Influence of parenteral nutrition on blood rheology and platelet aggregation in vitro.

BACKGROUND: Parenteral nutrition (PN) is a hyperosmolar solution composed of glucose, amino acids and a lipid emulsion, which is often used despite well-known side effects and complications. OBJECTIVES: In this study the hypothesis was tested that PN could affect hemorheology. METHODS: The influence of increasing plasma concentrations (0, 4, 10 and 25%) of the 3-in-1-mixture of PN on various rheological parameters were studied in vitro. The influence of the individual components was studied with plasma concentrations of 10, 10 and 5%, respectively. Hematological and coagulation tests were performed. Blood viscosity and red blood cell (RBC) aggregation were measured and platelet aggregation in flowing blood was assessed with a PFA-100 instrument. RESULTS: It was found that PN induced RBC shrinkage, which was partially reversible. It reduced RBC aggregation measured by low shear viscosity or RBC sedimentation. Platelet aggregation was strongly inhibited. Coagulation tests were not affected. Investigations with the single components of PN showed that the RBC shrinkage was mainly caused by the amino acid solution and the inhibition of platelet aggregation by all 3 components. The lipid emulsion in higher plasma concentrations led to echinocytosis, indicating that the lipids interact with the outer half of the membrane lipid bilayer. CONCLUSIONS: High concentrations of PN affect blood rheology in several ways. The strongest effect was an inhibition of platelet aggregation, which may have a clinical relevance. Other effects such as RBC shrinkage and decreased RBC aggregation occurred only at high PN concentrations, which are reached in vivo at the infusion site.

Studies on metabolically depleted erythrocytes.

Erythrocytes kept outside the blood circulation undergo progressive changes in metabolism, shape and function, which was the topic of this study. For that purpose, blood anticoagulated with either heparin, citrate or EDTA was incubated at temperatures of 5°C, 22°C or 37°C for 0 h, 24 h and 48 h, respectively. A temperature- and time-dependent decrease of glucose and ATP and increase of lactate and LDH were observed. An erythrocyte swelling and echinocytic shape transformation, which was also time- and temperature-dependent, was seen. Density-separated young and old erythrocytes behaved similarly. The degree of echinocytic shape transformation correlated with the increase in blood viscosity at high shear rate. Echinocytosis was partially reversible when erythrocytes were suspended in buffer containing 0.2% albumin. This phenomenon is specific for albumin, since molecules with a similar molecular weight (dextran 70, heat shock protein, protein C) had no effect. These finding may have an impact on blood banking and transfusion medicine.

Cocaine in high concentrations inhibits platelet aggregation in vitro.

Complications of cocaine administration are acute vascular occlusions such as myocardial infarction and stroke. We have studied the influence of cocaine on platelet function in vitro. For that purpose, citrated blood from healthy volunteers was incubated with cocaine concentrations of 0 (control), 10, 100, 1000, 2500, and 10'000 µmol/l plasma. Platelet aggregation was measured in whole blood under high shear flow conditions with a platelet function analyzer PFA-100 using either epinephrine (EPI) or ADP as a platelet activator, as well as in non-flowing blood measuring the change of impedance after the addition of either collagen or ADP (Chronolog-700 Aggregometer). In addition, platelet aggregation was measured by the change in light transmission in platelet rich plasma containing the same cocaine concentrations (Chronolog-700). Platelet aggregation in flowing whole blood (PFA-100) was not affected by cocaine up to 1000 µmol/l, partially inhibited by 2500 µmol/l and completely inhibited by 10'000 µmol/l cocaine. In non-flowing blood, platelet aggregation was decreased already at cocaine concentrations of 1000 µmol/l with ADP and 2500 µmol/l with collagen as a platelet activator. In platelet-rich plasma, aggregation was partially inhibited by 1000 and 2500 µmol/l and completely inhibited by 10'000 µmol/l cocaine. We conclude that platelet aggregation is inhibited by cocaine in vitro. This occurs, however, at concentrations above those measurable in vivo. These observations make it very unlikely that a direct platelet activation plays a role in vascular events complicating cocaine consumption.

The passage of a hemodialysis filter affects hemorheology, red cell shape, and platelet aggregation.

We investigated the influence of the passage of a hemodialysis filter on red blood cells (RBCs), platelets, and hemorheological parameters. After one hour of hemodialysis, blood was drawn from 15 patients immediately ahead and behind the dialysis filter. RBCs were fixed for morphological analysis. Blood viscosity was measured with a Couette viscometer (LS-30, Contraves), RBC aggregation with a Myrenne aggregometer, platelet aggregation in flowing whole blood and in platelet rich plasma. The passage of the hemodialysis filter increased the hematocrit from 34.0 ± 3.8 to 44.6 ± 8.7% (p < 0.01). Discocytes decreased from 73 ± 9 to 60 ± 15%, while echinocytes/knizocytes were more abundant 24 ± 9% and 38 ± 15%, respectively, p < 0.01). Blood viscosity increased from 3.77 ± 0.52 to 6.75 ± 2.21 mPa.s (p < 0.01). The RBC aggregation index decreased from 25.8 ± 5.0 to 20.9 ± 5.6 (p < 0.05). These changes were less pronounced when the blood flow rate was reduced from 350 to 100 ml/min. Platelet aggregation was slightly increased in flowing whole blood, but decreased in platelet rich plasma. At the end of hemodialysis, a small increase in abnormally shaped RBCs, hematocrit, and whole blood viscosity persisted; platelet aggregation in flowing whole blood was reduced in all patients. We conclude that the passage of a hemodialysis filter induced RBC shape changes, increased the hematocrit, whole blood and plasma viscosity, decreased RBC aggregation, and affected platelet aggregation.

[Histoplasmosis - an unusual African souvenir]. / Histoplasmose: ein ungewöhnliches Feriensouvenir.

HISTORY AND CLINICAL FINDINGS: A 24-year-old woman (student of biology) was part of a study group in Uganda. She developed fever and headache, which was empirically treated as malaria. After she had returned to Switzerland, a chest x-ray showed bilateral miliary nodular infiltrates. In assumption of an atypical pneumonia, she was treated with levofloxacin, although without success. On admission, she was in a bad general condition and was markedly dyspneic. Rales were heard over both lungs. INVESTIGATIONS AND DIAGNOSIS: CRP, liver enzymes and LDH were elevated. A lung function test revealed a marked impairment of the diffusion capacity. The chest x-ray showed a progression of the lung infiltrates. The informal medical data exchange among the group members by a virtual social network abbreviated our diagnostic workup substantially, since we heard that histoplasmosis had been assumed in another group member. It turned out that the affected persons had visited a colony of bats living in a cave inside the trunk of a tree. Antibodies against Histoplasma capsulatum were positive. TREATMENT AND COURSE: We began a treatment with itraconazole. The condition improved gradually; chest x-ray and lung function normalized after the 8 week treatment. CONCLUSION: Histoplasmosis with such a severe course is rare in immunocompetent humans, which indicates that the inoculum must have been very high. Soil contaminated with bats guano favours the proliferation of Histoplasma capsulatum. Our case is also an illustration of how the widespread use of electronic media can sometimes facilitate our work.

Platelets in vascular disease.

Platelets play a key role in primary hemostasis and in the pathogenesis of atherosclerosis and atherothrombotic events such as stroke and myocardial infarction. When a plaque ruptures, platelets adhere to the underlying collagen matrix, become activated and aggregate, which may lead to vascular occlusions. Hemorheological aspects are intimately involved in this process. The assessment of this platelet function in vitro is difficult and has not reached the stage of routine use. Inhibition of platelet aggregation is the corner stone of any treatment of vascular disease. It is achieved mainly by to mechanisms, inhibition of thromboxane formation by acetylsalicylic acid, and with ADP receptor antagonists such as clopidogrel. Newer agents are being developed with the difficult mission to inhibit platelet aggregation more efficiently, and simultaneously reduce the risk of bleeding.

Cocaine induces a reversible stomatocytosis of red blood cells and increases blood viscosity.

Severe side effects of cocaine consumption are vasoocclusive events such as myocardial infarction and stroke. We have hypothesized that cocaine could affect red blood cells (RBCs) and alter the rheological behaviour of blood. Heparinized blood from healthy volunteers was incubated with a final hematocrit of 45% with increasing cocaine concentrations: 0, 10, 100, 1000, and 10'000 µmol/L plasma. Time dependence of the shape change was tested in phosphate buffered saline containing cocaine. RBCs were fixed in 1% glutaraldehyde for morphological analysis. Blood viscosity was measured with a Couette Viscometer (Contraves LS 30) at 37°C and a shear rate of 69.5 s⁻¹. RBC aggregation was assessed with a Myrenne aggregometer. Cocaine induced a dose-dependent stomatocytic shape transformation of RBCs, which was more pronounced in buffer than in plasma (plasma protein binding of the drug). Stomatocytosis occurs when a drug intercalates preferentially in the inner half of the membrane lipid bilayer. It was a time-dependent process with two components, an almost instant shape change occurring within 1 s, followed by a gradual further shape change during 10 min. Stomatocytosis was reversible by resuspension of the RBCs in cocaine-free buffer. This stomatocytic shape change increased whole blood viscosity at high shear rate from 5.69±0.31 mPa.s to 6.39±0.34 mPa.s for control and 10'000 µmol/L cocaine, respectively (p<0.01). RBC aggregation was not affected by the shape change. These effects occurred at a cocaine concentration, which is several-fold above those measured in vivo. Therefore, it is unlikely that hemorheological factors are involved in vascular events after cocaine consumption.

[Herbal drugs mimicking primary biliary cirrhosis]. / Pflanzliche Präparate sind nicht immer harmlos...

A woman, who consumed the recommended daily doses of Relaxane® and Hova® over several months was found to have elevated liver enzymes. A liver biopsy showed histologic changes consistent with primary biliary cirrhosis. After stopping treatment with Relaxane® and Hova® we observed a decline of the increased liver enzymes to normal levels two months later. A second biopsy of the liver three months later showed a clear decline of the initial histologic changes.

The influence of bevacizumab on platelet function.

Systemic treatment with bevacizumab is associated with increased rates of arterial and venous thromboembolism and haemorrhage. In order to investigate the pathophysiological mechanism involved, platelet adhesive and aggregatory functions were tested with a platelet function analyser (PFA-100®) in an in vitro study and in a longitudinal clinical observation study. For the in vitro study, blood from ten healthy volunteers was incubated with different concentrations of bevacizumab (0-1000 µg/ml plasma) and vascular endothelial growth factor (0-500 µg/ml). In the clinical observation study, PFA-100® closure times (CTs) and soluble P-selectin (sP-selectin) serum levels as a serological marker of platelet activation were assessed in 20 patients with metastatic cancer who were treated with bevacizumab in addition to cytotoxic chemotherapy. No significant changes of PFA-100® CTs were observed in the in vitro study. In the clinical observation study, mean PFA-100® CTs after treatment with bevacizumab were unchanged. sP-selectin was decreased after bevacizumab infusion by 18% (p = 0.045), which could suggest an inhibitory action on platelets. Our data do not support the view that increased platelet activation or increased platelet adhesiveness and aggregation by bevacizumab are relevant mechanisms for thrombus formation in clinical practice.

Activation of N-methyl D-aspartate (NMDA) receptors has no influence on rheological properties of erythrocytes.

PURPOSE: Red blood cells (RBCs) express N-methyl D-aspartate (NMDA) receptors on their surface. We tested if NMDA receptor activation or inhibition had an influence on RBC deformability and aggregability. METHODS: Heparinized blood was drawn from healthy volunteers and centrifuged. RBCs were washed twice and resuspended with a hematocrit of 30% in a same buffer solution containing 3% dextran 70. Aliquots were prepared: a) control; b) containing 100 µM homocysteic acid (NMDA receptor agonist); c) 100 µM memantine (NMDA receptor inhibitor) and 100 µM homocysteic acid. RBC suspension viscometry (Contraves LS-30) was done at 37 °C with shear rates of 37.6 s(-1) and 0.1 s(-1). RBC aggregability was assessed with a Myrenne aggrometer and sedimentation rate. RESULTS: Neither NMDA receptor activation nor inhibition had an influence on biophysical properties of RBCs. RBC suspension viscosity at a shear rate of 37.6 s(-1) was 3.62 ± 0.16, 3.61 ± 0.13, and 3.62 ± 0.16 mPa.s for control, homocysteic acid, and memantine + homocysteic acid, respectively, indicating an unchanged RBC deformability. The RBC aggregability parameters (low shear viscosity, Myrenne aggregometry at stasis (M) and 3 s(-1) (M1), and the sedimentation rate) showed no influence of either memantine and/or homocysteic acid. A large interindividual variability in RBC aggregability was observed. A good correlation was found between M, M1 and sedimentation values, but not with low shear viscosity values. CONCLUSIONS: An activation or inhibition of NMDA receptors on RBCs has no influence on their deformability and aggregability. RBC aggregability varies largely among individuals, which was consistently detected by the sedimentation rate and the Myrenne aggregometer, but not by low shear viscosity, which should not be used for this purpose.

Metabolic depletion decreases the aggregability of erythrocytes.

We studied the influence of metabolic depletion on red blood cell (RBC) aggregability, which is a determinant of blood flow. Heparinized blood was stored at room temperature for 0, 24, and 48 h. RBCs were washed twice and resuspended in Tris-buffer containing 3% dextran 70 (hematocrit 30%). Suspension viscosities were measured at 37 °C and shear rates of 37.6 and 0.1 s(-1), RBC aggregability was analysed by the sedimentation rate, direct microscopic visualization and a Myrenne aggregometer. RBCs in autologous plasma showed an increasing echinocytic shape transformation, which was reversible in buffer. The viscosities of RBC suspensions in buffer remained unchanged at both low (0.1 s(-1)) and high shear rate (37.6 s(-1)), the latter result indicating an unchanged RBC deformability. RBC aggregability decreased: The RBC sedimentation rates were 40.7 ± 5.0, 29.3 ± 13.4, and 13.3 ± 11.2 mm/h (p < 0.001) at 0, 24, and 48 h, respectively, which correlated well with the visual aggregability index and the Myrenne aggregation parameters M and M1. We conclude that metabolic depletion for 48 h leads to RBC swelling and a reversible echinocytic shape transformation. These ATP-depleted, but normally shaped RBCs had a decreased aggregability. In contrast to all other methods used, low shear viscosity was inaccurate and should not be used to test RBC aggregability.

Acute effects of short-term exposure to second-hand smoke on induced platelet aggregation.

Passive smoking may increase cardiovascular events by yet insufficiently understood mechanisms. We, therefore, tested the hypothesis that passive smoking could affect platelet aggregation. Fourteen healthy non-smoking males were exposed to second-hand smoke during 60 min in a room with smokers, who maintained the CO-concentration between 4.5-7.0 ppm throughout that period. Citrated blood was drawn before and immediately after smoke exposure (which took place between 6 and 7 p.m.). The last 7 individuals had blood taken also at 9.00 a.m. before and the day after smoke exposure. Platelet aggregation was measured (a) in flowing whole blood using the platelet function analyser PFA-100, which determines the closure time (CT) of a collagen coated membrane pore by shear-induced platelet aggregation, and (b) with a Chrono-log 700 Aggregometer, assessing platelet aggregation either by the change of impedance in diluted whole blood or light transmission in platelet-rich plasma. After short term second-hand smoke exposure we did not observe an increase in platelet aggregation with any of the instruments. We conclude that acute exposure to second-hand smoke is unlikely to increase platelet aggregability. Other mechanisms must be involved in the increased risk of cardiovascular events associated with passive smoking.

The influence of erythrocyte aggregation on induced platelet aggregation.

Red blood cells (RBCs) affect platelet aggregation in flowing blood (primary hemostasis). We tested the hypothesis that RBC aggregation could influence platelet aggregation. RBC aggregation was altered in vitro by: (i) changing plasma aggregatory properties with 3.7 g% dextran 40 (D40), 3.0 g% dextran 70 (D70) or 1.55 g% dextran 500 (D500); (ii) changing RBC aggregatory properties by incubating RBCs in 50 mU/ml neuraminidase for 60 min (reduction of the surface sialic acid content, thus reducing electrostatic repulsion) and subsequent RBC resuspension in platelet rich plasma (PRP) containing 1 g% dextran 70. RBC aggregation was assessed with the sedimentation rate (ESR). Platelet aggregation was measured: (i) in flowing whole blood with a platelet function analyzer PFA-100(R), which simulates in vivo conditions with RBCs flowing in the center and platelets along the wall, where they adhere to collagen and aggregate; and (ii) in a Chrono-log 700 Aggregometer, which measures changes of impedance by platelet aggregation in whole blood or changes in light transmission in PRP. We found that RBC aggregation increased with increasing molecular weight of dextran (ESR: 4 +/- 3 mm/h, 34 +/- 14 mm/h and 89 +/- 23 mm/hfor D40, D70 and D500, respectively, p < 0.0001) and with neuraminidase-treated RBCs (76 +/- 27 mm/h vs 27 +/- 8 mm/h, respectively, p < 0.0001). Platelet aggregation measured in whole blood under flow conditions (PFA-100) and without flow (Chronolog Aggregometer) was not affected by RBC aggregation. Our data suggest that RBC aggregation does not affect platelet aggregation in vitro and plays no role in primary hemostasis.

Overhead rotation: A simple method to assess the mechanical stability of stored erythrocytes.

Erythrocytes loose some functional qualities during storage, which may influence the outcome after transfusion. One of them is mechanical stability, which determines their in vivo survival in the circulation. We have analyzed different forms of mechanical stress and have developed a simple, reproducible test for mechanical stability. Specimens of outdated erythrocyte units stored under routine conditions were investigated. Mechanical stress was applied either by rolling blood-containing 5 ml tubes at 15 rpm (Mixer 820, Swelab, Sweden) or overhead rotation at 10 rpm (Intelli-Mixer RM-2S Elmi, Skyline, Axon Lab AG, Baden, Switzerland). Free hemoglobin (Hb) in the supernatant was used as a parameter of membrane integrity. Stored erythrocyte units at the end of their "shelf-life" of 42 days had a median free Hb concentration of 1.8 g/l (25-75 percentiles: 1.8-2.6 g/l) corresponding to a spontaneous hemolysis rate of 0.31% (0.28-0.46%). In samples subjected to 24 h rolling, free Hb rose to 4.8 (4.0-7.0; p = 0.005). Overhead rotation for 24 h increased free Hb to 17.1 (12.2-27.9) g/l when 1.5 ml blood in 5 ml tubes were used, and to 38.0 (19.6-55.2) g/l when 4.5 ml in 5 ml tubes were used (p = 0.005 between the two groups), indicating that hemolysis during rotation depended on the blood volume. The type of tube also influenced the extent of hemolysis. A large variation was seen between different RBC units. The time course of hemolysis was an inverse exponential function; i.e. 2 h of rotation induced already 45% and 7 h 86% of the hemolysis measured after a 24 h rotation. We conclude that the rate of hemolysis after a standardized overhead rotation is a simple, useful laboratory test to determine the mechanical stability of stored erythrocytes. Large variations between different RBC units suggest that this may be valuable tool for the quality control of stored RBCs.

Reduced incidence of acute myocardial infarction in the first year after implementation of a public smoking ban in Graubuenden, Switzerland.

OBJECTIVE: On March 1st, 2008 a smoking ban in public buildings became effective in the Canton of Graubuenden, Switzerland. The aim of our study was to investigate, whether implementation of this new regulation was followed by a decrease in the incidence of acute myocardial infarction (AMI). PATIENTS AND METHODS: The Kantonsspital Graubuenden serves as a tertiary care hospital, possessing the only cardiac catheterization laboratory in the Canton of Graubuenden. Based on an excellent functioning network including all hospitals in the Canton of Graubuenden, virtually all patients experiencing an AMI in the Canton of Graubuenden are transferred to our hospital for either acute or early coronary angiography. Data of all patients with AMI undergoing coronary angiography at our hospital between March 1st, 2008 and February 28th, 2009 were collected prospectively. The data were then compared with those of the two corresponding 12-month periods preceding implementation of the public smoking ban. RESULTS: In the two years before adoption of smoke-free legislation, the number of patients with AMI was 229 and 242, respectively (p = ns). In the 12 months after implementation of the public smoking ban, the number of AMI patients dropped to 183 (p <0.05 vs. each of the previous 12-month periods), representing an overall 22% reduction in the AMI incidence within the first year after enactment of the new regulation. This reduction was driven by a significant decrease in the AMI incidence in men, nonsmokers, and individuals with established coronary artery disease, including those with prior AMI or prior percutaneous coronary intervention. CONCLUSIONS: Similar to other countries in Europe and various regions of the USA and Canada, implementation of a public smoking ban was followed by a significant early decline in the incidence of AMI in the Canton of Graubuenden, Switzerland.

Particulate matter inhalation during hay storing activity induces systemic inflammation and platelet aggregation.

The aim of this study was to investigate possible pathomechanisms behind the cardiovascular morbidity caused by inhalation of particulate matter (PM(10)). For that purpose, healthy volunteers were exposed to high PM(10) concentrations during a 2 h hay storing activity. Blood was drawn in the evening before and after PM(10) exposure and in the morning and evening of the day after exposure. The leukocyte count increased after PM(10) exposure with an initial increase of segmented neutrophils followed by banded forms. C-reactive protein increased over time. Fibrinogen and plasma viscosity became increased in the evening of the day after PM(10) exposure. Platelet aggregation was increased in the evening after PM(10) exposure. At the same time von Willebrand factor and factor VIII were increased, reflecting endothelial activation. These results confirm that acute inhalative exposure to high PM(10) concentrations during hay storage activity leads to a systemic inflammatory reaction, endothelial activation, and platelet aggregation.

How important is malnutrition? A prospective study in internal medicine.

BACKGROUND/OBJECTIVE: Data about the prevalence of malnutrition on hospital admission vary and follow-up data are scarce. We assessed the nutritional status of unselected patients on admission and discharge. SUBJECTS/METHODS: A total of 430 consecutively admitted patients were assessed and 168 patients hospitalized > or =6 days were reassessed on discharge. Assessment was carried out by the Mini Nutritional Assessment (MNA), weight and anthropometric measurements, bioelectrical impedance analysis, biochemical markers and a subjective clinical assessment by the physicians in charge. RESULTS: On admission, 47% of all patients were overweight (body mass index, BMI >25 kg m(-2)) and 8% underweight (BMI<18.5 kg m(-2)). In terms of the MNA 70% were adequately nourished, 20% were at risk for malnutrition and 10% were malnourished. By clinical judgment alone 18 (4.3%) malnourished patients according to MNA were missed. The 44 malnourished patients according to the MNA had significantly lower values for BMI, fat-free mass, fat mass, waist circumference, triceps skinfold thickness, hemoglobin, albumin, prealbumin, total cholesterol but higher values for C-reactive protein. Of the 168 patients staying > or =6 days in hospital, 57% lost and 39% gained weight. Only 1.9% of all patients (8 of 430) were malnourished and lost further weight during hospitalization. CONCLUSIONS: We found a low prevalence (10%) of malnourished patients on admission. Clinical judgment and to some extent anthropometrical measurement were helpful for assessing the nutritional status, laboratory values were not.

In vivo mechanical characterization of human liver.

The mechanical behavior of human liver has been characterized with aspiration experiments. Measurements have been performed in vivo under sterile conditions during open surgery. Twenty-three measurements on six healthy human livers were performed using the same loading history for each test, so to allow a direct comparison of the measured deformations. The measurement results are reported and the experimental uncertainties evaluated. One of the main objectives of the present paper is to share information on the in vivo mechanical response of human liver with the biomechanics research community: the present data can be used for mechanical model development and validation purposes. The parameters of a quasi-linear viscoelastic model have been determined from the experimental data by means of inverse finite element calculations. The corresponding linear elastic modulus is compared with values from the literature. In particular, a significant discrepancy has been found with respect to the values proposed by Carter et al. [Carter, F.J., Frank, T.G., Davies, P.J., McLean, D., Cuschieri, A., 2001. Measurement and modelling of the compliance of human and porcine organs. Medical Image Analysis 5, 231-236] and the reasons for this difference are discussed. The predictive capabilities of the quasi-linear viscoelastic model and the Rubin Bodner non-linear elastic-viscoplastic model are compared with respect to the tissue response in repeated aspiration cycles. Finally, for demonstration purposes, the constitutive model corresponding to the "average" liver response has been implemented into a finite element whole liver model and used for simulations related to liver surgery.

Erythrocyte storage in hypertonic (SAGM) or isotonic (PAGGSM) conservation medium: influence on cell properties.

BACKGROUND AND OBJECTIVES: Prolonged red blood cell (RBC) storage may be associated with increased post-transfusion morbidity and mortality. A contributing factor is RBC storage lesions. We analysed the role of additive conservation solutions, either hypertonic or isotonic, on such cell properties. MATERIALS AND METHODS: After blood donation in citrate-phosphate-dextrose as an anticoagulant, 10 RBC units were stored with saline-adenine-glucose-mannitol (SAGM; 376 mOsm/l) and 10 units with phosphate-adenine-glucose-guanosin-saline-mannitol (PAGGSM; 285 mOsm/l). Measurements were made on days 1 and 42 of storage. RESULTS: The mean cellular volume measured by centrifuged microhaematocrit increased from 87.6 +/- 3.1 fl to 100.7 +/- 4.3 fl in PAGGSM and to 92.2 +/- 2.5 fl in SAGM (P < 0.001) on day 1, after 42 days it was 95.8 +/- 4.0 fl and 93.8 +/- 3.9 fl, respectively. Spontaneous haemolysis and osmotic fragility were lower after storage in PAGGSM. Both additives showed a similar degree of echinocytosis, decreased RBC aggregability and deformability, and increased RBC suspension viscosity after storage. CONCLUSIONS: The isotonic PAGGSM prevented the initial RBC swelling caused by citrate-phosphate-dextrose less than hypertonic SAGM, but reduced the spontaneous haemolysis rate and osmotic fragility after 42 days of storage. All other parameters, such as echinocytosis, decreased RBC deformability and aggregability, and increased blood viscosity was similar for both additive solutions and remained a major problem of blood banking.