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.

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.

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.

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.

A prospective multicentre study on the safety of long-term intensive plasmapheresis in donors (SIPLA).

BACKGROUND AND OBJECTIVES: The safety of chronic intensive donor plasmapheresis has not been determined in large prospective studies examining dropout rates, dropout reasons and predictors of withdrawals. MATERIALS AND METHODS: Twenty-one plasma centres recruited 3783 donors who were switched from a moderate to an intensive plasmapheresis programme and observed over a 3-year period. Individuals weighing < 70 kg and > or = 70 kg donated 750 ml and 850 ml of plasma per session, respectively. The maximum of annual donations was limited to 60. Total serum protein (TSP) and haemoglobin (Hb) or haematocrit (Hct) were determined at each donation, and immunoglobulin G (IgG) at every fifth donation. Dropout rates, dropout reasons and potential predictors of withdrawal were analysed. RESULTS: Dropouts were predominantly due to socioeconomic (49.2% of all donors) or medical reasons not related to plasma donations (10.4% of all donors). Sixteen per cent of donors dropped out when IgG, TSP or Hb levels fell below threshold values. Severe clinical adverse events related to plasmapheresis were observed in five subjects. The incidence in severe cardiovascular diseases was lower in donors than in the general population. The risk factors that led to dropping out as a result of low IgG, TSP or Hb levels included younger age, female gender, low initial IgG levels and a high donation frequency. Neither body weight nor the amounts of plasma donated per kilogram of body weight per session were associated with ceasing due to medical reasons, whether related or unrelated to plasma donations. Females and males within the respective lowest body weight category were not at higher risk of dropping out. CONCLUSION: Long-term intensive donor plasmapheresis under conditions investigated in this study is safe. All donors weighing > or = 70 kg are safely able to donate 850 ml of plasma in each session up to 60 times per year, provided that they are carefully monitored.

The impact of different intensities of regular donor plasmapheresis on humoral and cellular immunity, red cell and iron metabolism, and cardiovascular risk markers.

BACKGROUND AND OBJECTIVES: Major studies are still lacking on the impact of differing intensities of long-term donor plasmapheresis, not only on total serum protein, albumin and immunoglobulin G (IgG), but also on humoral and cellular immunity, red cell and iron metabolism, and biochemical cardiovascular risk markers. MATERIALS AND METHODS: Three groups of donors, comprising 483 individuals undergoing differing intensities of long-term serial plasmapheresis, were entered into a cross-sectional study. A fourth control group consisted of 100 non-donors. In addition to measuring total protein, albumin and IgG levels, we determined parameters of humoral and cellular immunity, red cell and iron metabolism and recognized biochemical cardiovascular risk factors. RESULTS: The median annual net amount of plasma donated by the three donor groups was 37, 16 and 10 l, respectively (P < 0.0001). Donors had significantly lower total serum protein, albumin and IgG levels than non-donors (P < 0.0001), but the intensity of plasmapheresis had no influence on those parameters. Like non-donors, all plasma donors had normal humoral and cellular immunity. No increased rates of iron store depletion were observed in the three groups of plasma donors. Plasma donors were not at increased cardiovascular risk. CONCLUSIONS: Regular donor plasmapheresis of up to 45 l of plasma per year appears to be as safe as more moderate plasmapheresis programmes, with respect to the parameters analysed in this study. Individuals donating under these conditions did not develop impaired humoral and cellular immunity, iron store depletion, or increased cardiovascular risk with regard to established biochemical risk markers. Prospective studies are required to determine more exactly than in retrospective analyses the reasons why donors withdraw from plasmapheresis programmes.

IVBT-documented platelet function correlates with flow cytometric data.

Thrombocytopenic patients with identical platelet counts often show different bleeding tendencies owing to significant differences in the platelet function. This could be demonstrated by the in vitro bleeding test (IVBT). Using flow cytometry, we tried to find characteristics of platelet antigen expression in order to explain these differences in function. Thirty patients with bone marrow hypoplasia receiving 65 platelet transfusions (mainly from a cell separator) were observed for 3 to 29 days. Size, granulation and fluorescence of platelet-rich plasma (n = 522 samples) were evaluated using monoclonal antibodies against GP IIIb (collagen receptor), GP IIb/IIIa (fibrinogen receptor) and GP Ib (thrombin receptor). We defined separate gates for each antibody using the results from 50 normals and by laying an orthograde cross over the gate to divide the gate into four equal quadrants. The platelet populations were divided into four different groups according to the occlusion time (OT) of the IVBT and the Simplate time (ST). The thrombocytes with the most impaired function (OT > or = 485 s/ST > 30 min) had significantly less platelet fluorescence when marked with antibodies against GP IIIb and GP Ib than those with short OT and ST (OT < 100 s/ST < 15 min). Similar results were obtained when evaluating the data relative to the bone marrow status: patients with < 1000 WBC/microliters showed significantly less platelet fluorescence when marked with anti-GP IIIb and anti-GP Ib than thrombocytopenic patients, who had a spontaneous platelet rise beyond 30,000 platelets/microliters a few days later. One day after platelet transfusion, significantly more platelets with high GP IIIb and Ib expression could be found. We were also able to document better transfusion efficacy of platelet concentrates with high GP IIIb and Ib expression. Finally, patients with high bleeding scores showed less GP Ib expression on the platelets than patients with low bleeding scores. In summary, the IVBT-documented platelet function clearly corresponded to an increased expression of the collagen receptor and the thrombin receptor of platelets.

Thrombocytopenia-adapted in vitro bleeding test assesses platelet function in thrombocytopenic patients.

Platelet counts do not always reflect the true bleeding risk in chronically thrombocytopenic patients, and the posttransfusion platelet increments do not necessarily demonstrate that therapeutic efficacy. There are no easy and reliable tests yet permitting the determination of platelet function in thrombocytopenic patients. The in-vitro bleeding test (IVBT) with the Thrombostat 4000 proved to be a very sensitive and specific test for the detection of platelet disorders. In order to become suitable for the investigation of thrombocytopenic blood with platelet count between 5 x 10(9)/L and 50 x 10(9)/L, special modifications were necessary. We report on the evaluation of two thrombocytopenia-adapted modifications (TP-IVBT 150/120), first with blood of healthy donors made thrombocytopenic (three experiments with six blood samples each of different platelet concentrations and identical hematocrit) and then in a clinical study on 77 thrombocytopenic patients (69 with bone marrow hypoplasia, eight with autoimmune thrombocytopenia) receiving 267 platelet transfusions. The patients were followed over 15 days on average (1-67 days) by daily examinations (total 1,285 observation days). Most TP-IVBT measurements were carried out in triplicate, using the modification with the 120-microns filter (TP-IVBT 120) because it proved to be superior to the other modification. Additionally, cell counts, hematocrit, body temperature, platelet volume, platelet distribution width, expression of CD 36, 41a, 42b on platelets, Simplate bleeding time, and detailed analysis of bleeding signs were performed for the calculation of a bleeding score. There was a close correlation between TP-IVBT and platelet counts with thrombocytopenic normal blood (r2 = 0.81-0.94). This indicated the suitability of this test modification to examine platelet function in thrombocytopenic patients. The clinical study showed that the TP-IVBT helped at least to determine the platelet-related bleeding risk in thrombocytopenic patients. It allowed differentiation between hypoplastic and autoimmune thrombocytopenia in most cases. In addition, significant differences in platelet function of various diseases and of different bone marrow regeneration could be demonstrated. The TP-IVBT is well-suited for the control of platelet transfusion efficacy and may replace the in-vivo bleeding time in most cases. On the other hand, the test still shows too much of a variation and involves too much labor and cost for routine application.

A contribution to the indications for platelet transfusion and determination of its therapeutic efficacy.

The platelet count does not really reflect the true bleeding risk in chronically thrombocytopenic patients. Recently, we reported on two modifications of an in vitro bleeding test (IVBT) which appeared to be suitable for the evaluation of primary non-vascular hemostatis in thrombocytopenic and anemic patients (platelets 10-50,000/microL, hct 16-30 L/L). We report on the clinical study conducted with the IVBT modification which proved to be superior. Fifty thrombocytopenic patients, 42 with bone marrow hypoplasia and 8 with autoimmune thrombocytopenia, were followed up for a total of 686 days and received 161 platelet transfusions (mainly from cell separator). The IVBT was carried out with the Thrombostat 4000 in triplicate using 120 microns filters and evaluating the occlusion time (OT). Additionally, cell count, hematocrit, body temperature, platelet volume, platelet distribution width, Simplate time and a detailed analysis of bleeding signs for the calculation of a bleeding score were performed. The IVBT modification used allowed the determination of platelet-related bleeding risk in thrombocytopenic patients. With the IVBT, significant differences in platelet function in different patients could be demonstrated which primarily reflected the underlying disease. In addition, bone marrow regeneration correlated with platelet function. From the findings of this study, the authors formulate criteria for the indication of platelet transfusion which includes platelet function as well as the platelet count. Increased individual bleeding risk factors have to be considered too. But before generalization these criteria have to be verified by a controlled prospective study.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of bleeding risk in thrombocytopenic patients with platelet transfusion therapy.

In a clinical study (50 thrombocytopenic patients) we determined the bleeding risk and the platelet transfusion efficacy by a special modification of the in vitro bleeding test (IVBT, Thrombostat 4000). Additionally, cell count, hematocrit, body temperature, platelet volume and distribution width, Simplate bleeding time and a bleeding score were investigated. The use of the modified IVBT proved to be promising to find a clearer indication of platelet transfusion and to estimate its efficacy.

[Risk assessment and diminution in preoperative autologous blood donation]. / Risikoabwägung und -minderung bei präoperativer Eigenblutspende.

Preoperative autologous blood donation is only indicated if a positive balance between benefit and risk can be struck. In this contribution the different aspects to be considered are described and valued. By a mathematical formula we try to correlate the different aspects somewhat more objectively. In addition, we define 4 risk groups by the state of health of the patients which allow to estimate the risk of the patient by blood donation more easily and help to reduce it by selection of the appropriate donation procedure.

[Comparison of thrombocyte concentrates from buffy coats after 3 and 16 hours of storage]. / Vergleich zwischen Thrombozytenkonzentraten aus Buffy coat mit 3 und 16 Stunden Lagerungszeit.

Since extended storage of the buffy coat (BC) might be disadvantageous for the platelet function because of granulocyte proteases we investigated platelet concentrates (PC) prepared from BC which rested either for 3 h (n = 18) or 16 h (n = 41) before further preparation. We found significant differences especially in the morphology score, pH and lactate in favour of the PC from 3-hour-BC. The differences decreased during the 5-day storage. PC of unacceptable quality (n = 4) only derived from 16-hour-BC. Therefore, the use of PC from BC stored for more than 4 h at least requires an adequate quality control before delivery.

[Evaluation of a noninvasive method for storage control of platelet concentrates]. / Evaluation einer nichtinvasiven Methode zur Lagerungskontrolle von Thrombozytenkonzentraten.

We evaluated a system for storage of platelet concentrates (PC) which is thought to monitor the platelet function during storage by measuring the light transmission (Plateguard). Platelet function, morphology and metabolism altered during storage as usually. But the alterations did not correlate to light transmission. Only PC with very strong changes and final pH lower than 6.0 (4 of 59) showed different light transmission (exponential curves). Nevertheless the Plateguard can detect these unsuitable PCs if the software would be modified as proposed. In addition, several technical improvements are necessary before routine use.