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At least 217 records · Page 12Linked to original sources
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↗
PubMed1997

Viscosity of gums in vitro and their ability to reduce postprandial hyperglycemia in normal subjects.

Experiments were carried out in vitro with three viscous polysaccharides (guar gum, pectin, and carboxymethylcellulose (CMC) of similar initial viscosity submitted to conditions that mimic events occurring in the stomach and duodenum, and their viscosity in these situations was compared to their actions on postprandial hyperglycemia in normal human subjects. Guar gum showed greater viscosity than the other gums during acidification and/or alkalinization and also showed larger effects on plasma glucose levels (35% reduction in maximum rise in plasma glucose) and on the total area under the curve of plasma glucose (control: 20,314 +/- 1007 mg dl-1 180 min-1 vs guar gum: 18,277 +/- 699 mg dl-1 180 min-1, P < 0.01). Pectin, which showed a marked reduction in viscosity at 37 degrees C and after events mimicking those that occur in the stomach and duodenum, did not have a significant effect on postprandial hyperglycemia. The performance of viscosity and the glycemia response to CMC were at an intermediate level between guar gum and pectin. In conclusion, these data suggest that temperature, the process of acidification, alkalinization and exposure to intestinal ions induce different viscosity changes in gums having similar initial viscosity, establishing a direct relationship between a minor decrease of gum viscosity in vitro and a reduction of postprandial hyperglycemia.

Adult↗
PubMed1994

Bile viscosity in patients with biliary drainage. Effect of co-trimoxazole and N-acetylcysteine and role in stent clogging.

BACKGROUND: The main disadvantage of endoscopic insertion of an endoprosthesis is the tendency of the stent to clog after a few months. In this study we determined the role of bile viscosity in stent clogging. METHODS: Sixty patients were stented with 10 Fr 11-cm stents. The stents were electively removed after 2 months, and a bile sample was obtained simultaneously. Bile viscosity was measured with a coaxial rotation viscometer. The influence of treatment with antibiotics and a mucolytic agent on viscosity was assessed in a randomized trial. RESULTS: Bile viscosity correlated significantly with DNA and total protein concentration. After treatment with either N-acetylcysteine or co-trimoxazole a lower mean value of the viscosity was observed, but this was not statistically significant. There was no correlation between bile viscosity and the amount of sludge adhering to the stents. CONCLUSIONS: In most patients bile viscosity plays a limited role in stent clogging. Only in patients with excessively high viscosity do mucolytic agents or treatment with antibiotics seem to have a role.

Acetylcysteine↗
PubMedDate not supplied

Controlled release captopril microcapsules: effect of ethyl cellulose viscosity grade on the in vitro dissolution from microcapsules and tableted microcapsules.

Captopril microcapsules were prepared using four different viscosity grades of ethyl cellulose (core: wall ratios 1:1, 1:2 and 1:3) by temperature induced coacervation from cyclohexane. In vitro dissolution studies in 0.1 M hydrochloric acid showed that the drug release was dependent on the core to wall ratio, the viscosity grade of the ethyl cellulose and thus the total viscosity of the coacervation system. Viscosity grade of greater than 100 c.p. was unsuitable for microencapsulation by coacervation method at the concentration used. The surface characteristics of a 1:2 core to wall ratio were studied by scanning electron microscopy. The surface of the microcapsules prepared with 10 c.p. viscosity grade was comparatively more porous with larger size pores than 50 c.p. viscosity grade of ethyl cellulose. However, 300 c.p. viscosity grade showed incomplete wall formation. The microcapsules did not fragment during dissolution, alter in shape or size, or show evidence of enlargement of the surface pores. The tensile strength of tablets prepared at constant pressure from each batch of microcapsules (mean diameter 675 microns) increased as both the core to wall ratios and the viscosity of ethyl cellulose increased. The dissolution rate of the drug from tableted microcapsules was significantly delayed. The in vitro release gave best correlation with first order release kinetics when compared to zero-order and square-root-of-time equations.

Capsules↗
PubMedDate not supplied

Effect of viscosity and interfacial tension on particle size of cellulose acetate trimellitate microspheres.

The influence of the viscosity of the internal and external phases and the interfacial tension between the two phases, in the emulsion type of microencapsulation system was investigated. The viscosity of mineral oil (external phase) was measured by a capillary viscometer and the viscosity of cellulose acetate trimellitate solution (internal phase) was measured by a Brookfield viscometer. The viscosity of the two phases were measured prior to mixing and at 5 and 60 min after mixing the phases. It was observed that the viscosity of the mineral oil phase prior to mixing had little effect on the average diameter of the microspheres, until a high concentration of light mineral oil was used. A graph of viscosity ratio of the internal phase to the external phase shows that a minimum viscosity ratio may be required before particle size increases. Results are discussed with respect to viscosity effects of mineral oil and polymer solution, as influenced by the solvent uptake by the mineral oil. The interfacial tension between the two phases was measured by pendant drop method. Interfacial tension was measured at 5 and 60 min after the two phases came in contact. The interfacial tension between the mineral oil and polymer solution ranged up to 7 dyne/cm and the particle size was not affected appreciably by the interfacial tension. Particle size and morphological analysis of the microspheres were determined using microscopy and scanning electron microscope.

Benzoates↗
PubMed1990

Effects of blood viscosity on renin secretion.

The effects of alterations in blood and plasma viscosities on plasma renin activity (PRA) were studied in dogs anesthetized with pentobarbital. Blood viscosity was altered by changing the hematocrit (Hct) level by isovolemic exchange using packed red blood cells or plasma. Plasma viscosity was elevated by isovolemic exchange using Hct-matched blood with high molecular weight dextran (Dx, mean m.w. approximately 450,000) dissolved in plasma. Following control measurements of plasma and blood viscosities, plasma [Dx], PRA, Hct and hemodynamic functions, the dog was subjected to isovolemic exchange transfusions to either alter the Hct or administer the Dx. Various measurements were repeated 40-60 min after each exchange. Arterial pressure and renal blood flow remained relatively constant after exchanges; increases in plasma and blood viscosities were accompanied by a decrease in renal vascular hindrance (vasodilation) to keep the renal flow resistance at control level. PRA rose with increases in plasma [Dx] and viscosity, and the rise in PRA was best correlated with the decrease in renal hindrance. The changes in PRA and renal hindrance have the same regression line whether blood viscosity was altered by Hct variation or Dx administration. The results indicate that increases in viscosity cause a compensatory vasodilation of renal vessels to cause renin secretion.

Animals↗
PubMed1997

[Correlations between retinal fluorescein angiography and blood viscosity and other factors in patients with primary open angle glaucoma].

OBJECTIVE: To investigate the correlations between retinal fluorescein angiography and blood viscosity and other factors in patients with primary open angle glaucoma (POAG). METHODS: Multiple stepwise regression analysis was made to approach the correlation between each of the following blood vessel filling times: the arm-choroid (A-CT), arm-retinal artery (A-AT), and retinal artery-venous (A-VT) of the fundus fluorescein angiography (FFA) in 122 eyes with POAG and each of the following related factors in hemorheology: whole blood apparent viscosity at low, medium and high shear rates, plasma viscosity and hematocrit. Also, the same analysis was applied to investigate the correlation between each of the A-AT, A-VT of the FFA in 70 eyes with POAG and each of the following factors: systolic blood pressure, diastolic blood pressure, age and the whole blood apparent viscosity at low shear rate. RESULTS: The whole blood apparent viscosity at low shear rate was closely related to A-CT and A-AT, while hematocrit was closely related to A-VT of the FFA. The whole blood apparent viscosity at low shear rate and age, especially whole blood apparent viscosity, was closely related to A-AT, A-VT of the FFA. CONCLUSION: The blood viscosity can affect the filling times of the FFA in POAG.

Blood Viscosity↗
PubMed2000

Food viscosity as determinant for adaptive growth responses in rat intestine: long-term feeding of different hydroxyethyl celluloses.

Carbohydrate gelling agents can be regarded as being representative for the soluble and viscous fractions of dietary fibre. Their dietary concentration affects the consistency of the ingested food as well as the dilution of nutrients and energy. By feeding hydroxyethyl cellulose (HEC) differing in molecular mass, and thus in its viscosity properties, only the consistency of the diet was modified. Three HEC (of low (LV), medium (MV) and high viscosity (HV)) were employed in a 6-week feeding study with female rats to evaluate the effect of the viscosity on adaptive responses of intestinal growth variables. Each of the HEC was added in three increasing concentrations (8, 16, and 32%, w/w) to a fibre-free control diet to yield nine test groups besides a fibre-free and an additional, fibre-rich, cereal-based control group. Except for the highest concentration of the high viscosity product (32% HV-HEC), the dilution of the energy density of the diet was almost completely compensated by an increased food intake. With the same exception, energy utilisation was not impaired and, therefore, body-weight gains in the test groups were not significantly different from that in the control. Most other changes, e.g. increases in small intestinal length, mucosal DNA content, caecal and colonic weight, not only depended on the dietary concentration but also on the viscosity of HEC in a manner that either increasing the viscosity at a given dietary concentration or increasing the dietary concentration at a given viscosity led to the same results. These findings clearly prove the important role of the viscosity of the lumen content, as a mere physico-chemical factor, in determining adaptative growth responses in the intestinal tract of rats.

Animals↗
PubMed2001

High viscosity plasma expanders: Volume restitution fluids for lowering the transfusion trigger.

Hemorheological studies lead to the axiom that high plasma viscosity is detrimental and that it is beneficial to lower blood viscosity, a precept embodied in the practice of hemodilution, where improved perfusion is attributed to the lowering of blood viscosity. Hemodilution is limited by the transfusion trigger, hemoglobin content of blood of about 7-8 g/dl, which indicates when further volume replacements must restore oxygen carrying capacity with red blood cells (RBC). However, oxygen consumption and delivery are not compromised upon passing this landmark. The reduced blood viscosity does not transmit adequate pressure to the capillaries, causing functional capillary density (FCD) to decrease, jeopardizing organ function through the inadequate extraction of products of metabolism from the tissue by the capillaries. Studies in hemorrhagic shock show that survival is primarily determined by the maintenance of FCD and secondarily by tissue oxygenation. FCD is maintained as hematocrit is reduced beyond the transfusion trigger by increasing plasma viscosity, which transmits systemic pressure to the capillaries and induces vasodilatation through the increased shear stress dependent release of vasodilators. Consequently the transfusion trigger is also a "viscosity trigger" indicating when blood and plasma viscosity are too low. In this condition increasing plasma viscosity is beneficial and extends the transfusion trigger reducing the use of blood transfusions.

Animals↗
PubMed2000

Factors influencing blood viscosity: adult and newborn blood analysis.

Our finding of a decrease in blood viscosity in newborn infants compared with adults leads to analysis of this change by measuring blood viscosity, plasma fibrinogen concentration, plasma viscosity and mean corpuscular volume (MCV) of 24 adults and 16 newborn infants. Plasma proteins in newborn infants are synthesized to a lesser extent than in adults, therefore plasma fibrinogen concentration of newborn infants is less than that of adults. This causes decreased blood viscosity in newborn infants compared with adults. Secondly plasma viscosity of newborn infants is also less than that of adults. In the same situation this causes a decrease in blood viscosity in newborn. Thirdly. MCV of newborn infants is greater than that of adults because of young red cells. There is a negative correlation between blood viscosity and MCV. High MCV in newborns leads to low blood viscosity in newborn infants, compared with adults.

Adult↗
PubMed2001

[Whole blood viscosity measurement in acute myocardial infarction: feasibility and significance].

Thrombolytic agents and new antiplatelet drugs used in acute myocardial infarction (AMI) could change whole blood viscosity. The aim of this pilot trial is to compare blood viscosity at four shear rate levels among three groups of patients: AMI receiving thrombolysis with alteplase (n: 10), AMI eligible for primary angioplasty with abciximab (n: 10), healthy volunteers (n: 10). Viscosity measurement was obtained in 30 minutes with a Couette hemoviscosimeter. At baseline, blood viscosity level was higher in patients with acute coronary syndromes than in healthy volunteers (72 +/- 32 mPa.s versus 51 +/- 13 mPa.s, p<0.05). After thrombolysis, viscosity was higher at 90 minutes than at third day, paradoxically with fibrinogen elevation (72 +/- 32 mPa.s versus 58 +/- 27 mPa.s, p=0.01). In primary angioplasty with abciximab, viscosity decreased significantly (56 +/- 28 mPa.s versus 43 +/- 13 mPa.s, p=0.01). The effects of ionic contrast agent and abciximab are discussed. In healthy volunteers group, 100 mg aspirin once a day during 7 days reduces blood viscosity at high shear stress. The small size of the study population restricts correlation analysis with major clinical adverse events. A larger trial is necessary to evaluate the predictive value of whole blood viscosity in reocclusive and/or hemorrhagic events in those reperfusion strategies but also in case of thrombolytic agent and abciximab combination.

Adult↗
PubMed2002

[Studies on blood viscosity and external thrombus in patients with silicosis and silicosis complicated with tuberculosis].

OBJECTIVE: To explore the changes of blood viscosity and external thrombus in patients with silicosis and silicosis complicated with tuberculosis (TB). METHOD: Blood viscosity and external thrombus were measured in 288 patients with silicosis, 178 patients with silicosis complicated by TB and 150 healthy subjects. RESULTS: Blood viscosity and external thrombus value were significantly higher in the patients of silicosis and silicosis complicated with TB than in the healthy controls, except for patients of phase I of silicosis. Blood viscosity in the silicotics increased significantly with the advance of the disease, but no significant difference in external thrombus between patients in different phases. Apparent viscosity of whole blood significantly increased in the high-shear rate (200 s(-1)) and middle-shear rate (30 s(-1)) in patients of silicosis complicated with TB than in those without complication of TB at the same phases, but not seen in the low-shear rate (5 s(-1)) and in plasma viscosity, and the length and dried weight of external thrombus increased significantly too. There was no significant difference in blood viscosity and external thrombus between patients of silicosis at phase III and those of silicosis complicated with TB at the same phase. CONCLUSION: Blood in patients with silicosis appeared highly viscous and highly coagulant status. Blood viscosity and external thrombus value significantly increased with the advance of the disease, especially in the patients complicated with TB.

Adult↗
PubMed2003

Effects of powdered versus liquid barium on the viscosity of fluids used in modified swallow studies.

OBJECTIVE: To determine if the viscosity of thickened juice mixtures used in modified barium swallow studies significantly changes with the addition of powdered barium. We also describe a test formulation created using liquid barium, which has a negligible effect on juice viscosity. METHODS: The viscosities of water and standardized honey- and nectar-consistency juices mixed with different amounts of powdered barium were measured by timing the laminar flow of a given initial hydrostatic head of fluid under gravity though an orifice of fixed diameter. Standardized juices were then mixed with a liquid formulation of barium and with measured quantities of water to produce viscosities that more closely equated with those of the standardized juices. RESULTS: With the addition of powdered barium, viscosity increased in all fluids, most markedly with the nectar-consistency juice. Liquid barium formulations maintained the viscosities of the original thickened juices. CONCLUSION: Rendering juices radio-opaque with barium powder results in dramatic increases in the viscosity of the resulting mixture and compromises diagnostic accuracy. Liquid barium preparations have the advantage that they can be rapidly and accurately dispensed by syringe, and their use does not significantly increase the viscosity of the preparation.

Barium Sulfate↗
PubMed1992

[Changes of blood viscosity in patients undergoing cardiac surgery during cardiopulmonary bypass].

The patient undergoing open-heart surgery depends on hypothermia and cardiopulmonary bypass (CPB) to maintain organ perfusion during cardiac arrest. Increased blood viscosity during hypothermic CPB might be life-threatening, so hemodilution is imperative. Fourteen open-heart patients of ASA class II-III were included in this study. Pre- and intra-CPB viscosity changes were observed. Before CPB, 6 ml blood sample was drawn out from open-heart patients after systemic heparinization and another 6 ml blood sample was drawn out from the oxygenator after CPB was established. The hematocrit and relative viscosity of each sample in different temperatures were measured. The result revealed that as the temperature decreases, the viscosity of each sample increases apparently. As compared to the pre-CPB blood sample, the hematocrit of blood obtained intra-CPB decreases from 36.81 to 27.04, (p < 0.001), and the viscosity also decreases at all different temperatures (p < 0.001). Blood viscosity obtained at 37 degrees C pre-bypass is not statistically different from the sample at 25 degrees C during bypass. Obviously, increased viscosity due to hypothermia is buffered by hemodilution after using large amount of fluid as priming solution during CPB. Therefore, the hematocrit and viscosity remain within physiologic ranges.

Adult↗
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↗
PubMed1991

Effects of endurance training and long distance running on blood viscosity.

The effect of endurance training on blood viscosity was studied by comparing blood rheological properties in control subjects (untrained) and endurance trained subjects. The effect of running on blood viscosity was studied in the 33 endurance trained subjects before and after a 48-km mountain race (Sandia Wilderness Crossing Research Run). Runners started at an altitude of 1700 m, ran 26 km to 3300 m, then descended 22 km to finish at 1900 m. Venous blood viscosity (eta b) and plasma viscosity (eta p) were measured at 37 degrees C at shear rates of 11.25, 22.5, 45, 90, and 225.s-1, using a cone-plate viscometer. Endurance trained subjects had significantly higher pre-race blood viscosity at 11.25 and 22.5.s-1 than control subjects but similar plasma viscosity and hematocrits. Following the race, there was no significant change in mean hematocrit, but eta b increased significantly at all shear rates except 225.s-1. Plasma viscosity at 225.s-1 increased significantly from 1.44 to 1.53 cP following the run. Since eta b did not increase, an increase in red cell deformability is inferred. The mechanism of the increase in eta b at lower shear rates in runners is due in part to the higher plasma viscosity. An additional mechanism at lower shear rates is in an increase in red cell aggregation. Increased plasma fibrinogen was measured in six of six resting subjects taken from 1600 m to 3300 m and is speculated to be the mechanism of enhanced aggregation and deformability in the runners.

Adult↗
PubMed1987

[Increase in erythrocyte and plasma viscosity in patients with atherosclerotic vasculopathy of different sites].

Peripheral atherosclerotic arteriopathies are characterised by increased blood viscosity and, according to some, by a reduction in red blood cell deformability. Red blood cell viscosity was studied in 40 atherosclerosic patients (14 carotid and 26 aortoiliacofemoral lesions). All patients were subjected to the standard diagnostic examination (Doppler velocimetry, etc.). Fifty healthy non-smokers of the same sex and 20 heavy smokers were studied as controls. The viscosity of the whole blood, and plasma and blood fibrinogen were assayed. In studying erythrocyte viscosity, cells poor in leucocytes and platelets suspended in a saline phosphate buffer were employed. The atherosclerotic patients presented significantly higher mean levels of erythrocyte viscosity (p less than 0.01) and the increase in plasma viscosity and blood fibrinogen was also statistically significant. The viscosity of the whole blood was also increased in these patients (p less than 0.001). The increase in blood viscosity in subjects with peripheral arteriopathies therefore appears to be attributable to the plasma and to rheological alterations in the red blood cells.

Adult↗
PubMed1987

[Hemorrheologic disorders in obese patients. Study of the viscosity of the blood, erythrocytes, plasma, fibrinogen and the erythrocyte filtration index].

Risk factors for atherosclerosis are often associated with haemorheological changes. On this point, obesity (recently advocated as an independent risk factor) was not much studied and with not univocal results. We have studied 70 obese patients (BMI greater than 30) and 50 healthy subjects (BMI less than 25). Among obese 26 had no more pathologies, 29 had hypertension, 3 suffered from ischemic heart disease, 3 suffered from occlusive arteriopathy, 9 were hyperlipidemic, 10 were smokers. We determined plasma viscosity and whole blood viscosity (at haematocrit corrected to 45% too). Washed erythrocytes, poor in leucocytes and platelets and resuspended in phosphate-buffered saline, were used for study of erythrocyte viscosity and deformability. Obese patients showed raised mean blood viscosity values when compared to healthy controls (p less than 0.01); an even more significant increase (p less than 0.001) was found concerning plasma viscosity and fibrinogen. Erythrocyte viscosity and red blood cell filterability index did not show any significant difference. We found no significant correlation between viscosity values and presence of hypertension, hyperlipidemia and smoking habit among obese. In conclusion, the higher vasculopathy incidence might be caused by an increase in blood viscosity, mostly due to plasmatic component. This fact appears to be independent from the presence of atherosclerosis complications or other risk factors.

Adult↗