Clinical Hemorheology and Microcirculation

Blood viscosity factors and fetal erythrocyte aggregability were investigated with light transmission (Myrenne device) during a cross‐sectional study of blood drawn in utero by cord venepunctures in 119 normal fetuses between 18 and 39 weeks gestation. There was a progressive increased blood viscosity at native hematocrit ( p<{} 0.01) explained by a gradual increase in both hematocrit (from 33% to 40%, p<{} 0.05) and Dintenfass’ ‘Tk’ RBC rigidity index ( p<{} 0.05), while plasma viscosity remained constant at 1.18 ± 0.01 mPa.s as well as the h/&eegr; ratio &lpar;188.4 &plusmn; 2.7 mPa<formula>^{-1} .s ^{-1} ). The RBC aggregation index ‘M’ remained almost equal to zero (mean value: 0.04 ± 0.01) before 32 wk gestation and then increased ( p<{} 0.05) until delivery. The upper physiological limit for this parameter before 32 wk (mean ± 2 SD) is 0.18. The RBC aggregation index ‘M1’ remained constant during pregnancy at 2.98 ± 0.26, i.e., the upper physiological limit for this parameter during the intrauterine life (mean ± 2 SD) is 7.85. Both fibrinogen ( r={} 0.479, p<{} 0.05) and albumin ( r={} 0.494, p<{} 0.01) correlated with time so that the albumin/fibrinogen ratio remained stable. We then studied with the laser retrodiffusion technique the venous blood of 20 women (18–43 yr, 37–40 wk gestation) and the cord blood of their newborns at birth, comparing RBC aggregation of: mothers (M), maternal RBCs resuspended on newborn plasma (MF), newborn RBCs resuspended on maternal plasma (FM), and newborns (F). Aggregability is higher in M (RBC aggregation time M {}<{} MF {}<{} FM {}<{} F; p<{} 0.01); RBC aggregation index at 10 s M {}>{} MF {}>{} FM {}>{} F; p<{} 0.01), with in turn the symmetric inverse picture for the partial disaggregation threshold (M {}>{} MF {}={} FM {}>{} F). Thus RBC disaggregability is higher in newborns, and suspensions on maternal and newborn plasma suggest that half of this difference in aggregability (and disaggregability) between fetal and adult blood results from plasma factors and another half from erythrocytes.

In order to further characterize the alterations of erythrocyte aggregation described in ovarian cancer, we measured it with laser backscattering in eleven women suffering from ovarian cancer (mean age: 44.7 ± 3.6, extreme values: 28–61 yr) compared with thirteen matched control women. Blood rheology exhibited a wide variability in cancer patients, with some unusually high values of plasma viscosity and/or RBC aggregation in individual cases. The only significant differences were found for the RBC disaggregation threshold which was higher in patients than in controls (78.06 ± 10.14 vs 52.6 ± 3.15 s ^{-1} , p<{} 0.05), while hematocrit was lower (34.45 ± 1.42 vs 38.23 ± 0.75, p<{} 0.05). A negative correlation between hematocrit and corrected blood viscosity on the whole sample of subjects ( r={} 0.454, p<{} 0.05) indicates that hematocrit is decreased in subjects prone to high viscosity, resulting in similar values of apparent blood viscosity in controls and patients. Thus, a lower disaggregability of RBCs is evidenced in women with ovarian cancer, as well as a tendency to blood hyperviscosity compensated by a reduction of hematocrit which suggests that there may be some degree of ‘viscoregulation’.

Since oral contraceptives (OC) are known to impair blood fluidity and to increase the risk of venous and arterial thrombosis, while acetylsalicylic acid (ASA) decreases the thrombotic risk and modifies some rheologic parameters, we compared the hemorheologic effects of ASA on blood rheology between women treated by OC and women who never received this medication. 25 women under OC were compared to 25 matched women who had never used OC. Blood viscosity (MT90 viscometer) and RBC aggregation (Myrenne aggregometer and AFFIBIO erythroaggregometer) were measured before and 1 hr after women received per os 100 mg ASA, after an overnight fast. The only significant difference between women under OC and controls was an increased RBC aggregation (‘M’ index + 28%, p<{} 0.04; Affibio aggregation time - 21%, p<{} 0.03). On the whole sample of 50 women as well as in the subgroup of women under OC, ASA decreased RBC partial disaggregation threshold ( - 1.7%, p<{} 0.01). These results confirm that RBC aggregation is increased under OC and suggest that 100 mg ASA acutely induces a partial reversal of this RBC hyperaggregation.

In cancer patients impaired blood rheology in the presence of coagulation activation may reduce blood flow in the vascular microcirculation that favors thrombosis but may also support tumor progression and metastasis. In 451 patients with gynecological cancer and 177 patients with corresponding benign tumor disease preoperatively, during adjuvant treatment, when venous thrombosis (VT) or cancer progression was diagnosed hematocrit (micro centrifuge), hemoglobin, leukocytes, platelets (Coulter Counter); red blood cell (RBC) aggregation (aggr.) during stasis and low shear conditions (MA 1, Myrenne), plasma viscosity (viscosimeter KSPV 1 Fresenius), and fibrinogen (Multifibren Behring Dade) were investigated. One hundred and twelve healthy women served as controls. Preoperatively, mean plasma viscosity (pv) was significantly higher in cancer patients as compared to patients with the corresponding benign tumor disease (breast cancer: n={} 261; pv {}={} 1.32 vs. 1.27 mPa s; p={} 0.023; ovarian cancer: n={} 68; pv {}={} 1.39 vs. 1.31 mPa s; p<{} 0.001; endometrial cancer: n={} 70; pv {}={} 1.37 vs. 1.25 mPa s; p<{} 0.001; cervical cancer: n={} 52; pv = 1.33 vs. 1.26 mPa s; p={} 0.004). RBC aggr. was significantly lower in controls compared to the preoperative values in cancer patients but mean (median) values (RBC aggr. stasis < 21) were within the normal range in all. Preoperatively, plasma viscosity was a significant risk factor for the overall survival in ovarian cancer patients ( p={} 0.02) and for subsequent thrombosis in ovarian ( p={} 0.02) and cervical cancer patients ( p={} 0.007). In the multivariate analysis plasma viscosity was an independent prognostic marker for the overall survival of breast cancer patients ( r={} 99.45; 95% CI: 7.32–980.2; p<{} 0.0001). An optimized preoperative cut‐off value above 1.40 mPa s (Log‐Rank‐test) was significantly associated with poor outcome in the Kaplan–Mayer survival estimates, even in node‐negative breast cancer.

In gynecologic cancer patients the combination of an increase in RBC aggregation and plasma viscosity impairs blood‐flow‐properties and may induce hypoxia in the microcirculation that favors thrombosis, settlement of tumor‐cells and thus metastasis. Improvement of blood fluidity and thus oxygen transfer in the tumor‐vascular‐microcirculation may increase susceptibility of systemic anti‐cancer therapy.

X‐ray irradiation of blood is an effective way to prevent transfusion‐associated graft‐versus‐host disease. Red blood cells (RBCs) from normal donors suspended in mannitol‐adenine‐phosphate (MAP) medium were irradiated with X‐ray of 15 and 35 Gy in minimum dose. The change of deformability of the RBCs during storage at 4°C for 4 weeks was examined under shear stress of 13–130 dyn/cm ^2 using a rheoscope, in relation to the hematological and biochemical properties. (1) The deformability of RBCs was decreased during the storage, and it was further decreased by the irradiation. In addition, the number of undeformable RBCs against a given shear stress increased after the irradiation. (2) The cell volume gradually decreased, while the intracellular hemoglobin concentration increased. These changes were accelerated by the irradiation. The echinocytic transformation during the storage was not accelerated by the irradiation. (3) The content of aggregated proteins reducible with beta‐mercaptoethanol in RBC membrane increased during the storage, but was not increased by the irradiation. Membrane lipid peroxidation was not increased during the storage and by the irradiation. (4) Leakage of potassium ions from RBCs during the storage was accelerated by the irradiation. In conclusion, shear‐induced deformation of RBCs stored in MAP medium was impaired by X‐ray irradiation, mainly due to dehydration caused by excess leakage of potassium ions from RBCs.

Erythrocyte aggregation was determined by a novel method enabling the quantification of the aggregation process in whole blood. Blood samples of 47 healthy pregnant women and 39 preeclamptic patients were examined. Subjects within each group were matched for the gestational age. It was found that RBC aggregation increases with the gestational age in healthy pregnancy and further increases in preeclampsia. Addition of low‐molecular weight dextran (MW = 9300) to blood samples of both healthy pregnant women and preeclamptic patients reduces RBC aggregation in a concentration‐dependent manner. The obtained results indicate alterations in plasma composition as the primary factor for the increased RBC aggregation in both normal and pathological pregnancy. It is suggested that adsorption of low‐molecular weight dextran on the RBC membrane reduces the surface concentration of plasma bridging molecules thereby reducing RBC aggregation toward normal.

Experimental evidences underline that hemorheological alterations observed in acute myocardial infarction (AMI) are strictly involved in the decreased perfusion of the damaged area and in the extension of the necrotic regions. We have analyzed whole blood filterability as an index of erythrocyte deformability in 60 AMI patients compared with 30 patients with non‐acute coronary artery disease and 52 healthy subjects.

Nucleopore polycarbonate membranes with a pore diameter of 5 µm and a filtering pressure of -20 cm H _2 O were used. The results are expressed as the volume of whole blood filtered in 1 minute (index of filterability, IF). In normal subjects IF was 1.16 ± 0.24. Among AMI patients IF was 0.70 ± 0.30 at admission, 0.68 ± 017 at day 10 and 0.78 ± 0.14 at day 20. These values were significantly lower than those obtained in normal subjects and in patients with non‐acute coronary artery disease. In addition, AMI patients treated with thrombolytic therapy showed, at admission, a significantly higher IF value than that obtained in patients who did not receive thrombolytic treatment (0.85 ± 0.34 vs 0.60 ± 0.22; p<{} 0.01). These results demonstrate an evident reduction of whole blood filterability in AMI patients that may be considered as an index of erythrocyte deformability. Thrombolytic therapy seems to have a positive effect on blood filterability and may produce beneficial effects through its therapeutical action other than the lysis of the coronary thrombus.

Rat red blood cells (RBC) exhibit low aggregation tendency in autologous plasma and in standard aggregating media (e.g., 3% Dextran 70; MW: 70 kD). In experimental studies performed on rats, 3% Dextran 70 was found to be an unsuitable suspending medium to test the “aggregability” of RBC in a standard medium. It has been observed that solutions of higher molecular weight polymers (i.e., dextran, MW: 500 kD; polyethylene glycole, MW: 35 kD; polyvinylpyrrolidone, MW: 360 kD), at low concentrations were strong aggregators for rat RBC. Among these polymer solutions 0.5% Dextran 500 and 0.75% polyvinylpyrrolidone 360 were found to be the most suitable suspending media, to distinguish between the aggregability of RBC from septic and control rats. Therefore, these two polymer solutions are recommended as the standard aggregating media for rat RBC, to test the RBC aggregability.