Effect of total leucocyte count on whole blood filterability in patients with peripheral vascular disease

Shear-induced Filter Blockage. A Population Based Appraisal of a Method for the Assessment of Platelet, White Cell and von Willebrand Factor Interactions

Blood behaviour under shear-stress is assessed by a filter method in the Caerphilly Prospective Heart Study. Associations with haemostatic and lifestyle factors in 941 men aged 55 to 69 years are reported. The importance of platelets in filter blockage is confirmed, and roles for white cells and plasma viscosity in determining flow prior to blockage are identified. The aspect of platelet activity involved in blockage appears to be independent of mechanisms mediated by cyclo-oxygenase and adenosine diphosphate. von Willebrand factor however is associated with filter blockage, probably as an inter-platelet ligand. Fibrinogen is not required for blockage. Men regularly consuming alcohol or garlic supplements show reduced blockage, and biochemical mechanisms are suggested which might explain these associations. No effects of aspirin, smoking or consumption of fish oil supplements were noted. Shear-induced filter blockage is a simple method for measuring complex flow-dependent interactions of haemostatic factors. Its application in a wide range of investigations, including epidemiological studies, would appear to be appropriate.

Interleukin-6 as a central mediator of cardiovascular risk associated with chronic inflammation, smoking, diabetes, and visceral obesity: down-regulation with essential fatty acids, ethanol and pentoxifylline

Increased plasma levels of fibrinogen and C-reactive protein (CRP), as well as leukocytosis, are now established as risk factors for the thromboembolic complications of vascular disease. Chronic inflammation or infection associated with an acute-phase response--notably, periodontal disease and smoking-induced lung damage--are likewise known to increase cardiovascular risk. A common etiologic factor in these conditions may be interleukin-6 (IL-6), acting on hepatocytes to induce acute-phase reactants that increase blood viscosity and promote thrombus formation. Recent evidence that hypertrophied adipocytes release IL-6, and that hyperglycemia evokes IL-6 production by endothelium, may explain why plasma fibrinogen is increased in visceral obesity and poorly controlled diabetes. IL-6 is released by a range of tissues in response to stimulation by the monocyte-derived cytokines interleukin-1 and tumor necrosis factor; by suppressing production of these cytokines, fish oil, alpha-linolenic acid, and pentoxifylline can reduce IL-6 synthesis. Moderate ethanol consumption, as well as sex-hormone replacement, also appear to inhibit IL-6 production or activity. These practical protective measures may be of particular value to patients with pre-existing atheroma and elevated plasma levels of acute-phase reactants. Since IL-6 plays a crucial physiological role in osteoclast generation and activation, these measures may also aid preservation of bone density.

Nitric oxide deficiency, leukocyte activation, and resultant ischemia are crucial to the pathogenesis of diabetic retinopathy/neuropathy--preventive potential of antioxidants, essential fatty acids, chromium, ginkgolides, and pentoxifylline

Impaired microcirculatory perfusion appears to be crucial to the pathogenesis of both neuropathy and retinopathy in diabetics. This in turn reflects a hyperglycemically mediated perturbation of vascular endothelial function that entails overactivation of protein kinase C, reduced availability of nitric oxide, increased production of superoxide and endothelin, impaired insulin function, diminished synthesis of prostacyclin/PGE1, and increased activation and endothelial adherence of leukocytes. These dysfunctions may be addressed with a supplementation program that includes high-dose antioxidants, fish oil, gamma-linolenic acid, chromium, arginine, carnitine, and ginkgolides. Pharmaceuticals likely to be of benefit in this regard include pentoxifylline, probucol, replacement estrogens, and inhibitors of angiotensin converting enzyme and aldose reductase.

Development of vascular complications in diabetes

Chronic complications of diabetes are dominated by disorders of the vascular system. They are a much larger burden on both diabetic patients and overall medical costs than diabetes itself. Large vessel problems are far more frequent than microvascular disorders. Loss of arterial elasticity alters arterial flow patterns and increases microcirculatory peak flow rates. Hyperglycemia may directly disrupt elastin formation. Diabetic leg artery disease may be generated by nerve damage, reversing this interactive contribution sequence. The major anatomic feature of microangiopathy in long-term diabetes is an unevenly distributed thickening of the intima of smaller arterioles. The thickening is primarily due to accumulation of type IV (basement membrane) collagen. Arterioles change local vessel diameter to adjust blood distribution to meet current needs. The thickening compromises the maximum local blood flow that may be achieved by this means. Compromise of maximal arteriolar dilatation does not disrupt exercising muscle but in the kidney, retina, and possibly in nerve, local circumstances can generate serious damage. Each of these system's responses has unique features that mediate its vulnerability, but all these organs show arteriolar hyalinization. The increased arteriolar accumulation of type IV collagen appears to be a response to the tangential force generated by flow over local endothelial cells. An increase in peak arteriolar wall force is mediated by a diabetes-specific doubling of erythrocyte membrane curvature change resistance. Red cell aggregation rate determines the rate of damage. The same nonspecific burden may also predispose to heart disease and stroke. Intensive metabolic control improves red cell deformability and protects against arteriolar damage. Therapies that address the rheologic problem more directly may add to the effectiveness of good diabetes control in the future.

Band 3 antagonists, p-azidobenzylphlorizin and DIDS, mediate erythrocyte shape and flexibility changes as characterized by digital image morphometry and microfiltration

Two nonpenetrating membrane probes, p-azidobenzylphlorizin (p-AzBPhz) and 4,4'-diisothiocyano-2,2'-stilbene disulfonate (DIDS), have been shown in earlier studies to induce dose-dependent changes in red blood cell (RBC) shape and volume at the same low concentrations that inhibit anion transport. In the present work, these ligand-induced morphology and rheology changes were studied using video digital image morphometry (VDIM) and microfiltration techniques. The results of these experiments corroborate our earlier investigation. RBCs were filmed using a Nomarski optics microscope with video camera attachment and cell size and shape changes were computer analyzed using VDIM. Low microM p-AzBPhz or DIDS levels caused collapse of the cell's biconcave structure and cell flattening occurred within 1-2 sec after drug exposure. Higher doses of either agent converted cells to a new steady-state in which a concurrent limited increase in erythrocyte volume and blunt membrane protrusions were produced. These changes were reversed in less than 2 sec by washing the drug from the membrane. Both ligands increased the deformability of RBCs in a dose-dependent manner as determined by filtration through Nuclepore polycarbonate filters (3 microns pore diameter). The improvement in deformability of drug-treated sickle cells was much more dramatic than for normal cells at low p-AzBPhz concentrations. These results support our earlier conclusions that the ligands, through a common interaction with band 3, induce volume-associated cytoskeletal alterations which lead to changes in morphology and flexibility.

Decreased leukocyte deformability after acute cigarette smoking in humans

Acute cigarette smoking increases the sequestration of neutrophils in the lungs of humans. This may be due to the delayed transit of cells in the pulmonary microcirculation, which may result from a reduction in cell deformability as suggested by in vitro studies of smoke-exposed neutrophils. In order to support this hypothesis we wished to determine if a reduction in leukocyte deformability could be measured in whole blood exposed to smoke in vitro or in vivo. Whole blood filterability, which largely reflects leukocyte deformability, was measured as the pressure developed by filtration of diluted whole blood through a micropore membrane. Whole blood filtration pressures did not change when blood was exposed to smoke in vitro or in venous blood after acute smoking in vivo. However, arterial blood sampled from chronic smokers during acute smoking showed a consistent reduction in leukocyte deformability associated with a small increase in plasma elastase. To assess whether these changes were induced by oxidants in cigarette smoke, we measured the levels of the antioxidant glutathione (GSH), erythrocyte (RBC) membrane fragility, and products of lipid peroxidation in plasma and RBC in blood exposed to smoke in vivo and in vitro. No change in RBC lipid peroxidation or membrane fragility could be detected after in vitro smoke exposure, possibly because of the high antioxidant capacity of the RBC. However, reduced blood GSH levels and increased levels of lipid peroxidation products were detected in plasma, reflecting oxidant stress. In contrast, we were unable to detect evidence of an increased oxidant burden in blood after acute smoking in vivo, in either arterial or venous blood samples.(ABSTRACT TRUNCATED AT 250 WORDS)

The white blood cell count and risk for coronary heart disease

In conclusion, the WBC count has been demonstrated in several epidemiologic studies to be a strong independent predictor of future coronary heart disease. Although it is not possible at this point in time to be certain that the elevated WBC count is a cause rather than a consequence of ischemic heart disease, recent pathophysiologic studies suggest that the white blood cell, in particular the neutrophil, is instrumental in the pathogenesis of myocardial ischemia. It is conceivable that patients who develop acute myocardial ischemia have abnormal leukocyte function before the onset of the acute event, which provides a pathophysiologic milieu for the progression of the atherosclerotic process. Future research must focus on further elucidation of the properties of WBCs and clarification of the role of the activated neutrophil in the process of vascular injury. Quantitative and qualitative changes in leukocyte function may have important implications in the development of CHD.

Alterations in erythrocyte rheology in patients with severe peripheral vascular disease: 1. Cell volume dependence of erythrocyte rigidity

The erythrocyte rigidity of patients suffering from severe peripheral vascular disease (PVD) was measured by a filtration method using 3 microns pore size filters. Filtration pressures for both PVD patients and normal subjects showed a cell volume dependency, and patient filtration pressures were normalized to cell volume to evaluate intrinsic, ie, nonvolume dependent, abnormalities in erythrocyte deformability. A significant (p less than 0.001) increase in cell rigidity was found in 44 of 54 PVD patients in comparison with volume-matched normal controls. No significant difference was found between patient mean corpusculer hemoglobin (MCH) and normal MCH at any given mean corpuscular volume (MCV), indicating that observed increases in erythrocyte rigidity are not attributable to changes in patient MCH. Therefore, the mechanism of increase in erythrocyte rigidity for PVD patients still needs further investigation into such parameters as levels of adenosine triphosphate,2,3-DPG, and membrane fluidity (calcium- and/or protein-binding membrane, cholesterol and phospholipid content of membrane, etc), as well as other aspects of erythrocyte physiology.

Effects of ticlopidine on the neurologic outcome and the hemorheologic pattern in the postacute phase of ischemic stroke: a pilot study

This double-blind pilot study observed the effects of a twenty-one day oral ticlopidine treatment (250 mg/twice daily) on the neurologic outcome and the hemorheologic pattern of 15 patients and 15 placebo-treated controls. Patients and controls (age range sixty-six to eighty-six years) were included in the study within twelve hours of the onset of ischemic stroke, confirmed clinically and by computerized tomography. Scores on Hachinski's Scale and the following hemorheologic parameters were monitored weekly for twenty-one days: fibrinogen levels, the whole blood, unfractionated white and red blood cell filterability rates (through 5-micron-pore-diameter filters using a constant-flow positive-pressure system), and the leukocyte count and activation (by microscopic observation). The results showed treatment with ticlopidine improved the neurologic outcome (Hachinski's Score +36%, p less than 0.03) slightly but significantly (p less than 0.001) increased the average values of the whole blood (+19%) and red cell (+17%) filterability rates and decreased fibrinogen levels (-17%).

Stable angina pectoris and controlled ischemia: what causes the abnormalities in whole blood filterability?

The determinants of the altered whole blood filterability observed during coronary ischemia are still under discussion. Since no studies have been carried out to date on what exactly causes these alterations during the early stages of controlled ischemia in coronary heart disease, a model was set up using a bicycle ergometer test (with a 25 W increase every 2 minutes). Blood samples were taken from 48 stable angina pectoris patients and from a group of 28 matched controls before and immediately after exercise and 8 minutes later. Plasma viscosity, the filterability (through 5 microns diameter pore filters) of whole blood, erythrocytes, and polymorphonuclear and mononuclear leukocytes (separated by density gradient) were monitored. Alterations in whole blood filterability could be linked only to an impairment in polymorphonuclear cell filterability in those stable angina pectoris patients who reported chest pain and/or whose ST segment depression was greater than or equal to 2 mm.

Leucocyte behaviour in controlled ischaemia of the calves

Whole blood filterability and leucocyte behaviour (number, activation, and subfraction filterability rates) were monitored at the earliest stage of peripheral ischaemia in 18 patients with stage II peripheral occlusive arterial disease (PAOD) and 20 matched controls. A model of controlled ischaemia, using exercise to stress leg circulation, was set up and blood samples were taken before exercise, at the onset of calf pain, and at recovery from peak exercise. Leucocytes were counted, separated into their subfractions on a Ficoll-Hypaque density gradient and by adhesion to Petri dishes, and filtered in buffer (like the whole blood suspensions) through 5 microns pore diameter Nucleopore filters. Unfractionated white cells, separated under gravity, with pseudopodia or cytoplasmic irregularities were regarded as activated. The whole blood filterability rate was significantly increased at the onset of calf pain and was associated with significant increases in the number of leucocytes and in the filterability rate of the monocyte subfraction, the latter persisting throughout the recovery period. No significant changes were observed in the other variables monitored, showing that impairments in white cell rheology may be associated with ischaemia.

Peripheral vascular disease. Rheologic variables during controlled ischemia

The quantitative and qualitative behavior of hemorheologic factors both at rest and after treadmill exercise in 30 male patients with stage II peripheral vascular disease compared with 20 sex- and age-matched healthy controls have been studied. The aim of our study was to identify functional rheologic markers for peripheral vascular disease. At rest, whole blood viscosity (corrected for hematocrit at both high and low shear rates), fibrinogen levels (4.23 +/- 1.39 vs. 3.23 +/- 1.5), and white blood cell count (7.05 +/- 1.25 vs. 6.03 +/- 1.28) were significantly different between patients and controls. After treadmill exercise, white blood cell counts increased in both patients and controls, whereas only the filterability of mononuclear leukocytes showed a significant variation in the patient group (5.47 +/- 1.54 vs. 7.26 +/- 2.00, p less than 0.002). In this group, mononuclear filterability improved during the recovery period. The results suggest a relation between exercise-induced ischemia of the lower limb and mononuclear filterability in patients with peripheral vascular disease. Mononuclear filterability could be a functional rheologic marker for peripheral vascular disease.

Blood rheology in vitro and in vivo

Blood rheology tests are traditionally used for detection of organic disease and for monitoring disease activity. More recently they have been used for prediction of blood flow in vivo, not only in overt hyperviscosity syndromes but also in the covert hyperviscosity of low-flow states. The traditional ESR test result increases with red cell aggregation induced by increases in large, asymmetrical plasma globulins. However, small increases in haematocrit and large increases in plasma viscosity each decrease the ESR, reducing both its diagnostic utility and its ability to predict blood flow in vivo. The ESR should be corrected to a standard haematocrit, or else replaced by the ZSR or plasma viscosity, which are more rapid, simple, sensitive and independent of haematocrit. For prediction of blood flow in vivo, these tests can be supplemented by measurement of whole-blood viscosity, which can be performed simply and cheaply in capillary viscometers at high shear rates. Whole-blood viscosity is determined by plasma viscosity, haematocrit and red cell deformability at high shear rates. Its measurement is useful in overt hyperviscosity syndromes, particularly in estimating the effect of red cell transfusion in anaemic patients with plasma hyperviscosity, hyperleukocytic leukaemias or sickling disorders. Blood viscosity should be related to the haematocrit or haemoglobin concentration in order to estimate oxygen delivery to tissues. Changes in blood viscosity can be compensated readily in the normal circulation but not in the compromised, low-flow circulation. In these circumstances, systemic increases in plasma viscosity, haematocrit, whole-blood viscosity, red cell aggregation and in the numbers of circulating rigid red or white blood cells can perpetuate low-flow states and ischaemia. Red cell deformability in narrow vessels is best measured by micropore filtration systems, in which the effect of white cells has been eliminated. Red cell deformability is reduced by change in shape, decrease in the ratio of surface area to volume, decreased membrane flexibility and increased internal viscosity (MCHC and inclusions). White cells have negligible effects on bulk-blood viscosity but have important effects on blood flow in narrow vessels, due to their high internal viscosity and their adhesiveness when activated. White cell filterability is lowest for monocytes and for activated granulocytes and these adhesive and rigid cells may have important effects on microcirculatory blood flow in low-flow states.

Blood rheology in general medicine and surgery

Traditionally, blood rheology tests have been used in diagnosis and monitoring of infection, rheumatic diseases and malignancy, and are still of clinical value in these conditions. In the last twenty years, clinical and epidemiological studies have shown that the haematological determinants of blood flow resistance (haematocrit, fibrinogen, white cell count and altered red and white cell rigidity) are also associated with nutritional, metabolic, endocrine and vascular disorders. Decreased red cell deformability may contribute to reduced red cell survival and anaemia in burns, malaria, liver disease and kidney failure. In trauma and inflammatory disease, overt hyperviscosity is usually prevented by vasodilatation and reduction in the haematocrit. However, low-flow states may arise systemically from haemoconcentration (contracted plasma volume, Chapter 3) in severe burns, inappropriate red cell transfusion, or dehydration due to illness; systemically in circulatory shock; and locally in venous thrombosis or arterial disease. In such circumstances, the intrinsic flow resistance of blood may perpetuate flow disturbance, ischaemia and thrombosis. Conversely, optimal levels of haematocrit, fibrinogen and white cell count may be lower than normal in low-flow states. Haemodilution by colloid infusion is beneficial in burns, shock, major surgery, prevention of postoperative venous thrombosis, chronic stable claudication and possibly in acute stroke and retinal vein thrombosis. Plasma exchange may be beneficial in severe Raynaud's phenomenon. Defibrination with ancrod is effective in prevention and treatment of venous thrombosis but its role in arterial disease is unproven. The benefits of streptokinase therapy in venous thrombo-embolism and acute myocardial infarction may be partly rheological, due to fibrinogen depletion. Drugs with rheological effects may be beneficial in intermittent claudication.

Leukocyte rheology in recent stroke

Eighteen patients with recent ischemic stroke were compared with an equal number of matched controls. Standardized suspensions of red cells as well as of red and white cells were filtered in a new filtration apparatus capable of discriminating between cell deformability and filter occlusion. Results show that red cell deformability, although slightly lower than in controls, is not significantly altered in stroke patients. Filter occlusion, however, was significantly higher in patients when red and white cell suspensions were filtered, but not when red cell suspensions were used, suggesting that white cell filterability is impaired after stroke, which could be due to decreased deformability and/or increased adhesiveness of leukocytes. Slowed white cell passage may also occur in the living microcirculation and may present an obstacle to nutritive flow in exchange vessels, possibly contributing to local ischemia and tissue necrosis after stroke.

Red cell and hemorheological changes in multiple sclerosis

Blood rheology in multiple sclerosis (MS) was investigated in 15 subjects with varying degrees of locomotor difficulties who were members of the local MS Society. Control data were obtained from blood samples from 25 male and 25 female normal blood donors. Whole blood viscosity was measured and blood filterability was assessed. Six MS females provided blood samples for scanning electron microscopy. Erythrocyte membrane fatty acids and phospholipids were assayed. Whole blood viscosity in MS females was higher than controls at 3 of 4 shear rates (p less than 0.001) but in MS males blood viscosity was higher only at shear rate of 1.0 s-1 (p less than 0.05). MS erythrocyte filtration rates were significantly lower than controls (p less than 0.001). Leucocyte counts in MS were greater than controls both in males (p less than 0.01) and females (p less than 0.001). MS erythrocyte morphology was greatly different from controls (p less than 0.0001) and erythrocyte membranes contained less sphingomyelin than controls (p less than 0.01) but more phosphatidylinositol plus phosphatidylserine (p less than 0.02). We conclude that, because our findings indicate an identifiable and potentially correctable abnormality, it is possible to envisage an inhibition of the progressive nature of MS, with the hope of a better prognosis for patients.

Blood rheology and myalgic encephalomyelitis: a pilot study

The blood rheology of EDTA-anticoagulated blood samples from blood donors and subjects considered to have myalgic encephalomyelitis was assessed by multiple shear rate viscometry and by multiple-pressure filterability. Although average viscosities of the two groups were different, the differences did not reach statistical significance. In contrast, the data from multiple-pressure filtration of whole blood showed significant differences between females at the lowest (2.5 cm of water) filtration pressure. It appears that the acute phase of the disorder is associated with changes in blood rheology which could impair microcirculatory blood flow. In contrast, the chronic state does not appear to be associated with rheological abnormalities.

Alterations in erythrocytes in hyperosmolar diabetic decompensation: a pathophysiological basis for impaired blood flow and for an improved design of fluid therapy

In a study of 10 diabetic patients, each of whom was in a severely decompensated state, notable alteration of blood flow properties was observed in those six patients who were hyperosmolar. In this form of diabetic decompensation, whole blood filtration was distinctly impaired. The additional impairment was shown to be due to an accumulation of solute within the erythrocytes occurring as a consequence of hyperosmolarity. The alterations in erythrocytes were revealed by Coulter blood count abnormalities and confirmed by osmotic fragility studies. When biochemical improvement was achieved in these patients, rapid resolution of the erythrocyte abnormalities occurred. Microvascular ischaemia due to such erythrocyte alterations may be a possible explanation for the characteristic cerebral disturbances of the hyperosmolar diabetic state. Altered blood flow properties would also promote vascular thrombosis, a common terminal event in the hyperosmolar non-ketotic syndrome with associated 50 per cent mortality. An improved design of the insulin and fluid replacement therapy for patients in hyperosmolar diabetic coma might be based on the findings of these and further studies.

Haematological and haemorheological changes associated with cigarette smoking

A prospective study was undertaken to establish the haematological and haemorheological changes associated with long standing cigarette smoking in 20 heavy smokers and to assess whether any such changes were reversible after smoking was stopped. Highly significant differences were observed in whole blood viscosity, plasma viscosity, plasma fibrinogen concentrations, packed cell volume, and carboxyhaemoglobin concentrations between smokers and non-smokers. Ten of the subjects were followed up for two weeks after stopping smoking by which time whole blood viscosity and carboxyhaemoglobin concentrations had improved significantly and indications of improvement could be seen in all other measurements. Two of these subjects were further followed up for two months when all the measured variables were comparable with those in non-smokers. No correlation could be established between carboxyhaemoglobin concentration and any of the other variables. Although patients' compliance may be difficult to obtain, further prospective studies would be required to confirm our findings.

Erythrocyte rheology

Erythrocyte deformability was formerly measured by its contribution to whole blood viscosity. It is now more commonly measured by filtration of erythrocytes through, or aspiration into, pores of 3-5 microns diameter and by the measurement of shear induced erythrocyte elongation using laser diffractometry. Recent improvements in the technology for erythrocyte filtration have included the removal of acute phase reactants from test erythrocyte suspensions, ultrasonic cleaning and reuse of filter membranes, awareness of the importance of mean cell volume as a determinant of flow through 3 microns diameter pores, and the ability to detect subpopulations of less deformable erythrocytes. Measurements of erythrocyte elongation by laser diffractometry, using the Ektacytometer, are also influenced by cell size and need to be corrected for mean cell volume. These advances have greatly improved the sensitivity and specificity of rheological methods for measuring the deformability of erythrocytes and for investigating the mode of action of rheologically active drugs.

Intermittent claudication: a double-blind crossover trial of pentoxifylline

The influence of the xanthine derivative pentoxifylline ('Trental' or BL191; Hoechst-Roussel) on exercise tolerance was measured in 38 subjects with stable, severe to moderately severe, intermittent claudication who completed a randomised, double-blind, placebo controlled, cross-over clinical trial. Patients received placebo tablets or 400 mg slow-release pentoxifylline tablets ('Trental 400') twice a day for one week, followed by three times daily for seven weeks, and then crossed over to receive the alternate preparation for another eight weeks. Claudication distance and walking distance were measured on a treadmill before starting treatment and again at four-week intervals during the trial. At the same times, red blood cell filterability, plasma fibrinogen concentration and blood viscosity, resting and post-ischemic calf muscle blood flow, and the resting and post-exercise ankle/brachial systolic pressure ratio were also measured. In this study, the observed effects of pentoxifylline treatment were no greater than those of placebo, even though serum levels of pentoxifylline and its hydroxy-metabolite were within the anticipated range. This was shown by a 'therapeutic effect ratio' of 0.98 for treadmill claudication distance and 0.96 for treadmill walking distance after within-patient analysis at the end of the cross-over (where a ratio of 1.0 means the test drug and placebo effects are identical). These ratios have 95% confidence limits of 0.72-1.34 and 0.74-1.25, respectively.

Red cell deformability and other haemorheological variables in stable coronary artery disease

In this study, red cell deformability and other haemorheological variables were measured in 40 patients who underwent cardiac catheterization for the investigation of chest pain. The patients were divided into two groups - those with extensive disease and those with less extensive or no disease. Deformability was assessed by a filtration method. There were no significant differences in filterability, haematocrit, plasma viscosity or plasma fibrinogen between the two groups of patients. However, those with extensive disease had significantly higher blood viscosity than those with less extensive disease. Thus the study was able to demonstrate an association between blood viscosity and extent of coronary artery disease but not between the individual determinants of blood viscosity (red cell deformability, plasma fibrinogen and haematocrit) and extent of disease.

The flow of blood cell suspensions through 3 microns and 5 microns Nuclepore membranes: a comparison of kinetic analysis with scanning electron microscopic examinations

This study was designed to investigate the effect of red and white cells on the flow of dilute suspensions of blood cells through 3 microns and 5 microns Nuclepore membrane filters. The rate of flow of blood cell suspensions through 3 microns or 5 microns membranes declines continually due to occlusion of pores by slow cells. The cells which occlude 3 microns pores exceed the number of white cells about seven-fold. Electron microscopic examination of a used membrane confirms that these slow cells are not white cells but are red cells which are visibly damaged. With 5 microns membranes, the number of slow cells is entirely consistent with them being white cells. Again, electron microscopic examination confirms that 5 microns pores are occluded by white cells. With both types of membrane, the same kinetic analysis is valid and yields information about the behaviour of red cells during the filtration procedure.

Erythrocyte deformability in peripheral occlusive arterial disease

A rheological study of 32 patients with peripheral occlusive arterial disease (POAD), compared with 32 matched healthy controls, has shown no loss of erythrocyte deformability as measured by filtration methods (using initial flow rate and positive pressure instruments, polycarbonate and silver membranes, and 3 microns and 5 microns diameter pores) or by viscometry (using laser visco-diffractometric and high shear rate viscosity methods). Erythrocyte ATP concentration in POAD was also normal. Patients with POAD showed a small (4 fl) increase in mean erythrocyte volume, associated with a raised serum gamma-glutamyl transpeptidase concentration, which correlated with erythrocyte filtration and viscometric measurements. Previous reports of impaired blood filterability in POAD probably reflect the effects of accompanying leucocytosis, plasma hyperfibrinogenaemia, or an increase in erythrocyte size, but not an intrinsic loss of erythrocyte deformability.

Evaluation of the contribution of red and white cells to the flow of suspensions of washed blood cells through 3 micron Nuclepore membranes

This study was designed to investigate a method of analysis which can quantitate the contribution of white cells to the flow of washed suspensions of blood cells. Such an analysis would obviate the need to remove white cells when studying the filterability of normal and abnormal red cells. The flow of suspensions of washed blood cells through a 3 micron Nuclepore membrane declines continually due to the occlusion of pores and the degree of pore occlusion is reduced significantly by the removal of the 'buffy coat' during the preparation of the suspension. These findings are in complete agreement with many other reports. However, a detailed kinetic analysis of the results suggests strongly that the white cell population makes a small contribution to the degree of pore occlusion which is caused largely by approximately 1% of the total red cell population. Despite the phenomenon and extent of pore occlusion, a kinetic analysis of the complete non-linear flow profile allows a measure of the deformability of red cells from filtration studies of washed but unfractionated blood cells.