[Determination of reference ranges of rheologic parameters: study of 653 randomly selected probands of the Aachen district]

Examination of the relation between red blood cell aggregation and hematocrit in human and various experimental animals

BACKGROUND

Red blood cell (RBC) aggregation plays an important role in the physiological processes of the microcirculation. The complete mechanism of aggregation is still unclear, and it is influenced by several cellular and plasmatic factors. One of these factors is the hematocrit (Hct).

OBJECTIVE

We hypothesized that the relation of RBC aggregation and Hct differs between species.

METHODS

From anticoagulated blood samples of healthy volunteers, rats, dogs, and pigs, 20, 40, and 60 %Hct RBC, autologous plasma suspensions were prepared. Hematological parameters and RBC aggregation was determined by light-transmission and light-reflection method.

RESULTS

Suspensions at 20%and 60%Hct expressed lower RBC aggregation than of 40%Hct suspensions, showing inter-species differences. By curve fitting the Hct at the highest aggregation value differed in species (human: 45.25%- M 5 s, 40.86%- amp; rat: 44.44 %- M1 10 s, 39.37%- amp; dog: 42.48%- M 5 s, 44.29%- amp; pig: 47.63%- M 5 s, 52.8%- amp).

CONCLUSION

RBC aggregation - hematocrit relation shows inter-species differences. Human blood was found to be the most sensitive for hematocrit changes. The more obvious differences could be detected by M 5 s by light-transmission method and amplitude parameter using light-reflection method.

Monitoring of Rheologic Variables During Postoperative High-Dose Brachytherapy for Uterine Cancer

Oxygenation of tumor tissue has recently been assed an important prerequisite for the effectiveness of radiotherapy in cervical cancer. Hyperviscosity is a common phenomenon in malignancy and a cause of reduced oxygen transport capacity that would favour tissue hypoxia. Hemorheological variables were serially tested preoperatively, during four cycles of fractionated adjuvant IR192 HDR after loading radiation (HDR-AL) of the vaginal vault (weekly intervals), and 6 months postoperatively in patients with cervical (n=12) and endometrial cancer (n=26). Women who were scheduled for benign tumor surgery served as controls (n=29). Preoperatively, in cervical and endometrial cancer patients, mean plasma viscosity (PV: 1.31±0.1 mPa s; p<0.05; 1.35±0.13 mPa s; p<0.001) and fibrinogen levels (383±46 mg/dL; p<0.05; 379±117 mg/dL; p<0.05) were higher as compared to the controls (1.25±0.07 mPa s; 314±89 mg/dL). Red blood cell aggregation at low shear and stasis (RBC agg.: 15.7±5.6; p<0.05; 29.6±9.1; p<0.05) was higher in endome-trial cancer patients as compared to the controls (13.7±3.4; 25.3±5.6). Postoperatively PV decreased in endometrial cancer patients and transiently increased in cervical cancer patients. After the third session of irradiation in both cancer groups, PV regained and at the 6-month checkup, levels were higher as compared to the values before surgery. Postoperatively fibrinogen levels increased and remained higher throughout HDR-AL and 6 months postoperatively. After surgery and during irradiation, anemia persisted in both cancer groups while hematocrit recovered after 6 months in endometrial cancer patients. Thrombosis was diagnosed in three patients postoperatively (7.9%) but in none during HDR-AL. While a temporary reduction of hyperviscosity is found postoperatively and during HDRAL in uterine cancer patients, 6 months after surgery RBC aggregation, PV, and hematocrit returned to the pretreatment range.

Measurement of plasma viscosity by free oscillation rheometry: imprecision, sample stability and establishment of a new reference range

BACKGROUND

Plasma viscosity (PV) is used in the investigation of hyperviscosity syndrome. We have evaluated the performance of a new bench-top free oscillation rheometer, ReoRox from Medirox, and established a new reference range.

METHODS

Performance of the free oscillation rheometry (FOR) method was evaluated examining within-run and between-run imprecision, duration of measurement and operator simplicity. Furthermore, influence of storage on the PV measurements was assessed and a reference range based on plasma from 585 healthy men and women was established.

RESULTS

Imprecision of the free oscillation rheometer was comparable to other viscometers and performance of the instrument was satisfying. The non-parametrical reference range established was 1.22-1.44 mPa s at 37℃ (2.5th and 97.5th percentiles).

CONCLUSIONS

We have established a FOR PV reference range to support clinical decision-making. Furthermore, we found high pre-analytical stability of the samples and an analytical imprecision comparable to other PV methods.

Blood rheology during chemotherapy in patients with ovarian cancer

The use of platinum based chemotherapy in ovarian malignancy and other cancer types is known to be associated with deep vein thrombosis. In a prospective study of 47 patients with ovarian cancer of International Federation of Gynecology and Obstetrics stage Ib-IV, serial rheological parameters were determined (plasma viscosity, red blood cell aggregation under conditions of stasis and low shear) in addition to hemoglobin, hematocrit, leukocytes, platelets, and fibrinogen. At the same time the incidence of deep vein thrombosis was recorded before, during six cycles of first line cisplatinum/epirubicin/cyclophosphamide chemotherapy, and 2 months thereafter (two-months check-up). Only six patients with previous deep vein thrombosis concomitantly received thrombosis prophylaxis once with 3000 anti Xa Units/day subcutaneously low molecular weight heparin (Certoparin, NOVARTIS) throughout chemotherapy. Before each cycle of chemotherapy impedance plethysmography was used for deep vein thrombosis screening and when this was suspected on the basis of physical examination or a pathological result of impedance plethysmography, ascending venography of both legs was performed. During chemotherapy, the venographically proven deep vein thrombosis incidence was 10.6%; (95% CI: 3.5-23.1) with no differences in occurrence between FIGO stages. Before operation mean plasma viscosity was higher in patients who developed deep vein thrombosis postoperatively (n = 5; 1.46 +/- 0.2 mPas) and during chemotherapy (n = 5; 1.49 +/- 0.1 mPas) as compared to those without deep vein thrombosis (1.38 +/- 0.2 mPas; p = 0.04). Postoperatively (before chemotherapy) none of the rheological variables were significantly different in patients with versus those without deep vein thrombosis during chemotherapy. Leukocyte and platelet counts decreased significantly during chemotherapy until the two-months check-up after chemotherapy while red blood cell aggregation (stasis & low shear), hemoglobin, and hematocrit showed a continuous but nonsignificant increase. The mean plasma viscosity, instead, declined into the normal range after the 4th cycle of chemotherapy (1.33 +/- 0.1 mPas) in patients without thrombosis. In contrast, mean plasma viscosity was increased to 1.48 +/- 0.1 mPas at the time of deep vein thrombosis diagnosis during chemotherapy. In the ovarian cancer patients of this study, the development of deep vein thrombosis postoperatively and during chemotherapy was associated with a hematocrit-independent increase in blood viscosity characterized by a high plasma viscosity and normal or low hematocrit, which was present before primary surgery as well as at the time of deep vein thrombosis diagnosis.

Hyperviscosity syndrome in patients with ovarian carcinoma

BACKGROUND

In patients with ovarian carcinoma, an hematocrit-independent hyperviscosity syndrome is often present. The syndrome is characterized by normal or low hematocrit and hemoglobin concentration, an elevated platelet count, and an increase in clotting factor turnover. Because deep vein thrombosis (DVT) often complicates the course of ovarian carcinoma, the aim of this study was to investigate the possible association of hyperviscosity syndrome with the development of DVT.

METHODS

Rheologic estimations of the blood included red blood cell (RBC) aggregation (stasis and low shear), plasma viscosity (pv), blood cell count, and fibrinogen, which were performed before primary surgery and the beginning of perioperative heparin thrombosis prophylaxis on 63 of 65 patients with Stage I-IV ovarian malignancy (according to the staging criteria of the International Federation of Gynecology and Obstetrics). Two patients who had had DVT 5-6 weeks in advance of the study were excluded from rheologic calculations. Thrombosis screening by impedance plethysmography was performed the day before primary major surgery; postoperatively on Days 1, 3, 5, 7, and 10; before each of 6 cycles of chemotherapy (once every 3 weeks); and thereafter once every 3 months during follow-up. All blood tests were also performed on 72 healthy women and 29 patients with benign ovarian tumor the day prior to surgery.

RESULTS

All ovarian carcinoma patients, including 7 patients with tumors of low malignant potential, were eligible for surgery, and all except those with Stage IV disease (n = 12) were macroscopically tumor free after surgery. Before surgery, RBC aggregation, pv, and platelet and fibrinogen concentrations were significantly higher (P < 0.05) in cancer patients than in either of the control groups, whereas hemoglobin (hb) and hematocrit (hct) were significantly lower in cancer patients than in healthy women (P < 0.001). Platelet, leukocyte, and fibrinogen concentrations were significantly correlated to disease stage, whereas pv, RBC aggregation, hb, and hct were not. The preoperative pv was significantly higher in patients who later developed DVT (n = 17; 1.46+/-0.13 mPas; P = 0.01) than in those who did not (1.34+/-0.14 mPas). Of all estimated preoperative variables, only pv was a significant risk factor for postoperative and subsequent DVT (RR: 29.84; 95% CI: 1.076-827.16; P = 0.04).

CONCLUSIONS

Our results confirm the presence of a hematocrit- and stage-independent hyperviscosity syndrome in untreated ovarian carcinoma patients. In addition, a high preoperative plasma viscosity was a significant risk factor for the development of DVT in the postoperative period and even thereafter.

Haemorheology in patients with branch retinal vein occlusion with and without risk factors

PURPOSE

The study was carried out to ascertain the role of blood viscosity in patients with branch retinal vein occlusion (BRVO) with and without risk factors.

METHODS

In 292 patients with acute BRVO (mean age 65 +/- 10 years) and 292 controls matched for gender, age, and cardiovascular risk factors, haematocrit, plasma viscosity, erythrocyte aggregation and erythrocyte rigidity were measured. A subgroup analysis in patients with and without risk factors was performed.

RESULTS

Haematocrit and plasma viscosity values were significantly higher in BRVO patients than in controls, but erythrocyte rigidity and erythrocyte aggregation did not differ. Subgroup analysis revealed no differences in haematocrit and plasma viscosity values between patients with and those without cardiovascular risk factors.

CONCLUSIONS

This study shows increased plasma viscosity and haematocrit values in patients with BRVO which are not associated with the presence of other cardiovascular risk factors. Thus, changes in blood fluidity appear to be important factors in the pathogenesis of BRVO.

Role of rheologic factors in patients with acute central retinal vein occlusion

PURPOSE

To assess the rheologic findings in acute central retinal vein occlusion (CRVO) with respect to associated risk factors, the clinical appearance of ischemic or nonischemic CRVO, and to elucidate the etiology of possible changes.

METHODS

The authors enrolled 173 patients with acute CRVO (ischemic, 33%; nonischemic, 67%) in this prospective study. One hundred seventy-three patients who were matched for age, sex, and cardiovascular risk factors served as control subjects. All patients underwent testing to determine hematocrit values, plasma viscosity (PV), erythrocyte aggregation (SEA), and erythrocyte rigidity (SER).

RESULTS

Hemocrit values and PV were increased significantly (P<0.01) in patients with ischemic and nonischemic CRVO compared with control subjects but did not differ significantly between the two groups. No significant differences were found in SEA and SER values between the clinical subsets of patients with CRVO and when the patients were compared with matched control subjects. Analysis revealed that hemocrit and PV values were (P<0.001) increased significantly independent of associated cardiovascular risk factors.

CONCLUSION

These results suggest that increased hemocrit and PV values may be contributing factors in the pathogenesis of CRVO.

Hemodilution therapy in central retinal vein occlusion. One-year results of a prospective randomized study

Systemic hemorheologic abnormalities may play a part in the pathogenesis of central retinal vein occlusions. A statistically significant elevation of plasma viscosity was found in patients with acute central retinal vein occlusion compared with control patients. Local retinal blood flow parameters including arteriovenous passage time and mean arterial dye bolus velocity were significantly altered in the central retinal vein occlusion patients compared with age-matched controls at baseline examination. We performed a randomized, prospective, single-blind clinical investigation to determine the effect of hemorheological manipulation on the clinical course and retinal blood flow of eyes with central vein occlusion. Hemodilution included plasma expansion with hydroxyethyl-starch, withdrawal of whole blood if the hematocrit was above 42%, and rheologic manipulation with parenteral pentoxifylline. We found a statistically significant improvement in visual acuity at 1 year post-treatment for the treated group compared with the control group (increase of visual acuity of 1.5 lines vs decrease of 1.5 lines). The retinal blood flow parameters were markedly improved soon after the institution of therapy, and this may have contributed to the improvement in visual acuity in the treated group. There was no statistically significant difference between the two groups in the progression to ischemic central vein occlusion.

Haemorheological parameters in patients with retinal artery occlusion and anterior ischaemic optic neuropathy

The haemorheological parameters haematocrit (Hct), plasma viscosity (PV), red cell aggregation (RCA), red cell filterability (RCF), apparent whole blood viscosity (WBV), and fibrinogen were measured in 31 patients with retinal artery occlusion (RAO), 25 patients with anterior ischaemic optic neuropathy (AION), and 19 patients with giant cell arteritis (GCA). The patient groups were compared with controls of same age and similar prevalence of cardiovascular risk factors. Patients with RAO and AION have a significantly decreased RCF in comparison with controls. All other parameters showed no differences. Patients with GCA had significantly decreased Hct and RCF and increased PV and fibrinogen. After 2 weeks of systemic treatment with high dose steroids in patients with GCA the plasma viscosity had returned to normal and was even lower than in controls, and the Hct and fibrinogen had reached normal levels.

[Variance, factors of influence and clinical relevance of plasma viscosity]

The problem of measuring plasma viscosity has been solved through the use of capillary and falling-ball viscosimeters which have a determination variance of less than 1%. On account of the influence of overeating, forced thirst, psychological and physical stress plasma viscosity should be determined in the morning; the patient should be fasting and well hydrated. Plasma viscosity is influenced by diseases with alterated plasma protein composition. An elevated viscosity also significantly increases the risk of developing an arterial occlusion. Since the physician can both decrease and increase plasma viscosity, it should be determined parallel to therapy. Accordingly, plasma viscosity is one of the most important rheological parameters.

Haemorheological changes in patients with retinal vein occlusion after isovolaemic haemodilution

In 83 patients with central retinal vein occlusion and branch vein occlusion we measured the haematocrit (HCT), plasma viscosity (PV), red cell aggregation (RCA), red cell filterability (RCF) and apparent whole blood viscosity (WBV). A control group (n = 41) was matched for sex, age, and cardiovascular risk factors. Measurements were performed before and after treatment with isovolaemic haemodilution (IHD). We found no significant differences between patients with retinal vein occlusion (RVO) and control subjects in haematocrit, plasma viscosity, red cell aggregation, and red cell filterability and no increased whole blood viscosity in the patient group. Patients with ischaemic retinal vein occlusion and non-ischaemic retinal vein occlusion did not show different haemorheological parameters either. After treatment with haemodilution, only the haematocrit and whole blood viscosity were significantly decreased, and there were no changes in plasma viscosity, red cell aggregation or red cell filterability.

[The clinical rheological laboratory]

To quantify the fluidity of blood it is not suitable to measure whole blood viscosity as blood is no Newton's fluid. For this reason, it is necessary to measure characteristic blood flow parameters direct. This study presents methods of measurement for plasma viscosity, haematocrit, thrombocyte aggregation, erythrocyte rigidity, erythrocyte aggregation and leukocyte adhesivity.

Abnormal hemorheological parameters in vertebrobasilar-insufficiency

Thirty-seven patients, aged 47 +/- 22 years, diagnosed suffering from vertebrobasilar insufficiency (VBI), underwent a hemorheological examination; 20% of these patients had no vascular risk-factor but none showed complete normal hemorheological findings. The distribution of hemorheological parameters was comparable to those in patients suffering from stroke or TIA. Abnormal were platelet-reactivity in 78%, plasma-viscosity in 57%, fibrinogen in 23%, red-blood-cell-aggregation in 13% and hematocrit in 11% of all cases. To obtain more information on how to classify common clinical symptoms i.e. headache in combination with vertigo it may be useful to introduce hemorheological parameters as platelet-reactivity, plasma-viscosity, fibrinogen, in the further laboratory examination of those patients.

Haemodilution with medium molecular weight hydroxyethyl starch in patients with peripheral arterial occlusive disease stage IIb

The basic therapy of peripheral arterial occlusive disease stage IIb, according to Fontaine, is exercise. It should be determined whether a mild hypervolaemic haemodilution with hydroxyethyl starch or Ringer lactate can produce a further increase in walking distance. For this purpose, three groups of 25 patients each were formed. One group exercised three times weekly and the second group, in addition to exercise, underwent a mild hypervolaemic to isovolaemic dilution therapy with HES for a period of 6 weeks. In the final group the haematocrit was reduced to the same extent by venesections and volume substitution using Ringer lactate. The walking distance in the HES group increased from 216 m to 311 m (44%), in the Ringer lactate group from 214 m to 258 m (20%), and in the exercise group from 213 m to 242 m (14%). On comparison of the groups, the increase in pain-free walking distance in the HES group differs significantly (P less than 0.05) from that achieved in the other groups. It was demonstrated that haemodilution with HES in combination with exercise brings about a clinical effect three times that achieved by exercise alone. Venesection with subsequent administration of Ringer lactate and exercise is superior to exercise alone but markedly inferior to the combination therapy with HES.

Effect of gemfibrozil on erythrocyte membrane lipids in geriatric patients

Twenty geriatric patients with primary or secondary hyperlipidemia and suffering from various other diseases received for three weeks once daily 900 mg gemfibrozil. The hyperlipidemia had not been treated before, and a cholesterol-reduced diet did not succeed in lowering total cholesterol below 6.75 mmol/l (260 mg/100 ml) and serum triglycerides below 1.97 mmol/l (175 mg/100 ml). The purpose of this study was to analyze the lipid composition of the erythrocyte membrane, serum lipids and rheological parameters before and after the therapy. Mean serum total cholesterol and triglyceride content decreased significantly by 16.3% (p less than 0.05) and 35.2% (p less than 0.01) on average, respectively. Aggregation of thrombocytes and of erythrocytes, thrombin time and partial thromboplastin time slightly varied during the three weeks' treatment, but without statistical significance. The content of total long-chain saturated fatty acids in the phospholipid fraction of the erythrocyte membrane decreased slightly from 41.3% to 40.9% (p less than 0.05), whereas the total w6-unsaturated fatty acids without the precursor linoleic acid increased by about the same extent from 15.66% to 16.0% (p less than 0.05). The molar ratio of phospholipid to cholesterol content decreased significantly (p less than 0.01) due to a reduced phospholipid content at the end of the therapy. In conclusion, in addition to reducing the serum lipids, gemfibrozil slightly effects the lipid composition of erythrocytes, but the effects of the varied concentrations of long-chain saturated and long-chain w6-unsaturated fatty acids in the phospholipid fraction on membrane fluidity might be compensated, at least partly, by the decrease of the ratio of membrane phospholipid to cholesterol.

Modern strategies for treatment of acute myocardial infarction: significance of haemostaseological and rheological findings

In spite of equivalent clinical efficacy of various thrombolytic agents for the treatment of acute myocardial infarction there is evidence of different drug-depending influences on the haemostatic and fibrinolytic system. In the present study 40 patients with acute myocardial infarction have been investigated. 20 patients received 750,000 and 1.5 mio U streptokinase (SK), respectively, 10 patients 30 mg anisoylated plasminogen streptokinase activator complex (BRL 26921) and 10 patients a combination of 200,000 U urokinase (UK) and 4.5 mio U pro-urokinase (PUK) as a short-term intravenous treatment. Reperfusion of coronary arteries has been achieved in 70 to 100 percent. Major not fatal bleedings occurred in 2 patients. One patient died within 72 hours after beginning of the myocardial infarction. The longest duration of fibrinolytic activity was observed in the BRL 26921 group (half-disappearance time close to 2 h). It was significantly shorter in the SK groups showing a dose-dependency. Plasma concentration of fibrinogen dropped beyond normal levels following SK and BRL 26921, but not under UK/PUK. Plasma viscosity correlated with fibrinogen decrease and displayed a dose-depending relationship with the presence of SK. Haemorheological effects are suggested to be important for the clinical efficacy of thrombolytic therapy in myocardial infarction.

Hemorheological parameters in patients with gynecologic malignancies

Thromboembolic events account for a significant number of complications during surgical and chemotherapeutic treatment for gynecologic malignancies. Besides changes in the hemostatic system, changes in hemorheological parameters facilitate initiation and promotion of thrombotic disease. We used a rheoaggregometer to determine erythrocyte aggregation and a capillary viscosimeter to evaluate plasma viscosity in patients with gynecologic malignancies at the time of primary diagnosis and during follow-up and compared the results to those for a normal control group. We found a significant elevation in plasma viscosity and erythrocyte aggregation as well as in fibrinogen and globulin concentrations in cancer patients. The extent of this rise was related to the tumor volume. Treatment with cisplatin, doxorubicin, and cyclophosphamide resulted in a further rise in erythrocyte aggregation which is attributed to a direct effect on the erythrocyte membrane. Thus, additional factors contributing to the risk of thrombosis in these patients were defined. Additional administration of rheologically active agents might improve the results of thrombosis prophylaxis.

Influence of the red blood cell Ca2+-ion concentration on the erythrocyte aggregation in stasis

Ca2+ ions were transported into the cell by incubation of the erythrocyte suspension with ionophore A23187, a lipophil electric neutral ion complexing substance. Erythrocyte aggregation could be increased twice, when doubling the intracellular Ca2+-ion concentration. Our measurements lead to the suggestion that an increase of the cytoplasmatic Ca2+ ion changes the physical and/or biochemical properties of the aggregation receptors on the membrane surface, i.e., cell-protein interactions are regulated by alteration of the intracellular Ca2+-ion concentration.

Effects of enzymatic blood defibrination in subcortical arteriosclerotic encephalopathy

Plasma hyperviscosity is a striking abnormality in patients suffering from subcortical arteriosclerotic encephalopathy (SAE) and is thought to perpetuate the chronic ischaemic demyelinating process of the periventricular white matter. Ancrod, a defibrinating enzyme, was given to 10 patients with SAE in an attempt to reduce plasma fibrinogen, which would thus normalise hyperviscosity. This was paralleled by a significant improvement of the initially abnormal retinal arteriovenous passage time, as well as a significant augmentation of the CO2-induced cerebral vasomotor response. This did not lead, however, to any clinical improvement with respect to performance of neuropsychological tests, recurrences of strokes during a 6 month observation period or improvement of various audiological parameters. The findings indicate that hyperviscosity in patients with SAE is merely an epiphenomenon. A potentially reversible, chronic penumbral state of the brain tissue apparently does not exist in SAE.

Hemorheologic variables in breast cancer patients at the time of diagnosis and during treatment

The increased risk of thrombosis seen in patients with malignancy also was recently confirmed in breast cancer patients undergoing hormonal or chemotherapeutic treatment. Besides changes within the coagulation system, alterations of hemorheologic variables have been implicated in the genesis of thrombosis. We evaluated plasma viscosity, erythrocyte aggregation, fibrinogen level, sedimentation rate, hematocrit concentration, and protein concentration in patients with breast cancer at the time of primary diagnosis and during follow-up with or without treatment. We then compared the results to a control group without malignant or infectious disease. Plasma viscosity and erythrocyte aggregation were significantly higher in patients with malignant disease, with a further increase at the time of dissemination. Plasma fibrinogen level was significantly higher only at the time of dissemination. The influence of therapy on hemorheologic variables was minor. Tumor volume was the most important factor. As individual values vary considerably and form a continuous spectrum, no cutoff line between normal and pathologic values can be defined. However, high values should induce further measures to diagnose metastatic disease. Second, these factors could explain the relative inefficiency of thrombosis prophylaxis in this patient group and suggest the addition of rheologically active drugs to the treatment regimen.

[Bag plasmapheresis in patients with stage IIb peripheral arterial occlusive disease]

The clinical effect of bag-plasmapheresis was investigated in 60 patients with peripheral arterial occlusive disease stage II according to Fontaine. The initial number of patients was subdivided in three groups of 20 individuals using a randomised double-blind placebo-controlled design. Each patient gave 300 ml of blood twice a week for a 6 week duration. Blood plasma was separated in two groups and replaced with Hydroxyethyl-starch (200/0.5 10%) in group 1 and with Laevulose 5% in group 2. Patients in group 3 received their whole blood without any processing. All patients had to undergo a physical training of 45 minutes three times a week. The group who received Hydroxyethylstarch presented a 20% increase in walking distance whereas the increase in the Laevulose group was 5% and approximately 1% in the group receiving whole blood. The increase in walking distance in the Hydroxyethylstarch-group was significant on the 0.1%-level and significantly better than the improvement in walking distance of the other groups. Additionally in this group plasma viscosity showed a 3% decrease, erythrocyte aggregation was reduced by 10%. Results in the Laevulose group were only half as good as in the Hydroxyethylstarch group while parameters remained unchanged in the whole-blood-group. Bag plasmapheresis with Hydroxyethylstarch as substitute leads to an improvement in the walking capacity and blood fluidity thus offering a promising therapy for peripheral vascular occlusive disease.

[Hemodilution in patients with stage IIb peripheral arterial occlusive disease: prospective randomized double-blind comparison of middle-molecular weight hydroxyethyl starch and low-molecular weight dextran solution]

Isovolemic hemodilution is a simple method of treating patients with peripheral arterial occlusion disease and hematocrit values of 43% or more. Dextran, a plasma substitute, has been used for that purpose since the early 1950s. However, the use of dextran in some diseases, e.g., hemorrhagic diathesis, kidney insufficiency, and microangiopathy is not without risk. Anaphylactic reaction, too, has occurred in some cases. Since the end of the 1970s hydroxyethyl starch, a plasma substitute, is available for the therapy of microcirculatory disorders and hemorrhagic diathesis. The side effects of hydroxyethyl starch are less serious and anaphylactic reactions are less frequent and moderate in extent. The clinical efficacy of both substances was compared in this survey. It could be stated that middle molecular hydroxyethyl starch is even clinically superior to low molecular dextran because the distance that the patients could walk increased significantly.

The role of plasma hyperviscosity in subcortical arteriosclerotic encephalopathy (Binswanger's disease)

Five haemorheological variables (haematocrit, plasma viscosity, red cell aggregation, red cell deformability and yield shear stress) and the plasma fibrinogen concentration were determined in blood samples from 21 untreated patients with subcortical arteriosclerotic encephalopathy (SAE, Binswanger's disease). The results were compared with those obtained in blood samples from 40 untreated patients with lacunar infarcts and from 275 healthy control subjects without vascular risk factors. Pathological ("solid body") flow behaviour was detected in the blood of both groups of patients (SAE and lacunar infarcts). However, highly elevated plasma viscosity was a consistent feature only of SAE. The authors present the hypothesis that the high plasma viscosity in patients with SAE may account for the progressive degeneration of cerebral white matter. It is postulated that microcirculatory abnormalities due to microrheological changes may be one of the many missing links in the pathophysiology of SAE.

[Predictor function of hemorheologic parameters with reference to the incidence of manifest circulatory disorders: Concept of the Aachen study]

The prevention of cardiovascular disease has up till now generally been limited to control of the classical risk factors. The primary problem of the risk factor model is, that although a statistically verified relationship exists between risk factors and vascular disease, an individual prognosis is presently impossible. Surveys that show a relation between risk factors and impaired blood fluidity support the conception that a change in blood fluidity could be considered an early detection screening of vascular diseases. Prospective studies have shown that the hematocrit is related to circulatory disturbances. The main aim of the present study was to determine the clinical relevance of rheological parameters (hematocrit, plasma viscosity, erythrocyte rigidity, thrombocyte aggregation, erythrocyte aggregation), and the importance of altered blood fluidity as a predictor of manifest cerebral, cardiac or peripheral vascular disturbance.

[Comparative study of low molecular dextran or hydroxyethyl starch as a volume substitute in hemodilution therapy]

Rheological therapy, as an immediate treatment in conjunction with physical therapy and the removal of risk factors, plays a significant role in the management of patients with peripheral vascular disease experiencing reduced walking tolerance. An essential element of rheological therapy is hemodilution. Currently, is still uncertain which plasma substitute solution would be the most appropriate in such cases. This study compared the effectiveness of low molecular hydroxyethyl starch to low molecular dextran during a 16-day hemodilution in combination to physical therapy. The clinical improvement observed with both plasma substitute solutions was comparable, yet in view of the cardiac volume overload, dextran demonstrates greater circulatory stress due to the transient pressure increase and more side effects. For this reason, we prefer to administer low or middle molecular hydroxyethyl starch in the dilution treatment of peripheral arterial occlusive disease as a chronic degenerative vascular disease.