Clinical Hemorheology and Microcirculation

Erythrocyte microrheology changes were measured by cation‐osmotic haemolysis in Wistar albino rats of both sexes. Erythrocyte membrane biophysical properties were estimated using the method of cation‐osmotic haemolysis (COH) described by Nicak and Mojzis [Comp. Haematol. Int. 2 (1992), 84–86]. COH in male rats was higher in low ionic strength medium (spectrin skeleton) but without of statistical significance. The significantly higher COH in male rats in comparison with female rats was observed in higher ionic strength media. COH and erythrocyte deformability is also discussed. We suggest that changes in biophysical state of spectrin skeleton are followed by changes in lipid bilayer properties.

Few studies have been performed in humans to investigate the effect of caloric restriction and consequent biomass reduction on hemorheologic parameters and their results are not concurrent.

In a previous paper we analyzed the rheological behavior of the blood in the IIMb/Fmβ inbred obese and hypertriglyceridemic strain in relation to its eumetabolic control [G.N. Hernández, C. Dabin, M.C. Gayol and M.L. Rasia, Hemorheological variables in a rat model of hypertriglyceridemic obesity and diabetes, Veterinary Res. Commun. 26 (2002), 625–635]. In this obese line it was shown a higher blood and plasma viscosity and an impaired red cell deformability compared to the eumetabolic one. The increased plasma viscosity was significantly and positively associated with fibrinogenaemia and lipidaemia and the impaired erythrocyte deformability with cholesterolemia and hypertriglyceridaemia.

The present study has been designed to find out the effect of a 30% food restriction on several biochemical and hemorheological parameters of these obese rats. Restriction resulted in a mean body weight 45% lower than ad libitum controls, preventing obesity and hypertriglyceridemia with minimal effect on glucose metabolism.

Regarding hemorheological parameters, caloric restriction led to a decrease in blood viscosity, due to the reduction in erythrocyte concentration, but not because of any improvement in erythrocyte deformability.

Haemorheological parameters, such as red blood cell deformability, membrane elastic modulus and membrane surface viscosity in twenty one thalassaemia heterozygous patients (14 β⁰/β and 7 β⁺/β) were compared with normal individuals (n=15). Parameters were measured applying a laser diffractometric method (ektacytometry). Thalassaemia erythrocytes showed statistically significant lower deformability and higher elastic modulus. Surface viscosity showed no significant differences in thalassaemia. Creep and recovery curves were registered by diffractometry. The normal recovery curve was fitted by a first order exponential decay function, expressing the fitting degree by the χ² coefficient. The shape of the recovery curve in β‐thalassaemia patients (β⁰/β or β⁺/β) was significantly different from the control group. The possible mechanism of red blood cells abnormal rheological behaviour in β‐thalassaemia minor could be explained by a surface charge reduction. Our results enable us to conclude that the shape of the recovery curve (χ² coefficient) could be considered as a marker that might be useful in β‐thalassaemia diagnosis.

Tetramethylpyrazine (TMP) and salvianolic acid B (SAB) are effective ingredients of Rhizoma Ligustici chuanxiong Hort. and Radix Salviae miltiorrhizae Bge., accordingly. The inhibitive effects of TMP, SAB and their combination on shear‐induced platelet aggregation (SIPA) were investigated in the present study. SD rats were used as blood donors to collect anticoagulated blood, the concentration of platelet‐rich‐plasma (PRP) was adjusted to 5×10⁵ μl. HAAKE rheometer RS 600 with sensor C60/0.5° was used as shear generator. Different doses of TMP and SAB and their combinations were added to the PRP. After constant shear of 15 Pa at 37°C for 360 seconds, PRP was transferred to a platelet aggregometer and SIPA was determined by turbidity. SIPA was inhibited by TMP and SAB in a dose‐dependent manner. SIPA was decreased from 48.6±4.6% of the control to 12.5±2.1% in the presence of TMP (1.46 mM) and SAB (10 μM) (P<0.0001). In conclusion, TMP and SAB have additive effects on inhibiting platelet aggregation induced by high shear stress.

Comparative animal studies showed the wide variation of whole blood and plasma viscosity, and erythrocyte aggregation among mammalian species. Whole blood viscosity and red blood cell aggregation is influenced by red cell fluidity. To evaluate differences in erythrocyte deformability in mammals, three species were investigated, whose erythrocytes have a different aggregation property: horse, as a species with high, dog with medium, and sheep with almost unmeasurable aggregation tendency. Erythrocyte deformability was tested ektacytometrically (Elongation Index [EI], LORCA, Mechatronics, Hoorn, Netherlands) at shear stresses from 0.30 to 53.06 Pa. Equine erythrocytes showed EI‐values from 0.047 at low shear stress to 0.541 at high shear stress. The EI from dog's erythrocytes ranged from 0.035 to 0.595. Sheep's erythrocytes had an EI of 0.005 at low and 0.400 at high shear stress. Although it might be presumed from the aggregation property that horse had the highest EI among the three species, the EI of canine erythrocytes exceeded the value in horses by 10% at high shear stress. Further, equine erythrocytes started to deform at higher shear stresses (1.69 Pa) than did canine and ovine cells, whose EI increased continuously with increasing shear stress. At moderate shear stress (1–5 Pa) deformability was even higher in the sheep than in the horse. However, at shear stresses higher than 5.34 Pa, equine red cell elongation clearly exceeded the values of sheep. We conclude that erythrocyte elongation is different between the animal species, not clearly linked with the aggregation property, and that the degree of deformability at various shear stresses is species‐specific.

Ligaria cuneifolia (R. et P.) Tiegh. (Loranthaceae) (Argentine mistletoe) is usually used in local folk medicine. This work focuses on the hemorrheologic parameters in the treatment with an aqueous extract of Ligaria cuneifolia (Lc) by two different administration routes: intraperitoneal (i.p.) and intravenous (i.v.). Adult male Wistar rats were injected by via i.p. or by via i.v. with: saline solution; 2.5 mg/100 g body weight of Lc and 5.5 mg/100 g body weight of Lc. The relative viscosity of blood (η_r)^45/Hct was measured showing that Lc‐treatment by via i.p. produced an increase of about 69% while Lc by via i.v. enhanced the parameter about 47%. All of Lc‐treated animals showed a significant increase in the rigidity index (RI). The mean corpuscular hemoglobin concentration (MCHC) exhibited an increase of about 15% in all the treated groups. Lc‐treatment by via i.p. produced a diminution of plasma cholesterol level associated with RI augmentation which induced an increase of (η_r)^45/Hct. By via i.v. Lc produces both RI and (η_r)^45/Hct augmentation by increasing MCHC but without modifying plasma cholesterol level, indicating a direct Lc‐action on the internal viscosity of the erythrocyte.

Clinical hemorheological and brain stem auditory evoked potential (BAEP) investigations were performed in patients with ischaemic brain stem stroke. Lesions were verified by MRI. 55 healthy persons with negative rheological and BAEP findings were used as controls (group A/1). 33 stroke patients with negative rheological parameters (group A/2) and 34 patients with hyperviscosity (group A/3) were also enrolled. In group A/3 bilateral pathological BAEP patterns were found, that could be explained by microcirculatory disturbances. 36 persons with verified blood hyperviscosity, but without neurological signs were also examined (group A/4). In this group, as in group A/3, either total lack of any waveforms, or a bilateral prolongation of wave III was observed. In 31 cases of group A/4, control BAEP was performed after effective haemodilution therapy, and 6–12 months later (group B/1). Here, normalization of rheological profile had a temporary beneficial effect on BAEP in 14 of 18 cases with former wave III prolongation, but had no effect on BAEP patterns in 13 cases, where lack of waves had been verified by the first investigation.

These data suggest that hyperviscosity can result in subclinical pathological symmetric BAEP patterns, both in ischaemic stroke patients and in hyperviscosity patients without neurological symptoms.

Purpose. The aim of the present pathophysiological studies was elucidation of the feasible mechanism of spread of the blood rheological disorders from the cerebral to systemic circulation, and vice versa.

Methods. The investigation was carried out in the critical care patients with the brain tissue damage related to stroke (cerebral ischemic infarcts as well as parenchymatous and subarachnoid hemorrhages). The applied diagnostic techniques provided us with valid and quantitative data revealing the degree of the red blood cell aggregability, the value of local hematocrit, and the blood plasma viscosity in the cerebral and systemic circulation. In addition, rabbits experiments were carried out for analysis of the hemorheological disorders associated with the brain damage.

Results. Despite the local character of the patients primary brain damage, the hemorheological disorders were found regularly spread not only over the cerebral hemispheres, but even also the systemic circulation. Under such conditions they might cause the generalized brain tissue damage and play significant role in the subsequent damage‐cascade of the whole brain. In addition, the rabbits experiments demonstrated pronounced hemorheological disorders in the cerebral cortex capillaries: increase of their numbers with RBC enhanced aggregation and blood stasis, as well as with lowering of the RBC deformability in the narrow capillary lumina. These changes befell simultaneously with increase of water contents in the cerebral tissue evidencing for edema development in the brain.

Conclusion. Local cerebral hemorheological disorders might spread over the whole brain via the systemic circulation, thus promoting a generalized brain damage and being responsible for the critical state of the patients.

Clinical complications of Extracorporeal Circulation (ECC) are the consequence of a systemic activation of cellular and humoral factors resulting in a dysregulation of the microcirculation. Previously we developed an animal model to study effects of ECC on the microcirculation in vivo. To prevent the systemic inflammatory reaction (SIRS) seen after ECC, colloids were used as priming solution.

Intravital fluorescence microscopy was used on the hamster skinfold chamber model. ECC was introduced and the ECC‐tube system was flushed with Ringer solution (control), with Dextran 60 (group I) or HES 10% (group II).

ECC for 30 minutes resulted in an increase in rolling and adherent leukocytes in postcapillary venules (Roller: 11±3% to 38%±20% 4 h after ECC, p<0.05, Sticker: 19±16 cells/mm² to 215±145 cells/mm² 4 h after ECC, p<0.05; n=7). Use of Dextran prevented L/E cell interaction (10±5%; 63±40 cells/mm² at 4 h), whereas HES affected only adherent white cells.

L/E cell interaction in the microcirculation is an indicator of the systemic activation induced by ECC. Dextran 60 prevented L/E cell interaction without side effects and may be preferable for ECC in regard to inhibition of SIRS.

The effects of various aldehydes such as secondary products of peroxidized lipids and other aldehydes on rheological parameters and their relation with aging process were studied. Malondialdehyde (MDA) in different concentrations can increase significantly viscosity and plastic viscosity of erythrocytes suspended in plasma and HEPES buffer solution. Simultaneously, oxidation induced by Fe²⁺ can also enhance the viscosity of erythrocyte suspensions. All of these data suggest that MDA as one of the most studied unsaturated carbonyl products of lipid peroxidation leading to protein crosslinking may carry important information in understanding carbonyl stress‐related rheological change in acute as well as chronic diseases and aging.