Clinical Hemorheology and Microcirculation

To evaluate the influence of metabolic quality on blood rheology plasmatic and cellular determinants were studied in otherwise healthy, young insulin-dependent diabetic patients with excellent (A; n=12; age: 32.1 ± 13 a (x ± SD); HbA1c: 5.2 HbA1c 0.4%), moderate (B; n=12; 26.4 ± 7.8 a; HbA1c: 7.7 ± 0.5%) and insufficient (C; n=14; 26.3 ± 7.9 a; HbA1c: 11.5 ± 1.8%) metabolic control, as well as in patients with manifest microangiopathy (= retinopathy) (D; n=10; 33.1 ± 8.6; HbA1c: 7.2 ± 1.9%) and in heal thy age-matched non-diabetic controls (N; n=12; 28.3 ± 4.7 a; HbA1c: 5.3 ± 0.2%). While plasma fibrinogen, (N: 242 ± 46 mg/dl; A: 259 ± 51 mg/dl; B: 277 ± 45 mg/dl; C: 287 ± 68 mg/dl; D: 307 ± 69 mg/dl) and alpha-2-macroglobulin (A: 185 ± 41 mg/dl; B: 207 ± 70 mg/dl; C: 211 ± 89 mg/dl; D: 228 ± 73 mg/dl) tended to increase with worsening of metabolic control and presence of microangiopathy, we found no significant differences between the groups in plasma viscosity (N: 1.61 ± 0.03 mPa.s; A: 1.64 ± 0.05 mPa.s; B: 1.70 ± 0.11 mPa.s; C: 1.68 ± 0.16 mPa.s; D: 1.66 ± 0.12 mPa.s) and in red cell aggregation (in stasis, arb. units) (N: 4.98 ± 1.04 aU*; A: 5.31 ± 0.78 aU*; B: 6.45 ± 1.55 aU; C: 5.57 ± 1.57 aU*; D: 7.33 ± 2.32 aU;* p<0.05 vs D; analysis of variance) in dependance of metabolic control. In contrast, red cell aggregation (stasis) was higher in patients with microangiopathy (n=10; 7.33 ± 2.32 aU) than in those without (n=52; 5.55 ± 1.36 aU; p<0.015) under comparable metabolic control (HbA1c; 7.2 ± 1.9% vs 7.5 ± 2.9%; n.s.), resembling the results for red cell aggregation at low shear rate (3/s) (with retinopathy: 9.2 ± 2.4 aU; without: 7.8 ± 1.5 aU; p<0.05).

Our data suggest that rheological parameters depend only marginally on metabolic control in young insulin-dependent diabetic patients without manifest macro- and microangiopathy. Thus, changes in blood rheology in patients with manifest macro- and microangiopathy should be interpreted rather as aggrevating consequence of the underlying vessel disease than as primary causal factor.

Since most stresses are known to modify blood rheology, we studied hemorheological parameters during labor and delivery, which are highly stressful physiological events. In 80 pregnant women we measured blood viscosity, plasma viscosity and red blood cell (RBC) aggregation during labor (before and after 4 cm dilatation), during delivery, and during delivery of the placenta. Blood viscosity at both native and corrected hematocrit increases (p<0.001) with a peak during delivery followed by a rapid normalization during delivery of the placenta (p<0.01). Hematocrit and plasma viscosity do not change during labor and delivery, but decrease during delivery of the placenta. RBC aggregation (physiologically increased during late pregnancy) acutely returns to normal during delivery (p<0.01). The transient increase in viscosity during delivery is explained by an increase in RBC rigidity as measured by Dintenfass ‘Tk’ (p<0.01) and a similar (nonsignificant) tendency to decrease RBC filterability measured by the hemorheometre. Thus, delivery is associated with a transient hyperviscosity syndrome which is mainly due to a decrease in RBC flexibility.

It is well established that the rheological properties of blood depend on the shear rate of the flow. At low shear rate of around 1 sec⁻¹, blood exhibits the property of a viscoelastic fluid. As the shear rate increases progressively, the blood transforms to thixotropic, pseudoplastic and then Newtonian fluid. In the shear rate range up to approximately 1 sec⁻¹, blood behaves viscoelastic and thixotropic. This time dependent, strain dependent and shear rate dependent rheological behavior of blood has been demonstrated experimentally in the literature. In this work, a rheological equation is developed for the characterization of both viscoelastic and thixotropic properties of blood. The equation is based on the Huang model of thixotropic property incorporated into the viscous component of the relaxation modulus of the general Maxwell model. Experimental data of rheological hysteresis of blood at low shear rate obtained by Bureau, Healy, Bourgoin and Joly was used to test the validity of representation of data by the developed equation. Ten sets of hysteresis data were tested. They can be divided into two different studies. The first study compared normal blood from a health human subject and the pathological blood from a diabetic patient. The second study shows the effect of neuraminidase treatment on normal blood. The shear rate ranges of hysteresis loops are 0 to 0.12 sec⁻¹ and 0 to 1.02 sec⁻¹. Results show that our rheological equation gives excellent representations of 10 sets of hysteresis loops with diversified rheological behavior. Therefore the rheological parameters in the equation can be used to compare normal blood behavior with that of pathological and neuraminidase modified bloods. This method of parameter comparison may lead to the detection of serious pathological conditions and be further developed to a clinical test. The method may also monitor the effectiveness of drug treatment to a patient as the patients blood sample rheological parameters return to that of normal healthy human subjects.

This study was undertaken to assess the hemorheological changes due to the presence of malignancy in human subjects and to find the usefulness of the hemorheological changes for the diagnosis and prognosis of malignancy and metastasis. 55 (40 males and 15 females) freshly detected head & neck cancer patients, of age group 30–70 years, were considered for this study. Head and neck cancers are a group of cancers having similar characteristics, hence analysed together. Parameters studied include whole blood viscosity (WBV), plasma viscosity (PV), red cell aggregation (RCA), red cell rigidity (RG), hematocrit (HCT), and concentrations of cholesterol (CHOL), total protein (PRTN), albumin (ALBN), triglyceride (TRG) and fibrinogen (FIBRN) in plasma. 80 (55 males & 25 females) blood samples from age and sex matched normal controls were also analysed for comparison. Cases were divided into two groups. One with moderate whole blood viscosity (Group-I) while the other with high whole blood viscosity (Group-II). The results show that there is significant increase in RCA, PV, RG and FIBRN in cancer patients. It was very interesting to note that in spite of significant elevation of whole blood viscosity in Group-II cases, the hematocrit values were within the normal range. Since HCT is the main factor influencing whole blood viscosity, we suspect the role of some other factor(s) in elevating the WBV. It is likely that tumour cells or their products are present in the blood causing increased WBV. It is also observed that patients with high whole blood viscosity were having the disease at a higher stage (Stage IV).

The aim of the present investigation is to evaluate the measurement of plasma viscosity, carried out by tube capillary viscometer and to compare the results with those of the dynamic apparent viscosity, determined by standardized rotational viscometer. The study was carried out in 28 clinically healthy volunteers. Gravity force capillary viscometers of Ubbelohde type were worked out in the laboratory for the purpose of the study. Simultaneous measurement of plasma viscosity was performed with the rheometer LS 30 Contraves with diameters of cylinders φ₁ = 11 mm, φ₂ = 12 mm, h = 8 mm, and the shear rates varying from 0.017 to 128.5 s⁻¹. All rheological measurements were carried out at 37°C. Certain nonlinearity at the low shear rate range is displayed when the plasma dynamic viscosity is measured by rotational viscometer. The mean plasma viscosity values vary between 3.15 mPa.s at 0.0237 s⁻¹ to 1.34 mPa.s at 128.5 s⁻¹. The mean values of the dynamic plasma viscosity, estimated by capillary viscometer are 1.34 ± 0.05 mPa.s. The viscosity values obtained with the capillary viscometer are slightly lower than those obtained with the Couette viscometer. This phenomenon is probably due to surface adsorbed proteins resulting in spuriously high torque.

In diabetics of type 1 and 2 we examined, in resting white blood cells (WBC), the filtration parameters (Initial Relative Flow Rate - IRFR, Clogging Rate - CR) employing the St. George Filtrometer, the polymorphonuclear cells (PMN) membrane fluidity, the PMN cytosolic Ca²⁺ content and the PMN membrane cholesterol/phospholipid ratio (C/PL). From the obtained data, it is evident that, while the IRFR of unfractionated WBC distinguishes normals from diabetics of type 1 and 2, the filtration parameters of the PMN and mononuclear cells (MN) do not show any significant difference. PMN membrane fluidity, PMN cytosolic Ca²⁺ content and PMN C/PL do not discriminate normals from diabetics of type 1 and 2. No relationship is evident between WBC filtration and metabolic parameters (fasting blood glucose level, serum cholesterol and triglycerides); no correlation is present between PMN filtration parameters, PMN membrane fluidity and PMN metabolic determinants (cytosolic Ca²⁺, C/PL).

Autoregulation is an active adaptive reaction by virtue of which cerebral blood flow remains constant despite variations in perfusion pressure. There exist an inverse relationship between cerebral blood flow and the viscosity of blood. The concept of autoregulatory mechanism for blood viscosity was suggested in the recent past. This autoregulatory mechanism which suffer a loss in ischemic stroke cases is quantitatively presented in the present investigation in terms of power law coefficients namely, n and k, through an empirical relation. Further it is shown that the blood viscosity autoregulation factor (A) in the follow-up stroke cases having no risk factor except age, is restored by seventh day to the range shown for age matched healthy controls. The quantification of already existing concept of blood viscosity autoregulation especially with reference to follow-up stroke cases may help the clinicians understand the relationship between the severity of disease and the extent of alteration in the resistance to the flow of blood. This method of analysis may reveal the action of drugs destroying or restoring the autoregulation in different diseases.

The Authors studied the haemorheological profile and retinopathy in a group of diabetic subjects affected by neuropathic plantar ulcer. The haemorheological evaluation demonstrated that whole blood viscosity (WBV) and red blood cell (RBC) aggregation were significantly increased (p<0.05) in the diabetic subjects with plantar ulcer compared with diabetic patients without this complication. The progression to more severe grades of retinopathy was more frequently observed (p<0.005) in such patients than in the group without plantar ulceration.

RBC deformability of rats for iron deficiency anemia (IDA) with and without sports was measured with Ektacytometry, and it was found that, compared with the normal group, the RBC deformability of IDA group decreased markably and the drop of RBC deformability for IDA with sports even further. A regressive equation between the hemoglobin concentration and RBC deformability was obtained. Results were discussed from a medical sports hemorheological point of view.

We examined the effect of defibrinogenation with batroxobin on the erythrocyte aggregability (RBC-A) in 16 patients with cerebral infarction during the acute phase (less than 72 hours after onset). Eight patients received a single intravenous administration of 10 units of batroxobin (BU), while the other 8 patients received 5 BU. The RBC-A was examined using the whole-blood erythrocyte aggregometer developed by us (Am. J. Physiol. 251, H1205–H1210, 1986) with concomitant measurement of the hematocrit, albumin:globulin ratio and concentration of fibrinogen. The RBC-A values before, and at 1,2, and 7 days after 10 BU administration were 0.154±0.017/s, 0.117±0.029/s (76% of the value before the administration, P<0.01), 0.105±0.029/s (68%, P<0.01), and 0.124±0.015/s (81%, P<0.01), respectively. The fibrinogen concentrations before, and at 1, 2, and 7 days after the batroxobin were 364±81 mg/dl, 150±35 mg/dl (41%, P<0.01), 129±35 mg/dl (35%, P<0.01), and 211±42 mg/dl (58%, P<0.01), respectively. On the other hand, the RBC-A values before, and at 1, 2, and 7 days after 5 BU administration were 0.143±0.021/s, 0.131±0.036/s, 0.130±0.028/s, and 0.141±0.029/s, respectively. The fibrinogen concentrations before, and at 1, 2, and 7 days after the batroxobin were 318±57 mg/dl, 255±60 mg/dl (80%, P<0.01), 259±68 mg/dl (81%, P<0.01), and 319±87 mg/dl, respectively. We conclude that a single intravenous administration of batroxobin at 10 BU reduced the RBC-A in patients with cerebral infarction during the acute phase in accordance with a decrease in the fibrinogen level. The effect appeared to last for more than 7 days.

Tissue hematocrit was determined in left ventricular myocardium slices in in situ frozen rat hearts and the influence of experimental plasma fibrinogen increments was investigated. Hematocrit values in 100 μm thick myocardial slices were estimated by measuring the activity of two different radionuclides labelling plasma (¹²⁵I-Albumin) and red blood cells (^99mTc). In the control group with physiological levels of fibrinogen, myocardial tissue hematocrit was highest at the layer adjacent to epicardium. It decreased linearly through the depth of myocardium, approaching a minimum at the myocardial layer closest to the endocardium. In the group with about two folds higher plasma fibrinogen concentration, plasma viscosity and red blood cell aggregation were about 50% higher. In this group, tissue hematocrit difference between epicardial and endocardial layers existed, however this difference was more likely due to a step change, rather than a linear gradient. These findings confirm those physiological mechanisms underlying the hematocrit reduction in small blood vessels might be affected by hemorheological alterations.

Treatment of human erythrocytes with micromolar concentrations of tert-butyl hydroperoxide causes changes in the physical properties of the cells as evidenced by decreased deformability. The deformability changes followed a lag period which was reciprocally related to the concentrations of hydroperoxide. Ascorbic acid was able to delay these changes or reverse them for a period of time. Oxidation of ascorbic acid was observed, under the same conditions, which was correlated to the ability of both oxy- and met-forms of haemoglobin to catalyse the oxidation of ascorbic acid by tert-butyl hydroperoxide. It seems likely that ascorbic acid acts both as inhibitor of the oxidative activation of haemoglobin, which leads to deformability changes and as substrate for the haemoglobin catalysed tert-butyl hydroperoxide decomposition.