Blood Viscosity Factors Research Articles

Which sub-compartments of fat mass and fat-free mass are related to blood viscosity factors?

The size of body compartments is a determinant of several factors of blood viscosity. Red cell aggregation is proportional to fat mass while hematocrit is proportional to both fat-free mass and abdominal adiposity, but which parts of these body components are involved in this relationship is not known. Segmental bioelectrical impedance analysis (sBIA) provides a possibility to delineate the relationships more precisely between various subdivisions of the body and blood viscosity factors, going farther than preceding studies using non segmental BIA. In this study we investigated in 38 subjects undergoing a standardized breakfast test with mathematical modelling of glucose homeostasis and a segmental bioelectrical impedance analysis (sBIA) the relationships between the various compartments of the body and viscosity factors. Blood and plasma viscosity were measured with the Anton Paar rheometer and analyzed with Quemada's model. The parameters better correlated to hematocrit are fat free mass (r = 0.562) and its two components muscle mass (r = 0.516) and non-muscular fat-free mass (r = 0.452), and also trunk fat mass (r = 0.383) and waist-to hip ratio (r = 0.394). Red cell aggregation measurements were correlated with both truncal and appendicular fat mass (r ranging between 0.603 and 0.728). Weaker correlations of M and M1 are found with waist circumference and hip circumference. This study shows that the correlation between lean mass and hematocrit involves both muscle and non-muscle moieties of lean mass, and that both central and appendicular fat are determinants of red cell aggregation.

Effectiveness and Safety of Fufang Danshen Dripping Pill (Cardiotonic Pill) on Blood Viscosity and Hemorheological Factors for Cardiovascular Event Prevention in Patients with Type 2 Diabetes Mellitus: Systematic Review and Meta-Analysis.

Background and Objectives: Diabetes can cause various vascular complications. The Compounded Danshen-Dripping-Pill (CDDP) is widely used in China. This study aimed to analyze the effectiveness and safety of CDDP in the blood viscosity (BV) with type 2 diabetes mellitus (T2DM). Materials and Methods: We conducted a systematic search of seven databases from their inception to July 2022 for randomized controlled trials that used CDDP to treat T2DM. To evaluate BV, we measured low shear rate (LSR), high shear rate (HSR), and plasma viscosity (PV). Homocysteine and adiponectin levels were also assessed as factors that could affect BV. Results: We included 18 studies and 1532 patients with T2DM. Meta-analysis revealed that CDDP significantly reduced LSR (mean difference [MD] -2.74, 95% confidence interval [CI] -3.77 to -1.72), HSR (MD -0.86, 95% CI -1.08 to -0.63), and PV (MD -0.37, 95% CI -0.54 to -0.19) compared to controls. CDDP also reduced homocysteine (MD -8.32, 95% CI -9.05 to -7.58), and increased plasma adiponectin (MD 2.72, 95% CI 2.13 to 3.32). Adverse events were reported less frequently in the treatment groups than in controls. Conclusions: CDDP is effective in reducing BV on T2DM. However, due to the poor design and quality of the included studies, high-quality, well-designed studies are required in the future.

Buyang Huanwu Decoction alleviates blood stasis, platelet activation, and inflammation and regulates the HMGB1/NF-κB pathway in rats with pulmonary fibrosis

Ethnopharmacological relevanceQi deficiency and blood stasis are identified to be pathological factors of pulmonary fibrosis (PF) in traditional Chinese medicine (TCM) theory. Buyang Huanwu Decoction (BYHWD) is a traditional Chinese prescription ameliorating Qi deficiency and blood stasis. Aim of the studyThe objective of this study was to investigate the anti-fibrosis effect of BYHWD and the potential molecular mechanism in rats. Materials and methodsBleomycin was used to construct PF rat models. 27 PF rats were randomly divided into three groups based on treatments: model group (saline solution, n = 9), low-dose BYHWD group (3.5 g/kg, n = 9), and high-dose BYHWD group (14.0 g/kg, n = 9). Moreover, 9 normal rats were used as the blank group. The blood viscosity, coagulation indexes (APTT, TT, PT, and FIB), platelet-related parameters (PLT, PDW, MPV, PCT, and PLCR), platelet microparticles (PMPs), and inflammatory factors (IL-2, IL-10, IL-1β, IL-6, IL-8, IL-17, IFN-γ, TNF-α, PAC-1, HMGB1, NF-κB, and TF) were determined. The lung tissue samples of rats were observed after hematoxylin-eosin (HE) staining. The full component analysis of the BYHWD extract was performed using the ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method. The signaling pathway included into the study was selected on the basis of bioinformatics analysis and the results of the phytochemical analysis. The expression levels of genes and proteins involved in the selected signaling pathway were detected. ResultsCompared to the blank group, the whole blood viscosity, PLR, PDW, MPV, PCT, PLCR, PMPs, and the levels of IL-1β, IL-6, IL-8, IL-17, TNF-α, PAC-1, HMGB1, NF-κB, and TF were increased, while the levels of IL-2 and IL-10 were decreased in the model group. Both low-dose BYHWD and high-dose BYHWD reversed these PF-induced effects in spite of the fact that low-dose BYHWD had no significant effect on the level of NF-κB. In addition, BYHWD ameliorated PF-induced inflammation in the rat lung tissue. The phytochemical analysis of the BYHWD extract combined with the bioinformatics analysis suggested that the therapeutical effect of BYHWD on PF was related to the HMGB1/NF-κB pathway, which consisted of NF-κB, IKBKB, ICAM1, VCAM1, HMGB1, and TLR4. Both RT-qPCR and western blot analyses showed that PF induced increases in the expression levels of NF-κB, ICAM1, VCAM1, HMGB1, and TLR4, but a decrease in the expression level of IKBKB. Moreover, both low-dose BYHWD and high-dose BYHWD exerted the opposite effects, and recovered the expression levels of NF-κB, ICAM1, VCAM1, HMGB1, TLR4, and IKBKB, despite the fact that low-dose BYHWD had no effects on the mRNA expression levels of NF-κB or TLR4. ConclusionsIn summary, BYHWD alleviated PF-induced blood stasis, platelet activation, and inflammation in the rats. Our study suggested BYHWD had a therapeutic effect on PF and was a good alternative for the complementary therapy of PF, and the potential molecular mechanism was modulation of HMGB1/NF-κB signaling pathway, and it needs further study.

Leg electrical resistance predicts venous blood viscosity and hematocrit.

We previously reported that whole body bioelectrical impedance analysis (BIA) measurements are correlated to some hemorheologic factors, suggesting a relationship between viscosity factors and electric properties of flowing blood not only in vitro but also in vivo. Recently we reported that with segmental BIA (analyzing the body considered as composed of 5 cylinders) predictive equations for various determinants of blood viscosity were closer than for the wole body. Another widely used BIA technique uses leg-to-leg impedance measurements so that two cylinders (the two legs) are analyzed. We investigated whether impedance measured with this technique (Tanita TBF-300) is also a predictor of blood viscosity factors. From viscometric measurements performed on venous blood drawn in recreative athletes over the range of shear rates 1 to 6000 s-1 (RHEOMETRE Anton Paar CP 50-1), we found a correlation between leg-leg resistance at 50 kHz (Rx[50 kHz]) and blood viscosity at 1000 s-1 (η1000= 0.0051 Rx[50 kHz] + 1.3265; r = 0.521 p = 0.028 yielding a prediction of η1000 (Bland Altman plot: bias 0.05 [RANGE - 0.24; 0.34]. Neither plasma viscosity nor the red cell rheology index «k» of Quemada's model are correlated with Rx[50 kHz], but hematocrit (Hct) does (Hct (%) = 0.0217 Rx[50 kHz] + 33.783; r = 0.480 p = 0.044) yielding a prediction of Hct (Bland Altman plot: bias - 0.11, [range - 1.67; 1.45]. The discrepancy between actual and predicted Hct is also correlated with resistance at 50 kHz (r = 0.575 p = 0.031) as does the discrepancy between actual and predicted Hct/viscosity ratio (r = -0.651 p = 0.006). Therefore, as other previously studied methods, leg to leg BIA predicts viscosity, suggesting that blood rheology may influence the passage of an electric current in the legs.

Association between Blood Viscosity and Cardiovascular Risk Factors in Patients with Arterial Hypertension in a High Altitude Setting.

Background Blood viscosity is a determinant of vascular resistance, and it is expected to contribute to blood pressure. Arterial hypertension (HTN), in addition to other cardiovascular risk factors, contribute to cardiac morbidity. Our study aimed to establish the association between cardiovascular risk factors including HTN and whole blood viscosity in Ecuadorian patients.Material and methodsWe studied 132 patients with the diagnosis of HTN. Fifteen cardiovascular risk factors were analyzed. The association between whole blood viscosity (WBV) and the number of cardiovascular risk factors was studied. The association between blood viscosity and risk factors was analyzed.Results One hundred and thirty-two patients were analyzed. Blood viscosity was associated with a number of cardiovascular risk factors. Creatinine, uric acid, total cholesterol, and low-density lipoprotein (LDL) values were significantly higher in patients with high blood viscosity.Conclusion Blood viscosity is a physiological variable associated with a number of cardiovascular risk factors in hypertensive patients. Such risk factors are related to renal function and lipid profiles. In high-altitude residents, polycythemia is common, and the consequences of high hematocrit on cardiovascular morbidity in this setting deserve special attention and warrant further research.

One-year follow-up of blood viscosity factors and hematocrit/viscosity ratio inelite soccer players.

We investigated to what extent aprediction 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: 18-32yr, 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 afunction 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 aclose 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.

« Optimal » vs actual hematocrit in obesity and overweight.

Equations of blood viscosity provide aprediction of the 'optimal' hematocrit' (hct) as the hct resulting in the highest value of the bell-shaped curve of hematocrit/viscosity ratio h/η. We investigated if overweight and obesity have an influence on these parameters. We compared 32 normal weight subjects, 40 overweight (BMI 25-30) and 38 obese subjects. There was no difference in the theoretical curve of h/η. The actual h/η is the same in the 3 groups but is always higher than the theoretical h/η in all groups. The actual h/η is lower in overweight than controls (p = 0.011). Modeling yields the same value of theoretical optimal hct across BMI classes. The 3 groups have the same values of actual hct, but actual is significantly lower than optimal in all cases (p < 0.001). Hematocrit is lower than predicted due to adiscrepancy between predicted and actual h/η which is due to the inter-subject variability of RBC rigidity ... The discrepancy between optimal and actual h/η is negatively correlated to RBC rigidity indexes even if the model uses afixed value of these indexes. Thus keeping in mind that the optimal hct should not be the same in the various parts of the vascular bed, its theoretical prediction with Quemada's equation appears to predict avalue higher than actual hematocrit but well correlated to it, and the agreement between optimal and actual hct is dependent on RBC flexibility. This leads to think that the body sets hematocrit below its ideal value in sedentary subjects in order to cope with the need of increasing blood viscosity factors in case of exercise without impairing O2 supply to tissues.

Acute and Short Term Hyperoxemia: How about Hemorheology and Tissue Perfusion?

Acute and Short Term Hyperoxemia: How about Hemorheology and Tissue Perfusion? Tissue perfusion is a major factor determining the prognosis, morbidity and mortality in ICU patients. Perfusion may carry on via uninterrupted delivery of sufficient substrate and oxygen to the tissues. From this point of view, determinants of tissue perfusion that routinely mentioned are cardiac output, vascular tonus, oxygen diffusion and transportation. The impact of blood viscosity and related hemorheological factors on microcirculation and tissue perfusion is frequently neglected. Under physiological circumstances, compensatory mechanisms maintain the stability of perfusion. However, it is well-established that the changes in aggregation and deformability of red blood cells are concomitant with alterations in blood fluidity at hypoxic conditions and this fact enhances the severity of hypoxemia. On the contrary, acute hyperoxemia is performed to achieve therapeutic goals or to prevent predicted hypoxemia during ICU facilities. Although the effects of hyperoxemia on vessel reactivity and ROS generation were previously indicated, its impact on hemorheology and tissue perfusion are not clear. Further studies are needed to disclose the influence of acute hyperoxemia performed during cardiopulmonary resuscitation, intubation, sedation, tracheal suction, etc., on tissue perfusion in critically ill patients.

Normal reference value of whole blood viscosity (230 s− 1) of old women and geographical factors

AimThis paper aims at supplying a scientific basis for standardizing the normal reference value of whole blood viscosity (230s−1) of Chinese old women. MethodsThe research is made to study the relationship between the normal reference value of 6707 samples of whole blood viscosity (230s−1) of old women and seven geographical factors in 70 areas in China. ResultsIt is found that the correlation between geographical factors and the normal reference value of whole blood viscosity (230s−1) of old women is quite significant (F=30.137, P=0.000). According to the normal reference value of old women's whole blood viscosity (230s−1) and geographical factors, one regression equation is inferred by using the method of enter regression analysis: Ŷ=13.47+0.0006383X1−0.001083X2−0.1379X3−0.05098X4−0.0008578X5−0.06221X6+0.2114X7±0.55.In the above equation, Ŷ is the reference value of whole blood viscosity (230s−1) of old women (mPa·s); X1 is the altitude (m); X2 is the annual sunshine duration (h); X3 is the annual mean air temperature; X4 is the annual mean relative humidity; X5 is the annual precipitation amount; X6 is the annual range of air temperature; X7 is the annual mean wind speed (m/s); and 0.55 is the value of the residual standard deviations. ConclusionIf geographical values are obtained in a certain area, the normal reference value of whole blood viscosity (230s−1) of old women in this area can be obtained by using the regression equation. Furthermore, according to the geographical factors, China can be divided into eight regions: Northeast China Region, North China Region, Shanxi–Shaanxi–Inner Mongolia Region, Middle and lower reaches of the Yangtze River Region, Southeast China Region, Northwest China Region, Southwest China Region and Qinghai–Tibet Plateau Region.

Contribution of blood viscosity in the assessment of flow-mediated dilation and arterial stiffness

Flow-mediated dilation (FMD) is a non-invasive index of endothelial function. In an attempt to standardize FMD for shear stimulus, shear rate (velocity/diameter), rather than shear stress (viscosity*velocity/diameter), is commonly used as a surrogate measure, although it is limited by individual differences in blood viscosity. The purpose of this study was to determine the contribution of whole blood viscosity to FMD and other key measures of vascular function. Blood viscosity, FMD, carotid artery compliance, and carotid-femoral pulse wave velocity (cfPWV) were measured in 98 apparently healthy adults varying widely in age (18-63 years). Whole blood viscosity was not significantly correlated with FMD, cfPWV, or carotid artery compliance. Shear rate was a stronger correlate with FMD than shear stress that takes blood viscosity into account (r = 0.43 vs 0.28). No significant differences were observed between whole blood viscosity and traditional risk factors for cardiovascular disease. Age was positively correlated with cfPWV (r = 0.65, p < 0.001) and negatively correlated with FMD (r = -0.24, p < 0.05) and carotid artery compliance (r = -0.45, p < 0.01). Controlling for viscosity did not reduce the strength of these relations. These results indicate that whole blood viscosity does not significantly impact measures of vascular function and suggests that the common practice to use shear rate, rather than shear stress, in the adjustment of FMD is valid.

No effect of increased water intake on blood viscosity and cardiovascular risk factors

Observational data have suggested that increased water intake decreases the risk of CHD. A postulated mechanism is that increased water ingestion reduces blood viscosity. The aim of the present study was to assess the effect of increased fluid intake on blood viscosity. Men (n 67) and postmenopausal women (n 27) with one or more risk factors for CVD who reported intake of < or =0.5 litres water daily were randomised to a control group (n 31), an intervention group (n 32) that increased their daily water intake by 1 litre/d and an intervention group (n 31) that ingested 1 litre blueberry juice/d. All were encouraged to continue their usual diet and lifestyle. Whole-blood viscosity and blood and urine chemistries were measured by standard techniques after 2 and 4 weeks. Urine volume increased (by a median of 872 and 725 ml in the water and blueberry juice groups, respectively, v. 10 ml in the control group; P< or =0.002), confirming the subjects' adherence to the protocol. Urine osmolality and urinary levels of Na, K and creatinine decreased in the water and blueberry juice groups v. the controls (P<0.05). No change was seen in whole-blood viscosity or in levels of fibrinogen, total protein, lipids, glucose, insulin, C-peptide or other chemistry and haematology variables. In conclusion, a postulated protective effect of increased water or fluid intake is not explained by a change in blood viscosity and increased fluid intake does not influence CVD risk factors in the short term.

In health and in a normoxic environment, V̇o2 max is/is not limited primarily by cardiac output and locomotor muscle blood flow

The following letter is in response to the Point:Counterpoint series “In health and in a normoxic environment, Vo2max is/is not limited primarily by cardiac output and locomotor muscle blood flow” that appeared in the February issue (vol 100: 744–748, 2006, <http://jap.physiology.org/content

Hemorheological Changes during Human Aging

Various researchers have reported an association of hemorheological, hematological and metabolic changes with human aging. In this article an attempt has been made to review the present understanding of hemorheological changes and their probable role in the development of certain disorders/diseases during aging. The rise in fibrinogen, blood viscosity, plasma viscosity, red cell rigidity, fibrin degradation products and early activation of the coagulation system are some of the most prominent findings. It is generally agreed that a rise in blood viscosity factors leads to a state of hypoperfusion which results in impaired microcirculation. The cumulative effect of these changes appears in the form of a disturbed blood flow profile in older subjects leading to the development or aggravation of various circulatory disorders. Many studies indicate that hemorheological parameters that change in a number of diseases prevalent during aging include hypertension, stroke, diabetes. In addition correlations found between hemorheological parameters in the aged and decrements in certain cognitive functions and behavioral patterns suggest that hemorheological changes contribute to nonclinical aging changes.

Whole Blood Viscosity, Blood Pressure and Cardiovascular Risk Factors in Healthy Blood Donors

Fossum E, Høieggen A, Moan A, Nordby G, Velund TL, Kjeldsen SE. Whole blood viscosity, blood pressure and cardiovascular risk factors in healthy blood donors.Whole blood viscosity contributes to the total peripheral resistance and has been suggested to be a risk factor for cardiovascular disease. Whole blood viscosity was measured using a direct technique in 105 healthy blood donors and in addition to establishing our reference values, the relationship to blood pressure and other cardiovascular risk factors was assessed. Whole blood viscosity correlated with systolic blood pressure (r = 0.29, p = 0.003), cholesterol (r = 0.21, p = 0.034), cholesterol/HDL cholesterol ratio (r = 0.33, p = 0.01), triglycerides (r = 0.37, p < 0.0005), body mass index (r = 0.29, p = 0.003) and waist-hip ratio (r = 0.30, p = 0.002). Subjects with systolic blood pressure > 130 mmHg (n = 16) had higher whole blood viscosity (p = 0.017) than those with lower blood pressure. Whole blood viscosity was significantly lower in women (n = 52) than in men at all shear rates (0.045 > p > 0.001). These results suggest that even in a population of healthy normotensive blood donors of a wide age range and either gender, there are positive correlations between directly assessed whole blood viscosity and a number of the components of the metabolic cardiovascular syndrome including systolic blood pressure, weight and blood lipids.

Blood perfusion studies in cerebrovascular accidents, hypertensives, diabetics and healthy controls

The objective of this study was to compare peripheral microvasculature status non-invasively in heal thy controls and recent stroke cases having history of hypertension. The high risk group of patients viz. hypertensives and diabetics were also included in the study. We used a combination of Laser Doppler flowmetry and reactive hyperemia test along with parallel estimation of blood viscosity factors such as, hematocrit, red cell rigidity, plasma viscosity and biochemical parameters. Reacti ve hyperemia was induced by arterial occlusion for 3.5 min. duration in the forearm of all four groups. Basal skin perfusion before inducing reactive hyperemia (Per bas)' did not vary significantly in any group. However, the increased maximum skin perfusion after inducing reactive hyperemia (Permax ) in the case of stroke and hypertension were found significantly different (p<0.05) as compared to healthy controls. The recovery time (Trh) i.e., time taken for induced maximum perfusion to return to basal value, were significantly less in stroke (p<0.05) and hypertensive groups (p<O.OOl) whereas it was significantly high in diabetic group «0.02) as compared to healthy controls. A reduced Trh may be considered as an indicative of myogenic dysfunction while a delayed Trh may be regarded as an indicative of metabolic dysfunction. Further the calculation of two dimensionless microcirculatory parameters reactive hyperemia perfusion index (RHPI) and reactive hyperemia time index (RHTI) were proposed for use in preliminary screening of the degree of myogenic or metabolic dysfunction in various disease conditions. The correlation of above mentioned parameters with blood viscosity factors were discussed.

Exercise Training and Bleed Viscosity in Patients With Ischemic Heart Disease

Several studies have suggested that regular exercise in healthy persons improves blood viscosity. 1–5 Regular exercise and exercise training have been shown to have several beneficial effects, including the prevention and modification of hypertension, hypercholesterolemia, diabetes mellitus, and obesity, and to have a role in both the primary and secondary prevention of coronary vascular events. 6 Whether exercise training, as prescribed in standard cardiac rehabilitation programs, can improve blood rheology has not been previously investigated. This study assesses whether a standard 10-week program of moderate-intensity aerobic exercise training had beneficial effects on whole blood viscosity and the factors that influence it among consecutive patients with ischemic heart disease who enrolled in cardiac rehabilitation.

Discussion on the relation between the average Chinese female whole blood viscosity (230 S −1) and geographic factors

Discussion on the relation between the average Chinese female whole blood viscosity (230 S −1) and geographic factors

The variation with gestational age of the rheological properties of the blood of the new-born.

A study has been made of the variation of blood viscosity and related factors with the gestational age of neonates from 24 weeks to normal term. Viscosity increases significantly over this period by 36% at high shear rate (128.5 s-1) and 250% at low shear (0.277 s-1). The high shear rate changes can be explained largely by the effects of variations in haematocrit and plasma viscosity. At low shear rate the same factors are involved together with changes in the plasma protein composition, in particular the age-related increase in the concentration of the proteins known to induce rouleaux formation. The variation in the degree of sialination of fibrinogen with gestational age may also play a part.

Modifications of blood rheology during aging and age- related pathological conditions

In principle there should not be any increase of blood viscosity factors (plasma viscosity, blood viscosity, aggregation of red blood cells, rigidity of red blood cells, dynamic thrombus formation) with aging in a healthy population. Such an increase would be due to pathological caused and not to aging per se. The pathological causes of the increase in the blood viscosity factors often observed in the elderly could be ascribed to the following: use of drugs (e.g. cigarette smoking); lack of exercise; unbalanced diet; psychological states such as anxiety and depression; presence of diseases such as heart disease or cancer or diabetes (although these disorders have the same effect in a younger population). The principal viscosity factors are explained, and their role in tissue perfusion, occlusions, infarctions and other disorders is described. This review will hopefully serve as an introduction to the studies of the haemorheology of aging. A counteraction of the elevation of blood viscosity factors might be helpful in ameliorating many diseases typical of aging, and should allow elderly people to remain active much longer.

Methods and instrumentation used in practice of clinical haemorheology.

The aim of practice of clinical haemorheology is to study patients who might present themselves with or without any clinical symptoms but who might suffer from silent or overt cardiovascular disorders, some forms of cancer, anxiety, etc. A presence and a prognosis of these disorders are linked to an increase and/or abnormality of one or more of the blood viscosity factors: blood viscosity, plasma viscosity, red cell aggregation and rigidity, platelet aggregation, ability for formation of thrombi, flow instability, etc. Hyperviscosaemia might be present in spite of normal or low viscosity of the whole blood. Different disorders can be described by 'profiles of viscosity factors' which form a rheological fingerprint specific to a particular disease or a group of disorders. Determination of viscosity factors is carried out utilizing a series of instruments: (a) rotational viscometers, (b) capillary viscometers, (c) erythrocyte sedimentation tubes in 20C and 37C water tanks, (d) variable frequency thrombo-viscometer, (e) slit-capillary photo-viscometer, etc. One known factor which is not measured routinely is 'inversion phenomenon', and this is due to complexity and expense of measurements. Biochemical studies, including fibrinogen assay and estimation of ABO blood groups, are carried out. Effect of drugs on blood viscosity factors can be studied in vitro or in vivo.