Association of elevated plasma viscosity with small vessel occlusion in ischemic cerebral disease

Introduction

Elevated plasma viscosity (PV) is observed in patients with vascular risk factors, such as diabetes mellitus or arterial hypertension. In this study we investigated the association of plasma viscosity and the different clinical and radiological entities of cerebral ischemia.

Methods

PV of 465 consecutively admitted patients with clinical symptoms of acute cerebral ischemia without radiological signs of bleeding was measured. Data is expressed as median [range] unless stated otherwise. p < 0.05 was considered statistically significant.

Results

Patients with acute cerebral ischemia (TIA or Stroke) showed increased PV (TIA 1.27mPas [1.07-1.53], stroke 1.27mPas [1.07-1.56]) compared to patients without cerebral ischemia (Mimics) (1.23mPas [1.06-1.42]). The group with radiologically proven small vessel disease (SVD) had a significantly higher mean values of PV (1.29mPas [1.06-1.54]) compared to those with signs of large vessel disease or cardioembolic events (1.22mPas [1.07-1.56], p < 0.001).Patients with chronic heart failure (p = 0.007), arterial hypertension (p < 0.001) and diabetes mellitus (p = 0.002) had higher PV compared to patients without these cardiovascular risk factors. Hyperlipidemia or nicotine abuse showed no relation to PV.

Conclusion

Elevated PV is not only associated TIA and Stroke but is also found in patients with radiological signs of cerebral SVD. High levels of PV could be an underestimated risk for TIA and Stroke and participate in the complex pathophysiology of SVD. Prospective observational and interventional studies are warranted for further evaluation of PV in neurological ischemic diseases.     

Risk factor identification and assessment in hypertension and diabetes (RIAHD) study

The RIAHD (Risk factor Identification and Assessment in Hypertension and Diabetes) study was conducted as a non-interventional study in 699 patients with hypertension without additional risk factors (low-risk) or with additional risk factors (high-risk), primarily diabetes and/or micro/macroalbuminuria (MA/A). The RIAHD study aimed to assess novel cardiovascular risk factors (RFs) such as blood viscosity, inflammatory markers and selected genetic polymorphisms. In addition, the RIAHD study also aimed to examine home versus office blood pressures (BPs), objective cardiovascular risk according to ESH/ESC Systematic Coronary Risk Evaluation systems (SCORE) and subjectively expressed risk (clinical judgment) by physicians and patients. The health economic impact of other RFs, associated clinical conditions and target organ damage was also studied by evaluating healthcare utilization and sick leave in high-risk patients. In terms of circulating RFs, measured and calculated whole blood viscosity did not differ between the high and low-risk patient groups. Fibrinogen was significantly increased in the high-risk group, while hsCRP did not differ between the two groups. Self-measured BPs at home differed from BPs measured in the office. The average systolic home BPs was 11.8 mmHg lower in the low-risk group and 6.7 mmHg lower in the high-risk group. The diastolic home BPs averages differed 7.1mm Hg and 4.1mmHg from office BPs in the low-risk and high-risk groups, respectively. A higher home BP compared with the office BP, i.e. masked high BP values, was found in 21% of patients in the low-risk group and 32% of patients in the high-risk group. Global CV risk assessment (high-risk or low-risk) by the physicians corresponded well to objective risk evaluation (ESH/ESC) in the high-risk hypertensive patients, while physicians tended to underestimate the patients CV risk in the low-risk group (without diabetes and/or MA/A). Proper global risk assessment by judgement is often difficult in cardiovascular patients. The RIAHD study emphasizes the importance of performing a more extended RF assessment in hypertensive patients with as well as without diabetes and/or micro/macroalbuminuria in order to expose the full RF profile.     

Mechanotransduction and the homeostatic significance of maintaining blood viscosity in hypotension, hypertension and haemorrhage

The increase of plasma and blood viscosity is usually associated with pathological conditions; however, elevation of both parameters often results in increased perfusion and the lowering of peripheral vascular resistance. In extreme haemodilution, blood viscosity is too low and insufficient to maintain functional capillary density, a problem that in experimental studies is shown to be corrected by increasing plasma viscosity up to 2.2 cP. This effect is mediated by mechanotransduction-induced nitric oxide (NO) production via shear stress in the endothelium as shown by microelectrode perivascular measurements of NO concentration. Moderate elevations of blood viscosity by increasing haematocrit ( approximately 10%) result in comparable reductions of blood pressure and peripheral vascular resistance, an effect also NO-mediated as it is absent after Nomega-nitro-L-arginine methyl ester treatment and in endothelial nitric oxide synthase-deficient mice. These findings show that the rheological properties of plasma affect vessel diameter in the microcirculation leading to counterintuitive responses to the changes in blood and plasma viscosity. Application of these findings to haemorrhagic shock resuscitation leads to the concept of hyperosmotic-hyperviscous resuscitation as a modality for maintaining the recovery of microvascular function.     

Erythrocyte transport efficacy of human blood: a rheological point of view

BACKGROUND: Large-scale epidemiological studies have demonstrated that both anaemia and polycytaemia are independent cardiovascular risk factors. This was substantiated by the Framingham study, which demonstrated a U-shaped relation between haemoglobin concentration and mortality. It was previously noted that delineating the corresponding haematocrit/blood viscosity ratios in the function of haematocrit provided a distribution of an inverted U-shaped curve. The peak appeared physiologically important because it denotes a healthy balance between a relatively high oxygen binding capacity and a moderately low blood viscosity. It was the aim of this study to examine the mathematical relationship between the haematocrit and haematocrit/blood viscosity ratio. MATERIALS AND METHODS: In a retrospective study, the haemorheological data of 32 healthy controls, 52 outpatients with hyperlipidaemia and 120 outpatients with Raynaud's disease were analyzed. Whole blood viscosity was measured with Hevimet 40 capillary viscometer at 37.0 degrees C and at shear rates of 10 s(-1), 90 s(-1) and 200 s(-1). RESULTS: Haematocrit/blood viscosity ratios in the function of haematocrit values showed a Gaussian association in the healthy subjects, hyperlipidaemic and Raynaud's disease outpatient groups. Peak values (i.e. the rheologically optimal haematocrit) were shear-rate and group dependent and were found at 44.3%, 43.5% and 38.3% in controls, hyperlipidaemic and Raynaud's disease patients, respectively, at a shear rate of 90 s(-1). CONCLUSIONS: This is one of the first reports in which a theoretically optimal haematocrit value was determined using the haematocrit/blood viscosity ratio. Further studies are needed to examine the potential clinical usefulness of this approach.     

Dynamics of Dense Suspensions of Star‐Like Micelles with Responsive Fixed Cores

Summary: PBMA‐PCEMA block copolymer micelles, consisting of poly(2‐cinnamoyloxyethyl methacrylate) (PCEMA) cross‐linked core and poly(butyl methacrylate) (PBMA) hairs (shell), are used as model responsive soft colloids, where the core swelling can be tuned by changing solvent quality. Our extensive dynamic light scattering study, complemented by viscosity and small angle neutron scattering (SANS) measurements, demonstrates the richness of dynamics of such dense micellar suspensions and in particular the strong influence of solvent‐mediated core swelling on the concentration dependence of the self‐diffusion. Brownian dynamics (BD) simulations using appropriate effective core‐core interactions support these findings. Such novel micelles offer new possibilities for controlling the interactions and macroscopic properties of colloidal suspensions.

The self‐diffusion coefficient D for core‐shell particles, as calculated from the Brownian dynamics simulations.     

MVIS-2035全自动血液流变分析仪参数评价

目的对MVIS-2035全自动血液流变分析仪的参数进行评价，探讨血液流变检测的临床价值。方法用MVIS-2035全自动血液流变分析仪分别测定健康人（56例）、心脑血管疾病患者（56例）的血液流变学改变，并用国家物质中心调配的标准液（高黏度油、中黏度油、低黏度油和血浆黏度油）测定批内精密度和批间精密度。结果全血高、中、低黏度批内精密度变异系数（CV）在切变率200／s、30／s、3／s时均小于2％，批间全血低黏CV在切变率200／s、30／s、3／s时为2．59％、2．79％13．22％，其余CV均小于2％。血浆黏度批内、批间变异系数分别为1．31％、2．49％。病人组与对照组比较，除血液屈服应力（fc）的差异无统计学意义外（P〉0．05），全血高切、中切、低切黏度（ηb）、血浆黏度（ηp）、红细胞聚集指数（Arbe）、红细胞刚性指数（IR）、红细胞电泳时间（EPT）均有显著性差异（P〈0．01）。结论用MVIS-2035全自动血液流变分析仪测血液流变的精密度好，结果可靠，可用于临床诊断心脑血管疾病与疗效监测。     

血液粘滞度对血压水平的影响程度

目的研究血液粘滞度对血压水平的影响程度。方法将体格检查者2561例作为研究对象,按血压水平将其分为正常血压组和高血压组,正常组1863例,高血压组698例。测量其血压、血糖、血脂、血液流变学的各项指标,用多元线性回归分析血液粘滞度对血压水平的影响。结果高血压组的血糖（GLU）、总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白胆固醇（LDL-C）、全血高切粘度（ηbH）、全血中切粘度（ηbM）、红细胞刚性指数（ERI）、红细胞变形指数（TK）等指标均明显高于正常血压组（P〈0.01）,高密度脂蛋白胆固醇（HDL-C）、红细胞聚集指数（EAI）则低于正常血压组（P〈0.01）。多元线性回归显示,血压水平与GLU、TC、TG、LDL-C、ηbm、全血低切粘度（ηbL）、ERI、TK相关。收缩压水平的复相关系数R=0.345,确定系数R2=0.119（F=43.071,P〈0.01）;舒张压水平的复相关系数R=0.331,确定系数R2=0.111（F=39.872,P〈0.01）。结论血液粘滞度通过多种途径影响血压水平,是影响血压水平的一个重要因素,它可以解释大约11%的血压水平的变异。     

低能量血管内激光治疗对脑梗死患者血黏度及预后的影响

血液黏度异常增高是引起脑梗死的主要原因之一，尤其老年人。如能及时有效的防治血液黏度的异常改变，将有利于脑梗死形成的预防。对2004年4月至2005年2月72例脑梗死住院患者采用低能量半导体血管内激光治疗和单纯血栓通进行了治疗前后不同切变率条件下血液黏度值和脑梗死预后影响的分析。现将结果报道如下。     

虎杖苷降低急性血瘀模型大鼠血液粘度的研究

目的 :探讨虎杖苷降低急性血瘀模型大鼠血液粘度的作用。方法 :采用大鼠急性血瘀模型 ,以全血高切变率及低切变率粘度值、红细胞压积值、血小板粘附率、纤维蛋白原含量、血浆粘度为观察指标。结果 :虎杖苷可以显著降低模型大鼠的纤维蛋白原含量和血小板粘附率 ,其药效对血浆粘度降低所致全血粘度降低比其它原因所致更显著 ,它主要通过降低血浆粘度来降低全血粘度 ,从而显著改善大鼠血液循环。结论 :虎杖苷对血液粘度降低有重要应用价值。     

人参Rb组皂苷对高脂血症大鼠血脂代谢的影响及其抗氧化作用

目的 :观察人参Rb组皂苷 (G-Rb)对实验性高脂血症大鼠血清总胆固醇、脂蛋白 胆固醇代谢的影响及其抗氧化作用。方法 :G-Rb按 50 ,100 ,200mg·kg^-1给大鼠连续灌胃 12d ,测血清总胆固醇、脂蛋白 胆固醇及过氧化脂质 (LPO)含量 ,血浆前列环素 (PGI₂ )和血栓烷A₂ (TXA₂ )水平 ,血清和肝脏超氧化物歧化酶 (SOD)活性及全血黏度 ,并观察肝脏脂肪沉积情况。结果 :G-Rb 100 ,200mg·kg^-1能明显降低甘油三脂 (TG) ,总胆固醇 (TC) ,低密度脂蛋白胆固醇 (LDL-c) ,TXA₂ ,LPO含量及全血黏度 ,并能明显提高实验性高脂血症大鼠高密度脂蛋白胆固醇 (HDL-c) ,PGI₂ 含量及SOD活性 ,亦能使TC/HDL-c及LDL-c/HDL-c比值明显降低 ,PGI₂ /TXA₂ 比值明显升高。病理检查可见肝脏脂肪沉积明显减轻。其作用明显优于洛伐他汀。结论 :G-Rb可能通过调节体内血脂代谢、提高PGI₂ /TXA₂ 比值及纠正自由基代谢紊乱发挥抗动脉硬化作用。