Measurement Of Blood Viscosity Research Articles

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.

Simultaneous measurement of red blood cell aggregation and viscosity: Light transmission slit rheometer

Aggregation of red blood cells (RBCs) is a major determinant of blood viscosity. There have not been available techniques for measuring RBC aggregation and viscosity, simultaneously. A laser transmission technique has been combined with a slit rheometry, which shows significant advances in rheometer design, operation and data analysis. A laser beam traverses a blood suspension flowing through a slit and is scattered by RBCs in the volume. The transmitted light is captured by a photodiode, linked to a computer, while the differential pressure variation is measured by a pressure transducer. Both measurements of the laser-transmitted intensity and pressure with respect to time enable to determine the aggregation index and the viscosity. The advantages of this design are in its simplicity, i.e., ease of operation and no moving parts, low cost and a short operating time. In addition, the slit-flow aggregometer can be easily used in a clinical setting owing to the incorporation of a disposable element that holds the blood sample.

Blood Viscosity of the Neonate

After completing this article, readers should be able to: 1. List the determinants of blood viscosity in the neonate. 2. List the causes of polycythemia and hyperviscosity in the neonate. 3. List the signs, symptoms, and diagnostic criteria for polycythemia and hyperviscosity. 4. Describe steps for prevention and treatment of polycythemia and hyperviscosity in the neonate. Blood viscosity is defined as resistance to the movement of blood. In a circular vessel or tube, the resistance (R) increases with increasing viscosity (V) of the moving fluid and with the resistance resulting from the vessel geometry (Z): R=Z · V. Thus, blood viscosity describes the contribution of blood rheologic factors to blood flow resistance. However, blood viscosity depends on several factors, and the importance of these factors differs among various vessels. The major determinants of blood viscosity are the hematocrit, plasma viscosity, red blood cell (RBC) aggregation, RBC deformability, leukocyte properties, vessel diameter, and the shear forces acting on the RBC. (1) The hematocrit generally is assumed to be the most important determinant of blood viscosity. Blood viscosity rises exponentially with increasing hematocrit (Fig. 1). A marked rise in blood viscosity is seen when the hematocrit exceeds 0.65 L/L, which typically is defined as the threshold for hyperviscosity of the blood. However, in narrow arteries and arterioles and in capillaries, the plasma viscosity becomes the dominant determinant of blood viscosity. The fetal hematocrit increases from 0.33 L/L in the 12th week of gestation to 0.45 L/L in the 30th week and 0.50 L/L in the 40th week at term. At birth, the hematocrit may rise markedly as a result of “blood transfusion” from the placenta to the neonate. (2) A postnatal hematocrit of 0.45 to 0.65 L/L is considered normal in the healthy term neonate. Figure 1. Blood viscosity in tubes that have a diameter of 50 …

Measurements of blood viscosity using a pressure-scanning slit viscometer

A newly designed pressure-scanning slit viscometer is developed to combine an optical device without refraction while measuring blood viscosity over a range of shear rates. The capillary tube in a previously designed capillary viscometer was replaced with a transparent slit, which is affordable to mount optical measurement of flowing blood cells. Using a pressure transducer, we measured the change of pressure in a collecting chamber with respect to the time, p(t), from which the viscosity and shear rate were mathematically calculated. For water, standard oil and whole blood, excellent agreement was found between the results from the pressure-scanning slit viscometer and those from a commercially available rotating viscometer. This new viscometer overcomes the drawbacks of the previously designed capillary viscometer in the measuring whole blood viscosity. First, the pressure-scanning slit viscometer can combine an optical instrument such as a microscope. Second, this design is low cost and simple (i.e., ease of operation, no moving parts, and disposable).

Blood Electrical Impedance Closely Matches Whole Blood Viscosity as Parameter of Hemorheology and Inflammation

AbstractRed blood cell aggregation (RBCa) is a sensitive inflammation marker. RBCa determination from erythrocyte sedimentation rate, ESR, is used since long, but is unspecific unless corrected for hematocrit, Ht. Whole blood viscosity measurement at low shear rate is also sensitive to RBCa but is cumbersome to apply. To investigate whether electrical blood impedance, being sensitive to spatial red cell distribution, can be a good alternative to determine RBCa in low shear conditions. Blood was collected from 7 healthy volunteers. From each 16 different samples were prepared with 4 different Ht’s and with 4 different fibrinogen concentrations. Viscosity was measured at low shear rate (4.04 s-1) with a rotational viscometer at 37˚C. Electrical blood impedance was measured during similar shear conditions and temperature in a specially designed cuvette. ESR was determined according to Westergren. A logarithmic increase of viscosity as well as of capacitance, Cm, is seen when fibrinogen rises and an exponential increase when Ht rises. However, ESR shows a logarithmic decrease with increasing Ht and an exponential increase when fibrinogen rises. The viscosity could be accurately described using an exponential model. Under similar low shear conditions and temperature in-vitro, either whole blood viscosity or electrical blood capacitance reflect red blood cell aggregation due to fibrinogen and Ht variation in a similar way.

Measurement of blood viscosity using mass-detecting sensor

A newly designed mass-detecting capillary viscometer is extended to measure the viscosity of whole blood over a range of shear rates without the use of anticoagulants in a clinical setting. In the present study as proof of principle, a single measurement of liquid-mass variation with time replaces the flow rate and pressure drop measurements that are usually required for the operation of a capillary tube viscometer. Using a load cell and capillary, we measured the change of mass flowing through capillary tube with respect to the time, m( t), from which viscosity and shear rate were mathematically calculated. For water and adulterated bloods, excellent agreement was found between the results from the mass-detecting capillary viscometer and those from a commercially available rotating viscometer. Also, the mass-detecting capillary viscometer measured the viscosity of unadulterated whole blood without heparin or EDTA. This new method overcomes the drawbacks of conventional viscometers in the measurement of the whole blood viscosity. First, the mass-detecting capillary viscometer can accurately and consistently measure the unadulterated blood viscosity over a range of shear rates in less than 2 min without any anticoagulants. Second, this design provides simplicity (i.e. ease of operation, no moving parts, and disposable) and low cost.

Observations on Blood Viscosity in Striped Bass, Morone saxatilis (Walbaum) Associated with Fish Hatchery Conditions

Blood viscosity and blood parameters were studied in striped bass, Morone saxatilis (Walbaum) under various fish hatchery conditions. Twenty-seven adult striped bass weighing between 1040 g and 1800 g were divided into four groups: (1) healthy fish; (2) short-term hypoxia, fish exposed to oxygen concentrations of 4 mg/L for four hours; (3) simulated transport, exposed to crowding with oxygen concentrations of approximately 8.4 mg/L; and (4) diseased fish, infected with henneguya causing inflammation of the gill surface leading to hypoxemia in these animals. Plasma and apparent (whole) blood viscosity measurements were made using a Wells-Brookfield cone/plate viscometer at ten different shear rates. At packed cell volumes (PCV) of 30% and 40% and at high shear rates (75 s−1 and 150 s−1) the hypoxic group had a significantly higher apparent blood viscosity when compared to healthy fish, likely the result of a significant increase in the total plasma protein concentration in this group. The diseased group had a significantly higher PCV than all other groups resulting in a significant increase in blood viscosity. No significant difference was observed among the four groups in mean cell volume, mean cell hemoglobin, and mean cell hemoglobin concentration. The increase blood viscosity noted in the hypoxic and diseased groups could lead to a decreased blood flow and oxygen delivery to the tissues.

A new method for blood viscosity measurement

The present study introduces the concept of a newly designed scanning viscometer with a capillary tube for use in measuring whole blood viscosity without the use of anticoagulants in a clinical setting. Both flow rate and pressure drop measurements that are usually required for the operation of a capillary tube viscometer are replaced with a single measurement of liquid-height variation with time. In addition, the present method overcomes the drawbacks of conventional viscometers in the measurement of the whole blood viscosity. First, with the present study, whole blood viscosity can be accurately and consistently measured at 37°C over a wide shear rate range including shear rates as low as 1 s −1. Second, the present method can measure whole blood viscosity over a range of shear rates in less than 2 min without any anticoagulants so that one can measure the viscosity for unadulterated blood.

Shear stress abnormalities contribute to endothelial dysfunction in hypertension but not in type II diabetes.

The relative contribution of the various hemodynamic and metabolic mechanisms leading to endothelial dysfunction may be different in specific vascular diseases. Since shear stress is one of the main mechanical stimuli of endothelial cells, the aim of this study was to investigate its contribution to endothelial dysfunction in two distinct vascular diseases, hypertension and type II diabetes. We measured the radial artery diameter at baseline, after ischemic vasodilation and after nitroglycerin vasodilation in 16 untreated patients with high blood pressure, in 15 type II normotensive diabetic patients and in 17 healthy controls. Wall shear stress was evaluated by simultaneous measurements of whole blood viscosity and blood flow velocity. In diabetic patients, whole blood viscosity was significantly higher whereas wall shear stress was similar compared to controls. In hypertensive patients, whole blood viscosity was higher and wall shear stress was lower than in controls. Endothelium-dependent vasodilation was impaired in both hypertensive and diabetic patients (P < 0.01) after adjustment for age, sex, body mass index and postnitroglycerin vasodilation. When adjustments were made for maximal systolic shear stress, endothelium-dependent vasodilation remained lower in the diabetic patients (P < 0.01), but not in those with high blood pressure compared to controls. In hypertension, endothelium-dependent vasodilation is mainly due to a chronic decrease in shear stress (the most important physiological stimulus of the endothelial cells) with no major intrinsic endothelial cell dysfunction. In contrast, in diabetics, the lower endothelium-dependent vasodilation was not the result of an altered shear stress.

Comparison of blood viscosity in red-eared sliders (Trachemys scripta) adapted to cold and room temperature

Red-eared sliders (Trachemys scripta) in their northern range undergo hibernation at temperatures of about 5 degrees C, which may result in a profound bradycardia and a drop in blood pressure leading to very slow blood flows. Blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. To investigate the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, cold environment (5 degrees C) or room-temperature environment (25 degrees C). At the end of 5 months treatment, hematocrit values, plasma protein concentration, and whole-blood viscosity values were determined for each turtle. Blood viscosity measurements were determined at five shear rates (3.75, 15, 30, 75, and 150 s-1) at 5 degrees C and 25 degrees C for all animals. No significant differences were found in hematocrit or plasma protein values between cold-adapted and room temperature-adapted animals. Whole-blood viscosity between groups at any shear rate at a temperature of 5 degrees C was also nonsignificant. The only significant difference in blood viscosity between turtles adapted to cold and room temperature occurred at a shear rate of 3.75 s-1 at 25 degrees C. The whole-blood viscosity of red-eared sliders, whether adapted to cold or to room temperature, tended to be lower as compared to other vertebrates under similar conditions of temperature, shear rate, and hematocrit. This innate lower blood viscosity may compensate for the potential detrimental effects on blood viscosity brought about by the low temperatures and decreased shear rates that occur in these animals during hibernation.

Comparison of blood viscosity in red‐eared sliders (Trachemys scripta) adapted to cold and room temperature

Red-eared sliders (Trachemys scripta) in their northern range undergo hibernation at temperatures of about 5°C, which may result in a profound bradycardia and a drop in blood pressure leading to very slow blood flows. Blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. To investigate the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, cold environment (5°C) or room-temperature environment (25°C). At the end of 5 months treatment, hematocrit values, plasma protein concentration, and whole-blood viscosity values were determined for each turtle. Blood viscosity measurements were determined at five shear rates (3.75, 15, 30, 75, and 150 s–1) at 5°C and 25°C for all animals. No significant differences were found in hematocrit or plasma protein values between cold- adapted and room temperature-adapted animals. Whole-blood viscosity between groups at any shear rate at a temperature of 5°C was also nonsignificant. The only significant difference in blood viscosity between turtles adapted to cold and room temperature occurred at a shear rate of 3.75 s–1 at 25°C. The whole-blood viscosity of red-eared sliders, whether adapted to cold or to room temperature, tended to be lower as compared to other vertebrates under similar conditions of temperature, shear rate, and hematocrit. This innate lower blood viscosity may compensate for the potential detrimental effects on blood viscosity brought about by the low temperatures and decreased shear rates that occur in these animals during hibernation. J. Exp. Zool. 281:157–163, 1998. © 1998 Wiley-Liss, Inc.

Reduced number of circulating monocytes after institution of insulin therapy--relevance for development of atherosclerosis in diabetics?

Twelve patients with Type II diabetes mellitus, insufficiently controlled with oral hypoglycemic agents, were studied before, after 2 months, and after 4 months on insulin therapy. For comparison the same variables were also studied in 10 healthy subjects. From the start, in the diabetic group, the authors found alterations in the hemorheologic parameters indicated by increased values for whole blood viscosity, plasma viscosity, red cell transit time (RCTT), and decreased values for white cell initial relative filtration rate (IrFR). In hematologic parameters they found increased values for mean corpuscular volume (MCV), leukocyte count, counts of neutrophils and monocytes, and a decreased count of lymphocytes. They also found increased values in the lipid parameters P-triglycerides and Apo B/Apo A-I ratio, risk factors of coronary atherosclerosis. After 4 months of insulin treatment whole blood and plasma viscosity were still increased, but there was a partial improvement of lipoprotein abnormalities. Red and white cell filterability, however, tended to normalize. These results indicate that changes in blood cell filterability do not necessarily influence in vitro measurements of blood viscosity. The change in RCTT during the insulin treatment was associated with a decreased MCV and the change in white cell IrFR with a decrease in the number of monocytes. This change of white cell filterability during insulin therapy, probably due to a reduced number of monocytes, may be of interest in the study of atherosclerosis and circulatory disease in diabetics.

Venous dysfunction and the change of blood viscosity during head-up tilt.

The precise stimulus that induces vasovagal syncope is still unclear. We have previously demonstrated that the peripheral distribution of blood volume (venous pooling) is a strong predictor of tilt induced vasovagal reaction. We hypothesized that an increase in venous pooling during tilt accentuates the measured increase in blood viscosity. This hypothesis is based on the previously demonstrated increase in venous pressure and subsequent increase in transcapillary fluid transudation during tilt. The increased blood viscosity, in turn, increases vascular shear rate, which may alter the vasoconstrictive and other cardiovascular responses to decreased preload. We measured blood viscosity (supine and tilt) in 56 patients with a history of orthostatic intolerance (37 with venous pooling [VP] and 19 without venous pooling [non-VP]). VP and non-VP were separated into subgroups based on blood pressure and heart rate response to tilt. There was a positive correlation between blood viscosity and plasma aldosterone in the supine. In the group as a whole, neither supine blood viscosity nor its increase during tilt differed between VP and non-VP. However, the tilt induced increase of blood viscosity was significant only in patients with tilt provoked tachycardia plus normal blood pressure response in VP group. We suggest that the increase of blood viscosity in this group led to the normal blood pressure response. The positive correlation between supine blood viscosity and supine plasma aldosterone indicates that the normal blood pressure response in this group possibly was via stimulation of the renin-angiotensin-aldosterone system.

Nimodipine improves brain energy metabolism and blood rheology during ischemia and reperfusion in the gerbil brain

Whether nimodipine improves cerebral blood flow (CBF) and metabolism in cerebral ischemia remains a controversial issue. We investigated the effect of nimodipine on CBF, brain energy metabolism, using a laser-Doppler flowmeter and in vivo 31phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, and blood rheology during forebrain ischemia and reperfusion in gerbils. Eighty-three adult gerbils received nimodipine (1 μg/kg/min), or an equal volume of the vehicle, or saline, over 60 min prior to a transient forebrain ischemia for 60 min. We measured sequential changes in phosphocreatine (PCr) / inorganic phosphate (Pi) ratio, β-ATP/Pi ratio, and intracellular pH (pHi) during ischemia and reperfusion by 31P NMR spectroscopy, and the measurement of whole blood viscosity (WBV) at 60 min after reperfusion. CBF was measured continuously throughout the study by a laser-Doppler flowmeter. During forebrain ischemia, PCr/Pi and β-ATP/Pi ratios were higher significantly in the nimodipine-treated group (p < 0.05 and 0.01) than in the vehicle- or saline-treated groups. During reperfusion, PCr/Pi and β-ATP/Pi ratios recovered significantly only in the nimodipine-treated group (p < 0.05 and 0.01). The WBV at high shear rate (562.5 s−1) lowered significantly in the nimodipine-treated group (p < 0.05) compared with the vehicle- or saline-treated group. CBF was higher significantly only during administration of nimodipine in the nimodipine-treated group (p < 0.01) than other groups. Nimodipine improved brain energy metabolism and blood rheology during forebrain ischemia and reperfusion in the gerbil brain.

A Newly Designed Oscillating Viscometer for Blood Viscosity Measurements

A newly designed type of oscillating viscometer is described. The viscometer consists of either a tube or a rod oscillating at a resonance frequency with amplitudes in the micro- and nanometer range. A fluid flowing through the tube or surrounding th

A newly designed oscillating viscometer for blood viscosity measurements

A newly designed type of oscillating viscometer is described. The viscometer consists of either a tube or a rod oscillating at a resonance frequency with amplitudes in the micro- and nanometer range. A fluid flowing through the tube or surrounding the rod damps the torsional oscillations. The increase in the damping depends on the viscosity of the fluid and is used to determine viscosity. It was found that viscosity measurements are feasible during blood flow. This new type of viscometer may be useful to the study of biophysical properties of blood at the wall surface during flow and give new insights into blood flow. The device allows direct viscosity measurement on blood directly as it is drawn from the vein through the tube without any anticoagulant.

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.

Physiological modifications of blood viscosity and red blood cell aggregation during labor and delivery

Since most stresses are known to modify blood rheology, we studied .hemorheologlcal parameters during labor and delivery, which are highly stressful physiological events. In 80 pregnant women we measured blood viscosity, plasma viscosity and red blood cell (RBe) aggregation during labor (b~fore and atter 4 cm diratation), during delivery, and during ~elivery of the placenta. Blood viscosity at both native and corrected ,,ematocrlt increases (p < 0.001) with a peak during delivery followed by a rapid normalization during delivery of the placenta (p < 0.01). Hematocrit and plasma viscosity do not change during labor and delivery, but decrease during delivery of the placenta. RBe aggregation (physrologically increased during late pregnancy) acutely returns to normal during delivery (p<0.01). The transient increase hI viscosity during delivery is explained by an increase in RBe rigidity as measured by Dintenfass' 'Tk' (p <; 0.01) and a similar (nonsignificant) tendency to decrease RBe filterabilitY measured by the hemorheometre. Thus, delivery is associated with a transient hyperviscosity syndrome which js mainly due to a decrease in RBe flexibility.

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.

Blood viscosity and plasma proteins influencing it are increased in Type I diabetes in the DCCT

The Diabetes Control and Complications Trial (DCCT), an NIH-sponsored study at 29 institutions in the U.S. and Canada, was designed to examine the effects of intensive management in type I diabetes. Between 1983 and 1989, 1441 patients with and without mild retinopathy (primary and secondary) were randomized into two major treatment groups, intensively and conventionally treated patients. Retinopathy, nephropathy, and neuropathy were assessed periodically in each patient. In this study, levels of fibrinogen, haptoglobin, albumin and total protein were measured and viscosity of fresh blood was simultaneously evaluated in 45 local DCCT patients. Viscosity was measured at 17 rotation rates arranged logarithmically from .03 to 300 inverse seconds shear rate on blood adjusted to 41 % hematocrit by the addition or removal of its own plasma. Blood's time-based flow properties --- transient resistance and viscoelasticity --- were also assessed. Blood viscosity showed the greatest elevation (10 to 19%) in the 0.08-2.0 inverse second shear rate range. Increased low shear rate blood viscosity was found to be linked to fibrinogen and hemoglobin Alc levels. In addition to steady flow blood viscosity measurement, blood's time-based flow properties were also assessed at 15 inverse seconds shear rate. Transient resistance was increased 30% in diabetes; its elevation was found to be linked to both fibrinogen level and low shear blood viscosity. Diabetic blood's viscoelasticity at this high shear rate was much less strikingly increased than its transient resistance. Viscoelastic strain energy was correlated with fibrinogen, low shear viscosity, haptoglobin, and albumin level. Interleukin-6 (IL-6), a potent stimulator of fibrinogen and haptoglobin synthesis in hepatocytes in culture, was found to be elevated in diabetes, indicating that it is the likely mediator of the observed plasma protein changes. The altered blood flow properties observed in this well-characterized group of type 1 diabetes mellitus patients may playa role in development of diabetic complications.