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Annals of Medicine Feb 1993In clinical situations associated with disturbed blood flow, the primary focus is usually on improving cardiovascular performance. However, during recent decades, both... (Review)
Review
In clinical situations associated with disturbed blood flow, the primary focus is usually on improving cardiovascular performance. However, during recent decades, both basic science and clinical literature reports have presented evidence that the flow properties of blood must also be considered in these situations. Thus, the relatively new fields of haemorheology and clinical haemorheology have evolved; the former deals with the flow and deformation behaviour of blood, plasma and the formed elements of blood, whereas the latter relates to alterations of their behaviour in various pathophysiologic states. This review therefore summarizes some of the salient aspects of clinical haemorheology and of the determinants of blood flow properties (flow rate, haematocrit, plasma viscosity, red cell aggregation, red cell deformability). In addition, it briefly describes several clinical disorders associated with abnormal blood, plasma or cell rheology ('hyperviscosity syndromes' occurring in polycythaemia, leukaemia, sickle cell disease, paraproteinaemias).
Topics: Blood Viscosity; Erythrocyte Aggregation; Erythrocyte Deformability; Hematologic Diseases; Humans; Microcirculation; Plasma; Polycythemia
PubMed: 8435185
DOI: 10.3109/07853899309147854 -
British Journal of Anaesthesia Oct 1986
Topics: Anesthetics; Blood Viscosity; Humans
PubMed: 3768235
DOI: 10.1093/bja/58.10.1202-a -
Current Atherosclerosis Reports Apr 2014This review examines the emerging role of endothelial shear stress (ESS) and blood viscosity on the initiation and progression of atherosclerosis in peripheral arterial... (Review)
Review
This review examines the emerging role of endothelial shear stress (ESS) and blood viscosity on the initiation and progression of atherosclerosis in peripheral arterial disease. Among the variables determining ESS, blood viscosity has to date been the most overlooked by clinical researchers. Blood viscosity is a laboratory assessment that is minimally invasive and modifiable using pharmacologic therapy as well as by hemodilution. Monitoring and controlling blood viscosity not only modulates ESS, but also reduces peripheral vascular resistance and increases blood flow to the lower extremities.
Topics: Blood Viscosity; Endothelial Cells; Hemodynamics; Humans; Peripheral Arterial Disease; Stress, Physiological; Vascular Resistance
PubMed: 24519415
DOI: 10.1007/s11883-014-0404-6 -
Biorheology 2009The circulation is adapted to specific levels of blood viscosity resulting in a balance that simultaneously sets peripheral vascular resistance, blood pressure and... (Review)
Review
The circulation is adapted to specific levels of blood viscosity resulting in a balance that simultaneously sets peripheral vascular resistance, blood pressure and cardiac output, factors in part mediated by the production of nitric oxide by the endothelium. Although it is generally perceived that decreasing blood viscosity is beneficial for cardiovascular function, small increases of blood viscosity in normal healthy experimental subjects significantly improve cardiovascular function. These changes are within the normal variations of viscosity due to the variations of hematocrit in the healthy population. Hemodilution reduces blood viscosity, which is proposed to be physiologically beneficial. However, in extreme hemodilution, increased plasma viscosity via the use of viscogenic plasma expanders sustains microvascular and tissue function at significantly reduced levels of oxygen delivery. Studies in hemorrhagic shock resuscitation using oxygen carrying and non-carrying red blood cells show that restoration of blood viscosity is as important as restoration of oxygen carrying capacity. It is concluded that although hemodilution is indicated for reducing abnormally high blood viscosities, it is beneficial to increase plasma viscosity when hematocrit is reduced. Furthermore small increases in hematocrit may be beneficial due to the related increase in blood viscosity, independently of the increase of oxygen delivery capacity.
Topics: Animals; Blood Viscosity; Hematocrit; Hemodilution; Humans; Microcirculation; Oxygen Consumption; Shock, Hemorrhagic; Vascular Resistance
PubMed: 19581725
DOI: 10.3233/BIR-2009-0539 -
Thrombosis and Haemostasis May 1992
Review
Topics: Blood Pressure; Blood Viscosity; Cardiovascular Diseases; Humans; Risk Factors; Thrombolytic Therapy
PubMed: 1519206
DOI: No ID Found -
Clinical Hemorheology and... 2019The viscosity of a fluid is a measure of its resistance. It is the thickness and stickiness of blood, and a direct measure of the resistance of blood to flow through the...
BACKGROUND
The viscosity of a fluid is a measure of its resistance. It is the thickness and stickiness of blood, and a direct measure of the resistance of blood to flow through the vessels. Various factors in the blood have direct or indirect impact on blood viscosity. These hemorheological factors play an important role in the pathogenesis of many diseases. Glucose is one such factor, which, when increased in the blood, causes resistance in the blood flow.
OBJECTIVE
The present study is aimed to assess the changes in blood viscosity associated with hyperglycemia in rodents.
METHODS
Diabetic patients were grouped, depending on the duration of their diabetic status assessed by their increased HbA1c. Similarly rodents were subjected to acute or chronic hyperglycemic conditions in various experiments. In vivo, perfusion study was performed using micro probe in diabetic mice. Flow cytometry was used to assess the expression of VCAM-1 on endothelial surface.
RESULTS
An approximate 40% increase in blood viscosity is observed in individual who were diabetic for the past 15 years than those who were diagnosed just one year back. Similarly such increase in blood viscosity was evident in different experiments of rodents. Our in vivo perfusion study did not showed conclusive finding however long term hyperglycemia can have deleterious effect on flow rate. Vascular pathology which was evident from the data of flow cytometry, where increase in VCAM-1 expression on the endothelial surface was observed in response to glucose and in diabetic mice.
CONCLUSIONS
Hyperglycemia implicates the blood viscosity which in turn can have tedious effect on metabolic syndromes thus causing the serious effect in the tissue perfusion of an organs.
Topics: Animals; Blood Viscosity; Diabetes Mellitus, Experimental; Female; Hemodynamics; Humans; Hyperglycemia; Male; Metabolic Syndrome; Mice; Resin Cements
PubMed: 30056416
DOI: 10.3233/CH-180426 -
Clinical Hemorheology and... 2010Decreasing blood viscosity has been proposed since the advent of hemodilution as a means for increasing perfusion in many pathological conditions, and increased plasma... (Review)
Review
Decreasing blood viscosity has been proposed since the advent of hemodilution as a means for increasing perfusion in many pathological conditions, and increased plasma viscosity is associated with the presence of pathological conditions. However, experimental studies show that microvascular functions as represented by functional capillary density in conditions of significantly decreased viscosity is impaired, a problem corrected by increasing plasma and blood viscosity. Blood viscosity, primarily dependent on hematocrit (Hct) is a determinant of peripheral vascular resistance, and therefore blood pressure. In the healthy population Hct presents a variability, which is not reflected by the variability of blood pressure. This is due to a regulatory process at the level of the endothelium, whereby the increase of Hct (and therefore blood viscosity) leads to increased shear stress and the production of the vasodilator nitric oxide (NO), a finding supported by experimental studies showing that the acute increase of Hct lowers blood pressure. Studies that in the healthy population show that blood pressure and Hct have a weak positive correlation. However, when the effect of blood viscosity is factored out, blood pressure and Hct are negatively and significantly correlated, indicating that as blood viscosity increases, the circulation dilates. Conversely, lower Hct and blood viscosity conditions lead to a constricted circulation, associated with a condition of decreased NO bioavailability, and therefore a pro-inflammatory condition.
Topics: Blood Viscosity; Cardiovascular Physiological Phenomena; Hematocrit; Hemodilution; Humans; Hypertension; Microcirculation; Nitric Oxide; Vascular Resistance
PubMed: 20203362
DOI: 10.3233/CH-2010-1261 -
Clinical Hemorheology and... 2019We previously reported that whole body bioelectrical impedance analysis (BIA) measurements are correlated to some hemorheologic factors, suggesting a relationship...
We previously reported that whole body bioelectrical impedance analysis (BIA) measurements are correlated to some hemorheologic factors, suggesting a relationship between viscosity factors and electric properties of flowing blood not only in vitro but also in vivo. Recently we reported that with segmental BIA (analyzing the body considered as composed of 5 cylinders) predictive equations for various determinants of blood viscosity were closer than for the wole body. Another widely used BIA technique uses leg-to-leg impedance measurements so that two cylinders (the two legs) are analyzed. We investigated whether impedance measured with this technique (Tanita TBF-300) is also a predictor of blood viscosity factors. From viscometric measurements performed on venous blood drawn in recreative athletes over the range of shear rates 1 to 6000 s-1 (RHEOMETRE Anton Paar CP 50-1), we found a correlation between leg-leg resistance at 50 kHz (Rx[50 kHz]) and blood viscosity at 1000 s-1 (η1000= 0.0051 Rx[50 kHz] + 1.3265; r = 0.521 p = 0.028 yielding a prediction of η1000 (Bland Altman plot: bias 0.05 [RANGE - 0.24; 0.34]. Neither plasma viscosity nor the red cell rheology index «k» of Quemada's model are correlated with Rx[50 kHz], but hematocrit (Hct) does (Hct (%) = 0.0217 Rx[50 kHz] + 33.783; r = 0.480 p = 0.044) yielding a prediction of Hct (Bland Altman plot: bias - 0.11, [range - 1.67; 1.45]. The discrepancy between actual and predicted Hct is also correlated with resistance at 50 kHz (r = 0.575 p = 0.031) as does the discrepancy between actual and predicted Hct/viscosity ratio (r = -0.651 p = 0.006). Therefore, as other previously studied methods, leg to leg BIA predicts viscosity, suggesting that blood rheology may influence the passage of an electric current in the legs.
Topics: Adult; Blood Viscosity; Electric Impedance; Female; Hematocrit; Hemorheology; Humans; Leg; Male; Viscosity
PubMed: 31006677
DOI: 10.3233/CH-199003 -
Clinical Hemorheology and... 2019The relationship between blood viscosity (BV) and endothelial function is rather complex. An increase in BV causes an increase in blood flow resistance, with negative...
BACKGROUND
The relationship between blood viscosity (BV) and endothelial function is rather complex. An increase in BV causes an increase in blood flow resistance, with negative hemodynamic effects; on the other hand, a moderate increase in BV causes an increase in wall stress shear (WSS), and consequent beneficial effects. As a matter of fact, the effect of changes in BV on endothelial function is not yet clear.
OBJECTIVES
Aim of the present study was to evaluate in-vivo the effects of the acute reduction in BV on endothelial function, in healthy male subjects.
METHODS
Fourteen healthy male blood donors were studied before and 48 hours after blood donation. Blood and plasma viscosity were measured at 37C° with a cone-plate viscometer. Endothelial function was evaluated through flow mediated vasodilation (FMD).
RESULTS
Blood viscosity was reduced after blood donation (BV225 (cP) 4.53±0.59 vs.4.18±0.31, p < 0.05). FMD 50 s after cuff deflation was unchanged: 6.23±3.84 vs. 6.62±4.81, p = NS. The vasodilation, however, lasted longer and the area under the curve of FMD was significantly increased: 8.74±8.77 vs.16.14±8.65, p < 0.005.
CONCLUSIONS
The present results demonstrate that the acute reduction of BV prolongs vasodilation, without affecting the amount of vasodilatation, possibly as adaptive reaction allowing more time for oxygen release.
Topics: Adult; Blood Viscosity; Endothelium, Vascular; Humans; Male; Middle Aged
PubMed: 30909194
DOI: 10.3233/CH-180446 -
American Journal of Clinical Pathology Jun 2006This article discusses the fundamentals for measuring the viscosity of whole blood, serum, and plasma and its application to the diagnosis of hyperviscosity syndrome. We... (Review)
Review
This article discusses the fundamentals for measuring the viscosity of whole blood, serum, and plasma and its application to the diagnosis of hyperviscosity syndrome. We describe some of the terminology in the field, including relevant definitions, the different units of measure, and general principles of clinical laboratory viscosity measurement. The 3 main categories of instrumentation for viscosity measurement--capillary, falling-sphere, and rotational viscometers--are discussed. We compare the various types of instrumentation for their usefulness with various types of clinical specimens. Relevant features that may be important in selecting a viscometer are described. We describe our 1.5-year experience with the viscometer that we chose. We hope the information in this review will be useful to pathologists and clinical laboratory staff in explaining the available choices for measuring serum, plasma, and whole blood viscosity.
Topics: Blood Viscosity; Clinical Laboratory Techniques; Humans; Pathology, Clinical; Plasma; Serum
PubMed: 16830959
DOI: 10.1309/FFF7U8RRPK26VAPY