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PubMed1992

[Raynaud's phenomenon and blood viscosity].

Raynaud's phenomenon is mainly linked with cold provoked vasomotor perturbations, but also with rheological alterations since blood viscosity is enhanced by lowering temperature. Several methods are available for studying distal vascularization: peri-ungual capillaroscopy, digital plethysmography and laser-Doppler. Digital arteriography must be reserved to serious ischemia regarding the general anesthesia needed to avoid spasm. All these methods explore especially the vessel wall. Conservely, blood viscosity which has been developed for 25 years investigates the content of the vessel. Since 1965, numerous hemorheological studies pointed out the rheological disorders, especially those concerning plasma and blood viscosity. The most usual viscometry abnormalities revealed erythrocyte hyperaggregation, red cell hypodeformability, blood and plasmatic hyperviscosity. In a comparative study, 46 patients with Raynaud's phenomenon were studied: we performed peri-ungual capillaroscopy, plethysmography and viscosity measurements. The results demonstrated a link between capillaroscopy and thixotropy. Both investigations are never normal at the same time in connectivites and never abnormal at the same time in Raynaud's disease (primary Raynaud's phenomenon). In conclusion hemorheological studies showed nearly normal rheological parameters in Raynaud's disease, but abnormal rheological parameters in secondary Raynaud's phenomenon.

Adult↗
PubMed1990

Increased whole blood viscosity during coronary artery bypass surgery. Studies to evaluate the effects of soluble fibrin and poloxamer 188.

This study was designed to test the hypothesis that soluble fibrin complexes resulting from the trauma of surgery could produce elevated blood viscosity, to characterize the soluble fibrin polymers, and to evaluate in vitro the effect of a new hemorheologic agent, poloxamer 188, on viscosity in these abnormal situations. Ten patients undergoing aortocoronary bypass surgery were studied before and at various times after surgery. By 6 h after surgery, the mean hematocrit decreased by 23%, fibrinogen decreased 48%, and erythrocyte sedimentation rate decreased 33%, whole blood viscosity at a low shear rate rose on average of 69% and soluble fibrin rose 118%. Over the 6-day observation period, the concentrations of soluble fibrin paralleled the changes in viscosity, whereas the concentrations of fibrinogen varied nearly inversely with viscosity. The effects of various forms of fibrinogen and fibrin were tested by additions to normal blood. Soluble fibrin polymers, but not fibrin monomers, increased blood viscosity two to three fold. Poloxamer 188 reduced the viscosity of all patient samples to the normal range. These data support the hypothesis that increased whole blood viscosity at low shear rates is caused by hydrophobic adhesion of fibrin polymers to red cells and that poloxamer 188 normalizes viscosity by effectively disrupting the weak hydrophobic bonds.

Biopolymers↗
PubMed2004

Is hemoglobin desaturation related to blood viscosity in athletes during exercise?

Several studies have suggested that athletes with low hemoglobin saturation during exercise may experience impaired pulmonary blood gas exchange during maximal exercise. Blood viscosity may be implicated in exercise-induced pulmonary hemorrhage in race horses. We hypothesized that blood rheology may contribute to impaired gas exchange and reduced hemoglobin saturation during exercise in humans. A group of 20 highly trained endurance athletes participated in this study, 9 with low hemoglobin saturation during exercise (Low-SpO (2) group) and 11 with normal hemoglobin saturation (High-SpO (2) group). All subjects performed a progressive exercise test conducted to V.O (2max). Venous blood was sampled at rest, 50 % V.O (2max) and maximal exercise. Blood viscosity (etab) was measured at very high shear rate (1000 s (-1)) and 37 degrees C with a falling ball viscometer. The erythrocyte rigidity coefficient, "Tk", was calculated using the Dintenfass equation. At rest, no significant difference in etab was observed between the two groups (3.00 +/- 0.08 mPa . s vs. 3.01 +/- 0.04 mPa . s for the Low-SpO (2) and High-SpO (2) group, respectively). At 50 % V.O (2max) and maximal exercise, etab was higher in Low-SpO (2) (p < 0.01). Tk decreased in High-SpO (2) (p < 0.01) but remained unchanged in the other group during testing. The greater increase in etab in the Low-SpO (2) group during exercise may therefore have been due to the lack of reduction in Tk. As suggested by previous studies, the greater increase in blood viscosity in athletes with low hemoglobin saturation may lead to vascular shear stress. Whether this could impair the blood gas barrier and result in exercise-induced hypoxemia requires further study.

Adult↗
PubMed2005

The influence of two different hydroxyethyl starch solutions (6% HES 130/0.4 and 200/0.5) on blood viscosity.

We performed the current study to investigate the influence of 2 different hydroxyethyl starch (HES) solutions, the novel medium molecular weight HES 130/0.4 (6%) and HES 200/0.5 (6%), on plasma and whole blood viscosity in vitro and ex vivo in patients with severe head injury. For the in vitro experiments, blood was incubated with increasing concentrations (0%-50% vol/vol plasma) of either 6% HES 130/0.4 or 6% HES 200/0.5 solution. Plasma viscosity and whole blood viscosity (hematocrit [Hct] 45%) at high (94.5 s(-1)) and low (0.1 s(-1)) shear rates were determined. Both HES solutions increased plasma viscosity, but HES 130/0.4 to a lesser extent than HES 200/0.5. Whole blood viscosity was significantly less with HES 130/0.4 than with HES 200/0.5 at concentrations of 37.5% and larger. In the ex vivo study on 31 patients with severe cranio-cerebral trauma treated randomly with either HES 130/0.4 or HES 200/0.5 over several days, frozen plasma samples were thawed and plasma viscosity was determined. Blood was reconstituted with normal erythrocytes (0, Rh neg, Hct 45%) for whole blood viscosity measurements. In both groups plasma and blood viscosity tended to increase over time without statistical significance. Although the prominent effects found in vitro are not in keeping with the ex vivo data, they are likely to reflect the true clinical situation during repetitive, large-dose HES administration. We therefore conclude that HES 130/0.4 may have hemorheological advantages over conventional HES 200/0.5 when used in large quantities.

Blood Viscosity↗
PubMed1992

Hematocrit and whole blood viscosity in newborns: analysis of 100 cases.

Hematocrit (Hct) and whole blood viscosity was studied at a mean age of ten hours in 100 neonates. Group A (n = 25), were term normal newborns, Group B (n = 25) were preterms, Group C (n = 20) were term small for gestation (SGA) and Group D (n = 30) had perinatal hypoxia. Blood viscosity was estimated in all cases at shear rates 94.5, 51.2, 20.4 and 8.1 and intergroup variability in viscosity compared at shear rate 51.2. The mean hematocrit (Hct) (59.4%) and viscosity (8.2 cps) was higher in Group A as compared to other groups, but the difference was not significant (p greater than 0.05). The upper limit of viscosity in Group C (11.9 cps) was higher than in all other groups but this difference was also not significant (p greater than 0.05). With decrease in shear rates a reciprocal increase in viscosity was noted in all four groups. Seventeen neonates (17%) had polycythemia of which eight (47.5%) were SGA. Twelve per cent preterms were polycythemic. Only 3% of neonates had hyperviscosity. The mean Hct and viscosity of the 17 cases with polycythemia was 70.9 and 9.21 cps, respectively, which was significantly higher than mean Hct and viscosity of Group A (p less than 0.05). Partial exchange transfusions were done in five neonates with Hct greater than 75%, of which only one had hyperviscosity. Post-exchange viscosity was not estimated. Whereas, three neonates with polycythemia were symptomatic, none of these had hyperviscosity. A linear correlation between Hct and viscosity was observed (r = 0.67).

Blood Viscosity↗
PubMed2004

A blood-oxygenation-dependent increase in blood viscosity due to a static magnetic field.

As the magnetic field of widely used MR scanners is one of the strongest magnetic fields to which people are exposed, the biological influence of the static magnetic field of MR scanners is of great concern. One magnetic interaction in biological subjects is the magnetic torque on the magnetic moment induced by biomagnetic substances. The red blood cell is a major biomagnetic substance, and the blood flow may be influenced by the magnetic field. However, the underlying mechanisms have been poorly understood. To examine the mechanisms of the magnetic influence on blood viscosity, we measured the time for blood to fall through a glass capillary inside and outside a 1.5 T MR scanner. Our in vitro results showed that the blood viscosity significantly increased in a 1.5 T MR scanner, and also clarified the mechanism of the interaction between red blood cells and the external magnetic field. Notably, the blood viscosity increased depending on blood oxygenation and the shear rate of the blood flow. Thus, our findings suggest that even a 1.5 T magnetic field may modulate blood flow.

Adult↗
PubMed2002

Effects of antihypertensive therapy on hemorheological profiles in female hypertensive patients with initially low or high whole blood viscosity.

This study was designed to examine changes of hemorheological parameters in essential arterial hypertension subjects following antihypertensive drug therapy. Eighty two female subjects were enrolled, and sub-divided into two groups based upon their high shear whole blood viscosity being lower (L) or higher (H) than normal controls. Equal numbers of L and H subjects were then treated for four weeks with one of four agents: angiotensin-converting enzyme inhibitor (ACE-inhibitor, Spirapril - 6 mg/day); calcium antagonist (Isradipin - 5 mg/day); beta-1-blocker (Talinolol - 100 mg/day); diuretic (Indapamide - 1.5 mg/day). Both prior to and following drug treatment for six weeks, hemorheological measurements included plasma viscosity; high and low shear whole blood viscosity, hematocrit, fibrinogen and RBC aggregation. Treatment with each of the four drugs significantly (p<0.05) reduced blood pressure in both the L and H groups. However, the hemorheological effects of antihypertensive drug therapy differed markedly between groups: plasma and whole blood viscosity were significantly elevated in the L groups whereas these parameters were significantly decreased in the H groups. Fibrinogen levels and RBC aggregation decreased in both groups, whereas hematocrit was unaffected. These results thus suggest that the rheologic effects of antihypertensive drug therapy depend strongly on the initial, pre-treatment status of the subject, and that for some subjects, such therapy can result in adverse hemorheological alterations.

Antihypertensive Agents↗
PubMed1989

Blood viscosity and hearing levels in the Caerphilly Collaborative Heart Disease Study.

Data from 342 men who are participants in the Caerphilly Collaborative Heart Disease Study were used to replicate a previous report of a significant relationship between measures of whole-blood viscosity and hearing levels in persons with sensorineural hearing impairment. In the unselected data, there were significant relationships between measures of whole-blood viscosity at high shear rates and hearing threshold levels at 2000 and 4000 Hz, even after accounting for the effects of age and socioeconomic group. In a subset of the data containing 124 persons selected on the basis of likely sensorineural hearing impairment, there were significant relationships between whole-blood viscosity and hearing level at all frequencies, with stronger effects at the higher frequencies. The data support the contention of a potentially important relationship between whole-blood viscosity and sensorineural hearing impairment.

Audiometry, Pure-Tone↗
PubMed1992

Blood viscosity parameter correlation with types of leukemia.

We investigated the hemorheological, hematological and biochemical parameters in 30 cases of acute lymphocytic leukemia (ALL), 21 cases of acute myelogenous leukemia (AML) and 30 cases of chronic myelogenous leukemia (CML). The parameters studied include whole blood viscosity, plasma viscosity, erythrocyte sedimentation rate (ESR), red cell filterability, hematocrit, platelet count and aggregation, fibrinogen, hemoglobin, leucocyte count, bleeding time and lactate dehydrogenase activity (LDH). In the cases of ALL we observed significant decrease in whole blood viscosity, hemoglobin, hematocrit and platelet count but an increase in plasma viscosity, fibrinogen, bleeding time and LDH activity. In the cases of AML, we observed increase in whole blood viscosity, plasma viscosity, ESR, fibrinogen, leucocyte count, bleeding time and LDH activity but decrease in the hemoglobin, hematocrit and platelet count. In the cases of CML, we observed an increase of whole blood viscosity, plasma viscosity, ESR, fibrinogen elevation but decreases in bleeding time. In all cases, red cell filterability was unaffected.

Blood Sedimentation↗
PubMed1993

[Blood viscosity and related factors in patients with primary open-angle glaucoma].

The blood viscosity and related factors were determined in 31 patients with primary open-angle glaucoma (POAG) and 30 normal subjects. It was found that (1) the blood viscosity was significantly higher in the POAG group than in the normal controls, as were also the plasma viscosity, the hematocrit, the fibrinogen content, the index of erythrocyte aggregation and the blood yielding stress, and (2) there was no difference in the value of TK which was a measure of erythrocyte deformability between the two groups. The study showed that patients with glaucoma had blood hyperviscosity which could be caused by the elevated hematocrit and plasma viscosity. The possible relevance of blood hyperviscosity to glaucomatous optic atrophy was discussed.

Adult↗
PubMed2000

Hematocrit, volume expander, temperature, and shear rate effects on blood viscosity.

UNLABELLED: Our goal was to determine and predict the effects of temperature, shear rate, hematocrit, and different volume expanders on blood viscosity in conditions mimicking deep hypothermia for cardiac operations. Blood was obtained from six healthy adults. Dilutions were prepared to hematocrits of 35%, 30%, 22.5%, and 15% using plasma, 0.9% NaCl, 5% human albumin, and 6% hydroxyethyl starch. Viscosity was measured over a range of shear rates (4.5-450 s(-1)) and temperature (0 degrees -37 degrees C). A parametric expression for predicting blood viscosity based on the study variables was developed, and its agreement with measured values tested. Viscosity was higher at low shear rates and low temperatures, especially at temperatures less than 15 degrees C (P: < 0.016 for all conditions in comparison with 37 degrees C). Decreasing hematocrit, especially to less than 22.5%, decreased viscosity. Hemodilution with albumin or 0.9% NaCl decreased blood viscosity more than hemodilution with plasma or 6% hydroxyethyl starch (P: < 0.01 for all cases). The derived mathematical model for viscosity as a function of temperature, hematocrit, shear rate, and diluent predicted viscosity values that correlated well with the measured values in experimental samples (r(2) > 0.92, P: < 0.001). IMPLICATIONS: A theoretical model for blood viscosity predicted independent effects of temperature, shear rate, and hemodilution on viscosity over a wide range of physiologic conditions, including thermal extremes of deep hypothermia in an experimental setting. Moderate hemodilution to a hematocrit of 22% decreased blood viscosity by 30%-50% at a blood temperature of 15 degrees C, suggesting the potential to improve microcirculatory perfusion during deep hypothermia.

Adult↗
PubMed1983

A comparison of blood viscosity between the adult sheep and newborn lamb. The role of plasma and red blood cell type.

Adult sheep and newborn lamb blood viscosity (Vc) have been compared by taking into account not only the hematocrit, but also the type of the red cells (adult or fetal) in the circulation and the plasma Vc. At all shear rates studied the whole blood Vc of the adult was higher than that of the newborn. Plasma Vc was 1.58 +/- 0.18 centipoises in the adult compared to 1.21 +/- 0.19 in the newborn group (P less than 0.001). The mean relative apparent viscosity (whole blood Vc/plasma Vc) was higher in the newborn although the difference was not significant.

Animals↗
PubMed1985

Blood viscosity responses to maximal exercise in endurance-trained and sedentary female subjects.

To assess whether the rheological properties of blood might be altered by exercise, we measured whole blood viscosity, plasma viscosity, and its components in healthy female subjects before, immediately after, and 1 h after maximal upright exercise using the Bruce graded exercise protocol. Forty-seven female subjects (15 sedentary, 14 who ran 5-15 miles/wk, and 18 who ran greater than 50 miles/wk), ages 18-43 yr, were evaluated. Whole blood viscosity, measured with a cone and plate viscometer, increased an average of 12.6% with exercise. The increase was greater than can be attributed to the observed 8.9% increase in hematocrit alone due to a coincident increase in plasma protein concentration. However, plasma viscosity did not rise to the degree expected, likely due to a disproportionate observed loss of fibrinogen from the protein pool. These changes were independent of conditioning level or aerobic capacity. In this cross-sectional study, there appears to be no adaptive adjustment in females to physical conditioning that results in changes in blood viscosity.

Adult↗
PubMed2002

Acidosis induced by lactate, pyruvate, or HCl increases blood viscosity.

PURPOSE: Serum lactate correlates with the severity of disease and the mortality in shock. It is not clear if lactate is only a marker or a mediator of disease. We tested the hypothesis that acidosis induced by lactate and pyruvate affects blood flow properties. MATERIALS AND METHODS: Human blood was incubated with additional lactate (0-50 mmol/L) or pyruvate (0-25 mmol/L) for 1 hour at 37 degrees C. Blood viscosity was measured at high (94.5 s(-1)) and low (0.1 s(-1)) shear rate. Hematocrit was measured with an electronic particle counter as well as centrifugation. RESULTS: A total of 50 mmol/L additional lactate produced acidosis (pH 6.4) and increased whole-blood viscosity at high shear rate (94.5 s(-1): 6.53 +/- 0.51 mPa.s vs 4.94 +/- 0.18 mPa.s for control, n = 5, P <.001) and low shear rate (0.1 s(-1): 93.9 +/- 18.6 mPa.s vs 53.5 +/- 7.7 mPa.s, n = 5, P <.001). Simultaneously, an increased centrifuged hematocrit was observed (about 7% with 50 mmol/L lactate, P <.001), indicating eryth-rocyte swelling. These changes were reversible on removal of lactate. The addition of 25 mmol/L pyruvate also induced acidosis and increased blood viscosity and centrifuged hematocrit. When HCl was used to induce a comparable pH level decrease, a similar increase in blood viscosity and hematocrit were observed. CONCLUSIONS: Pronounced acidosis induced by either lactate, pyruvate, or HCl impairs blood flow properties, which may contribute to the understanding of the pathophysiology of critical illness.

Acidosis↗
PubMed2004

[Blood viscosity modifications in patients with presbycusis].

OBJECTIVE: [corrected] To evaluate the existence of blood viscosity alterations in presbyacusis as an eventual pathophysiological mechanism. MATERIAL AND METHODS: Nine 75 year-old subjects bearing of bilateral slowly progressive sensorineural deafness were considered to be studied on a yearly basis in a ten year folow-up period, evaluating the binaural hearing loss in speech tones (500, 1000, 2000 and 3000 Hz). Hemorheological profile on peripheral blood included total blood viscosity (BV) at different shear rates (SR), blood filterability (BF), erythrocyte deformability and aggregability (EA). RESULTS: There was a trend of all parameters towards hyperviscosity, with an increase at ten years of BV at high SR and EA at total stasis which were statistically significant. The level of deafness correlated significativelly to low values of BF and increases on BV at high SR. CONCLUSIONS: Presbyacustic patients do show hemorheological evidences that suggest a tendency towards hyperviscosity as a predisposing factor for hearing loss.

Aged↗
PubMed1981

Increased blood viscosity as the pathogenic agent in minimal change nephrosis: a new hypothesis.

It is proposed that minimal change nephrosis (MCN) is the result of impaired glomerular blood flow to slightly increased blood viscosity or to an abnormality of an autoregulatory mechanism controlling glomerular perfusion pressure or to unusually small efferent arterioles, or to combinations of these factors. The functional response to any of such changes would be an increase in intraglomerular pressure. If the pressure exceeded a critical level albumin would be able to pass into Bowman's space after deforming the pressure-dependent thixotropic basement membrane. In response to the presence of albumin in Bowman's space, epithelial cell foot process retraction would be initiated. The concentration of albumin capable of stimulating this reversible change in unknown. If it can be shown that MCN is a consequence of increased blood viscosity, then drugs having direct effects on blood viscosity might offer alternatives to steroid treatment.

Albuminuria↗
PubMed1995

[An epidemiological study on blood viscosity and intraerythrocytic calcium in a group of high-school students selected according to their family histories].

An epidemiological study was performed in a group of secondary school students selected according to their family history to assess whether changes exist in blood viscosity and intraerythrocytic calcium levels in young healthy subjects with positive family histories of arterial hypertension or cerebral and cardiac ischemic vasculopathies, compared to a control group with a negative family history of these disorders. A population of 130 secondary school students without any pathologies were subdivided into 4 groups: 1) with a positive family history of ischemic cardiopathy (ICP); with a positive family history of cerebral ictus; 3) with a family history of arterial hypertension; 4) a negative family history of these diseases. Total blood viscosity, hematocrit, plasma fibrinogen and intraerythrocytic calcium was evaluated in all groups. The results show that these parameters were within the normal range, as was to be expected in healthy subjects. Blood viscosity was also normal in all groups; intraerythrocytic calcium levels were slightly higher in groups with histories of cardiovascular disease and in particular there was an increased percentage of cases with values above the threshold level. Higher fibrinogen levels were also recorded, but always within the normal range, in the group with a positive history of ICP. The epidemiological study is important to assess whether a family pattern of cardiovascular disease can also influence such independent risk parameters as blood viscosity and intraerythrocyte calcium, owing to the possible greater frequency of development of cardiovascular disease.

Adolescent↗
PubMed1993

[Prognostic significance of baseline state of platelet aggregation and blood viscosity during gravitational plasmapheresis in patients with angina pectoris].

The study was undertaken to examine 56 patients (mean age 54.9 +/- 1.1 years) who had functional class III (n = 12), IV (n = 32), and unstable (n = 12) angina pectoris. Due to inefficacy of conservative therapy, all the patients underwent gravitation plasmapheresis (GPA). The parameters of induced platelet aggregation were examined by the Born-O'Brien method and blood viscosity on a rotor viscometer before, immediately and on days 1 and 3 after GPA. It was found that the baseline blood viscosity and platelet aggregation should be known to predict the natural history of angina in the following 1-3 days after GPA. There was a pronounced positive clinical effect in higher blood viscosity and platelet aggregation. An improvement in the clinical course of the disease and its stabilization were not observed in the baseline lower blood viscosity and platelet in patients with progressive angina.

Adult↗