Hemorheological disturbances in patients with chronic cerebrovascular diseases

Hemorheological disturbances may occur in more than 40% of patients with ischemic cerebrovascular diseases. In this study the changes of rheological factors--hematocrit, plasma fibrinogen concentration, whole blood and plasma viscosity, red blood cell aggregation and deformability were investigated in 297 patients (173 males, 124 females, mean age 60 +/- 11 years) with transient ischemic attack or chronic phase (> 3 months after onset) ischemic stroke, and in 73 healthy volunteers (35 males, 38 females, mean age 38 +/- 7 years). Hematocrit, plasma and whole blood viscosity were significantly (p < 0.0001) elevated in cerebrovascular patients compared to controls. Plasma fibrinogen concentration (p < 0.001), red blood cell aggregation (p < 0.05) and deformability (p < 0.01) were also impaired in stroke patients. Hemorheological disturbances were dominant in stroke patients with diabetes, hyperlipidemia and smoking habits. Hematocrit, plasma viscosity and red blood cell aggregation showed a significant (p < 0.025-0.001) correlation with the severity of carotid artery stenosis. We could not find any characteristic distribution of rheological parameters among the three subtypes of brain ischemia. Our results show that all of the measured rheological parameters are significantly impaired in chronic ischemic cerebrovascular disorders, especially in diabetic, smoking and alcoholic patients. They correlate with the severity of the carotid artery stenosis, but there is no association with the type of ischemic stroke.     

Hemorheological study in patients with coronary artery disease

Hemorheological parameters (viscosity of whole blood, plasma viscosity, hematocrit, velocity of red blood cells) were studied in 30 patients with coronary artery disease (15 patients with acute myocardial infarction, 15 patients with chronic angina), 14 subjects at high risk for ischemic heart disease and 14 normal volunteers matched for sex and age. Viscosity of whole blood was high in all coronary disease patients and in high-risk subjects as compared with controls. Velocity of red blood cells was significantly decreased in these patients. On the other hand, plasma viscosity and fibrinogen values were in the normal range in both groups and hematocrit was only slightly elevated in patients with angina. Furthermore, there were no changes in rheological parameters during the period of observation (1 week). We can suppose that the hyperviscosity is due, above all, to the decreased red blood cell deformability both in coronary disease patients but also in high-risk subjects. It is probable that red blood cell damage is present before the acute ischemic event, and that is a preexisting cause and not a consequence of it.     

Association between hemorheological alterations and metabolic syndrome

The contribution of hemorheological alterations in the prothrombotic condition in patients with metabolic syndrome (MS) remains a question of debate. We aimed to determine the association between MS and hemorheological parameters by means of a case-control study in 61 MS patients and 89 controls without MS. We determined blood viscosity at 230 s(-1) (Brookfield DVIII viscosimeter); plasma viscosity (Fresenius capillary plasma viscosimeter); erythrocyte aggregation at stasis and 3 s(-1) (MA-1 erythrocyte aggregometer); erythrocyte deformability (Rheodyn SSD at shear stresses of 12, 30 and 60 Pascals) and fibrinogen, along with anthropometric, lipidic and inflammatory parameters. MS patients showed increased blood viscosity (p = 0.018), plasma viscosity (p < 0.001), fibrinogen (p < 0.001), erythrocyte aggregation (p < 0.001), and decreased erythrocyte deformability (p = 0.033). In the multivariate regression analysis, fibrinogen and triglycerides predicted plasma viscosity and erythrocyte aggregability, whereas erythrocyte deformability was associated with alterations in the hydrocarbonate metabolism. Blood viscosity related to abdominal obesity. The logistic regression analysis revealed that of all the MS components, only hypertriglyceridemia independently predicts plasma hyperviscosity (OR 3.75 CI 1.44-9.77 p = 0.007) and erythrocyte hyperaggregability (OR 2.41 CI 1.00-5.80 p = 0.050). Erythrocyte hyperaggregability (EA > 8.23) and hyperfibrinogenemia (fibrinogen > 358 mg/dL) were independent predictors of MS: OR 3.34, 95% CI 1.40-7.93, p = 0.006 and OR 2.42 95% CI 1.04-5.66, p = 0.041, respectively. We conclude that MS is associated with an altered hemorheological profile related to inflammatory, lipidic and glucose intolerance parameters which could favor the development of thrombo-embolic and athero-thrombotic events in MS patients.     

Associations of blood rheology and interleukin-6 with cardiovascular risk factors and prevalent cardiovascular disease

Haemorheological variables (whole-blood, plasma and relative blood viscosity, haematocrit, red cell aggregation, white cell count and fibrinogen) were measured in 753 men and 821 women aged 25-74 years, and related to cardiovascular risk factors and prevalent cardiovascular disease (CVD). Men had higher levels than women of blood viscosity, haematocrit, corrected viscosity and relative viscosity. Post-menopausal women had higher levels than pre-menopausal women of blood viscosity, haematocrit, corrected blood viscosity, plasma viscosity and fibrinogen: each of these differences was completely or partly abolished by use of hormone replacement therapy. Serum total cholesterol, triglycerides, diastolic blood pressure, body mass index and smoking markers showed positive associations with most rheological variables, whereas HDL-cholesterol, plasma vitamin C and social class showed inverse associations. Rheological variables were associated with prevalent CVD after age-adjustment. However, after multiple risk factor adjustment only plasma viscosity and red cell aggregation showed significant (P<0.04) associations in both men and women (comparing top to bottom quarters). Plasma interleukin-6 (measured in a 25% subsample of 196 men and 221 women) correlated significantly with age, fibrinogen, white cell count, plasma and blood viscosity, current smoking, and (in men) with low serum vitamin C levels; but not with other major risk factors or with prevalent cardiovascular disease.     

The effect of aspirin on hemorheological parameters of patients with diabetic retinopathy

Hemorheological factors play an important role in the pathogenesis of severe complications of diabetes. The diabetic retinopathy is the leading cause of blindness in patients aged 20-65 years. In our study we investigated the effect of aspirin on the hemorheological parameters in patients with different diabetic retinopathies.Hemorheological parameters (hematocrit, fibrinogen, plasma and whole blood viscosity, red blood cell aggregation) of diabetic patients with non-proliferative (n=14, mean age: 66 years) and proliferative retinopathy (n=8, mean age: 48 years) were measured. The results between the two groups were compared: twelve patients were taking aspirin (group A), while ten patients were not (group B).Hematocrit, fibrinogen, plasma and whole blood viscosity were significantly higher (p < 0.05-0.001) in patients with diabetic retinopathy who did not take aspirin than in those who took. No significant difference was observed in red blood cell aggregation parameters between the two groups. We could not find any significant difference in the measured parameters between patients with non-proliferative and proliferative diabetic retinopathy.According to our results, all the measured hemorheological parameters were in the pathological range, although aspirin treatment could decrease these factors and thus may help to prevent the progression of severe diabetic retinopathy and perhaps blindness.     

Plasma fibrinogen in relation to the severity of arteriosclerosis in patients with stable angina pectoris after myocardial infarction

BACKGROUND: Authors both of retrospective and of prospective studies have demonstrated that there is a relationship between concentration of fibrinogen in plasma and the angiographically determined severity of coronary heart disease (CHD). OBJECTIVE: To determine the relevance of the plasma fibrinogen concentration for the severity of CHD, particularly in cases with additional arteriosclerotic changes in the extracranial arteries supplying the brain [cerebrovascular disease (CVD)], in the pelvic/leg arteries [peripheral occlusive arterial disease (POAD)], or in both. PATIENTS AND METHODS: In a retrospective cross-sectional survey the cardiological and angiographical status of a total of 1112 male and 299 female patients with stable angina pectoris after sustained myocardial infarction and an age-matched control group of 326 male and 138 female subjects with no clinical symptoms of CHD was determined, together with measurements of plasma fibrinogen, dynamic plasma viscosity and D-dimers. RESULTS: More than two-thirds of the patients with arteriosclerosis had plasma fibrinogen concentrations in the uppermost tertile of the control range (men > 2.75; women > 2.83 g/l). Plasma fibrinogen concentration was correlated to the severity of CHD (for men r = 0.173, P < 0.001; for women r= 0.144, P < 0.013). Patients with generalized arteriosclerosis had higher plasma fibrinogen concentrations than did those suffering from CHD only (for men, control 2.65 +/- 0.51, CHD 3.07 +/- 0.73, CHD plus POAD 3.17 +/- 0.77 and CHD plus POAD plus CVD 3.45 +/- 0.78 g/l; for women, control 2.69 +/- 0.44, CHD 3.25 +/- 0.67, CHD plus POAD 3.19 +/- 0.77, CHD plus POAD plus CVD 3.60 +/- 0.84 g/l). Multivariate analysis showed that C-reactive protein, D-dimers and dynamic plasma viscosity accounted for 48.2% (for men) and 49.4% (for women) of the variance in plasma fibrinogen concentration. CONCLUSIONS: Our findings demonstrate that there is not only a correlation between plasma fibrinogen concentration and the severity of CHD, but also a correlation to the incidence of additional POAD or CVD.     

Plasma lipids and blood viscosity in patients with cerebrovascular disease

It is known that plasma lipids could increase the cerebrovascular risk through alteration of the hemorheological profile. The aim of the study was to evaluate the relationship between blood viscosity parameters and plasma lipids in patients with cerebrovascular disease (CVD). The study included 43 patients with transient ischemic attacks (TIAs), 53 patients with chronic unilateral cerebral infarctions (UCI) and 57 patients with risk factors (RF) for CVD. Whole blood viscosity (WBV) at different shear rates by Couette rotational viscometer Contraves Low Shear 30, plasma viscosity (PV) with capillary viscometer, hematocrit (Hct), fibrinogen (Fib), Cholesterol (Chol), triglycerides (Tg) and high-density lipoproteins (HDL) were examined in all patients and in a control group of 56 presumed healthy subjects. The hemorheological results showed increase of Hct, Fib, WBV and PV in the patients with TIAs and UCI; it was more pronounced in the UCI patients. Significant increase of Hct and WBV in the group with RF for CVD was also found. The elevation of Chol and Tg predominated in the patients with UCI and in the subjects with RF for CVD. These lipid variables correlated significantly with PV in the TIAs and RF for CVD groups. Conclusion is drawn about the significance of plasma Tg for decrease of blood fluidity and for impairment of the cerebral circulation in CVD.     

Hemorheological parameters in correlation with the risk factors for carotid atherosclerosis

The study aimed to follow the relationship between some hemorheological variables and the main risk factors (RF) for carotid atherosclerosis (CA). Carotid atherosclerosis was evaluated by color duplex sonography of the carotid arteries in 18 patients with RF for CA, 31 patients with transient ischemic attacks (TIAs), 21 patients with chronic unilateral cerebral infarctions (UCI) and 11 healthy subjects without RF for CA. The examined hemorheological variables were whole blood and plasma viscosity, hematocrit and fibrinogen. They were correlated with intima-media thickness (IMT) of the common carotid and the internal carotid arteries and with other main RF for CA: hypertension, diabetes mellitus, coronary heart disease, and hyperlipidemia. The hemorheological investigation showed an increase in blood and plasma viscosity at different shear rates and it was more expressed in the group with UCI. The neurosonographic investigation revealed an increase in the IMT and carotid artery stenoses in the patients' groups with CVD. These were also more frequent in the patients with UCI. Different correlations were established between the hemorheological parameters, the IMT of the carotid arteries and other RF for CA. In the group with UCI, the hematocrit and the whole blood viscosity correlated significantly with the IMT, arterial blood pressure and cholesterol values. These data confirm the influence of the hemorheological parameters on carotid blood vessel walls and on blood flow in patients with CVD.     

Fetal hemorheology in normal pregnancy and severe preeclampsia

Hemorheological parameters were determined in 45 pairs of mothers with severe preeclampsia and their newborns in comparison with 45 women with uncomplicated pregnancies and their newborns. In both groups we investigated red cell deformability, the plasma viscosity, the red cell aggregation (during stasis and low flow), the macromolecules fibrinogen and factor VIIIR:Ag (VWF), and the blood count parameters hemoglobin, hematocrit, white cells, platelets, reticulocytes, MCV, MCHC. Cholesterol and triglycerides were correlated to the parameter of red cell deformability measured as red cell elongation. We found a significant lower plasma viscosity, red cell aggregation, fibrinogen, cholesterol, triglycerides and VWF in cord blood with a close association between plasma viscosity and fibrinogen (r = 0.56, p = 0.001). The red cell deformability measured as red cell elongation was statistically higher in the cord blood compared to the mothers and associated with a higher MCV. In contrast the MCHC values remained unchanged. Hematocrit and hemoglobin in the cord blood were higher than in the mothers. The incidence of fetal hyperviscosity-polycytemia syndrome in women with severe preeclampsia was between 4.7% and 4.9%. An elevated red cell aggregation was found in 2.8% (stasis) and 4.8% (low flow state), respectively. We conclude that in fetal blood the higher hematocrit and the presence of larger red cells do not cause impaired fetal hemorheology.     

Hemorheological alterations in patients with diabetic retinopathy

Hemorheological factors play an important role in the pathogenesis of different cardiovascular diseases. Diabetes mellitus resulting in micro- and macroangiopathies is one of the major risk factors for cardiovascular diseases. In our present study the hemorheological parameters (hematocrit, plasma fibrinogen level, plasma and whole blood viscosity, red blood cell aggregation) of 30 diabetic patients (mean age: 57 +/- 12 years) and 30 healthy volunteers (mean age: 31 +/- 10 years) were examined. The fundus appearance of patients showed diabetic retinopathy; non-proliferative stage in 22 cases, preproliferative or proliferative stage in 8 cases. The measured hemorheological parameters of the examined patients were in the pathological range and were significantly higher than those of healthy volunteers (hematocrit: p < 0.01; plasma fibrinogen: p < 0.001; plasma viscosity: p < 0.01; whole blood viscosity: p < 0.001; red blood cell aggregation: p < 0.01). In our study there was not significant difference in the hemorheologic variables of patients with different stages of retinopathy. Our results propose the importance of hemorheologic factors in the development of diabetic microangiopathy.     

Hemorheological disturbances in cerebrovascular diseases

The aim of the study was to evaluate the possible relationship of the hemorheological disturbances with the clinical symptoms and some risk factors (RF) for cerebrovascular diseases (CVD). The study included 68 patients with CVD, 29 with transient ischemic attacks (TIA) and 39 with chronic unilateral cerebral infarctions (UCI) and 47 healthy control subjects. A questionnaire for RF for CVD was filled. Hemorheological variables: leucocytes, hemoglobin, hematocrit, fibrinogen (Fib), plasma (PV) and whole blood viscosity (WBV) at different shear rates by Couette rotational viscometer Contraves Low Shear 30 were investigated and the hemorheological indices of erythrocyte aggregation (IEA), erythrocyte deformability (IED) and of oxygen transport to tissues (TO(2)) were calculated. The arterial hypertension was the most frequent RF in the examined patients'. The hemorheological investigation showed significant increase of Fib in the patients with TIA and of PV and WBV in both patients' groups. The comparative study of the hemorheological variables with the RF for CVD showed predominating significant correlations with blood pressure (systolic, diastolic and mean) values, with age, cholesterol, physical activity and the body mass index. Our study confirms the possibility the hemorheological variables to be accepted as RF for development of stroke and for its recurrences.     

Hemorheological mechanisms in Alzheimer's disease

OBJECTIVE: The aim of the present study was to elucidate the underlying mechanisms responsible for hemorheological abnormalities in elderly patients with Alzheimer's disease (AD). SUBJECTS AND METHODS: Twenty-one patients with AD and twenty-three age-matched healthy controls (CON) were studied. We used a controlled-shear rate rheometer generating various flow fields in vitro for simulating blood flow in vivo. The applied experimental techniques provided valid and quantitative data for the analysis of hemorheological abnormalities associated with AD. Principal blood biochemical parameters and hemorheological parameters, including blood viscosity, erythrocyte deformability, erythrocyte aggregation and oxygen transport efficiency of blood were assessed. RESULTS: The results show no statistically significant difference in most of the blood biochemical parameters between the AD patients and the CON, except that fibrinogen concentration and mean corpuscular cell volume level of erythrocytes (MCV) were significantly higher in the AD patients. Hemorheological parameters including blood viscosity, plasma viscosity, and blood viscoelasticity in the AD patients were considerably higher than the respective factors in the CON. Owing to the MDA levels of the AD patients being significantly higher than that of the CON, the AD patients also showed a decrease in erythrocyte deformability and an increase in blood flow resistance despite the lack of any significant difference in erythrocyte rigidity. In addition, the erythrocyte aggregation of AD patients was higher than that of the CON and reduced oxygen transport efficiency of blood was observed in the AD patients. CONCLUSIONS: The hemorheological abnormalities found in AD patients may be explained by the parallel findings of oxidative damage on erythrocyte membranes that could result in a decrease of erythrocyte deformability. Furthermore, the oxidative stress-induced elevation of fibrinogen concentration could lead to accelerated erythrocyte aggregation as a consequence of a rise in blood viscosity and blood viscoelasticity. Taken together, these factors may impair the oxygen transport efficiency of blood in AD patients.     

Hemorheological investigations in patients with polycystic kidney disease

Polycystic kidney disease (PKD) is associated with an increased incidence of hypertension and cardiovascular abnormalities. As hemorheology is an important hemodynamic determinant and may contribute to vasculopathies we measured whole blood viscosity and red blood cell (RBC) and plasma rheological factors in 38 patients with PKD and compared this data with similar measurements in age- and sex-matched healthy controls. Renal function was assessed by plasma creatinine concentration. Analysis of the data showed that the PKD group had a significant reduction in mean hematocrit and an increase in mean plasma viscosity and mean plasma fibrinogen concentration. Intrinsic RBC rheology assessed by standardised viscosity measurements was impaired in patients with PKD compared to control subjects. The changes in plasma and RBC rheology did not however result in increased whole blood viscosity in the patients with PKD due to the reduction in hematocrit level. Correlation analyses demonstrated a significant relationship between increased plasma creatinine concentration and lower hematocrit, decreased whole blood viscosity and impaired RBC deformability but not with increased plasma viscosity or plasma fibrinogen concentration. This study shows that although PKD is associated with mild abnormalities in plasma rheology and intrinsic RBC rheology these changes are offset by a reduction in hematocrit. The changes in RBC rheological determinants in PKD appeared to be related to the degree of renal impairment.     

The possible role of hemorheology in atherothrombogenesis.

Conventional risk factors predict only about 30-50% of incidental cases in cardiovascular diseases, which are still the leading cause of death in western societies. During the last decade, the importance of thrombosis as an essential mechanism in acute myocardial infarction (AMI) and stroke has been established. The introduction of thrombolysis has led to an impressive reduction in AMI case fatality and possibly also to a substantial amelioration of its prognosis. Evidence from experimental, clinical and epidemiological studies suggest, that several hemostatic and hemorheological factors (e.g., fibrinogen, Factor VII, plasma viscosity, hematocrit, red blood cell aggregation, total white cell count) might not only play an important role in the evolution of acute thrombotic events, but may also take part in the pathophysiology of atherosclerosis. An increasing number of studies reports altered hemostatic and hemorheological parameters to be associated with smoking, hyperlipoproteinemia, and high blood pressure, as well as with adverse dietary habits and other life-style factors. To date, their way of interaction with the atherosclerotic process is poorly understood. Hemorheological or hemostatic mechanisms that might promote thromboatherogenesis include the predisposition to thrombosis via a hypercoagulable state, the enhancement of atherosclerosis by fibrinogen and its metabolites, and finally the reduction of blood flow through various rheological effects (e.g., increase in plasma viscosity and red cell aggregation, or leukocyte activation). Future research should focus in more detail on the interrelationship between accepted risk factors and the hemostatic system as well as hemorheological parameters. Deeper insight into the mechanisms involved might lead to new preventive strategies as well as to therapeutic procedures in the management of atherosclerosis and associated thrombotic events.     

Hemorheological and hemodynamic parameters in patients with essential hypertension and their modification by alpha-1 inhibitor drug treatment

Hemorheological factors play an important role in the pathogenesis of different cardiovascular diseases. The hemorheological and hemodynamic parameters in essential hypertension and their possible modification by antihypertensive treatment were examined in the following two studies. In the first study the fundus appearance and hemorheological parameters (plasma and whole blood viscosity (WBV), fibrinogen level) of 33 hypertensive patients (mean age: 55 years) were examined. The fundus appearance showed retinopathy in all the cases between stages I-III. All the measured hemorheological parameters of the examined patients were in the pathological range (WBV at 90 s(-1): 5.18 mPa s) and were significantly (p < 0.01) higher than in healthy controls (WBV at 90 s(-1): 4.18 mPa s). The hemorheological factors showed a parallel deterioration with the fundus appearance, namely their values were significantly (p < 0.01) higher in patients with a fundus appearance stage III (WBV at 90 s(-1): 6.02 mPa s) than stage I (WBV at 90 s(-1): 4.51 mPa s). These results show that there is a correlation between hemorheological parameters and fundus appearance in hypertensives, and this suggests that hemorheological factors may play a role in the development of hypertensive retinopathy. In the second study the hemorheological and hemodynamical effects of Doxazosin, a selective alpha-1-adrenoreceptor blocker agent, was examined in twenty patients (mean age: 54 years) with essential hypertension. Hemorheologic (hematocrit, fibrinogen, plasma and whole blood viscosity) and hemodynamic (cardiac output and index, total peripheral resistance) parameters and plasma lipids were determined. The measurements were carried out before the beginning of the treatment, after 1 week and after 12 weeks treatment periods. Besides significant reduction of blood pressure and total peripheral resistance (p < 0.001), a decrease in cholesterol (p < 0.001) and triglycerides (p < 0.01) levels and a beneficial effect on hemorheological parameters was detected. Fibrinogen and plasma viscosity decreased significantly (p < 0.01). Hematocrit value was also lower after one week (p < 0.001), then an increase could be seen. Whole blood viscosity showed similar changes as hematocrit, but the degree of its final increase was slighter, which was supported by the significantly lower value of corrected blood viscosity (p < 0.05). All these findings indicate that hemorheological factors may play a role in the pathogenesis and in the development of organ damages in hypertension.     

Gender differences in hemorheological parameters of coronary artery disease patients

Plasma fibrinogen concentration, plasma and whole blood viscosity (WBV) are independent risk factors of coronary artery disease (CAD). Fibrinogen seems to be a relatively stronger risk factor for women than for men, but men are more endangered by higher hematocrit (Hct) and WBV than women are. We have previously reported that a theoretically optimal Hct value can be determined using Hct/WBV ratio in healthy subjects, hyperlipidemic and Raynaud's disease patients. Our aim was to examine whether Hct/WBV ratio is differently correlated with Hct in men and women with proven CAD. In a retrospective study we analysed the hemorheological data of 162 CAD outpatients (107 men and 55 women). Coronary angiography, echocardiography and impedance cardiography were performed. Hemorheological parameters (Hct, fibrinogen level, plasma viscosity, WBV), blood picture, serum lipid concentrations were determined and Hct/WBV ratio was calculated. Mean ages of male and female patients were similar (54.9 and 55.4 years, respectively), but men had significantly higher coronary angiography score than women. Mean left ventricular ejection fraction, stroke volume index and cardiac index showed no significant differences in men and women. Similarly, lipid concentrations, fibrinogen levels and plasma viscosities demonstrated no statistical differences. However, Hct, WBV and Hct/WBV ratios were significantly higher in male than in female patients (p < 0.00001; p < 0.00001 and p < 0.005, respectively). The most striking gender difference was found in the correlation between Hct/WBV ratio and cardiac index. Men older than 56 years showed negative, women positive correlation (r = -0.485, p = 0.01; r = 0.468, p = 0.006, respectively). This study demonstrates that Hct/WBV ratio as a rheological oxygen carrying capacity parameter is positively correlated with the cardiac index as it can be expected. However, the correlation is negative in elder men indicating an unhealthy relation between hemodynamic and hemorheologic parameters.     

老年单纯舒张型高血压患者血液流变学和左心参数改变

对３５例老年单纯舒张型高血压患者血液流变学和左心参数测定的结果表明：老年单纯舒张型高血压患者血液粘度高于正常人，左心结构和舒张功能随病程的延长而出现异常。推测血液粘度增高，特别是高切变率血粘度增高和纤维蛋白原增加可能参与老年单纯舒张型高血压患者舒张压的形成，老年单纯舒张压升高也是心脏靶器官损害的危险因素。     

Hypertriglyceridemia is associated with an elevated blood viscosity Rosenson: triglycerides and blood viscosity

Elevated blood viscosity is a predictor of cardiovascular disease. The major determinants of blood viscosity are hematocrit and plasma viscosity. Plasma triglycerides elevate plasma viscosity; however, the contribution of plasma triglycerides to blood viscosity after adjustment for other major covariates has not been reported. This cross-sectional study of 257 adult subjects evaluated the associations between fasting plasma lipids, fibrinogen, total serum protein, hematocrit and blood viscosity. Blood viscosity was measured at 37 degrees C with a coaxial cylinder microviscometer at shear rates of 100 and 1 s(-1). Blood viscosity values are reported both as uncorrected measurements and measurements corrected to a hematocrit of 45% by a regression equation. Uncorrected blood viscosity at a shear rate of 100 s(-1) was significantly associated with triglycerides, fibrinogen, high density lipoprotein (HDL) cholesterol, total serum protein, and hematocrit using stepwise multivariate regression analysis. When corrected blood viscosity at 100 s(-1) was the dependent variable, there were statistically significant associations with triglycerides, HDL cholesterol, and total serum protein. Corrected blood viscosity at 1 s(-1) was significantly associated with triglycerides, fibrinogen, total serum protein, and an indicator variable for diabetes mellitus. This study supports an additional mechanism whereby triglycerides may contribute to cardiovascular risk.     

The hemorheological effects of raloxifene in postmenopausal women with osteoporosis. Results of a 3-year placebo-controlled clinical trial

Raloxifene, the prototype of the selective estrogen receptor modulators, has been associated with an increased risk of venous thromboembolism. As hemorheological factors may be involved in thrombus formation this placebo-controlled study investigated whether raloxifene was associated with changes in determinants of blood viscosity. Fifty-seven post-menopausal women were randomly assigned to receive placebo, raloxifene 60 mg/day, or raloxifene 120 mg/day for 36 months. Venous blood samples were collected at baseline and at 12-monthly intervals and used to measure hematocrit, whole blood and plasma viscosity and plasma fibrinogen concentration. Time- and treatment-related changes in the grouped and pooled data was analysed using ANOVA with repeated measures and correlation matrices. The mean values of all the hemorheological indices showed small inconsistent changes within the normal reference range over the 36-month period of the study. There was a small but significant decrease over time in high shear rate blood viscosity and plasma viscosity in raloxifene-treated subjects compared to those receiving placebo (p<0.05). Correlation analyses showed the anticipated relationships between blood viscosity and hematocrit and plasma viscosity levels and also between plasma viscosity and plasma fibrinogen concentration. No subject developed a thromboembolic vascular event during the study. These results show that compared with placebo treated-subjects, long-term raloxifene treatment in post-menopausal women, at a dose of either 60 or 120 mg daily, was not associated with adverse changes in hemorheological factors that may contribute to venous thromboembolism.     

Effects of posture and ergometer-specific exercise modality on plasma viscosity and plasma fibrinogen: the role of plasma volume changes

The aim of the present study was ascertain the effects posture and exercise modality on the main determinants of blood rheology. Thirteen subjects performed two exercise trials, in random order, at approximately 70% VO(2) max for 45-min. One trial was performed on a motorized treadmill at an intensity corresponding to 70% VO(2) max, while the other was performed on a stationary pike at an intensity corresponding to 70% VO(2) max. In the cycling trial subjects stood for 30-min, followed by sitting for 30-min then cycled for 30-min at 70% VO(2) max. In the treadmill trial, subjects sat for 30-min followed by standing for 30-min then ran on the treadmill for 30-min at 70% VO(2) max. Variations of body postures prior to exercise were associated with opposite changes in plasma volume, plasma viscosity and plasma fibrinogen. When post exercise raw data were not adjusted for plasma volume changes, a significant increase (p < 0.05) in plasma viscosity and plasma fibrinogen was found with no difference between the cycling and running trials. However, the increase in plasma viscosity and fibrinogen were no longer apparent when the raw data post exercises were adjusted for plasma volume changes. Changing body posture from standing to sitting and vice versa were associated with opposite changes in plasma volume and mirrored the changes in plasma viscosity and fibrinogen. In addition, ergometer-specific vigorous exercises at the same relative intensity, irrespective of its modality, transiently increased plasma viscosity and plasma fibrinogen mainly due to exercise-associated haemoconcentration.