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PubMedDate not supplied

On whole blood viscosity measurements in healthy individuals and in rheumatoid arthritis patients.

Different methods of measuring whole blood viscosity using a couette rotational viscometer were compared to establish its use in clinical rheumatological practice. The relationship between blood viscosity and hematocrit was approximately exponential and no significant differences in the slopes were found between healthy controls and rheumatoid arthritis patients. Correction of native blood viscosity to a standard hematocrit of 40% by extrapolation from a standard regression curve, established by concentration/dilution of samples from healthy persons to correct for hematocrit differences and at shear rate 92s-1, was the best method for differentiating between viscosities of patients and controls. It was also the least laborious method, requiring the smallest amounts of blood and having the lowest method error. Native blood viscosity, corrected blood viscosity, plasma viscosity and red cell aggregation were all significantly higher and hematocrit significantly lower in rheumatoid arthritis patients than in controls.

Adolescent↗
PubMed1992

Fibrinogen and viscosity as risk factors for subsequent cardiovascular events in stroke survivors.

OBJECTIVE: To investigate whether abnormalities in blood viscosity predict a poor prognosis for subsequent cardiovascular events in stroke survivors. DESIGN: Nested case-control study among a cohort of survivors of a first stroke, followed for an average of 2 years. Patients with a second stroke, myocardial infarction, or cardiovascular death were matched with patients who did not have such events (control patients). SETTING: Buchberg-Klinik, Bad Tölz, Germany, a specialized center for stroke rehabilitation. PATIENTS: A total of 625 consecutive patients. Twenty-one patients (3.5%) were lost to follow-up. Sixty pairs were matched. MEASUREMENTS: Native and hematocrit-standardized blood viscosity at three shear rates, hematocrit, plasma viscosity, fibrinogen, erythrocyte sedimentation rate, total leukocyte count, and the matching variables. RESULTS: Eighty-five patients had a second stroke, myocardial infarction, or died due to a cardiovascular event. Patients with re-events had higher blood viscosity and fibrinogen levels than the control patients. In the 60 matched pairs, the mean of the paired differences between patients with re-events and control patients was 5.03 mPa.s (95% CI, 1.262 to 8.941; P = 0.01) for native blood viscosity at shear rate 0.7 s-1, for plasma viscosity, 0.044 mPa.s (CI, 0.006 to 0.083; P greater than 0.02), and for fibrinogen, 0.056 g/L (CI, 0.010 to 0.101; P greater than 0.02). Odds ratios were significantly increased only for plasma viscosity (odds ratio, 2.86; CI, 1.06 to 8.43) and fibrinogen (odds ratio, 3.67; CI, 1.31 to 11.69). CONCLUSIONS: Hyperfibrinogenemia is an independent risk factor for cardiovascular events in stroke survivors. Intervention trials with fibrinogen lowering measures may be warranted.

Aged↗
PubMed1999

Distribution of blood viscosity values and biochemical correlates in healthy adults.

OBJECTIVE: Increase in the viscosity of blood predict clinical manifestation of atherothrombotic vascular disease. The clinical utility of viscosity measurements in cardiovascular risk factor requires a reference value established from a healthy disease free population. METHODS: Blood viscosity (based on empirical Merill's formula), fibrinogen, haematocrit and lipid profile were measured in 100 fasting healthy nonsmoking adults (50 men, 50 women). RESULTS: The mean (+/- SD) blood viscosity values were 0.030 +/- 0.015 dyne/cm2. Men had higher viscosity values than women. Also, men had higher triglycerides, haematocrit as well as fibrinogen as compared to women. CONCLUSION: This study provides reference values for the blood viscosity, fibrinogen haematocrit and lipid profile. Viscosity measurements may improve identification and risk stratification of patients at high risk for atherothrombotic vascular disease and its complications.

Adult↗
PubMed2001

Viscosity dependence of protein dynamics.

The influence of solvent viscosity on protein dynamics was investigated with molecular dynamics simulations of factor Xa in two solvents differing only in viscosity, by a factor of 10. We obtained this viscosity change by changing the masses of the solvent atoms by a factor of 100. Equilibrium properties of the protein, that is, the average structure, its fluctuations, and the secondary structure, show no significant dependence on the solvent viscosity. The dynamic properties of the protein, that is, the atom-positional correlation times and torsional angle transitions, however, depend on the solvent viscosity. The protein appears to be much more mobile in the solvent of lower viscosity. It feels the influence of the solvent not only on the surface but even in its core. With increasing solvent viscosity, the positional relaxation times of atoms in the protein core increase as much as those of atoms on the protein surface, and the relative increase in the core is even larger than on the surface.

Computational Biology↗
PubMed1975

Changes in arterial pressure, viscosity and resistance during cardiopulmonary bypass.

Large changes in arterial pressure and systemic vascular resistance are frequently observed at the onset of and during cardiopulmonary bypass, particularly when hemodilution is employed. In order to assess the extent to which these changes are induced by changes in blood viscosity, we measured viscosity, pressure, and flow in a series of 17 patients. Hemodilution was used in Group A (12 patients) but not in Group B (5 patients). At the beginning of cardiopulmonary bypass, the arteriovenous pressure difference decreased an average of 53.8 per cent in the Group A patients, concomitant with a 41.7 per cent decrease in blood viscosity. The arteriovenous pressure difference in the Group B patients increased an average of 6.4 per cent, while the blood viscosity increased by 8 per cent. A nomogram was theoretically derived for the Group A patients, which allows rapid estimation of the extent of viscosity-induced hypotension for a given volume of priming fluid, initial patient hematocrit, and patient weight. After correction for viscosity changes due to hemodilution, the Group A patients were found to exhibit essentially normal values of systemic vascular resistance at the start of bypass, with a mean of 1,155 dynes-sec./cm.5. On the other hand, the Group B patients had elevated resistance values, with a mean of 1,611 dynes-sec./cm.5. During perfusion, the resistance of both groups tended to increase, sometimes by 100 per cent or more. In some cases, however, the resistance values changed in an erratic fashion. These effects were not due to changes in blood viscosity.

Adolescent↗
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↗
PubMed2001

[The influence of controlled ethanol consumption on whole blood and plasma viscosity].

UNLABELLED: The aim of this study was to establish whether the single controlled ethanol consumption changes hemorrheological parameters. It has not been clear whether single alcohol intake in well controlled experimental conditions has had an influence on hemorrheological parameters. Twenty nine healthy men volunteers aged 20-30 have been examined. All volunteers have showed normal renal and hepatic function tests and have not suffered from hematological or cardiovascular diseases. The examined men have been randomly divided in two groups: the examined one: 19 persons aged 21-30 years, and the control group aged 20-28 years. The examined group has been treated with ethanol in quantity of one gram per kg of body weight during ten minutes. After one and half, three and five hours after the alcohol consumption fast venous blood samples with K2EDTA as an anticoagulant have been drown from anticubital vein. The following parameters have been determined before drinking ethanol and after at one and half, three and five hours: whole blood viscosity at 1s-1 divided by 300s-1, the plasma viscosity, the corrected--for--hematocrit 45% viscosity of blood, yield stress--calculated from Casson's equation on the basis of flow curve, blood morphology, arterial pressure and heart rate. The hematocrit-corrected viscosity has been remarkably elevated after 1.5 and 3 hours at all shear rates (e.g. from 20.6 +/- 2.0 mPas before to 25.1 +/- 2.5 mPas after 1.5 h from ethanol consumption; p < 0.001). Yield stress of blood has been increased after ethanol consumption too. Plasma viscosity has been significantly higher after five hours. In controls there have not been any time depended changes in rheological and hematological parameters. CONCLUSIONS: The controlled consumption of ethanol in quantity of 1 gram per 1 kg of body weight has caused the following changes in hemorheological parameters: increase of corrected--for--45% hematocrit--whole blood viscosity, increase of plasma viscosity and increase of yeald stress.

Adult↗
PubMed1992

Blood and plasma viscosity in diabetes: possible contribution to late organ complications?

It has been postulated that an increased whole blood and plasma viscosity contribute to diabetic organ complications. Blood viscosity was measured in 30 controls and four groups of insulin-dependent diabetic patients at three shear rates: 70 sec-1, 0.5 sec-1 and 0.05 sec-1. Results were compared before and after correction for a haematocrit of 0.45. Twenty-five patients without organ complications, 21 with microalbuminuria, 13 with overt nephropathy and 12 patients with leg ulcerations were studied. Blood and plasma viscosity were normal in the patients without organ complications and with microalbuminuria. Plasma viscosity was significantly elevated in the diabetic patient with nephropathy and leg ulceration. After correction for haematocrit blood viscosity was also higher in these two groups, although this was only significant in the group with leg ulceration. In conclusion blood and plasma viscosity were only elevated in the patients with major organ complications and not in the patients without or with early complications. Therefore it is unlikely that an elevation of blood or plasma viscosity contributes early in the pathogenesis of diabetic organ damage.

Adult↗
PubMed2003

[Low viscosity composites as materials for orthodontic bonding].

A new type of composite materials, referred to as low viscosity composites, has been introduced onto the dental market. Little has been published yet concerning the biological and mechanical properties of these new materials, and the practitioner has to rely on the information, provided by the manufacturer. The low viscosity composites are hybrid composites, with a decreased amount of filler particles. This results in a lower viscosity, which makes these materials more appropriate in certain situations. Since the filler loading of these materials is decreased, one could expect inferior mechanical properties, compared to the conventional and hybrid composites. Therefore, the indications for using low viscosity composites are limited. In this article we propose to use low viscosity composites for the bonding of lingual retainers and implant-borne transpalatal arches. The explicit feature of flow, is very attractive for these indications, because a minimum of finishing is needed, when a low viscosity composite is used in these situations. Since there is no direct occlusal bite force put on the composite, the fact that the mechanical properties of a low viscosity composite could be inferior to those of a conventional composite, can be disregarded. A protocol for fixing lingual retainers and implant-borne transpalatal arches is proposed in the article, with other tips, concerning the fabrication of the retainers themselves.

Composite Resins↗
PubMed2004

Type 2 diabetics with higher plasma viscosity exhibit a higher blood pressure.

Among hemorheologic parameters, plasma viscosity is one of the most studied in epidemiology, so that it has emerged as an independent risk factor. In diabetes, plasma viscosity is frequently elevated. For this reason we tried to define characteristics of non-insulin dependent diabetics with high plasma viscosity (>1.45 mPa.s) and whether they were more insulin resistant and/or exhibited other hemorheologic disturbances. 12 subjects (age 56.1+/-11.7; BMI 28.6+/-4.8) were thus found to have a value of plasma viscosity >1.45 mPa.s. They were compared to 20 age and BMI-matched NIDDMs. Patients have similar insulin sensitivity, HbA1c, and fibrinogen. RBC aggregation, rigidity and hematocrit were not significantly different. Whole blood viscosity at high shear rate was slightly higher (p=0.05). When corrected for hematocrit whole blood viscosity is no longer different. However, hematocrit was not lower in subjects with hpl >1.45. By contrast blood pressure was markedly higher (systolic: 177.5+/-2.5 mmHg vs 140+/-8 mmHg, p<10(-8); diastolic 110+/-14 vs 83+/-9 mmHg, p<10(-9); mean 132+/-18 mmHg vs 102+/-7 mmHg p<10(-9)). Therefore, in NIDDM, higher plasma viscosity, regardless insulin resistance and adiposity, is strongly related to blood pressure.

Blood Glucose↗
PubMed2005

Influence of contrast media (iopromide, ioxaglate, gadolinium-DOTA) on blood viscosity, erythrocyte morphology and platelet function.

The influence of contrast media on blood viscosity, erythrocyte morphology and platelet function was studied. In vitro blood was incubated with iopromide (Ultravist), ioxaglate (Hexabrix) or gadolinium-DOTA (Dotarem). Plasma viscosity and whole blood viscosity were measured and the mean erythrocyte volume and morphology were assessed. Platelet aggregation was measured with a PFA-100 instrument. In an ex vivo study on patients receiving these contrast media the same measurements as described above were done. All contrast media increased blood viscosity at high shear rate in a dose dependent manner (e.g. with ioxaglate: from 4.9+/-0.2 mPa x s to 8.6+/-0.5 mPa x s at 160 mg I/ml), decreased low shear viscosity (for ioxaglate: from 44.9+/-2.5 to 27.7+/-4.8 mPa x s), increased plasma viscosity (ioxaglate: from 1.2+/-0.1 to 2.8+/-1.3 mPa x s), decreased the mean erythrocytic volume (ioxaglate: from 89.7+/-1.4 to 79.7+/-2.0 fl) and decreased platelet aggregation. Iopromide induced an echinocytic shape transformation of erythrocytes. Ex vivo a decreased hematocrit and a consecutively decreased whole blood viscosity were found with iopromide and ioxaglate. We conclude that contrast media influenced blood rheology, erythrocytes and platelet aggregation in vitro and ex vivo.

Adult↗
PubMedDate not supplied

[Changes of pH and kinematic viscosity of the contents of gall-bladder at the pre-gallstone stage of cholelithiasis].

The aim of the work was to study the indicators of pH and kinematic viscosity of the contents of the gall-bladder at receiving B-portion and their changes after a 7-hour period according to the biliary sediment of patients and to establish their link to the infection. Total 31 patients aged 25-55 with biliary sediment in lumens of their gall-bladders (a general group) and 5 healthy patients (a control group) were studied by us. In all cases the markers of the virus of Hepatitis B in blood serum were determined and ultrasonic examination of gall-bladder was carried out by us prior to the duodenal intubation. B-portion was subjected to bacteriological research for aerobes and anaerobs, and pH and kinematic viscosity (eta=mm(2)/sec) were determined. The patients from the control as well as from the general group after a 7-hour period were redetermined pH and Kinematic viscosity of B-portion. Kinematic viscosity was determined with a capillary viscosimeter, and pH was fixed by a method of potentiometer. Statistical treatment was undertaken by the method of ANOLA p<0,05. During the duodenal intubation the mean value of pH within the control group was fixed at 6.74, and the mean value of the kinematic viscosity was 1.34, and after a 7-hour period the same indicators constituted 6.87 and 1.35 mm(2)/sec, respectively. The same indicators within the general group during duodenal intubation were the following: 7.26 and 1.99 mm(2)/sec, and after a 7-hour period the same indicators were 7.78 and 2.19 mm(2)/sec, respectively. There was a significant statistical difference between the mean values of pH and kinematic viscosity of the contents of gall-bladder of the patients from the control and general groups. During a 7-hour period, there was also a significant statistical difference between the changes of the same indicators. The difference was even greater in case of infection. Following the above-mentioned we can conclude that in case of sediment in the lumen of gall-bladder, inclination of pH to alkalinity and increase in kinematic viscosity of the contents is one of the most important criteria of lithogenicity of gall-bladder contents, and one of the reasons for such changes is chronic infection of a gall-bladder.

Adult↗
PubMed2006

Capillary blood viscosity in microcirculation.

As known, at the arteriolar level there is the highest resistance to the flow due to the section and to the velocity with an average pressure fall of 50 mmHg (from 85 to 35 mmHg). This resistance is expressed in sec(-1) by the ratio W/2r. This ratio is very high with an average value of 332 sec(-1) and viscosity at this high shear-rate is negligible. At the capillary level the pressure fall is 11.5 mmHg but the vascular resistance W/2r is much lower, on average 32 sec(-1). We can say that if a resistance of 333 sec(-1) corresponds with a pressure fall of 50 mmHg, then a resistance of 32 sec(-1) should correspond with a pressure fall of 4.8 mmHg. The highest pressure fall is due to another kind of resistance which we can define as "Capillary Blood Viscosity" because it depends on the rheological and structural characteristics of the blood. Our instrument reproduces the structure of the capillary district in an experimental model and measures the General Blood Viscosity (GBV) and the Capillary Blood Viscosity (CBV) at the same shear-rate and in particular at the low shear-rate when in non-Newtonian fluids the highest increase in viscosity appears. Consequently, at the capillary, viscosity is dominant with respect to the other geometric and physical resistances. Moreover, the percentage ratio between the GBV and the CBV gives a physical measure of erythrocyte deformability. Knowing viscosity at shear-rate present in the circulatory system, we can obtain the size of RBCs aggregates in the different circulatory districts and their characteristics expressed like "aggregation bond". Changes in CBV are the only possibility in clinical practice to improve the circulatory flow in the capillary district because it is not sure that changes in the arteriolar section can improve the capillary flow or rather open arterio-venous anastomosis. Moreover, in the systemic circulation the aggregate size allows us to point out the phenomenon of cell adhesion because the presence of several receptors involves also the other blood cells. Finally the size and the stability of the RBCs aggregates can modify the endothelial thrombo-resistance.

Arthritis, Rheumatoid↗
PubMed1991

[Erythrocyte viscosity-deformability-aggregation. A clinical reality].

Current clinical practice and indications for drug therapy for vascular pathologies of different etiology reveal the need to measure blood viscosity, either on the spot or at the site of greatest impact. The Authors propose as easily performed method of calculation using Reid's well-known technique, which, based on the measurement of hematic filterability using filters with different sized pores, gives the viscosity of the various fractions which make up overall viscosity but which have a different impact on areas of the circulation and their functions: total blood viscosity, corpuscolar viscosity, plasma-erythrocytic viscosity. These are quantified in cP as a values which is independent of the degree of sanguification and are markers of a functional flow datum. Erythrocytic deformability, expressed as a percentage of the inverse viscous impact of red cells on total blood viscosity, is restricted to a narrow range in the control population, and is therefore a very reliable parameter for the assessment of pathological and pharmacological changes. In addition to normal values, changes in subjects suffering from thalassemia are used as a paradigmatic example of structural and morphological erythrocytic changes without other associated diseases. A model table illustrates the methods of calculation used to obtain the degree of filtration in cP from filtration data.

Blood Viscosity↗
PubMed1977

[Blood viscosity in ischemic heart disease with different types of hyperlipoproteinemia].

Fifty patients with chronic forms of ischaemic heart disease were examined, their blood viscosity being determined with the aid of a rotational viscosimeter, and their hematocrit and fibrinogen levels being measured. Some increase in blood viscosity was found in patients with ischaemic heart disease with a tension shift of 0.7 and 0.5 dyn/cm2. In analysing the interrelationship between the blood viscosity figures and the risk factors inherent in ischaemic heart disease it was found that smoking results in an increasing blood viscosity with low tension shifts. The highest blood viscosity with low tension shifts. The highest blood viscosity values were found in patients with IIb and IV types of hyperlipoproteinemia. A direct correlation was established between the level of triglycerides and blood viscosity with a tension shift of 0.7 dyn/cm2.

Adult↗
PubMed1987

Effects of plasma hyperviscosity on skeletal muscle blood flow and blood viscosity in vivo.

The effect of plasma hyperviscosity on skeletal muscle blood flow and blood viscosity in vivo was studied. Blood flow and viscosity in vivo were determined in the isolated and vasodilated calf muscle of one hind limb in dogs. Plasma hyperviscosity was induced by suspending red blood cells in concentrated and isotonic solutions of low molecular weight dextran in saline. Viscosity in vivo was determined by comparing pressure-flow relationships for blood and a reference solution. Blood viscosity in vitro was determined in a Wells-Brookfield cone-plate viscometer. Determinations were made for plasma viscosities of 1.3, 2.2 and 4 cP. It was found that blood flow and viscosity in vivo were strongly dependent on plasma viscosity and that the effects in vivo could be predicted from values obtained in vitro.

Animals↗
PubMed1989

[Blood viscosity is a chronic adjustment factor of arterial vasodilatation in humans].

Arteriolar geometry and blood viscosity, the two main factors determining vascular resistance were studied in 44 normotensive subjects and 106 hypertensive patients at the brachial circulation level. Vascular resistance was calculated as the ratio between mean blood pressure and mean arterial flow determined by pulsed Doppler. Blood viscosity at 240 sec-1 was measured with a coaxial cylinder viscometer: Compared to controls, hypertensive patients had higher vascular resistance (161 + 8 vs 124 + 9 mmHg.ml-1.sec, P less than 0.05) and higher viscosity (4.75 + 0.05 vs 4.50 + 0.07 mPasec, P less than 0.01). Vascular resistance was negatively correlated to blood viscosity both in control (r = 0.48; P less than 0.001) and in hypertensive (r - 0.39, P less than 0.001) groups. Arteriolar equivalent radius (a) calculated from Poiseuille's equation from the relation a = (8 mu/pi R) 1/4 was positively correlated to viscosity in the two regressions were statistically different (P less than 0.001) indicating that at higher viscosity levels, arteriolar equivalent radius had lesser increase in normotensive than in hypertensive groups. Thus chronic increase in blood viscosity is accompanied by a small vessels vasodilatory phenomenon which seems less efficient in normotensive than in hypertensive subjects and might contribute in part to the mechanisms of vascular resistance elevation observed in hypertension.

Adult↗
PubMedDate not supplied

The effect of contrast medium viscosity on the blood-brain barrier after intracarotid injection in the rabbit.

This study was undertaken to investigate the role of contrast medium viscosity in blood-brain barrier disruption after carotid angiography. Test solutions were injected into the carotid arteries of rabbits, and the degree of disruption was assessed by using 99mTc-pertechnetate and Evans blue as quantitative and qualitative markers, respectively. The seven test solutions consisted of basic solutions of physiological saline, iopromide, or methylglucamine iothalamate plus solutions derived from these by the addition of sufficient gelatin to augment their viscosities considerably. The solutions were injected over a 30-sec period, resulting in doses that varied inversely with viscosity. One of the high-viscosity solutions was also injected as a fixed dose, equal to the mean injection volume of its low-viscosity counterpart, without regard to the time used. Statistical comparison between the effects of the solutions showed that, under the conditions of the study, contrast medium viscosity, either by itself or as a consequence of its association with hyperosmolality, has no significant effect on the blood-brain barrier. However, under conditions of constant injection volume, higher viscosity solutions may require increased injection times, and this may lead to increased disruption of the blood-brain barrier.

Animals↗