Whole-blood viscosity

Therapy is directed at reducing whole blood viscosity where this is signiflcantly raised. Small volume venesections, in which 250 ml as opposed to 500 ml of whole blood, are carried out at 2- or 3-week intervals. It should be noted that studies have demonstrated impairment of cerebral blood flow and a shortened survival in these individuals so that such intervention is appropriate in the severe cases. 

Mechanism of action that provides symptom relief with pentoxifylline is poorly understood but is thought to involve red blood cell deformability as well as a reduction in fibrinogen concentration, platelet adhesiveness and whole blood viscosity (75). The recommended dose of pentoxifylline is 400 mg three times daily with meals. Pentoxifylline causes a marginal but statistically significant improvement in pain-free and maximal walking distance (a net benefit of 44 m in the maximal distance walked on a treadmill (95% Cl, 0 14 to 0 74) based on meta-analyses of randomized, placebo-controlled, double-blind clinical trials (76). At the same time pentoxifylline does not increase the ABI at rest or after exercise (56). Pentoxifylline may be used to treat patients with intermittent claudication however, it is likely to be of marginal clinical importance (56,77). Medical therapies... 

Vascular access thrombosis has been reported in up to 26% of patients treated with epoetin alfa (3,34,38). Most of the failures occurred in poljdetrafluoroethylene grafts. There was no comparison with patients not treated with epoetin. It has been suggested that the increased risk of extracorporeal circuit clotting and the higher heparin requirements during hemodialysis may not be due to a hypercoagulable state, but rather to an increase in erythrocyte mass and consequently in whole blood viscosity (66). 

In patients with ulcerative colitis, intravenous administration of 40 ml daily of dong quai extract inhibited platelet activation (Dong et al. 2004). Intravenous administration of 200 ml daily of a 25% solution of dong quai for 20 days to patients with acute ischemic stroke resulted in decreases in a number of hematological parameters including platelet adhesion rate, platelet electrophoresis time, and whole blood adhesion, and an increase in prothrombin time (Tu and Huang 1984). A reduction in whole blood viscosity was observed for approximately 3 hours in people orally administered a dong quai extract (Terasawa et al. 1985). 

The n-3 LC-PUFA have a beneficial effect on plasma triglycerides, high blood pressure, whole-blood viscosity, and platelet function they inhibit the expression of cell-adhesion molecules, shift the eicosanoid profile to one of lesser thrombotic and inflammatory potential, improve vessel-wall compliance, and have antiarrhythmic potential (1,2). A number of intervention trials have associated the consumption of fish with decreased mortality from CVD (3-5). High doses of fish oil eliminate both vascular thrombus as well as vascular lesion formation (6). In men who had had a recent myocardial infarction, low-dose dietary supplementation with n-3 LC-PUFA, in addition to the recommended secondary prevention treatments, reduced by 45% the risk of sudden cardiac death, but not the risk of nonfatal myocardial infarction (7). It has been shown to mitigate the course of coronary atherosclerosis in humans (8). 

Gum-Saline. Gum is a galactoso—gluconic acid having molecular weight of approximately 1500. First used (16) in kidney perfusion experiments, gum—saline enjoyed great popularity as a plasma expander starting from the end of World War I. The aggregation state of gum depends on concentration, pH, salts, and temperature, and its coUoid oncotic pressure and viscosity are quite variable. Conditions were identified (17) under which the viscosity would be the same as that of whole blood. 

Plasma or serum can be regarded as a Newtonian fluid. The viscosity of plasma at 37 °C is approximately 1.2 cp. In contrast, whole blood shows non-Newtonian behavior, its viscosity decreasing with an increasing shear rate, but with a decreasing hematocrit. 

Sweeney JD, Labuzzetta JW, Michielson CE, Fitzpatrick JE (1989) Whole blood aggregation using impedance and particle counter methods. Am J Clin Pathol 92 794-797 Turitto VT (1982) Blood viscosity, mass transport, and throm-bogenesis. Prog Hemost Thromb 6 139-177... 

Paraproteinaemia poses a special problem, since an increased viscosity may be measured both in whole blood and in serum or plasma. Paraproteinaemia occurs in Waldenstrom s disease (osteochondrosis of the capital femoral epiphysis), in multiple myeloma or non-Hodgkin lymphoma. Samples taken from these patients may reveal a change in flow properties due to viscosity. A change in the flow properties, however, will slow down the penetration of the sample material into the reagent layers so that the reaction can take place only with some delay. This results in analysis data that are too low. If the sample material (serum or plasma) is diluted, as in the case of the Seralyzer system, these problems are absent. 

The results indicate that the linear ranges of glucose and lactate (oxidase reactions) in whole blood correspond well with those of the same metabolites in buffers. The sensor methods and the reference methods were in good correlation for all analytes. The precision for the standards in buffers was always better (about 2-3%) than that of the blood samples. This was ascribed in part to the instability of the metabolite concentrations in blood, particularly that of lactate. In addition, the blood viscosity and the nonspecific heat in the reaction can also affect the final results. 

Since the original description by Waldenstrom, it has become clear that this syndrome is not confined to raacroglobulinemia, and so it is better called viscosity syndrome. It has been found in some 4% of IgG-inyelomatosis H22), occasionally with IgA paraprotein and even with Bence Jones proteinemia, usually due to polymerization [reviewed by Somer (S19)], and it is also recorded with IgE (01). With regard to viscosity syndromes due to paraproteins the relevant abnormality is detected in viscosity measurements on either whole blood, plasma, or serum (S19) the latter is the most convenient. This is not the case in polycythemia, etc. (W5). 

Hemodilution has been proposed as a method to reduce abnormal blood viscosity to treat retinal vein occlusion. In this procedure, whole blood is withdrawn and the same volume of a plasma expander such as hydroxyethyl hemadon or hydroxyethyl starch is reinjected until the hematocrit is decreased to approximately 35%. 

In rats intravenously administered the compound puerarin (dose not specified in available English language translation), a reduction in the viscosity of whole blood and plasma, blood yield stress, and the maximum rate of platelet aggregation was observed in animals with acute blood stasis (Pan et al. 2003). 

Axial accumulation of RBCs leaves behind a lower viscosity plasma skimming layer near the microchannel wall, which is, otherwise, a region of higher rates of strain. Consequently, the apparent viscosity of the whole blood sample decreases, and effects of this reduction become significantly prominent as size of the RBCs approaches hydraulic radius of the microchannel, leading to enhanced rates of fluidic transport. 

The rheology of blood flow is complex. The specific gravity of plasma and red cells is 1.03 and 1.10, respectively. Blood plasma is a Newtonian fluid with a viscosity equal to 0.00012 Pa s. Whole blood is a non-Newtonian fluid with a viscosity that depends on the shear rate, hematocrit, and temperature. Experimental data on the variation of the viscosity of blood as a function of shear rate for different hematocrits... 

The physical properties of the fluids are very important. Thin fluids are easy to move or move within. Thick fluids are just the opposite. The physical property that measures fluid thickness is called viscosity, and the viscosity of water is about 50-100 times as large as the viscosity of air. Dissolving or suspending materials in the water can enhance its viscosity very much. The viscosity of whole human blood is about 10 times that of water. 

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