Echogenicity variations from porcine blood II: the "bright ring" under oscillatory flow

Echogenicity variations from porcine blood were observed in a mock flow loop under pulsatile flow in a series of experiments (Paeng et al. 2004). In this paper, oscillatory flow was generated to further investigate the cyclic and radial variation of blood echogenicity and its origin and mechanisms by several parameters, including stroke volume, stroke rate, mean steady flow and transducer angle, using a GE LOGIQ 700 Expert system. The echogenicity at the center of the tube was enhanced during acceleration and lower during deceleration, and the expansion and collapse of the "bright ring" was observed twice per cycle. The "black hole," a central echo-poor zone surrounded by a hyperechoic zone, was barely observable under oscillatory flow, and these patterns differed from those under pulsatile flow. The cyclic and radial variation of echogenicity under oscillatory flow was affected by such hemodynamic parameters as stroke volume, stroke rate and mean steady flow. It was suggested that rouleaux might be aligned at an angle of about 25 degrees relative to the tube axis during the acceleration phase, based on the experimental results reaching a maximum of the echogenicity variation at a transducer angle of 25 degrees. Radial distribution of rouleaux alignments was proposed to be another important factor to blood echogenicity variation, in addition to combined effects of shear rate and flow acceleration on erythrocyte aggregation and blood echogenicity. The weak cyclic variation of echogenicity was also observed from the porcine erythrocyte suspensions under pure oscillatory flow, but not under pulsatile flow. It is postulated that the echogenicity variations from erythrocyte suspensions are from red cell deformation.     

Doppler power variation from porcine blood under steady and pulsatile flow

Although a number of recent studies have demonstrated that the echogenicity of blood varies as a function of time under pulsatile flow, the fundamental mechanisms responsible for it are still uncertain. To better understand this phenomenon, the Doppler power from porcine blood and polystyrene microsphere suspensions was measured at the center of the tube as functions of two crucial parameters, flow velocity and stroke rate (for pulsatile flow), under steady and pulsatile flow in a mock flow loop. In the present study, the experimental results were obtained with a 10-MHz pulsed Doppler system with a frequency response estimated more accurately by electronic injection, and validated by comparing to the radiofrequency (RF) signal acquired from the same Doppler instrument. The results show that the Doppler power from microspheres and porcine red blood cell (RBC) suspensions did not vary appreciably (< 2 dB), with either the speed or stroke rate (for pulsatile flow only) under steady and pulsatile flow. It was found that the Doppler power from porcine whole blood under steady flow decreased with the speed by approximately 13 dB from 3 to 33 cm/s and was only 3 dB higher than that from RBC suspension at 33 cm/s, suggesting minimal RBC aggregation in whole blood at this speed. The apparent cyclic variation from whole blood was observed at 20 and 40 beats/min (BPM). The cyclic variation became more obvious as the speed and stroke rate decreased. The mean Doppler power over a cycle increased as the peak speed decreased. The Doppler power reached a maximum near peak systole and a minimum at late diastole at the center of the tube. This pattern cannot be explained by RBC aggregation due to the shear rate alone, and may be attributed to acceleration and deceleration along with aggregation. The cyclic variation was not observed at 60 BPM, probably because of a lack of time for aggregation to occur.     

High Spatial and Temporal Resolution Observations of Pulsatile Changes in Blood Echogenicity in the Common Carotid Artery of Rats

Previous studies have found that ultrasound backscatter from blood in vascular flow systems varies under pulsatile flow, with the maximum values occurring during the systolic period. This phenomenon is of particular interest in hemorheology because it is contrary to the well-known fact that red blood cell (RBC) aggregation, which determines the intensity of ultrasound backscatter from blood, decreases at a high systolic shear rate. In the present study, a rat model was used to provide basic information on the characteristics of blood echogenicity in arterial blood flow to investigate the phenomenon of RBC aggregation under pulsatile flow. Blood echogenicity in the common carotid arteries of rats was measured using a high-frequency ultrasound imaging system with a 40-MHz probe. The electrocardiography-based kilohertz visualization reconstruction technique was employed to obtain high-temporal-resolution and high-spatial-resolution time-course B-mode cross-sectional and longitudinal images of the vessel. The experimental results indicate that blood echogenicity in rat carotid arteries varies during a cardiac cycle. Blood echogenicity tends to decrease during early systole and reaches its peak during late systole, followed by a slow decline thereafter. The time delay of the echogenicity peak from peak systole in the present results is the main difference from previous in vitro and in vivo observations of backscattering peaks during early systole, which may be caused by the very rapid heart rates and low RBC aggregation tendency of rats compared with humans and other mammalian species. The present study may provide useful information elucidating the characteristics of RBC aggregation in arterial blood flow.     

The Effect of Flow Acceleration on the Cyclic Variation of Blood Echogenicity Under Pulsatile Flow

It has been shown that the echogenicity of blood varies during a flow cycle under pulsatile flow both in vitro and in vivo. In general, the echogenicity of flowing whole blood increases during the early systole phase and then reduces to a minimum at late diastole. While it has been postulated that this cyclic variation is associated with the dynamics of erythrocyte aggregation, the mechanisms underlying this increasing echogenicity with flow velocity remain uncertain. The effect of flow acceleration has also been proposed as an explanation for this phenomenon, but no specific experiments have been conducted to test this hypothesis. In addition, the influence of ultrasonic attenuation on the cyclic variation of echogenicity requires clarification. In the present study, a Couette flow system was designed to simulate blood flowing with different acceleration patterns, and the flow velocity, attenuation, and backscattering coefficient were measured synchronously from 20%- and 40%-hematocrit porcine whole blood and erythrocyte suspensions using 35-MHz ultrasound transducers. The results showed ultrasonic attenuation exerted only minor effects on the echogenicity of blood under pulsatile flow conditions. Cyclic variations of echogenicity were clearly observed for whole blood with a hematocrit of 40%, but no variations were apparent for erythrocyte suspensions. The echogenicity did not appear to be enhanced when instantaneous acceleration was applied to flowing blood in any case. These findings show that flow acceleration does not promote erythrocyte aggregation, even when a higher peak velocity is applied to the blood. Comparison of the results obtained with different accelerations revealed that the cyclic variation in echogenicity observed during pulsatile blood flow may be jointly attributable to the effect of shear rate and the distribution of erythrocyte on aggregation.     

Echogenicity variations from porcine blood I: the "bright collapsing ring" under pulsatile flow

The temporal and radial variations of the echogenicity from porcine blood were investigated using a linear M12L transducer with a GE LOGIQ 700 Expert system. The "bright collapsing ring" (BRCR) phenomenon, a bright echogenic ring converging from the periphery to the center of the tube wall and eventually collapsing during a pulsatile cycle in cross-sectional B-mode images, was observed from porcine blood in a mock flow loop within a 0.95-cm diameter tube under certain flow conditions. The BRCR phenomenon from porcine blood was stronger as the peak speed was increased from 10 to 25 cm/s, and the mean echogenicity and the "black hole" (BLH) phenomenon, a central echo-poor zone surrounded by a bright hyperechoic zone, became weaker. As stroke rate was increased from 20 to 60 beats/min (bpm), both the BRCR and the BLH phenomena became weaker. These two phenomena were observed at three transmitting frequencies (9, 11 and 13 MHz). As hematocrit was increased from 12 to 45%, the BRCR phenomenon became more apparent. The nonlinear behavior of backscatter as a function of hematocrit reaching a maximum at hematocrit of 10 approximately 20% was observed near the tube wall, but it changed at the center of the tube, indicating the importance of hemodynamics on the ultrasonic backscatter from flowing blood. The combined effects of shear rate and acceleration on red blood cell aggregation are suggested as a possible mechanism for these phenomena.     

Simultaneous measurement of red blood cell aggregation and whole blood coagulation using high-frequency ultrasound

This study aims to investigate the feasibility of using high-frequency ultrasound (HFUS) for simultaneous monitoring of blood coagulation and red blood cell (RBC) aggregation. Using a 35-MHz ultrasound scanner, ultrasound speckle data were acquired from whole blood samples of three experimental groups of rats, including 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-treated, noncoagulation and normal control groups. The variations of blood echogenicity, the shape parameters of probability distribution of speckle intensity (skewness and kurtosis) and the correlation coefficient between two consecutive speckle data were calculated as a function of time starting from immediately after taking blood. The blood echogenicity increases rapidly to plateaus at the early stage of measurement for all the experimental groups caused by the formation of RBC aggregates. The DIDS-treated group exhibits the lowest echogenicity level due to the inhibitory effect of DIDS on RBC aggregation. The correlation analysis between consecutive speckle patterns seems to be useful to examine the variation of blood fluidity and the progress of clot formation. Whole blood coagulation is observed to be accelerated by DIDS treatment. In addition, the results of skewness and kurtosis analysis indicated that RBC aggregates may be disrupted during blood coagulation. The present study suggests that HFUS has good potential for simultaneous monitoring of RBC aggregation and blood coagulation to examine the relationship between them.     

Simultaneous assessment of red blood cell aggregation and oxygen saturation under pulsatile flow using high-frequency photoacoustics

We investigate the feasibility of photoacoustic (PA) imaging for assessing the correlation between red blood cell (RBC) aggregation and the oxygen saturation (sO₂) in a simulated pulsatile blood flow system. For the 750 and 850 nm illuminations, the PA amplitude (PAA) increased and decreased as the mean blood flow velocity decreased and increased, respectively, at all beat rates (60, 120 and 180 bpm). The sO₂ also cyclically varied, in phase with the PAA for all beat rates. However, the linear correlation between the sO₂ and the PAA at 850 nm was stronger than that at 750 nm. These results suggest that the sO₂ can be correlated with RBC aggregation induced by decreased mean shear rate in pulsatile flow, and that the correlation is dependent on the optical wavelength. The hemodynamic properties of blood flow assessed by PA imaging may be used to provide a new biomarker for simultaneous monitoring blood viscosity related to RBC aggregation, oxygen delivery related to the sO₂ and their clinical correlation.OCIS codes: (110.5125) Photoacoustics, (170.1470) Blood or tissue constituent monitoring     

Cyclic and Radial Variation of the Echogenicity of Blood in Human Carotid Arteries Observed By Harmonic Imaging

To better understand the characteristics of erythrocyte aggregation in flowing blood, echogenicity variation in blood was observed both in vitro and in vivo. However, few noninvasive observations of blood echogenicity variation during the cardiac cycle in human arteries have been reported. In the present study, to reduce the dynamic range between the blood vessel lumen and the surrounding tissue, coded harmonic images were acquired from human carotid arteries using a GE LOGIQ 700 Expert system (GE, Milwaukee, WI, USA) with an M12L probe, which enabled the noninvasive detection of the cyclic and radial variation of echogenicity in arterial vessels. It was found that blood echogenicity increased during systole, reaching a maximum at peak systole and then decreased to a weak level during diastole. The echogenicity profiles of blood along the vessel diameter were found to be approximately parabolic in the cardiac cycle, except for the hypoechoic zone near the center of the vessel at peak systole. The present results for human carotid arteries corroborate previous in vitro observations that showed a cyclic and radial variation of blood echogenicity, which was thought to be caused by the enhancement of erythrocyte aggregation due to the combined effects of flow acceleration and shear rate during systole. (E-mail: kwonho@gmail.com)     

Cyclic changes in blood echogenicity under pulsatile flow are frequency dependent

Previous in vivo and in vitro studies have demonstrated that blood echogenicity varies under pulsatile flow, but such changes could not always be measured at physiological stroke rates. The apparent contradiction between these studies could be a result of the use of different ultrasound frequencies. Backscattered signals from porcine blood were measured in a pulsatile Couette flow apparatus. Cyclic changes in shear rate for stroke rates of 20 to 70 beats per minute (BPM) were applied to the Couette system, and different blood samples were analyzed (normal blood and blood with hyperaggregating erythrocytes promoted with dextran). To confirm that cyclic echogenicity variations were observable, spectral analysis was performed to verify if changes in echo-amplitude corresponded to the stroke rate applied to the flow. Echogenicity was measured with two single-element transducers at 10 and 35 MHz. At 35 MHz, cyclic variations in backscatter were observed from 20 to 70 BPM. However at 10 MHz, they were detected only at 20 BPM. For all cases except for hyperaggregating red blood cells (RBCs) at 20 BPM, the magnitude of the cyclic variations were higher at 35 MHz. We conclude that cyclic variations in RBC aggregation exist at physiological stroke rates, unlike what has been demonstrated in previous in-vitro studies at frequencies of 10 MHz. The increased sensitivity at 35 MHz to small changes in aggregate size might be the explanation for the better characterization of RBC aggregation at high stroke rates. Our results corroborate in-vivo observations of cyclic blood echogenicity variations in patients using a 30-MHz intravascular ultrasound catheter.     

Statistical variations of ultrasound signals backscattered from flowing blood

The statistical distributions of ultrasonic signals backscattered from blood have recently been used to characterize hemodynamic properties, such as red blood cell (RBC) aggregation and blood coagulation. However, a thorough understanding of the relationship between blood properties and the statistical behavior of signals backscattered from flowing blood is still lacking. This prompted us to use the statistical parameter to characterize signals backscattered from both whole blood and RBC suspensions at different flow velocities (from 10 to 60 cm/s) and hematocrits (from 20% to 50%) under a steady laminar flow condition. The Nakagami parameter, scaling parameter, backscatter amplitude profile and flow velocity profile across a flow tube were acquired using a 10 MHz focused ultrasonic transducer. The backscattered signal peaked approximately at the centerline of the flow tube due to the effects of RBC aggregation, with the peak value increasing as the flow velocity of whole blood decreased. The Nakagami parameter increased from 0.45 to 0.78 as the flow velocity increased from 10 to 60 cm/s. The probability density function (PDF) of signals backscattered from flowing whole blood conformed with a pre-Rayleigh distribution. The Nakagami parameter was close to 1 for signals backscattered from RBC suspensions at all the flow velocities and hematocrits tested, for which the PDF was Rayleigh distributed. These differences in the statistical distributions of backscattered signals between whole blood and RBC suspensions suggest that variations in the size of dynamic scatterers in the flow affect the shape of the backscattered signal envelope, which should be considered in future statistical models used to characterize blood properties. (E-mail: j648816n@ms23.hinet.net and shyhhau@cycu.edu.tw)     

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.     

Fractional flow reserve-based 4D hemodynamic simulation of time-resolved blood flow in left anterior descending coronary artery

BackgroundThe purpose of this study was to investigate the feasibility of the non-invasive assessment of hemodynamic parameters with computational fluid dynamics in left anterior descending coronary artery based on invasive fractional flow reserve.MethodsA left coronary artery model based on computed tomography angiography was reconstructed using MIMICS 18.0 for computational fluid dynamics analysis. With actual fractional flow reserve measured from the patient, 4D hemodynamic profiles of time-resolved blood flow were simulated.FindingsThe 4D blood flow simulation could provide extensive information of blood flow status. Hemodynamic parameters, such as velocity, wall shear stress and pressure were simulated throughout the cardiac cycle. There might be high flow velocities and high wall shear stress in the stenotic region throughout the whole cycle, both of which peaked in the case of the maximum inlet differential pressure. The reverse flow and vortex were detectable at the downstream areas beneath the stenotic site. The pressure remarkably increased near the proximal stenotic end and declined in the mid-stenosis. Moreover, the simulation results provided detailed and accurate mass flow measurements of hemodynamic parameters as well.InterpretationThe computational fluid dynamics analysis of 4D blood flow based on fractional flow reserve is feasible in left anterior descending coronary artery. It presents the merits of providing both qualitative and quantitative information for further investigation of the links between hemodynamic parameters and left anterior descending artery stenosis.     

Measurement of the Doppler Power of Flowing Blood Using Ultrasound Doppler Devices

Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser–receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and echogenicity of flowing blood were compared with those obtained in several previous studies.     

Simultaneous measurement of vibrations on arterial wall upstream and downstream of arteriostenosis lesion and their analysis

Acute myocardial infarction and cerebral infarction are generally known to be caused primarily by the rupture of atherosclerotic plaques. It is thus necessary for clinical treatment to predict the rupture of these plaques. Blood-flow velocity around atherosclerotic plaques increases as the arteriostenosis lesion progresses, resulting in turbulence downstream of the lesion. The resulting change in blood pressure produces shear stress, and change in this stress affects the rupture of the atherosclerotic plaques. Cerebral ischemic paroxysm and cerebral infarction have been reported to occur in a high percentage of cases in which inner vessel diameter has decreased to less than 70% of its original diameter as a result of stenosis. This explains the use of standard ultrasonic diagnostic equipment to measure blood flow in the screening of the carotid arteries. On the other hand, the noise signal radiated from an aneurysm as a result of blood flow has been measured using the bruit sensor used to diagnose cerebrovascular diseases. Many unsolved problems with regard to the relationship between noise and turbulence in blood flow remain, however. Here, small vibrations on the arterial wall were measured transcutaneously and analyzed both upstream and downstream of the atherosclerotic plaque of a human carotid artery. Characteristics of the resultant vibrations upstream of the stenosis clearly differed from those downstream of it. These results should prove useful in predicting the rupture of atherosclerotic plaques.     

Cyclic changes of blood echogenicity in high-frequency ultrasound.

Ultrasound images from human arteries obtained in vivo with an intravascular 30 MHz ultrasound imaging device show that blood echogenicity changes during the cardiac cycle. Quantitative measurements of blood echogenicity during the cardiac cycle suggest that these variations may be related to changes in the state of erythrocyte aggregation, which are induced by varying shear rate.     

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.     

Increased shear rate resistance and fastest kinetics of erythrocyte aggregation in diabetes measured with ultrasound

OBJECTIVE—To measure with ultrasound the increased erythrocyte aggregation (EA) kinetics and adhesion energy between erythrocytes in patients with type 2 diabetes and poor metabolic control.RESEARCH DESIGN AND METHODS—Blood samples were analyzed in a Couette rheometer at 32 MHz following shear rate reductions from 500 s⁻¹ to residual shears of 0 (stasis), 1, 2, 10, 50, 100, and 200 s⁻¹. The increase in EA was determined with the integrated backscatter coefficient as a function of time and shear rate.RESULTS—The time required to form aggregates was shorter in diabetic patients at shear rates below 200 s⁻¹ (P < 0.01). Erythrocytes formed larger aggregates in diabetic patients than in control subjects (P < 0.05 at 2 to 100 s⁻¹).CONCLUSIONS—Ultrasound can potentially noninvasively demonstrate, in vivo and in situ, the impact of local abnormal EA on arteriovenous flow disorders in diabetes.Flow disorders in diabetes often lead to severe outcomes in various organs and tissues; abnormal rheology of erythrocytes (RBC) likely impairs macro- and microcirculatory blood flow, tissue oxygenation, and vascular tone regulation in affected patients (1–3). Diabetic retinopathy is attributed to microvascular flow disorders and enhanced RBC aggregation (4). Erythrocyte aggregation (EA) and plasma viscosity are also predictive of diabetic foot syndrome deterioration (5). EA is a reversible phenomenon responsible for increased blood viscosity at low shear rates. RBC hyperaggregation can also promote flow stasis and thrombosis in macrocirculation. This study proposes an ultrasound method that has the potential to noninvasively detect early rheological disorders in situ in blood vessels. The method is based on backscattering of ultrasound by blood; it measures the extent of EA and its shear rate dependency.     

脂肪肝病人血液流变学的临床观察

目的对临床确诊的脂肪肝病人,同时伴有甘油三酯增高者,比较其血液流变学各参数的变化,以探讨对临床脂肪肝诊断的实用价值.方法分别测定86例患者的全血粘度、血浆粘度、甘油三酯等9项血液流变学指标.结果 86例脂肪肝病人全血粘度(高切、低切)、红细胞电泳时间及甘油三酯同时增高者61例,占70.9%.全血粘度(高切、中切、低切)、血浆粘度、全血还原粘度、红细胞聚集指数、红细胞电泳时间、甘油三酯同时增高者19例,占22.1%.单纯全血粘度低切增高者6例,占7%.结论脂肪肝病人血液流变学各参数的影响主要是全血粘度及红细胞电泳时间有明显的改变,甘油三酯的增高对血浆粘度及全血还原粘度影响不太明显.可作为临床对脂肪肝病人辅助诊断检查的一项重要参考指标.     

Micro-PIV measurements of blood flow in extraembryonic blood vessels of chicken embryos

The hemodynamic characteristics of blood flow are important in the diagnosis of circulatory diseases, since such diseases are related to wall shear stress of cardiovascular vessels. In chicken embryos at early stages of development, it is possible to directly visualize blood flow inside blood vessels. We therefore employed a micro-PIV technique to assess blood flow in extraembryonic venous and arterial blood vessels of chicken embryos, using red blood cells (RBCs) as tracers and obtaining flow images of RBCs using a high-speed CMOS camera. The mean velocity field showed non-Newtonian flow characteristics. The blood flow in two venous vessels merged smoothly into the Y-shaped downstream vein without any flow separation or secondary flow. Vorticity was high in the inner regions, where the radius of curvature varied greatly. A periodic variation of temporally resolved velocity signals, due to beating of the heart, was observed in arterial blood vessels. The pulsating frequency was obtained by fast Fourier transform analysis using the measured velocity data. The measurement technique used here was useful in analyzing the hemodynamic characteristics of in vivo blood flow in chicken embryos.     

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。