Capacity for red blood cell aggregation is higher in athletic mammalian species than in sedentary species

The purpose of this study was to show that two rheological parameters, red blood cell (RBC) sedimentation rate and apparent blood viscosity at low shear rate, characterizing the degree of RBC aggregation, correlate significantly with the maximal mass-specific rate of oxygen consumption or aerobic capacity (VO2max). Comparisons were made within two groups of similarly sized athletic and sedentary species: group 1, pronghorn antelope, dog, goat, and sheep; and group 2, horse and cow. The pronghorn antelope (Antilocapra americana) is one of the most athletic mammals, and we have obtained data on the rheological properties of blood from this species for the first time. The values of apparent viscosity at hematocrit = 40% and shear rate = 0.277 s-1 measured in a rotational viscometer were 59.5, 42.6, and 9.1 cP for antelope, dog, and sheep blood, respectively, and 55.3 and 11.5 cP for horse and cow blood, respectively. The viscosity values for antelope, dog, and sheep blood can be correlated with aerobic capacity: ln viscosity = 4.48-106.3 VO2(-1)max (r2 = 0.998; P < 0.05). The values of RBC sedimentation rate at hematocrit = 40% were 12.8, 7.0, and 0 mm/h for antelope, dog, and sheep blood, respectively, and 45.3 and 0.1 mm/h for horse and cow blood, respectively. Therefore, the data showed that the athletic species exhibit a consistently higher degree of RBC aggregation than do the corresponding nonathletic species.     

Autonomous nervous regulation of circulation during prolonged isolation studied with analysis of the cardiac rhythm variability]

As many as 185 patients with stage I-III hypertensive disease were examined, their age ranging between 30 and 70 years. Investigation of rheologic properties of blood involved determination of hematocrit value, blood viscosity, aggregation of erythrocytes, platelets, content of fibrinogen, products of fibrin cleavage. It has been ascertained that in patients with stage I hypertensive disease, disorders of rheologic properties of blood are characterised by disturbances in the platelet link of the bloodflow, with the degree being dependent on the cerebral symptomatology; those in patients with stage II hypertensive disease were evidenced by high values for blood viscosity; as to stage III disease complicated by disordered cerebral bloodflow, the degree of rheologic abnormalities may characterize the course and outcome of the disease.     

Paraproteinemia: blood hyperviscosity and clinical manifestations

Many of the clinical features of paraproteinemia result from impairment of blood flow through the vascular tree because of blood hyperviscosity. Studies were carried out in 65 patients with serum paraproteins (31 with IgG, 25 with IgM, and 9 with IgA) to examine the relationship between the blood viscosity and the frequency of selected clinical features. The blood and plasma viscosities were measured at low rates of shear. Blood hyperviscosity was present in 91% of the patients and plasma hyperviscosity in 75% of the patients. In each of the three immunoglobulin classes both the blood and plasma viscosities increased logarithmically with the paraprotein concentration being greatest in the case of IgM. In addition, the relationship between the hematocrit and the logarithm of blood viscosity tended to be linear at any given protein concentration. In patients with very high levels of paraprotein the blood viscosity was modified by low hematocrits; the latter was below 30 in 70% of patients in whom the concentration of paraprotein was above 4 g/100 ml. The prevalence of clinical complications involving the retinal circulation, the peripheral vascular system, and the central nervous system increased markedly with increasing blood viscosity, measured at 0.18 S-1. One or more of these regions was affected in greater than 80% of patients with blood viscosity above 60 centipoise and in less than 23% of patients with blood viscosity below 40 centipoise. These observations illustrate the complex relationship between blood viscosity, concentration of paraprotein, immunoglobulin class and hematocrit, and emphasize the importance of measuring the whole blood viscosity at low rates of shear in determining the risk of vascular complications.     

Managing mental health

AIM: To establish changes of and correlations between erythrodieresis and blood rheology in hereditary hemochromatosis (HHC). MATERIALS AND METHODS: Hemorheologic indices (asymptomatic blood and plasma viscosity, that of blood at low shift speed, red cell deformity and aggregation) were studied in 42 HHC patients and 23 healthy donors. The patients were divided into groups by homozygous (groups 1 and 2) or heterozygous (groups 3 and 4) allel genes and sex (females-groups 2 and 4, males-groups 1 and 3). RESULTS: All the patients had increased resistance of red cells in high percentage of their high-resistance populations (correlation index 0.8-0.9) due to destruction and elimination from the circulation. These changes were more pronounced in males, similar in homo- and heterozygotes. The presence in the peripheral blood of red cells with high resistance is associated with a 25-30% decrease in the red cell rigidity, in groups 1 and 3 this decrease reached 30-40%. To a certain degree high deformity and aggregation of red cells is explained by high plasma viscosity (correlation index 0.4). Plasma viscosity was high in all the patients of all groups. CONCLUSION: HHC runs with rejuvenascence of erythroid cells. Changed activity of erythrodieresis and damage to red cells at the level of microcirculation may be involved in iron metabolism disturbance and development of tissue hemosiderosis.     

The effect of Leboyer delivery on blood viscosity and other hemorheologic parameters in term neonates

OBJECTIVE: This study was done to compare postnatal alterations in blood viscosity, hematocrit value, plasma viscosity, red blood cell aggregation, and red blood cell deformability in term neonates undergoing both early umbilical cord clamping and delivery according to the Leboyer method. STUDY DESIGN: The umbilical cords of 15 healthy, term infants were clamped within 10 seconds of birth (early cord clamping), and 15 infants delivered according to the Leboyer method were placed on the mother's abdomen, and the umbilical cords were clamped 3 minutes after birth. Hemorheologic parameters were studied in umbilical cord blood at 2 hours, 24 hours, and 5 days from the time of delivery. RESULTS: The residual fetal placental blood volume decreased from 45 +/- 8 ml/kg (x +/- SD) after early cord clamping to 25 +/- 5 ml/kg after delivery by the Leboyer method. After Leboyer-method delivery, the hematocrit value rose from 48% +/- 5% at birth to 58% +/- 6% 2 hours after delivery, 56% +/- 7% at 24 hours, and 54% +/- 8% after 5 days. Blood viscosity in the Leboyer-method group increased by 32% within the first 2 hours but did not change significantly during the following 5 days. Plasma viscosity, red blood cell aggregation, and red blood cell deformability were not affected by the mode of cord clamping. CONCLUSIONS: Delivery by the Leboyer method leads to a significant increase in blood viscosity as a result of increasing hematocrit value, whereas other hemorheologic parameters are similar to those of infants with early cord clamping.     

Internalization of G protein-coupled receptors in single olfactory receptor neurons

The cardiovascular effects of human albumin (Alb) and three human hemoglobin (Hb) solutions, dextran-benzene-tetracarboxylate Hb, alphaalpha-crosslinked Hb, and o-raffinose-polymerized Hb were compared in anesthetized rabbits undergoing acute isovolemic hemodilution with Hct reduction from 41.4 +/- 2.7 to 28.8 +/- 1.6%. The impact of the vasoconstricting properties of Hb was examined by measuring heart rate (HR), mean arterial pressure (MAP), abdominal aortic, and femoral arterial blood flow, vascular resistance (VR), and aortic distension during the first 3 h after hemodilution. The impact of the hemorheological parameters was assessed by measurements of hemodiluted blood viscosity. In contrast to Alb, the Hb solutions elicited an immediate increase in MAP (20-38%). The effects of Alb and Hb solutions on HR, as well as on aortic and femoral arterial blood flow, were similar. VR decreased with Alb (20-28%) and increased with all three Hb solutions (30-90%), but the MAP and VR rising trends were different with each Hb solution. Aortic distension decreased in Hb groups compared with the Alb group for the first 60 min. The viscosity of hemodiluted blood was similar for all groups at high shear rates but was dependent on the viscosity of the solutions at low shear rates. We conclude that the vasoconstriction elicited by the Hb solutions overrides the vasodilation associated with viscosity changes due to hemodilution and would be the major factor responsible to the cardiovascular changes.     

Epidermiology and associated risk factors of hyperlipoproteinemia

With the world-wide increase of the number of ischemic heart diseases the significance of the so-called factors of risk which initiate an arteriosclerosis or can deteriorate it, respectively, has increased. In the Dresden study concerning the most important factors of risk we found the following frequencies: obesity 8.2%, hyperlipoproteinemia 7.4%, hyperuricemia 3.8%, diabetes mellitus 2.0%, hypertension 17.2% and smoking 30.3%. From the investigations results the great significance of the combination of factors of risk which has a potentiating effect. The hyperlipoproteinemias of type III-V most frequently show a disturbed carbohydrate tolerance and hypertension. In them also the most frequent severe changes of the ECG appear. Myocardial infarctions concerned above all type II-IV. Apparantly concerning the vascular system patients with the combination hyperlipoproteinemia and carbohydrate metabolism are particularly endangered. The "metabolic syndrome" (obesity, diabetes mellitus, hyperlipoproteinemia, hyperuricemia, steatosis hepatis) with the increase of the viscosity of blood and plasma as well as disturbances of coagulation together with other factors of risk further the development of arteriosclerosis or has a directing influence on it. Nevertheless, the concept of the significance of the factors of risk is not able to predict the risk in every case. With the help of the apoproteins the metabolic risk is to be more exactly estimated by the determination of the lipid values in the individual classes of lipids or by classification.     

Elvin Semrad''s contributions to the everyday practice of psychotherapy

Sepsis is associated with altered blood rheology. Fluid infusion is an essential component of therapy for septic shock. The purpose of this study was to compare the rheologic changes associated with saline, albumin, and hydroxyethyl starch in sepsis. Whole blood was obtained from five normal controls and five patients with severe sepsis. The samples were centrifuged, and the erythrocytes were resuspended in autologous plasma or autologous plasma plus the buffy coat at an hematocrit (Hct) of 40%. The sample was diluted to an Hct of 30%, 20%, and 10% with saline, albumin, or hydroxyethyl starch. Viscosity was measured at low and high shear rates and erythrocyte aggregation was measured by the ratio of viscosity at low to high shear rates. Erythrocyte deformability was assessed by filtration. The viscosity of hydroxyethyl starch was greater than saline, albumin, or autologous plasma (p < .01). Erythrocyte viscosity was greater (p < .01) and deformability less (p < .01) in septic blood compared with normals. Dilution with hydroxyethyl starch increased erythrocyte viscosity as compared with saline (p < .01) and albumin (p < .01). Erythrocyte deformability was decreased with both hydroxyethyl starch (p < .001) and albumin (p < .05) compared with saline. Increased erythrocyte aggregation was also observed with hydroxyethyl starch (p < .05) and albumin (NS) in septic cells when compared with saline. These data indicate that hydroxyethyl starch increases blood viscosity, decreases erythrocyte deformability, and increases erythrocyte aggregation when compared with saline. These changes are less significant with albumin. In patients with sepsis, these effects may further compromise the already altered erythrocyte rheology.     

Blood viscosity and risk of cardiovascular events: the Edinburgh Artery Study

We examined the relationships of whole blood viscosity and its major determinants to incident cardiovascular events (ischaemic heart disease and stroke) in a prospective study of a random population sample of 1592 men and women aged 55-74 years (the Edinburgh Artery Study). 272 fatal and non-fatal cardiovascular events occurred during 5 years of follow-up (cumulative incidence 17.1%). Age and sex adjusted mean levels of blood viscosity (3.70 v 3.55 mPa.s), haematocrit (46.2 v 45.7%), haematocrit-corrected blood viscosity (3.57 v 3.48 mPa.s), plasma viscosity (1.35 v 1.33 mPa.s) and fibrinogen (2.88 v 2.67 g/l) were significantly higher in subjects who experienced events than in subjects who did not. The relationships of these rheological variables to cardiovascular events were at least as strong as those of conventional risk factors (smoking habit, diastolic blood pressure, and low-density lipoprotein cholesterol). After adjustment for these conventional risk factors, the associations of blood viscosity and haematocrit remained significant for stroke, but not for total events; whereas the associations of plasma viscosity and fibrinogen remained significant for total events and for stroke. These findings suggest that increased blood viscosity may be one plausible biological mechanism through which increases in haematocrit and fibrinogen may promote ischaemic heart disease and stroke. Randomized controlled trials of viscosity reduction in the prevention of cardiovascular events (e.g. by lowering high levels of haematocrit or plasma fibrinogen) are suggested.     

Echinocytosis induced by haemodialysis

BACKGROUND: Haemodialysis, widely used to treat patients with renal failure, is not always well tolerated. Different mechanisms have been postulated for this. We analyzed the influence of haemodialysis on erythrocyte morphology and blood rheology. METHODS: Twenty-two haemodialysed patients were studied immediately before haemodialysis, after 30 min, and at the end of haemodialysis with biocompatible membranes. Haematological routine was measured, the erythrocyte morphology was assessed on glutaraldehyde-fixed cells and blood viscosity was determined. RESULTS: Erythrocytes underwent various degrees of echinocytic shape transformation after 30 min of haemodialysis, which was completely reversible at the end. In a repetition of the investigations during a subsequent haemodialysis other patients were affected. A plasmatic factor caused echinocytosis since the incubation of control erythrocytes in patients plasma induced a similar, even more marked shape transformation and, vice versa, patient echinocytes regained a discocytic shape when incubated in buffer. The degree of echinocytosis was related to an increased blood viscosity at high shear rates (r=0.800, P<0.01). Echinocytosis was not accompanied by obvious clinical reactions. CONCLUSIONS: Reversible echinocytosis and an increase in blood viscosity is often seen during haemodialysis, which may affect the circulation in patients at risk.     

不锈冷轧带钢表面光洁度的控制

在生产中，不锈冷轧带钢的表面光洁度一般用粗糙度进行控制，其粗糙度越低，光洁度越高。应使用低粗糙度和低微小缺陷面积率的不锈热轧带钢，高的总压下量，低粘度轧制油和平整率达到1％的工艺轧制可获得较高光洁度的不锈冷轧带钢。高速钢轧辊轧制的不锈冷轧带钢的光洁度优于模具钢轧辊。     

Whole blood viscosity and haematocrit are associated with internal carotid atherosclerosis in men

BACKGROUND: Alterations in blood viscosity and haematocrit have been described in patients with coronary and cerebrovascular diseases. The results have not been conclusive, as modifications of these parameters are often associated with the presence of coronary heart disease (CHD) risk factors. The aim of this study was to verify whether blood viscosity and haematocrit are increased in patients with carotid atherosclerosis, independently of the presence of CHD risk factors. METHODS: Male patients with internal carotid atherosclerosis (ICA+, n = 28) were selected from participants in a cardiovascular disease prevention campaign. Controls (ICA-, n = 28), also participating in the prevention campaign, were matched for age and all the classical CHD risk factors. Plasma lipids, glucose and fibrinogen were determined by routine methods. Cigarette smoking and current drug therapy was established by questionnaire. Whole blood viscosity was measured at shear rates of 450 and 225/s, using a cone-plate viscometer. Echo-Doppler of carotid arteries was performed with an ATL Ultramark 9 HDI using a 5-10 MHz multifrequency probe. RESULTS: Blood pressure, plasma lipids, glucose, body mass index, fibrinogen and plasma viscosity were similar in the two groups. ICA+ patients, compared with the ICA- group, had significantly greater values of blood viscosity (4.52 +/- 0.37 cP compared with 4.18 +/- 0.45 cP, P < 0.005 respectively; shear rate 450/s) and haematocrit (48.57 +/- 3.19% compared with 45.57 +/- 4.81%, P < 0.008 respectively). CONCLUSIONS: Our findings demonstrate that blood viscosity and haematocrit are increased in men with internal carotid atherosclerosis, independently of the presence of risk factors for atherosclerosis.     

In vitro effect of dextran-benzene-tetra-carboxylate hemoglobin on human blood rheological properties

While conducting pharmacological investigations into oxygen carriers, it is important to study the in vitro and in vivo rheological behavior of blood cells in the presence of such preparations. With regard to the original nature of human hemoglobin bound to benzene tetracarboxylate substituted dextran (Dex-BTC-Hb), it seemed necessary to study its rheological effect in a simulated in vitro hemorrhagic shock compensated by a blood substitute. The viscosity of substitutes was determined as well as several rheological parameters after 0, 3 and 6 hours incubation periods of red blood cells with substitutes: viscosity of blood-substitute mixtures at different levels of plasma substitution erythrocyte aggregation of blood-substitute mixtures by determining the velocity of rouleau formation and the cohesion of rouleau network. This work yielded several observations: The viscosity of Dex-BTC-Hb was slightly higher than those of solutions of native Hb, Dex-BTC T10, Dextran 40 (Plasmacair, modified fluid gelatin (Plasmion and hydroxyethyl starch 200 (Elohes). The substitution of a blood volume with Dex-BTC-Hb, corresponding to a compensated 45% hemorrhagic shock, slightly increased the viscosity of hemodiluted blood as compared to other substitutes. In the presence of Dex-BTC-Hb, the aggregation of erythrocytes appears to be increased as compared to standard solutions. Yet, the effect was close to that of Plasmion or Elohes.     

Blood viscosity and elevated carotid intima-media thickness in men and women: the Edinburgh Artery Study

BACKGROUND: Several hemostatic and rheological factors have been associated with incident cardiovascular events. However, there have been no reports on the relationship of rheological factors with early atherosclerosis and very few on hemostatic factors. We therefore studied the relationship between these factors and carotid intima-media thickness (IMT). METHODS AND RESULTS: The Edinburgh Artery Study measured fibrinogen, tissue plasminogen activator (tPA), fibrin D-dimer, von Willebrand factor (vWF), blood and plasma viscosities, and hematocrit as part of its baseline examination during 1988-1989. At the 5-year follow-up, valid measurements of IMT had been recorded in 1106 men and women 60 to 80 years old. In men, blood viscosity (P< or =.001) and its major determinants, plasma viscosity, fibrinogen (both P< or =.01), and hematocrit (P< or =.05), were all linearly related to IMT. Furthermore, blood viscosity, fibrinogen (both P< or =.01), and plasma viscosity (P< or =.05) remained significantly associated on multivariate analysis. Correcting blood viscosity to a standard hematocrit of 45% had little effect on its association. In men, there was a significantly increased risk of having an IMT above versus below the upper quartile of its distribution (1.05 mm) for SD increases in blood viscosity (P< or =.01), fibrinogen, corrected blood viscosity, and plasma viscosity (all P< or =.05). With the exception of plasma viscosity, these risks were unaffected by adjustment for other common cardiovascular risk factors. No significant associations were found between any of the hemorheological factors and IMT in women or for tPA, fibrin D-dimer, or vWF in either sex. CONCLUSIONS: These findings suggest that in men, blood viscosity and its major determinants are associated not only with incident cardiovascular events but also with the early stages of atherosclerosis. This may be one explanation for the link between rheological factors and events.     

Antihypertensive therapy of patients with cerebrovascular disease

In the acute phase of the stroke, it must be prudent to reduce blood pressure (BP) because the rapid reduction might cause the exacerbation of the perfusion pressure to the brain. The target BP level should be higher than the level of primary prevention as the blood pressure regulatory function is disturbed in acute phase. In chronic phase, BP should be reduced so slowly through the several months so as not to cause the ischemia of the brain by rapid reduction of BP. However, the optimal target BP level should be the same degree as the primary prevention level as far as the speed of reduction is taken into consideration. The several large scale trials, are now in progress to determine the optimal BP level for the secondary prevention in the patients with prion stroke.     

Effect of chronic anemia on the endothelium-dependent dilatation of the brachial artery

The effect of changes in main determinants of whole blood viscosity after red blood cell transfusion on endethel dependent dilatation of brachial artery was studied in patients treated with transfusion because of symptoms of chronic anaemia. PATIENTS AND METHODS: 10 patients were involved, 8 females 2 males, mean age 50.9 +/- 16.6 years. Following blood tests were performed at hospital admission: hemoglobin, red blood cell count, heamatocrit, white blood cell count, platelet count, plasma total protein, fibrinogen, plasma viscosity, blood urea nitrogen, creatinine, cholesterol, triglicerides. Flow mediated dilatation of brachial artery was determined, too. Blood tests and flow mediated dilatation study were repeated after transfusion. RESULTS: The main determinants of whole blood viscosity increased after transfusion. The increase of hemoglobin, red blood cell count, hematocrit were highly significant. The central flow velocity in brachial artery decreased at rest and during hyperemia as well. The flow mediated dilatation of brachial artery wasn't significantly changed by transfusion. CONCLUSIONS: Change of determinants of whole blood viscosity caused by transfusion didn't change the flow mediated dilatation of brachial artery. The probable reason for this that the increase of whole blood viscosity in associated with the decrease of central flow velocity. These two counteracting changes probably equal each other.     

The effect of hemodilution on regional myocardial function in the presence of coronary stenosis

Hemodilution decreases blood viscosity and circulatory input impedance and thus reduces afterload. Its use in treatment of LV power failure has been advocated, but the safe limits of isovolemic hemodilution are not known. Compensation of the reduced O2-capacity of the blood was therefore studied with normal and impaired coronary reserve. In 20 dogs the LAD was stenosed to a degree just not affecting the supplied region and central and coronary hemodynamics were studied. Regional myocardial function was assessed by ultrasound transit time between transducers implanted in the LV wall. Lowering the hematocrit to 15% by isovolumic exchange of blood for Dextran 60 increased CVP (18%), PAP (47%), LAP (64%), LVedP (46%), CO (67%), and flow to the intact area (LCA: 211%). Flow in the stenosed LAD increased slightly. Enddiastolic length (EDL) of LAD dependent muscle segments rose to 120% and their contraction amplitude deltaL was decreased by 46%. Whereas non-ischemic segments showed compensatory rise in deltaL (38%) at almost constant EDL (+9%). After release of the LAD stenosis EDL and deltaL returned to normal. During progressive anemia myocardial O2-demand is not adequately met if coronary reserve capacity is depleted. Reversion of hypokinesia after removal of the stenosis shows unimpaired myocardial function at a hematocrit as low as 15% provided the coronary circulation is intact.     

Major adverse reactions to yeast-derived hepatitis B vaccines--a review

Blood was taken from 49 Thoroughbred horses before and after racing at the track to determine if frusemide modified the apparent viscosity of the blood and to determine the effects of changes in shear rate and packed cell volume (PCV), associated with strenuous exercise, on apparent and relative viscosities. Small increases in apparent viscosity of the blood (at a specified PCV and shear rate) occurred in horses given frusemide compared to those receiving no frusemide; however, no differences were seen in relative viscosity. Although 2 groups of horses, those receiving frusemide before racing and those not receiving this drug were studied, the results suggest no influence of frusemide on any red blood cell variable that might modify apparent blood viscosity. Apparent viscosity of the blood was slightly (but significantly) higher after racing than before racing at any given PCV and shear rate, but relative viscosity was lower in the post race than in the prerace blood sample. The most important contributing factor to the increase in apparent viscosity in blood during racing is the increase in PCV, because the blood becomes nearly shear rate independent at shear rates likely to exist in the cardiovascular system during exercise. With an increase in PCV from 40 to 65% at shear rates above 225/s, apparent viscosity approximately doubled. However, this increase alone cannot account for the elevated pulmonary vascular pressure in the running horse, and additional factors, especially those causing the high left atrial pressure, must be considered. The cause of the elevated pressure may be multifactorial in nature.     

Venous dysfunction and the change of blood viscosity during head-up tilt

The precise stimulus that induces vasovagal syncope is still unclear. We have previously demonstrated that the peripheral distribution of blood volume (venous pooling) is a strong predictor of tilt induced vasovagal reaction. We hypothesized that an increase in venous pooling during tilt accentuates the measured increase in blood viscosity. This hypothesis is based on the previously demonstrated increase in venous pressure and subsequent increase in transcapillary fluid transudation during tilt. The increased blood viscosity, in turn, increases vascular shear rate, which may alter the vasoconstrictive and other cardiovascular responses to decreased preload. We measured blood viscosity (supine and tilt) in 56 patients with a history of orthostatic intolerance (37 with venous pooling [VP] and 19 without venous pooling [non-VP]). VP and non-VP were separated into subgroups based on blood pressure and heart rate response to tilt. There was a positive correlation between blood viscosity and plasma aldosterone in the supine. In the group as a whole, neither supine blood viscosity nor its increase during tilt differed between VP and non-VP. However, the tilt induced increase of blood viscosity was significant only in patients with tilt provoked tachycardia plus normal blood pressure response in VP group. We suggest that the increase of blood viscosity in this group led to the normal blood pressure response. The positive correlation between supine blood viscosity and supine plasma aldosterone indicates that the normal blood pressure response in this group possibly was via stimulation of the renin-angiotensin-aldosterone system.     

Noninvasive pump flow estimation of a centrifugal blood pump

A flow rate estimating method was investigated for a centrifugal blood pump developed in our institute. The estimated flow rate was determined by the power consumption, the rotating speed of the motor, and the hematocrit value. The power consumption and the rotating speed of the motor were measured with a wattmeter. The examinations were performed in a closed mock loop filled with goat blood with hematocrit values of 21.5%, 28%, 34%, and 42%. Measured values of blood viscosity were 2.47, 3.09, 3.71, and 5.07 mPa.s at a share rate of 37.5/s, respectively. A linear correlation between the power consumption and the pump flow rate was observed in all hematocrit values. But variations in hematocrit caused a difference in the flow rate up to 1.1 L/min at the same power consumption and rotating speed. Effects of blood viscosity on the flow estimation were corrected by the hematocrit value. The value of the coefficient of determination, R2, between the estimated flow rate and the measured flow rate was 0.988. These results may indicate that the flow estimating method calculated by the power consumption of the motor, the rotating speed, and the hematocrit value is useful in the clinical situation.