Viscosity of human blood hemodiluted with crystalline hemoglobin solution

Hemoglobin solution has been proposed as a blood substitute and, when administered intravenously, causes hemodilution that affects the viscosity of the circulation fluid. To quantitate the changes in viscosity, hemodilutions were made by mixing freshly drawn human blood with a 7-g/dl hemoglobin solution in different proportions. Viscosity measurements were made with a micro-cone plate viscosimeter at various shear rates. The results demonstrate that even at low or moderate hemodilutions with hemoglobin solution, the viscosity of blood decrease considerably at each shear rate investigated. The decrease of viscosity is greater with increasing hemodilution. A shear thinning effect is observed with whole blood and with each hemodiluted sample. The viscosity-hematocrit relationship, which could be demonstrated not only by cone-plate but also by the Ostwald viscosimeters at a fixed shear rate, shows that the concentration of red blood cells significantly affects the viscosity of blood. Hemodilution of blood with hemoglobin solution not only reduces the viscosity but also may improve the blood flow.     

How should blood rheology be measured in macroglobulinaemia?

Blood and plasma viscosity were measured in 13 patients with monoclonal macroglobulinaemia. Blood viscosity was measured at natural hematocrit and after adjustment to 45%. Studies were performed at three different temperatures, +24 degrees C, +32 degrees C and +37 degrees C. Plasma viscosity was measured in a rotational viscometer and in a capillary tube at the above-mentioned temperatures. Blood viscosity was to some extent related to the patients' symptoms, whereas a correlation between blood and plasma viscosity became less pronounced with decreasing shear rates, indicating that plasma viscosity is not a perfect indicator of blood viscosity in macroglobulinaemia. It was shown that red cell concentration, besides the concentration of monoclonal immunoglobulins (= paraproteins (PP)), is an important determinant of blood viscosity. The correlation between red cell concentration and viscosity became stronger with decreasing shear rate. Whole blood viscosity at low shear rates seems to be the best indicator of rheological symptoms in patients with macroglobulinaemia. It is concluded that blood rheology in patients with macroglobulinaemia is best studied at +32 degrees C to +37 degrees C in whole blood and at low shear rates.     

Immunoglobulins,complement and lysozyme in leg lymph of normal men

Blood and plasma viscosity were measured in 13 patients with monoclonal macroglobulinaemia. Blood viscosity was measured at natural hematocrit and after adjustment to 45%. Studies were performed at three different temperatures, +24°C, +32°C and +37°C. Plasma viscosity was measured in a rotational viscometer and in a capillary tube at the above-mentioned temperatures. Blood viscosity was to some extent related to the patients' symptoms, whereas a correlation between blood and plasma viscosity became less pronounced with decreasing shear rates, indicating that plasma viscosity is not a perfect indicator of blood viscosity in macroglobulinaemia. It was shown that red cell concentration, besides the concentration of monoclonal immunoglobulins (=paraproteins (PP)), is an important determinant of blood viscosity. The correlation between red cell concentration and viscosity became stronger with decreasing shear rate. Whole blood viscosity at low shear rates seems to be the best indicator of rheological symptoms in patients with macroglobulinaemia. It is concluded that blood rheology in patients with macroglobulinaemia is best studied at +32°C to +37°C in whole blood and at low shear rates.     

Effects of aggregation of red cells and linear velocity gradients on the correlation-based method for quantitative IVUS blood flow at 20 MHz

Recent computer simulations suggest that the presence of aggregates of red blood cells (RBCs), at random angles and lengths, does not affect the measurements of blood flow transverse to the ultrasound (US) beam direction using a correlation-based method and an intravascular (IV) US array catheter. However, in case of aggregates of RBCs aligned with the flow, measurements of simulated blood velocity are affected. Blood velocity gradients were also shown not to influence the correlation-based method for blood velocity estimation. The objective of this study was to quantify the influence of aggregates of RBCs and blood velocity gradients on the correlation-based method during in vitro experiments. For this purpose, measurements were performed on washed RBCs (no aggregation), normal human blood, and two types of diseased blood in which a lower or a higher level of aggregation was present. The decorrelation pattern of a circular US transducer as a function of transverse blood flow was studied using a Couette system. Changing the shear rate of the Couette system modified the aggregation level of RBCs and the velocity gradient. With the exception of the results at low shear rates and abnormally high aggregation levels, agreements were found between the autoconvolution of the acoustical beam (reference curve) and the radiofrequency (RF) decorrelation patterns. For the high shear rate present in coronary arteries, the correlation-based method for blood flow estimation should not be influenced by these phenomena.     

肾小球疾病血液流变性变化及其意义

目的　探讨原发性肾小球疾病时血液流变性的变化及其意义。方法　 30例肾小球疾病患者用日本DP6 0 0 1型锥板式粘度计分别测量切变率为 3.84、9.6 0、19.2 0、38.40、76 .80、192 .0 0、384.0 0s- 1 时的全血粘度 ,30 0 0rpm离心 30分钟测定红细胞比积 ,然后测量切变率为 192s- 1 时的血浆粘度 ,计算红细胞聚集指数、casson粘度及血液的屈服应力。结果　全组患者的全血粘度在 3.84s- 1 至 384.0 0s- 1 等 7个切变率时均明显高于对照组 ;红细胞比积有所升高 ,以肾病I型明显 (P <0 .0 5 ) ;血浆粘度无明显改变 ;红细胞聚集指数明显增高 (P <0 .0 1) ;血液的屈服应力也显著增高 (P <0 .0 1)。结论　肾小球疾病时血液处于高粘滞状态 ,这是病变持续发展和肾功能进行性恶化的重要发病机理 ,也是肾外血栓栓塞合并症发生的病理生理基础。     

中分子羟乙基淀粉200／0．5溶液对创伤休克病人血液流变特性的影响

目的：观察创伤失血性休克病人麻醉手术前快速输入10％羟乙基淀粉（10％HES 200／0．5）溶液后,血液流变学及血液循环指标的变化。方法：选择交通事故致创伤失血性休克病人30例（失血量10－30ml.kg^-1),于输液前后分别采取静脉血3ml,检测血液流变学指标：低切全血粘度（30．S^-1),高切全血粘度（200．s^-1),Hct,血浆粘度,红细胞聚集指数,红细胞变形指数,全程监测平均动脉压,心率,脉搏氧饱和度（SpO2),统计术中异体血液制品用量,结果：输注10％HES溶液后患者全血粘度明显降低,Hct降低,红细胞聚集指数降低 和红细胞变形指数升高等均有显著差异（P＜0．05或P＜0．01）,平均动脉压显著升高及心率明显减慢（P＜0．05或P＜0．01）,术中输异体血量明显少于失血量。结论：输入15－20ml.kg^-1的10％HES溶液能降低低血容量休克病人的全血粘度,Hct和红细胞聚集指数,从而优化病人的血液流变状态;迅速提高平均动脉压,减慢心率,改善微循环灌注,预防创伤失血性休克并发症,改善病人预后。     

Ultrasonic backscattering from porcine whole blood of varying hematocrit and shear rate under pulsatile flow

It was shown previously that ultrasonic scattering from whole blood varies during a flow cycle under pulsatile flow both in vitro and in vivo. It has been postulated that this cyclic variation may be associated with the dynamics of red cell aggregation because the shearing force acting on the red cell aggregates across the lumen is a function of time during a flow cycle. In all studies, the local shear rate variation as a function of time is unknown. The effect of shear rate on the red cell aggregation and, thus, on ultrasonic scattering from blood can only be merely speculated. One solution to this problem is to estimate the shear rate in a flow conduit by finite element analysis (FEA). An FEA computational fluid dynamics (CFD) tool was used to calculate local shear rate in a series of experiments in which ultrasonic backscattering from porcine whole blood under pulsatile flow was measured as a function of hematocrit and shear rate intravascularly with a 10-MHz catheter-mounted transducer in a mock flow loop. The results show that, at 20 beats per min (BPM), the magnitudes of the cyclic variation for hematocrits at 30, 40, and 50% were approximately 4 dB. However, at 60 BPM, the magnitude of cyclic variation was found to be minimal. The results also confirm previous findings that the amplitude and the timing of the peak of ultrasonic backscattering from porcine whole blood under pulsatile flow during a flow cycle are dependent upon the shear rate and hematocrit in a complicated way.     

Relation of in vivo blood flow to ultrasound echogenicity

The mechanism of echogenicity of flowing blood during real-time ultrasonography was investigated experimentally in vivo by scanning venous and arterial blood and venous blood subjected to varying degrees of obstruction. Luminal echoes were more intense in flowingblood of the vena cava than in aortic blood of dogs. Vena cava and portal echoes increased in intensity as flow was decreased progressively by obstruction. We believe that an important cause of echogenicity of flowing blood is red cell aggregation which is greatest at low shear rates (low flow velocity). Echogenicity decreases with increase in shear rate (higher flow velocity) which causes red cell disaggregation.     

The clinical importance of studying disorders in the rheological properties of the blood in hypertension patients

Altogether 118 patients with stages I-III essential hypertension were examined for hemodynamics and rheologic blood properties: total viscosity, deformability, aggregation, form and mechanical resistance of red blood cells, plasma osmolality, hematocrit, and red blood cell count. The data obtained indicate that in patients suffering from essential hypertension, there occur consistent abnormalities of hemorheology, correlating with the disease stage and some hemodynamic parameters. Early changes in red blood cell deformability and their discospheric transformation turned out to be the most specific in patients with essential hypertension. Red blood cell aggregation and hydrodynamic deaggregation underwent alterations mainly in complicated disease patterns.     

Blood rheology in the endotoxin-administered rabbits.

The effects of endotoxin on blood rheology were studied in rabbits. Non-treated six rabbits (Group A) were used to obtain control data. Thirteen rabbits who were administered 0.1 mg of endotoxin three times at intervals of 3 days were divided into two groups; seven rabbits (Group B) were injected with 1 ml saline solution as the vehicle for endotoxin at 7 days after the final administration of endotoxin, while the remaining six rabbits (Group C) were administered endotoxin at 0.2 mg/kg on the same day. Blood was sampled from the femoral artery 120 min after the final treatment. Blood viscosity was measured at a shear rate of 150 s-1 at 37 degrees C using a cone-plate viscometer. The passage time for a 5% red blood cell suspension and that for plasma were determined by filtration; the former represents erythrocyte deformability while the latter is related to plasma fluidity. The hematocrit, whole blood viscosity and erythrocyte deformability did not show significant differences among these three groups. The ratio of hematocrit to whole blood viscosity is considered to be an index of oxygen delivery from the hemorheologic point. This index did not show significant difference either. A good correlation was observed between whole blood viscosity and hematocrit in Group A, but not in the endotoxin-treated groups. The plasma fluidity was lower in Groups B and C than in Group A. These data indicate that plasma fluidity and the hematocrit-viscosity relationship are affected in endotoxin-treated rabbits, although blood viscosity, erythrocyte deformability and oxygen delivery hardly changed.     

急性肺感染患者血液流变学的改变

目的：研究急性肺感染患者血流变的改变。方法：对１１０例急性肺感 染患者及５０名正常对照者进行血液流变学指标检测。结果：急性肺感染患者的全 血粘度、血沉、全血还原粘度、血浆粘度、血沉方程Ｋ值、红细胞聚集及刚性指数、 纤维蛋白原浓度、由 ＡＤＰ、ＡＡ、Ｃｏｌ和 Ａｄｒ诱导的血小板聚集功能及红细胞变形能 力与正常对照组比较均有显著性差异（Ｐ＜０．０１）。结论：急性肺感染时有血流变的 改变,可引起机体代谢和功能失调。     

Abnormal rheology of oxygenated blood in sickle cell anemia

The viscosity of oxygenated blood from patients with sickle cell anemia (Hb SS disease) was found to be abnormally increased, a property which contrasts with the well recognized viscous aberration produced by deoxygenation of Hb SS blood. Experiments designed to explain this finding led to considerations of deformation and aggregation, primary determinants of the rheologic behavior of erythrocytes as they traverse the microcirculation. Deformability of erythrocytes is in turn dependent upon internal viscosity (i.e. the state and concentration of hemoglobin in solution) and membrane flexibility. Definition of the contribution made by each of these properties to the abnormal viscosity of oxygenated Hb SS blood was made possible by analysis of viscosity measurements, made over a wide range of shear rates and cell concentrations, on Hb SS erythrocytes and normal erythrocytes suspended in Ringer's solution (where aggregation does not occur) and in plasma. Similar measurements were made on the two cell types separated by ultracentrifugation of Hb SS erythrocytes: high density erythrocytes composed of 50 to 70% irreversibly "sickled" cells (ISC) and low density erythrocytes composed of over 95% non-ISC.Under all experimental conditions (hematocrit, shear rate, and suspending medium) the viscosity of ISC exceeds that of normal erythrocytes. The viscosity of non-ISC is elevated only in the absence of aggregation and over intermediate ranges of hematocrit. Analyses of the data reveal (a) an elevated internal viscosity of ISC: (b) a reduced membrane flexibility of both ISC and non-ISC, particularly at low shear rates; and (c) a reduced tendency for aggregation displayed by both cell types.The abnormal viscosity of oxygenated Hb SS blood can be attributed to the altered rheology of ISC and, to a lesser extent, of non-ISC. These studies assign a role to the abnormal rheology of Hb SS erythrocytes in the pathogenesis of sickle cell anemia, even under conditions of complete oxygenation.     

肾病综合征、急性肾小球肾炎患儿血液流变学动态观察及其相关因素分析

检测 NS 21例、AGN１１例患儿不同病期血液流变学指标表明，NS组急性期和缓解期低、中、高切变率 WBV和 RAI明显增高，ηｐ仅急性期升高；AGN组唯急性期呈低、中切变率 WBV、ηｐ和 RAI增高。此外对影响血液粘度的相关因素作了初步分析。提示血液流变学异常在肾小球疾病高凝状态形成中起重要作用。临床上应针对不同疾病采用合理抗凝治疗。     

Red cell aggregation and the echogenicity of whole blood.

To study the relationship between red cell aggregation and whole blood echogenicity, red cell aggregation was quantitated by a photometric method, whole blood echogenicity was quantitated by videodensitometry and sedimentation rate was quantitated by a modified Westergren method. Changes in red cell aggregation were produced by alterations in the hematocrit. The results showed that red cell aggregation increased in a linear fashion with increases in hematocrit. The sedimentation rate decreased in a linear manner with increases in hematocrit. Whole blood echogenicity showed a biphasic response, with an initial increase in echogenicity, peaking at hematocrits varying from 14-24% and decreasing thereafter. Over the physiologic range of hematocrits, an increase in the formation of red cell aggregates is associated with a decrease in the echogenicity of whole blood. Thus, red cell aggregates were not visible using our ultrasound equipment at physiologic hematocrits, and the echo contrast in blood under our experimental conditions at these hematocrits must represent either plasma spaces, platelet aggregates or possibly white cell aggregates. The association between spontaneous contrast and a propensity for thromboembolism imply that platelet aggregates are the most likely origin of in vivo echo contrast in flowing blood.     

Rheologic behavior of sickle and normal red blood cell mixtures in sickle plasma: implications for transfusion therapy

BACKGROUND: Guidelines for transfusion in sickle cell disease usually define an upper hematocrit (Hct) limit of 0.30 to 0.35 to avoid blood hyperviscosity. In vitro viscosity studies of normal (AA) and sickle (SS) red blood cell (RBC) mixtures in buffer appear to confirm that this Hct limit is optimal for oxygen delivery to vascular beds as judged by the ratio of Hct to viscosity, with this ratio often termed "oxygen or RBC transport effectiveness." In the absence of plasma, however, effects due to RBC-RBC interactions mediated by plasma proteins cannot be assessed. STUDY DESIGNS AND METHODS: To investigate the optimal Hct-to-viscosity ratio of RBCs in plasma, the rheologic effects of Hct (0.20-0.40), the proportion of SS RBCs (0-100%), and shear rate (1-1000/sec) for mixtures of oxygenated and deoxygenated SS and AA RBCs were evaluated in sickle plasma at 37 degrees C. RESULTS: RBC suspension viscosity was shear-dependent (i.e., viscosity decreased with increasing shear rate) and increased with Hct and proportion of SS RBCs. An "optimal" Hct level (defined as a maximal of the Hct-to-viscosity ratio) was seen only at shear rates above 50/sec. At lower shear rates (e.g., 5/sec), where plasma-mediated RBC-RBC interactions predominate, any increment in Hct was offset by a proportionally greater increase in viscosity, thus leading to a lower Hct-to-viscosity ratio. CONCLUSION: These results indicate the importance of plasma-mediated RBC interactions and suggest that the benefits of transfusion may vary depending on local flow rates (i.e., shear rates) and organ-specific hemodynamics.     

The effects of temperature on blood flow ultrasonic echogenicity in vitro.

An explanation of the mechanism of ultrasonic echogenicity in flowing blood is proposed based upon an in vitro study that indicates a causal relation between red cell aggregation and these echoes. Echogenicity was measured in vitro at 37 degrees, 24 degrees, and 0 degree C as blood flow shear rates were varied. Echogenicity increased at higher temperatures and lower shear rates. The directions of changes in blood echogenicity exactly paralleled previously known changes in red cell aggregation resulting from changes in temperature. The authors consider this to be further evidence that red cell aggregation is an important cause of low-intensity echoes observed in clinical ultrasonography of the heart and circulation.     

Red blood cell aggregability is increased by aspirin and flow stress, whereas dipyridamole induces cell shape alterations: measurements by digital image analysis

We evaluated the influence of pretreatment with aspirin in vitro , alone or combined with dipyridamole, on red cell aggregability. Samples were tested before and after being exposed to well-defined flow conditions. An aggregation rate was estimated through digital analysis of light microscopy images. Red cells of untreated blood that had been exposed to flow showed a higher aggregation rate (38.54 ± 1.63 vs. 27.52 ± 1.36; P  < 0.05). This effect was not observed in the absence of platelets. Treatment with aspirin induced a high aggregation rate, with or without exposure to flow conditions. Dipyridamole alone or combined with aspirin provoked echinocytosis, disturbing the rouleaux arrangement (rates ranging from 11.25 ± 1.91–13.62 ± 1.62). Washing red cells after treatment restored about 90% of echinocytes to their biconcave shape, but aggregation rate did not recover in parallel. These results highlight the influence of red cell–platelet interactions in the regulation of haemostasis and show how therapeutic agents can interfere with rheological phenomena.     

A型行为对脑梗死患者血液流变学的影响

目的研究A型行为对脑梗死患者血液流变学的影响.方法应用全国心身医学协作组编制的"A型行为类型问卷”筛选出A型行为(简称TAB组)和与之相匹配的非A型行为(简称非TAB组)脑梗死患者各45例,同时随机选取45例健康人员作为对照组.三组人员均于晨6时空腹抽静脉血进行血液流变学检测.结果TAB组患者全血低切粘度(1s-1)、红细胞压积、血浆粘度(100s-1)、红细胞聚集指数及血浆纤维蛋白原显著高于非TAB组及对照组(P<0.05).结论A型行为可能是导致脑梗死的危险因素之一;对A型行为给与适当的干预,应是脑梗死一级预防的内容之一.     

Alteration in the rheologic properties of plasmodium knowlesi-infected red cells. A possible mechanism for capillary obstruction

Red cells parasitized by Plasmodium knowlesi concentrate within the microcirculation of many organs including cerebral capillaries in rhesus monkeys. The possibility that P. knowlesi could alter the rheologic properties of red cells so that they are trapped within capillaries was investigated in the present study. The viscosity of P. knowlesi-infected red cells suspended in Ringer's solution was increased at all shear rates at hematocrits above 30%. At moderate parasitemia the resistance to flow through 5 mu polycarbonate sieves was increased; at high parasitemia the pores were obstructed. Mature trophozoites caused more obstruction than young trophozoites (rings) at any given level of parasitemia. The reduction of deformability of red cells infected by schizonts of P. knowlesi was further demonstrated by their exclusion from rouleaux in a plasma suspension. Therefore, the red cells infected by P. knowlesi become less deformable, and this reduction in red cell deformability may explain the obstruction of cerebral capillaries.     

30例脑动脉粥样硬化症患者血流变指标观察

对３０例脑动脉粥样硬化症男性患者进行了血液流变学指标检测。 结果显示患者的全血粘度、低切还原粘度、细胞压积、血液相对粘度、红细胞刚性指 数、红细胞聚集指数、纤维蛋白原浓度、脑血流量,与我院正常参考值在统计学上均 有显著差异,除脑血流量为减少外,其余均为增高。