Blood Viscosity Values Research Articles

Impact of blood viscosity on wall shear stress of large intracranial aneurysms

Objective To simulate the computational hemodynamics of large intracranial aneurysms and analyze the impact of blood viscosity on wall shear stress. Methods Eight large intracranial aneurysms at internal carotid artery between June 2013 and July 2013 were studied retrospectively. Among them,3 aneurysms were ruptured and 5 were unruptured.Pulsatile CFD simulations were carried out using three levels of blood viscosity(0.002,0.004,0.012 Pa·s).For each aneurysm model, the average wall shear stress(WSS) predicted by the three blood viscosity levels were compared. Results Blood viscosity has significant impaction on average wall shear stress of intracranial aneurysms and parent artery.Average wall shear stress increased significantly with the increase of blood viscosity.When blood viscosity was 0. 002,0. 004,0. 012 Pa·s,the average wall shear stress of aneurysms was(2. 79±2. 23),(5. 27±3. 72)and(11. 05±7. 56)Pa,respectively.The average wall shear stress of parent artery was(5. 61±2. 59),(9. 56±3. 74)and(22. 56±12. 41) Pa respectively.A reduction in wall shear stress between the parent artery and the aneurysm sac was found in all the cases. Conclusion Abnormal increase or decrease in blood viscosity may aggravate vascular wall damage and increase the risk of aneurysmal rupture.It is necessary to adopt patient-specific value of blood viscosity in future hemodynamic studies of intracranial aneurysms. Key words: Blood viscosity; Large intracranial aneurysm; Wall shear stress; Hemodynamics

Hemorheological changes and hematometric erythrocyte characteristics in rats after sodium nitrite intoxication

Sodium nitrite (NaNO2) is a precursor to a variety of organic compounds (pharmaceuticals, dyes and pesticides), but it is best known as a food additive. The aim of the study is to investigate the influence of acute (i.p.) treatment of Wistar rats with NaNO2 (at the dose of 50 mg/kg b.w.) on the blood rheological properties and erythrocyte hematometric indices (Hb, HCT, RBC, MCV, RDW, MCH, MCHC). The significant differences were not found in the whole blood viscosity (WBV) values of the control and NaNO2-treated groups. The changes in the erythrocyte hematometric indices were statistically significant for RDW, MCHC and MCH at the 1st hour, five- and ten days after NaNO2 administration. Interestingly, at the day 5th of the NaNO2 treatment we obtained statistically significant lower values for the RBC count, Hb, HCT, RDW, as well as elevated indices MCV (no statistically significant), MCH, MCHC. The results obtained indicate that hemorheological and hematometric parameters examined should be monitored in cases of acute exposure to nitrites — for the purposes of clinical toxicology. The quantitative values of hematometric indices reported in our experimental model could be suitable for predicting NaNO2 intoxication and methemoglobinemia in animals and humans.

Normal reference value of whole blood viscosity (230 s− 1) of old women and geographical factors

AimThis paper aims at supplying a scientific basis for standardizing the normal reference value of whole blood viscosity (230s−1) of Chinese old women. MethodsThe research is made to study the relationship between the normal reference value of 6707 samples of whole blood viscosity (230s−1) of old women and seven geographical factors in 70 areas in China. ResultsIt is found that the correlation between geographical factors and the normal reference value of whole blood viscosity (230s−1) of old women is quite significant (F=30.137, P=0.000). According to the normal reference value of old women's whole blood viscosity (230s−1) and geographical factors, one regression equation is inferred by using the method of enter regression analysis: Ŷ=13.47+0.0006383X1−0.001083X2−0.1379X3−0.05098X4−0.0008578X5−0.06221X6+0.2114X7±0.55.In the above equation, Ŷ is the reference value of whole blood viscosity (230s−1) of old women (mPa·s); X1 is the altitude (m); X2 is the annual sunshine duration (h); X3 is the annual mean air temperature; X4 is the annual mean relative humidity; X5 is the annual precipitation amount; X6 is the annual range of air temperature; X7 is the annual mean wind speed (m/s); and 0.55 is the value of the residual standard deviations. ConclusionIf geographical values are obtained in a certain area, the normal reference value of whole blood viscosity (230s−1) of old women in this area can be obtained by using the regression equation. Furthermore, according to the geographical factors, China can be divided into eight regions: Northeast China Region, North China Region, Shanxi–Shaanxi–Inner Mongolia Region, Middle and lower reaches of the Yangtze River Region, Southeast China Region, Northwest China Region, Southwest China Region and Qinghai–Tibet Plateau Region.

Stress-Induced Hyperviscosity in the Pathophysiology of Takotsubo Cardiomyopathy

Takotsubo cardiomyopathy (TC) is characterized by transient hypokinesis of the left ventricular apex or midventricular segments with coronary arteries without significant stenosis. It is often associated with emotional or physical stress; however, its pathophysiology is still unclear. In the present study, we analyzed the alterations in blood viscosity and markers of endothelial damage induced by sympathetic stimulation in patients with previous TC. Seventeen women (mean age 71 years) with previous TC, included and investigated in the TC Tuscany Registry, were compared to a control group of 8 age- and risk factor-matched women with chest pain and coronary arteries free of stenosis. All subjects underwent the cold pressor test (CPT). Before and after the CPT, the hemorheologic parameters (whole blood viscosity at 0.512 s(-1) and 94.5 s(-1), plasma viscosity, erythrocyte deformability index, and erythrocyte aggregation), catecholamines, plasminogen activator inhibitor-1 (PAI-1), and von Willebrand factor levels were assessed. The patients with TC had significantly greater baseline PAI-1 levels (p <0.01) and lower erythrocyte deformability index values (p <0.01). After CPT, both the patients with TC and the controls had a significant increase in several hemorheologic parameters, catecholamines, and von Willebrand factor levels and a decrease in erythrocyte deformability index. However, the PAI-1 levels were significantly increased only in the patients with TC. Compared to the controls, the patients with TC had significantly greater values of whole blood viscosity at 94.5 s(-1) (p <0.05), PAI-1 (p <0.01), von Willebrand factor (p <0.05) and lower erythrocyte deformability index values (p <0.01) after CPT. In conclusion, the results of the present study suggest that in patients with TC, the alterations in erythrocyte membranes and endothelial integrity induced by catecholaminergic storm could determine microvascular hypoperfusion, possibly favoring the occurrence of left ventricular ballooning.

Shear rate specific blood viscosity and shear stress of carotid artery duplex ultrasonography in patients with lacunar infarction

BackgroundThis study describes a new method for determining site-specific vascular shear stress using dynamic measures of shear rate and blood viscosity (BV) in the carotid arteries, and examines characteristics of carotid arterial shear stress among patients with lacunar infarction.MethodsVascular shear stress measurements were conducted in 37 patients (17 lacunar infarction patients and 20 control subjects) using duplex ultrasonography. Vessel wall diameters and velocities were measured in each arterial segment at peak-systolic (PS) and end-diastolic (ED) phases, for calculation of PS/ED shear rates. PS/ED shear stresses [dyne/cm2] were determined with PS/ED shear rates and shear-rate dependent BV values. For comparison, both values of hematocrit-derived BV and BV measurements at 300 s-1 were used for calculation of shear stress.ResultsAll cardiovascular disease (CVD) risk factors including BV values were similar between the two groups. In both common carotid arteries, PS and ED shear stresses were significantly lower in the patients with lacunar infarction than in controls in multivariate models that included age, sex, and other major CVD risk factors. PS and ED shear stresses using the shear rate specific BV were 4.5% lower and 7.3% higher than those using the two other BVs, respectively.ConclusionLacunar infarction was associated with reduced carotid arterial shear stress. The use of estimated BV for calculating carotid arterial shear stress provides more accurate assessment of the hemodynamic contribution of shear stress than previous models that have arbitrarily assigned a constant value to this dynamic flow property.

Influence of Electromagnetic Radiation Produced by Mobile Phone on Some Biophysical Blood Properties in Rats

Effects of electromagnetic radiation produced by mobile phone on blood viscosity, plasma viscosity, hemolysis, Osmotic fragility, and blood components of rats have been investigated. Experimental results show that there are significant change on blood components and its viscosity which affects on a blood circulation due to many body problems. Red blood cells, White blood cells, and Platelets are broken after exposure to electromagnetic radiation produced by mobile phone. Also blood viscosity and plasma viscosity values are increased but Osmotic fragility value decreased after exposure to electromagnetic radiation produced by mobile phone.

Dynamic changes of laboratory parameters of rats with type 2 diabetes and insulin resistance: defining their role in development of traditional Chinese medicine syndrome

To observe the development of Chinese medicine syndromes of rats with type 2 diabetes and insulin resistance by detecting dynamic changes of laboratory parameters. A total of 110 male Sprague-Dawley rats were randomly divided into control group (n=50) and model group (n=60) to observe the correlation between laboratory parameter changes and development of Chinese medicine syndromes. A rat model of type 2 diabetes and insulin resistance was established by feeding rats with high-calorie and high-fat diet together with peritoneal injection of streptozocin (30 mg/kg, once). At the end of 0, 6, 8, 10 and 12 weeks, 10 rats were randomly selected form each group and blood was taken from common carotid artery to detect contents of total cholesterol (TC), triacylglycerol (TAG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and leptin in serum, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) contents in plasma and whole blood and plasma viscosities. Compared with the control group, concentrations of TNF-α, IL-6, leptin and cAMP and ratio of cAMP/cGMP increased and content of cGMP decreased markedly from the 6th week to the 12th week. Concentrations of TC, TAG and LDL-C increased from the 8th week to the 12th week, while HDL-C decreased from the 10th week to the 12th week. Whole blood and plasma viscosity values under different shear rates increased significantly from the 10th week to the 12th week. Based on the understanding of markers which have close relationship with Chinese medicine syndromes of dual deficiency of qi and yin, turbid phlegm and blood stasis, combining with the dynamic changes of appearance behavior and laboratory parameters of this animal experiment, the authors speculate the development characteristics of Chinese medicine syndromes in rats with type 2 diabetes. The dynamic progress of Chinese medicine syndromes and pathology varies from dual deficiency of qi and yin to dual deficiency of qi and yin with turbid phlegm, and at last to the combination of dual deficiency of qi and yin, turbid phlegm and blood stasis.

The effects of chronic long-term intermittent hypobaric hypoxia on blood rheology parameters

The effect of chronic long-term intermittent hypobaric hypoxia (CLTIHH) on blood rheology is not completely investigated. We designed this study to determine the effect of CLTIHH on blood rheology parameters. Present study was performed in 16 male Spraque-Dawley rats that divided into CLTIHH and Control groups. To obtain CLTIHH, rats were placed in a hypobaric chamber (430 mmHg; 5 hours/day, 5 days/week, 5 weeks). The control rats stayed in the same environment as the CLTIHH rats but they breathed room air. In the blood samples aspirated from the heart, hematocrit, whole blood viscosity, plasma viscosity, plasma fibrinogen concentration, erythrocyte rigidity index and oxygen delivery index were determined. The whole blood viscosity, plasma viscosity, hematocrit and fibrinogen concentration values in the CLTIHH group were found to be higher than those of the control group. However, no significant difference was found in erythrocyte rigidity index and oxygen delivery index between the groups. Our results suggested that CLTIHH elevated whole blood viscosity by increasing plasma viscosity, fibrinogen concentration and hematocrit value without effecting the erythrocyte deformability. Hence, CLTIHH that may occur in intermittent high altitude exposure and some severe obstructive sleep apnea (OSA) patients may be responsible for hemorheologic changes in those subjects.

Calcium dobesilate may improve hemorheology in patients undergoing coronary artery bypass grafting

Calcium dobesilate is an angioprotective agent that has positive effects on hemorheological parameters. It is an antioxidant that increases endothelial-derived vasodilator substance secretion, there are none that analyze its effects during the postoperative period of patients undergoing myocardial revascularization. We aimed to determine the effects of calcium dobesilate on hemorheological parameters, such as reduced glutathione and malondialdehyde in patients with ischemic heart disease undergoing myocardial revascularization in the postoperative period. One hundred and thirty-four patients operated for coronary heart disease were included in this study. Hemorheological, oxidant and antioxidant parameters were measured two days after surgery and after a period of treatment with calcium dobesilate. Then, 500 mg of calcium dobesilate was given twice a day to one group of 68 patients for three months. The control group was composed of 66 patients who did not receive this medication. The increase in the erythrocyte deformability index was found to be significant compared with both the pretreatment values and with the 1st and 2nd values of the control group after calcium dobesilate administration, whereas there were no significant changes in blood viscosity, glutathione (GSH) or malondialdehyde (MDA) values after the calcium dobesilate administration. The same improvement in the CCS class was observed in patients regardless of they received the calcium dobesilate treatment. In the present investigation, the same improvement in the CCS class was observed in patients regardless of they received the calcium dobesilate treatment. Improvements with calcium dobesilate were statistically significant only in the increase in erythrocyte flexibility.

Influence of blood viscosity to cerebral blood flow in older humans compared to young subjects

Objective Since blood viscosity (BV) is one of the most important factors determining blood flow, this study aimed to investigate the possible correlation between increased blood viscosity and reduction of regional cerebral blood flow (rCBF) in healthy ageing. Methods Male subjects were distributed in two groups: “young”, aged 20–30 (27 volunteers), or “elderly”, aged 60–70 (50 volunteers). Whole blood viscosity was obtained with a Wells-Brookfield Cone/Plate Viscometer. Cerebral blood flow was analysed by means of single photon emission computed tomography (SPECT). Results The mean BV values were 3.28 ± 0.43 mPa in the group of young volunteers and 4.33 ± 0.73 mPa in the group of elderly volunteers ( t = −6.9, p < 0.0001). The elderly had a lower blood flow than the young in the following regions: bilateral parietal; temporal–parietal and temporal of the left hemisphere. Pearson’s correlation between BV and rCBF showed a good inverse correlation when the BV was above 3.95 ± 0.83 mPa. Conclusions Our results point to a close relationship between the two parameters analysed, BV and rCBF. The impairment in rCBF observed in the elderly volunteers might be due to an increase in BV, among other factors. Significance These findings suggest interesting possibilities for the treatment/prevention of brain ageing.

Rheologic, haemostatic, and coagulative variables in type II hyperlipoproteinemic subjects

The aim of the study was to evaluate the direct influence of cholesterol and triglycerides on the rheologic-coagulative pattern. Blood rheologic properties (blood plasmatic and seric viscosity, whole blood and red cell filterability), some coagulative factors (fibrinogen, levels of clotting factors VII and VIII activity), and beta-thromboglobulin and platelet factor 4 were studied in 156 men aged 40–54 years, 87 with type II hyperlipoproteinemia (46 type IIa and 41 type IIb) and 69 normolipemic controls. Smokers and patients with arterial hypertension, diabetes mellitus, or cardiovascular clinical manifestations were excluded. Increased blood viscosity (shear rate 225 sec-1,p<0.01) and higher value of beta-thromboglobulin and platelet factor 4 (p<0.001 both) were observed in type IIb hyperlipoproteinemic patients. Levels of fibrinogen and factor VII and VIII activity did not differ in hyperlipemic patients and controls. After multiple regression analysis, levels of platelet factor 4, plasma viscosity, and fibrinogenemia were positively related with triglycerides concentration; total cholesterol concentration was positively related to fVII activity and inversely with red cell filterability. We conclude that the rheologic-coagulative pattern is more severely altered in type IIb than in type IIa hyperlipoproteinemia, and that these alterations are strictly related to the severity of the increase in trigly cerides and cholesterol levels.

Hemorheology and vascular reactivity in patients with diabetes mellitus type 2

The study aimed to investigate the hemorheological parameters in patients with diabetes mellitus type 2 and to estimate their relationship with the cerebral and cutaneous blood flow and their responses to postural changes. The basic hemorheological constituents: hematocrit (Ht), fibrinogen (Fib), whole blood (WBV) and plasma viscosity (PV) were examined in 20 patients with diabetes mellitus type 2 and in 10 healthy age and sex matched controls. Blood flow velocity in the middle cerebral artery (MCA) was measured by transcranial Doppler monitoring at rest and during 5-min head-up tilt. Also laser Doppler-recorded tiptoe skin blood flow was investigated and venoarteriolar reflex perfusion responses to postural impact was monitored. Significant increase of Fib and WBV at shear rates of 0.0237 s(-1) to 128.5 s(-1) in the patients in comparison to controls was found. The postural challenge caused decrease of the cerebral blood flow velocity and increase of the resistance index (RI) in the diabetic patients. The initial mean skin perfusion values of the tiptoes and the venoarteriolar constriction response indices were significantly higher in the diabetes group. In the patients with diabetes mellitus type 2 the increased blood viscosity values were associated with impaired cerebrovascular and peripheral vascular responces.

Computer simulations of atherosclerotic plaque growth in coronary arteries.

A three dimensional mathematical model with a linear plaque growth function was developed to investigate the geometrical adaptation of atherosclerotic plaques in coronary arteries and study the influences of flow wall shear stress (WSS), blood viscosity and the inlet flow rate on the growth of atherosclerotic plaques using computational plaque growth simulations. The simulation results indicated that the plaque wall thickness at the neck of the stenosis increased at a decreasing rate in the atherosclerosis progression. The simulation results also showed a strong dependence of the plaque wall thickness increase on the blood viscosity and the inlet flow rate. The progression rate in a coronary artery was lower with a higher inlet velocity flow rate and higher with a smaller value of the blood viscosity.

Whole blood viscosity assessment issues III: Association with international normalized ratio and thrombocytopenia.

Background:Anticoagulant and antiplatelet therapies are being used interchangeably or in combination. While international normalized ratio is assessed to determine anticoagulant's contraindication/need, whole blood viscosity is not assessed to determine the need for antiplatelet.Aims:The objective of this study is to investigate whether whole blood viscosity value is associated with levels of international normalized ratio and platelet count.Materials and Methods:De-identified archived clinical pathology data for the year 2008 were audited. All cases of international normalized ratio, which were concomitantly tested for haematocrit and total proteins, were extracted (n=7,387). Whole blood viscosity levels were extrapolated. Whether differences are associated with normal vs. high international normalized ratio and thrombocytopenia vs. thrombocytosis were evaluated.Results:Multivariate analysis show that whole blood viscosity levels statistically significantly differs between international normalized ratio and platelet counts (p<0.001). Platelet count is statistically significantly lower in low blood viscosity when compared with hyperviscosity and normoviscosity (p<0.001). Conversely, international normalized ratio is statistically significantly higher in low blood viscosity relative to hyperviscosity (p<0.001) and normoviscosity (p<0.002). No difference was observed between hyperviscosity and normoviscosity in platelet count or international normalized ratio.Conclusion:The observation corroborates with previous reports to suggest putting into perspective the specificity of whole blood viscosity relative to stasis, against which antiplatelet is employed. It indicates that low whole blood viscosity is synonymous to high international normalized ratio whereby anticoagulant and antiplatelet therapies are contraindicated. International normalized ratio, platelet count and blood viscosity are laboratory indices to consider in constituting antiplatelet monitoring panel.

Effects of hydration and dehydration on blood rheology in sickle cell trait carriers during exercise

This study compared the hemorheological responses of a group of sickle cell trait (SCT) carriers with those of a control (Cont) group in response to 40 min of submaximal exercise (exercise intensity, 55% aerobic peak power) performed in two conditions: one with water offered ad libitum, i.e., the hydration (Hyd) condition, and one without water, i.e., the dehydration (Dehyd) condition. Blood and plasma viscosities, as well as red blood cell rigidity, were determined at rest, at the end of exercise, and at 2 h recovery with a cone plate viscometer at high shear rate and 37 degrees C. The SCT and Cont groups lost 1 +/- 0.7 and 1.6 +/- 0.6 kg of body weight, respectively, in the Dehyd condition, indicating a significant effect of water deprivation compared with the Hyd condition, in which body weight remained unchanged. Plasma viscosity increased with exercise and returned to baseline during recovery independently of the group and condition. As previously demonstrated, resting blood viscosity was greater in the SCT carriers than in the Cont group. Blood viscosity increased by the end of exercise and returned to baseline at 2 h recovery in the Cont group in both conditions. The blood viscosity of SCT carriers did not change in response to exercise in the Dehyd condition and remained elevated at 2 h recovery. This extended hyperviscosity, in association with other biological changes induced by exercise, could be considered as a risk factor for exercise-related events in SCT carriers, similar to vasoocclusive crises, notably during the recovery. In contrast, the Hyd condition normalized the hyperviscosity and red blood cell rigidity of the SCT carriers, with blood viscosity values reaching the same lower values as those found in the Cont group during the recovery. Adequate hydration of SCT carriers should be strongly promoted to reduce the clinical risk associated with potential hyperviscosity complications.

CARDIOVASCULAR RISK ASSESSMENT AND SUPPORT TECHNIQUES: Whole blood viscosity assessment issues I: Extrapolation chart and reference values.

Background:There are many different methods for the assessment of whole blood viscosity, but not every pathology unit has equipment for any of the methods. However, a validated arithmetic method exists whereby whole blood viscosity can be extrapolated from haematocrit and total serum proteins.Aims:The objective of this work is to develop an algorithm in the form of a chart by which clinicians can easily extrapolate whole blood viscosity values in their consulting rooms or on the ward. Another objective is to suggest normal, subnormal and critical reference ranges applicable to this method.Materials and Methods:Whole blood viscosity at high shear stress was determined, from various possible pairs of haematocrit and total proteins. A chart was formulated so that whole blood viscosity can be extrapolated. After determination of two standard deviations from the mean and ascertainment of symmetric distribution, normal and abnormal reference ranges were defined.Results:The clinicians’ user-friendly chart is presented. Considering presumptive lower and upper limits, the continuum of ≤14.28, 14.29 – 15.00, 15.01 – 19.01, 19.02 – 19.39 and ≥19.40 (208 Sec-1) is obtained as reference ranges for critically low, subnormal low, normal, subnormal high and critically high whole blood viscosity levels respectively.Conclusion:This article advances a validated method to provide a user-friendly chart that would enable clinicians to assess whole blood viscosity for any patients who has results for full blood count and total proteins. It would make the assessment of whole blood viscosity costless and the neglect of a known cardiovascular risk factor less excusable.

Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation

Objective The mechanisms by which smoking and hypertension lead to increased incidence of intracranial aneurysm (IA) formation remain poorly understood. The current study investigates the effects of these risk factors on wall shear stress (WSS) and oscillatory shear index (OSI) at the site of IA initiation. Methods Two ( n = 2) IAs from two patients with history of smoking and hypertension were artificially removed with the help of software @neuFuse (Supercomputing Solutions ®, Bologna, Italy) and the vessel geometry reconstructed to mimic the condition prior to IA formation. Two computational fluid dynamics (CFD) analyses were performed on each data-set by using in turn the normal physiological values of blood viscosity (BV), and high BV values specific to smoking and hypertension, obtained from literature. Results At normal BV, high WSS (>15 Pa) was observed at the site of IA initiation in both patients. When BV values specific to smoking and hypertension were used, both the areas affected by high WSS (>15 Pa) and the maximum WSS were increased whilst the magnitude and distribution of OSI showed no significant change. Conclusions Long-term exposure to high WSS may result in an increased risk of IA development. An incremental increase in areas of high WSS observed secondary to smoking and hypertension may indicate a further increase in the risk of IA initiation. Interestingly, the relationship between BV and the area of increased WSS was not linear, reflecting the need for patient-specific CFD analysis.

Effect of Blood Hematocrit and Erythrocyte Deformability on Adenosine 5′-Diphosphate Platelet Reactivity in Patients With Acute Coronary Syndromes on Dual Antiplatelet Therapy

Previous studies have explored the association between hemorheologic alterations and aspirin resistance, pointing out the possible interaction between hematologic components and platelet responsiveness to antiplatelet drugs. The aim of this study was to evaluate the association between hemorheologic variables and residual platelet reactivity in patients with acute coronary syndromes (ACSs) who underwent percutaneous coronary intervention on dual antiplatelet therapy. The study population included 528 patients with ACSs. Hemorheologic studies were performed by assessing whole blood viscosity at 0.512 and 94.5/second, plasma viscosity, and erythrocyte deformability index. Post-treatment platelet reactivity was investigated by measuring platelet aggregation by adenosine 5'-diphosphate (ADP) 10 mumol and a value >70% was defined as high ADP platelet reactivity. Significantly (p <0.01) lower values of hematocrit and erythrocyte deformability and higher values of whole blood viscosity at 94.5/second were found in patients with high ADP platelet reactivity. At multivariate analysis, lower values of hematocrit and erythrocyte deformability index and higher values of whole blood viscosity at 94.5/second and leukocytes (highest vs lowest tertile) also resulted in an independent association with high platelet reactivity, except for leukocytes, after simultaneous adjustment for hematocrit, leukocyte count, and erythrocyte deformability index. In conclusion, these results demonstrate the influence of hematocrit and of erythrocyte deformability on ADP platelet reactivity. These variables could be considered to optimize treatment with antiplatelet therapy in these patients.

Oxygen delivery index in homozygous sickle cell disease: steady and crisis states

One of the common complications of sickle cell disease is the vaso-occlusive crisis or sickle cell crisis which could result in impaired oxygen delivery to the tissues. This study investigates the oxygen delivery index (ODI) in 38 patients with homozygous sickle cell anaemia. Thirty-three patients were in the steady state and five were experiencing crisis at the time of recruitment. Whole blood viscosity was measured with a Wells Brookfield viscometer at a shear rate of 230 sec–1 and haematocrit was measured with an AC Tron Coulter Counter. The ODI, which is an indirect measure of the capacity of blood to deliver oxygen to tissues, was calculated as the ratio of haematocrit to whole blood viscosity values. There was no statistically significant difference in the ODI between the steady and crisis states, suggesting that tissue oxygenation is not the only factor involved in the sickle cell crisis.

Hemorheological changes after intravenous gammaglobulin administration in patients with neurological disorders

Hemorheological changes due to intravenous gammaglobulin (IVIg) administration have been considered to influence blood viscosity and this way the blood flow in microcirculation. The study was carried out in the group of 10 patients with various neurological disorders (seven with polyradiculoneuropathy, two suffering from myasthenia and one with multiple sclerosis). Patients were treated routinely with intravenous gammaglobulin infusion (Sandoglobulin, Sandoz, 24 g a day in the course of 5 days therapy). The following hemorheological factors were estimated: relative blood viscosity, plasma viscosity, red cell deformability and erythrocytes aggregation. For rheological examination the microviscosimeter Low Shear 40 (Contraves) was used. Each patient was examined two times: before treatment initiation and at the end of therapy after five days. At the comparison of first and last measurements a significant increase of plasma viscosity (p<0.04) was found, whereas erythrocyte deformability was significantly improved (p<0.05). The value of relative blood viscosity at shear rate of 0.1 s(-1) was significantly decreased (p<0.05) and statistically unchanged at other studied shear rates. The results suggest an existence of a protective feedback mechanism in the studied group of patients which has been exemplified by the red cell elasticity improvement.