic' group than the normal group. Hypochromic microcytic red cell changes present in 14 patients in the 'polycythaemic' group did not have any noticeable influence on whole blood viscosity at a given haematocrit value, since plasma protein factors override any possible effect of these red cell changes. The range of observed whole blood viscosity results in the 'polycythaemic' patients at the same haematocrit (0.46) was equivalent to the effect on whole blood viscosity of a rise in haematocrit from 0.41 to 0.51. Since there is such a range of whole blood viscosity at the same haematocrit, the haematocrit alone does not necessarily give a precise assessment of the viscosity of a whole blood sample. Since there is evidence from other publications that blood flow in vitro may be critically influenced by whole blood viscosity, this lack of precision should be considered when treating patients at risk of vascular occlusive episodes.

Adult↗
PubMed1978

Accentuation of heart sounds in anemia: an effect of blood viscosity.

The effect of blood viscosity on the intensity of heart sounds was investigated in 25 anemic patients and 41 control subjects. Calibrated phonocardiograms showed that in anemic patients, the aortic component of the second sound was of greater amplitude (54 +/- 3 vs. 33 +/- 3 dyn/cm2) (P less than 0.001). The pulmonary component of the second sound and the first sound were also of higher amplitude in anemic patients (both P less than 0.001). The viscosity of blood of anemic patients was lower (0.029 +/- 0.001 vs. 0.045 +/- 0.001 poise) (P less than 0.001). Blood pressure was comparable among the two groups. Sound produced by closure of a normal porcine valve in an in vitro flow system also showed an accentuated sound with liquids of lower viscosity. Augmented diastolic vibrations of the closed valve, shown by high-speed motion pictures, accompanied the accentuated sound. These observations suggest that the accentuated second sound in anemic patients results from the lower blood viscosity, which reduces the damping forces that act upon the semilunar valve as it vibrates after closure. The reduced damping would allow augmented vibrations that result in an accentuated sound.

Anemia↗
PubMed2005

The influence of lipoproteins on whole-blood viscosity at multiple shear rates.

Whole-blood viscosity appears to be an independent predictor of stroke, carotid intima-media thickening, and carotid atherosclerosis. The purpose of this study was to examine for relationships between whole-blood viscosity and blood lipids in young healthy subjects over a range of shear rates. Twenty-seven healthy men and women aged 10 to 25 years having a range of low-density lipoprotein (LDL) cholesterol values 88 to 258 mg/dL and body mass index z scores -1.18 to 2.64 SDs were studied. Whole-blood viscosity at shear rates from 1 to 1000 per second was measured using an automated capillary viscometer. Blood lipids were measured using standard techniques. Triglyceride-rich lipoproteins were isolated by ultracentrifugation at density of <1.020 g/mL, and a high ratio of cholesterol to triglyceride was used as an indicator of lipoprotein remnants. Whole-blood viscosity at shear rates of 100 to 1000 per second showed significant negative correlations with apolipoprotein A-1, but not with high-density lipoprotein cholesterol. Whole-blood viscosity at a shear rate of 1000 per second correlated with LDL cholesterol and inversely with LDL size. On stepwise multivariate analysis, apolipoprotein A-1 accounted for 14.7% of the variation in whole-blood viscosity at a shear rate of 150 per second. This study points to the importance of high-density lipoprotein particle number on whole-blood viscosity at physiological shear rates. The physiological significance of the relationships between whole-blood viscosity and LDL cholesterol and LDL particle size at a very high shear rate remains to be determined.

Adolescent↗
PubMed1991

Blood viscosity measurement for screening of affecting blood circulation.

An in vitro screening test for drugs that decrease blood viscosity was carried out on many pharmacologically active compounds such as Ca-antagonists, alpha-antagonists, beta-antagonists, alpha, beta-antagonists, alpha-agonists, beta-agonists, alpha, beta-agonists, autacoids and others. The results revealed that various types of microcirculatory-improving drugs, vasodilators, and antagonists decreased blood viscosity, while the agonists and autacoids had no significant effect. These findings suggest that this assay is useful for screening compounds related to hemorheology.

Animals↗