Comparison tests for plasma viscosity measurements

Objective: The accompanying thrombocytosis is referred to as the major factor associated with thromboembolism in iron deficiency anemia (IDA). Increased viscosity may increase the risk of thrombosis. We hypothesized that increased platelet count -with reactive thrombocytosis- might also affect plasma viscosity. We planned to evaluate the influence of normal and high platelet count on plasma viscosity in IDA patients. Material and Methods: The patient population consisted of fifty-three newly diagnosed and untreated women aged between 18 and 62 years with IDA. Group 1 consisted of 33 patients, platelet levels below 400 x 109/L. Group 2 consisted of 20 patients, platelet levels above 400 x 109/L. Measurements of plasma viscosity were performed using Brookfield viscometer. Results: Mean plasma viscosity was found as 1.05 ± 0.08 mPa.s. in Group 1, and 1.03 ± 0.06 mPa.s. in Group 2. Mean plasma viscosity was not statistically different. White blood cell count was significantly higher in Group 2. Vitamin B12 levels were significantly higher in Group 2, while folic acid levels were higher in Group 1 (p=0.011 and p=0.033). Plasma viscosity was correlated with erythrocyte sedimentation rate (r=0.512 p=0.002) in Group 1 and inversely correlated with vitamin B12 (r=−0.480 p=0.032) in Group 2. Conclusion: Despite the significant difference between groups in terms of platelet count, no significant difference was detected in plasma viscosity and this finding could be explained as the following; 1-These platelets were not thrombocythemic platelets; 2-Similar to the theory about leukocytes, higher platelet counts – even non-thrombocythemic – may increase plasma viscosity; 3-Evaluating platelet count alone is not sufficient and the associating red-cell deformability should also be taken into account; and 4-Although other diseases that could affect viscosity are excluded, some definitely proven literature criteria such as fibrinogen, hyperlipidemia, and the inflammatory process should also be evaluated by laboratory and clinical measures.

Reference intervals for whole blood viscosity using the analytical performance-evaluated scanning capillary tube viscometer

Pregnancy is a dynamic process associated with changes in vascular and rheological resistance. Maternal maladaptation to these changes is the leading cause of pregnancy complications such as preeclampsia. This study aimed to assess the hemorheological alterations in pregnancies with a high risk for preeclampsia in the first trimester. Ninety-two pregnant women were allocated into the high preeclampsia risk group (37 cases) and control groups (55 cases). Plasma and whole blood viscosity and red blood cell morphodynamic properties, including deformability and aggregation were assessed by Brookfield viscometer and laser-assisted optical rotational cell analyzer (LORRCA) at 11-14 gestational weeks. Whole blood viscosity was significantly higher in the high-risk group at all shear rates. Plasma viscosity and hematologic factors showed no differences between the groups. Hematocrit levels positively correlated with high blood viscosity only in the high-risk group. There were no significant changes in the other deformability and aggregation parameters. Changes in the whole blood viscosity of pregnant women with high preeclampsia risk refer to impaired microcirculation beginning from the early weeks of gestation. We suggest that the whole blood viscosity is consistent with the preeclampsia risk assessment in the first trimester, and its measurement might be promising for identifying high-preeclampsia-risk pregnancies.

Blood viscosity at 10 shear rates, plasma viscosity, packed cell volume, plasma fibrinogen, serum alpha 2-macroglobulin, and serum proteins were measured in 83 patients with low-tension glaucoma (LTG) and 23 patients with 'high-tension glaucoma' (HTG: at least one IOP reading above 40 mmHg) and compared with those in 50 controls. Blood and plasma viscosity values and packed cell volume were significantly higher in the LTG group than those in controls. The HTG and the LTG groups differed only in plasma viscosity, but smoking and drinking habits in the HTG patients were greatly different from those in LTG patients and controls, thus preventing interpretation of data in the HTG group. Within the LTG group viscosity values were highest in a subgroup designated earlier by us as focal ischaemic LTG, whereas another subgroup, senile sclerotic LTG, did not show significant differences compared with controls. These findings may indicate a factor in the pathogenesis of visual field defects and disc cupping in some patients with LTG.

IntroductionMany studies suggest that elevated triglyceride levels are associated with increased long-term risk of stroke, including transient ischemic attacks. In addition, elevated triglyceride levels independently contribute to plasma viscosity and decreased blood flow. However, no consensus has been reached regarding the significance of hypertriglyceridemia as an independent risk factor for ischemic stroke.Case presentationWe report the case of a patient admitted to our hospital for sudden onset of coma. Laboratory test results revealed he had high blood glucose (28.2mmol/L), high glycated hemoglobin (11.4 percent), considerably high serum triglyceride levels (171.5mmol/L; type V hyperlipoproteinemia), and high plasma viscosity (1.90mPa/s) with normal β-hydroxybutyric acid levels. His triglyceride levels decreased after administering intravenous fluids. Our patient’s consciousness level improved gradually over three days. All serum lipid levels decreased seven days after admission.ConclusionsThe findings in our patient’s case are likely explained by triglyceride-mediated hyperviscosity causing a transient ischemic attack. In the present report we suggest that when several tests do not reveal the cause of stroke-like symptoms, measurement of plasma viscosity may be informative.

An erythrocyte transport function (ETF) is proposed, as an index of the efficiency of the circulation of red cells. Under defined conditions, this ETF is shown to be proportional to the ratio of haematocrit to whole-blood viscosity (phi/eta), a ratio already used by Chien. The variations of phi/eta with phi, at selected driving pressures in a capillary viscometer, are presented, both for normal and for pathological blood samples. Maximal values of phi/eta appear generally to occur at haematocrits of about 42%, and are strongly dependent upon plasma viscosity. They are also influenced by shear. The concept of 'isograds' (curves of phi/eta against phi at constant velocity gradient) is introduced, and is analysed in technical appendices which also deal with rates of shear in capillary and rotational viscometers when Newtonian or shear-sensitive liquids are measured.

A method of isolating surface tension and yield stress effects in a U-shaped scanning capillary-tube viscometer using a Casson model

The viscosity of whole blood measured at low shear rates is determined partly by shear resistance of the red cell aggregates present, stronger aggregation increasing the viscosity in the absence of other changes. Effects of cell deformability can confound interpretation and comparison in terms of aggregation, however, particularly when the plasma viscosity is high. We illustrate the problem with a comparison of hematocrit‐adjusted blood from type 1 diabetes patients and controls in which it is found the apparent and relative viscosities at a true shear rate of 0.20 s $^{-1}$ are lower in the patient samples than age matched controls, in spite of reports that aggregation is increased in such populations. Because the plasma viscosities of the patients were higher on average than controls, we performed a series of experiments to examine the effect of plasma protein concentration and viscosity on normal blood viscosity. Dilution or concentration by ultrafiltration of autologous plasma and viscosity measurements at low shear on constant hematocrit red cell suspensions showed (a) suspension viscosity at 0.25 and 3 s $^{-1}$ increased monotonically with plasma protein concentration and viscosity but (b) the relative viscosity increased, in concert with the microscopic aggregation grade, up to a viscosity of approximately 1.25 mPa‐s but above this the value the relative viscosity no longer increased as the degree of aggregation increased in concentrated plasmas. It is suggested that in order to reduce cell deformation effects in hyperviscous pathological plasmas, patient and control plasmas should be systematically diluted before hematocrit is adjusted and rheological measurements are made. True shear rates should be calculated. Comparison of relative viscosities at low true shear rates appears to allow the effects of red cell aggregation to be distinguished by variable shear rate viscometry in clinical blood samples.

Flow behavior of neonatal and adult erythrocytes in narrow capillaries

The viscosity evaluation in Plasma is extremely useful in the clinical evaluation of different diseases. A procedure is presented, based on Protonic Magnetic Resonance, for the evaluation of the dynamic viscosity in Blood Plasma and in hemoglobin solution from the determination of the transverse relaxation time (T2). To experimentally determine the T2 value, the impulse series Carr-Purcell-Meiboon-Gill was used in a MARAN DRX console (OXFORD INSTRUMENTS) and a homogeneous magnetic system (B0 = 0.095T). Values were obtained for the viscosity of the blood plasma and hemoglobin of 1.68 ± 0.12 mPas and 12.78 ± 3.55 mPas respectively, which agreed with the determined, in the same samples, using an Ostwald viscometer (1, 45 ± 0.06 mPas for the plasma and 12.82 ± 3.35 mPas for the dissolution of hemoglobin). The dynamic viscosity of the blood plasma was determined in 236 patients with Multiple Myeloma (2.19 ± 0.58 mPas), 142 with Drepanocytic Anemia (2.20 ± 0.79 mPas) showing statistically significant increases with respect to the characteristic values of the controls (1.68 ± 0.12mPas). Magnetic Relaxation is an option to evaluate plasma viscosity because it minimizes the volume of sample needed and eliminates the need to wash the viscometer between determinations. Magnetic Relaxation can compensate its relative high cost, compared with other Viscosimetry methods, facilitating other determinations of utility in several diseases.

Fibrinogen, plasma viscocity, and the white blood cell count predict ischaemic heart disease, but there is less certainty for their predictive power for ischaemic stroke. Studying stroke and ischaemic heart disease in the same cohort prospectively allows comparison of predictive strengths. The Caerphilly and Speedwell cohorts consist of a population sample of 4,860 men aged 45-59 years at recruitment who had baseline measurements of fibrinogen, plasma viscosity, and white blood cell counts. After 15-19 years of follow-up, men in the two cohorts experienced 312 ischaemic strokes and 557 ischaemic heart disease events. Mean fibrinogen, plasma viscosity and white blood cell counts differed significantly after adjustment for confounding factors between men with and without ischaemic heart disease, 0.25 g/l (95% CIs 0.1 8-0.32); 0.036 cp (95% CIs 0.027-0.044); 0.67 x 10(9)/l (95% CIs 0.50-0.84) respectively. The same measurements showed no significant differences after adjustment for the same confounding factors for men with and without ischaemic stroke, 0.05 g/l (95% CIs -0.04-0.14); 0.008 cp (95% CIs -0.003-0.019); 0.16 x 10(9)/l (95% CIs -0.06-0.38) respectively.

A simple laboratory measurement for discrimination of transudative and exudative pleural effusion: Pleural viscosity

Some studies indicate that obesity is associated with rheological disturbances. Because there are usually sex differences in the type of obesity we decided to evaluate rheological differences between male and female obese patients. We studied 18 morbidly obese men, mean age 43.66 +/- 11.32 years, mean body mass index (BMI) 49.82 +/- 6.03 kg/m2 and 20 obese females, mean age 40.6 +/- 11.86 years, mean BMI 47.41 +/- 8.81 kg/m2. Blood and plasma viscosity measurements were performed using a cone-plate viscometer (Brookfield DV-II). Erythrocyte elongation and red blood cell (RBC) aggregation were measured using the Laser-assisted Optical Rotational Cell Analyser (LORCA). Whole blood viscosity and RBC deformability expressed by the elongation index were significantly higher in obese men. We did not observe differences in plasma viscosity, corrected blood viscosity and aggregation parameters among the obese population. Blood viscosity correlated with selected RBC aggregation indices. We conclude that morbidly obese patients presented sex-dependent differences in some rheological properties. This study indicates a relation between erythrocyte aggregation indices and blood viscosity in obese populations.

Sauna effects on hemorheology and other variables.

Blood viscosity and blood pressure: role of temperature and hyperglycemia