[Platelet retention test Homburg (RTH) and drug monitoring of platelet adhesive properties of von Willebrand factor]. / Plättchen-Retentionstest Homburg: Drugmonitoring der Plättchenadhäsivität des von-Willebrand-Faktors.

Platelet plug formation is initiated by the process of platelet adhesion, mainly mediated by the von Wille-brand factor (VWF). Therefore, apart from established criteria the platelet adhesion property is a further criterion to determine VWF e. g. in diagnosis and treatment of von Willebrand disease (VWD). The new platelet retention test Homburg (RTH) is designed to close this gap. It is characterized by its non-thrombogenic filter with interconnecting pores, which retains platelets from blood when pressed through this filter due to the resulting shear stress. The RTH, in particular, proved to be highly sensitive in detecting the platelet adhesive property of VWF after its release from endogenous storage sites by desmopressin or infusion in VWD patients or its supplementation in vitro.

Prestorage inline filtration of whole blood for obtaining white cell-reduced blood components.

BACKGROUND: Preliminary studies have indicated that the inline filtration of whole blood is a feasible method of obtaining white cell (WBC)-reduced packaged red cells (RBCs) and WBC-reduced fresh-frozen plasma (FFP) while using only one filter. STUDY DESIGN AND METHODS: An inline WBC-reduction filter, specially designed for this purpose and integrated in a "top-top" system, was used in the preparation of 24 units of WBC-reduced RBCs (RBC-F) and FFP (FFP-F) in each of two transfusion centers (Vienna and Göttingen). Twelve conventionally prepared units of RBCs (RBC-C) and FFP (FFP-C) served as controls. WBC contamination was assessed in each unit with the Nageotte chamber. Several coagulation measures were evaluated by using standardized test systems. RESULTS: The median WBC contamination in RBC-F was 27,000 per unit in Vienna and 50,000 in Göttingen. In FFP-F, the median WBC contamination was 13,000 (Vienna) and 31,000 (Göttingen) per unit. Coagulation factors I, V, VIII, and XI in FFP-F were not different from those in FFP-C. In addition, markers for the activation of coagulation and fibrinolysis--that is, factor XIIa, prothrombin fragments, thrombin-antithrombin complexes and fibrinogen degradation products--were not greater in FFP-F. CONCLUSION: Blood components prepared from inline-filtered whole blood meet the standards for WBC-reduced RBCs and FFP. The protein profile of FFP-F is not altered, and markers for the activation of coagulation and fibrinolysis show no increase.

[Virus inactivated plasma]. / Virusinaktiviertes Plasma.

Two different virus inactivated plasma preparations are available in Germany. Methylene blue ephotoxidized (MB) plasma is plasma from a single donation, which is photoxidized using 1 microM methylene blue and visible light (1 hour 60,000 Lux). Photochemical inactivation reduces HIV by at least 5 log10, but also fibrinogen is altered. To date, the clinical significance of this finding is still unclear, since prospective clinical studies are lacking. Solvent detergent (SD) plasma is manufactured from a pool of about 2000 plasma donations, and triton-X-100 and tri-n-butyl-phosphate (TNBP) are added for virus inactivation. HIV and hepatitis viruses are thus reduced by 5 to 6 log10. SD treatment reduces protein S and alpha-2-antiplasmin by about 40%. Clinical studies have already demonstrated, that SD plasma is comparable with untreated, native fresh frozen plasma in terms of efficacy.

[Leukocyte filtration of stored whole blood for preparation of components]. / Leukozytenfiltration von Vollblutkonserven vor der Komponentenpräparation.

Prophylaxis of infection and alloimmunisation is the main reason for leucocyte depletion by filtration of blood components. The question is whether all red cell concentrates (RCC) should be filtered and whether plasma has to be filtered, too. For leucocyte-poor units whole blood was filtered before preparation using the 'top and bottom' system. These units of buffy-coat-poor RCC and plasma were compared with components filtered after preparation. Non-filtered RCCs and plasmas served as a control. By prefiltration of whole blood and filtration of components we obtained RCCs and plasmas with less than 1 x 10(5) leucocytes in every unit. In conclusion, leucocyte filtration before preparation seems to be an easy and cost-effective method in order to get two filtered components (RCC and plasma) with one filter.

[Platelet membrane glycoproteins in thrombocytapheresis and platelet concentrates]. / Thrombozytenmembran-Glycoproteine in Thrombapherese- und Thrombozytenkonzentraten.

Membrane glycoprotein (GP) expression on platelets changes during preparation of concentrates and storage. Recent studies proved that the increased expression of the GMP-140 (CD 62), a GP appearing on platelets after activation, correlates with the in vivo recovery of transfused platelets. We therefore investigated the expression of this and three other GP (GP IIb/IIIa, GP, Ib, GP 53), detected by flow cytometry, in normal controls and in platelet concentrates prepared by four different methods (apheresis, preparation from buffy coat, from pooled buffy coat and platelet-rich plasma) after preparation and during storage. Furthermore we investigated the influence of filtration, radiation and washing platelet concentrates on the expression of GP. The results can be summarized as follows: (1) The mean surface fluorescence (MF) is a better parameter for the evaluation of preparation and storage lesions than the total number of positive cells. (2) The mean fluorescence of GP Ib in platelet concentrates is generally lower than in normal controls and decreases continuously during storage; there is a small loss of GP Ib through washing and filtration. (3) GP IIb/IIIa fluctuates during preparation and storage, therefore it is not suitable for evaluation of quality. (4) The percentage of CD 62 positive cells and their mean fluorescence is higher in platelet concentrates than in normal controls and increases during storage continuously. There is a weak correlation of CD 62 with CD 63. (5) The changes of GP in apheresis concentrates and concentrates obtained from whole blood are similar after preparation and during storage.

Inactivation of viruses in fresh-frozen plasma.

Methylene blue (MB) or solvent/detergent (SD) treatment is used for the inactivation of lipid-enveloped viruses in plasma. One important characteristic of the SD treatment is the necessity to pool plasma from different donors, thus inducing the risk of spreading infectious particles. MB treatment can be applied to single-donor plasma, causing no greater infectious risk than conventional fresh-frozen plasma (FFP). However, the virucidal efficacy of the SD method regarding HIV, HBV and HCV has been significantly better examined and proven than the MB treatment. Most of the therapeutic constituents of both plasma products are well maintained; coagulation factors decrease by roughly 5-20%. SD treatment reduces protein S and alpha 2-antiplasmin by approximately 40%, whereas MB treatment leads to a significant photooxidative alteration of fibrinogen with a disturbance of fibrin polymerization. As current studies show, the use of either plasma product is obviously not limited by acute or chronic toxicity. Several studies are in progress to evaluate the relevance of alterations in FFP quality which may affect the clinical efficacy of virus-inactivated plasma.

[Methylene blue/light treatment of virus inactivated human plasma: production and clinical experience]. / Durch Methylenblau/Licht-Behandlung virusinaktiviertes Humanplasma: Herstellung und bisherige klinische Erfahrungen.

A photodynamic procedure to inactivate viruses in fresh plasma for therapeutical use is carried out by illuminating single units of plasma with visible light in the presence of the phenothiazine dye methylene blue. The blood bag systems of all common suppliers can be used for this purpose. Photodynamic treatment only moderately influences the activities of plasma proteins. One of the most sensitive parameters is the thrombin time which is prolonged, dependent on dye concentration and illumination time. Under the chosen conditions (1 microM methylene blue, 1 h illumination time, about 50,000 lx), the increase is approximately 25%. A drug monitoring study indicated that photodynamically treated fresh plasma is as well tolerated as conventional fresh-frozen plasma. Between February and the end of July 1992 about 31,000 units of the virus-inactivated product were distributed to clinics within Lower Saxony.

[Comparative analysis of various plasmapheresis methods--modern procedures of mechanical plasma collection compared with each other and with manual bag centrifugation procedures]. / Vergleichsanalyse verschiedener Plasmapheresemethoden--Moderne Verfahren apparativer Plasmagewinnung im Vergleich untereinander und mit dem manuellen Beutel-Zentrifugationsverfahren.

Four plasmapheresis procedures (manual blood bag centrifugation plasmapheresis, and the three plasmapheresis machines P.C.S./Haemonetics, Autopheresis-C/Baxter-Travenol, Plasmapur Monitor/Organon Teknika) were studied comparatively. The three machine procedures could be performed more easily and more rapidly and were well accepted by donors, autologous donors (patients) and staff. Compared with the traditional, well established manual procedure, a possible impairment of the plasma donors seems reduced rather than raised. Activation of the hemostatic system of the donors, measured with very sensitive methods, was found to be less pronounced when plasmapheresis was performed with the machines than when it was performed conventionally. The plasma product obtained by machine plasmapheresis was found to be of higher quality. All three systems showed less activation of the clotting system. Especially the plasma obtained by the P.C.S. showed a higher clotting factor yield. Plasma obtained by the Autopheresis-C and by the Plasmapur Monitor (both systems are equipped with filters) was markedly less contaminated with cells. The recently found low activation of the clotting system of plasma recipients, however, showed no differences when plasma obtained conventionally or by the Plasmapur Monitor was used. In summary, the new machine plasmapheresis devices offer a good alternative to the conventional blood bag centrifugation method and set new standards for the production of high quality plasma.

[Initial experiences with methylene blue virus inactivated fresh frozen plasma: results of a clinical and in vitro study]. / Erste Erfahrungen mit Methylenblau-Virus-inaktiviertem Fresh-Frozen-Plasma: Ergebnisse einer klinischen und einer In-vitro-Studie.

Methylene blue (MB) has recently been introduced to inactivate viruses in single donor fresh frozen plasma (FFP) units. In the first clinical study 519 units of MB-treated FFP were given to 103 patients. No specific clinical side effects with adverse reactions were recorded. However, after thawing, clots were observed in 9 of the first 110 units, although the medical staff had thawed the MB-FFP in exactly the same manner as the conventional FFP in which clots are extremely rare. The possible effects of methylene blue were investigated by subsequent in vitro experiments: Methylene blue together with light led to generation of fibrin(ogen) derivatives which have an increased tendency for aggregation but cannot be normally clotted by thrombin and even seem to interfere with normal fibrin polymerization. Inadequate conditions during plasma preparation such as long illumination or temperatures above 40 degrees C enhanced the generation of these fibrin(ogen)-derivatives. In addition, special requirements for producers and users of MB-FFP and further investigations are necessary in order to prevent complications.

Determination of soluble fibrin: a comparison of four different methods.

The determination of soluble fibrin (SF) in plasma was compared using four different methods. The SF-ELISA immunologically measures the concentration of desAA- and desAABB-fibrin while the SF-tPA-test is based on activation of plasminogen by tissue plasminogen activator (tPA) in the presence of fibrin; the SF-PS-turbidimetry assay relies on the protamine sulphate (PS) -induced aggregation of fibrin in plasma whereas the SF-erythrocyte-agglutination-test (SF-EAT) detects soluble fibrin by its aggregation with fibrin monomers attached to test erythrocytes. Soluble fibrin was generated in vitro by addition of thrombin or ancrod to plasma. In these experiments the soluble fibrin values of the four methods correlated well with each other and with the fibrinopeptide A release, especially in ancrod-induced fibrinogen turnover (r greater than 0.93). This high correlation is remarkable, considering the fact that the methods are based on different principles. Detection of thrombin-induced soluble fibrin was more sensitive; differences between ancrod and thrombin action were observed as well, probably due to different forms of soluble fibrin. A delayed increase of SF-PS-turbidimetry values in particular during the thrombin action can be attributed to a lack of detectable aggregation of soluble fibrin at low concentrations due to its solubility in plasma. Subsequently, soluble fibrin was measured in samples from patients. The SF-ELISA and SF-tPA-test were highly sensitive and correlated better than the other methods with each other, but all correlations were less satisfactory compared with the in vitro studies. These weaker correlations might be explained by the heterogeneity of soluble fibrin determined by inter- and intraindividually varying concentrations of fibrinogen and its different derivatives in plasma samples from patients. All methods provided reliable results with differences in sensitivity, specificity and practicality. The SF-tPA-test, SF-PS-turbidimetry, and SF-EAT are practical methods for routine use whereas the SF-ELISA is a highly reliable and by far the most sensitive and specific method thus offering new insights into pathogenesis of fibrinaemia and related diseases.

[Neuronal nets]. / Neuronale Netze.

Neural networks are used as models of cognitive systems. On the basis of results from brain research, the processing of knowledge and information can be conceived as occurring through parallel interaction of multiple but simple and uniform processor elements in a network structure. In these 'neural networks' knowledge is stored in a distributed way throughout the network and subjected to parallel processing. According to Hebb's concept of synaptic plasticity, the process of learning is based on the strengthening of the links between the processing elements. The implementation of network models in electronic data processing systems allows for simulation of cognitive phenomena such as learning and forgetting or abilities such as recognition of acoustical or optical patterns, in a more efficient way than conventional computer programming. Neural network modelling can help to understand the abilities and disorders of the brain.

[Comparison of 4 plasmapheresis procedures]. / Vergleich von vier Verfahren zur Plasmapherese.

In recent years the collection of plasma has been increasingly carried out by apparative plasmapheresis. In the University Hospitals of Göttingen and Würzburg the plasmapheresis machines PCS from Haemonetics, Autopheresis-C from Baxter, as well as Plasmapur-Monitor from Organon-Teknika, were compared with each other and with the conventional centrifugation of blood bags; experiences in routine use were complemented by specific studies. Altogether, the apparative methods distinguished themselves through a high quality of retransfused blood and collected plasma. Furthermore, practicability, donor compatibility and donor safety resulted in good acceptance by both donors and staff.

Application of a network structure in a knowledge-based system for medical diagnostics.

Systems supporting diagnostic decision making have been designed more often on the base of production rules than on semantic nets. One reason for that might be that concepts to process information on the latter structures are still rare. In this study the application of a semantic net is described. Via creation of various views, different sets of information are defined, depending on their meaning in the semantic net. Projections, which are in general a combination of mappings and set operations, are used to infer a set of information from another. The developed system was written in Pascal, the semantic net was implemented using a network-like pointer structure. The concept has been used to develop PROJECTOR, an expert system for differential diagnosis based on a semantic net. The structure has turned out to be fast and compact enough to allow large amounts of data to be handled easily even with a personal computer.

[Anesthesiologic and intensive care aspects of severe pre-eclampsia with HELLP syndrome]. / Anästhesiologische und intensivmedizinische Aspekte der schweren Präeklampsie mit HELLP-Syndrom.

From 1984 to 1988 22 patients with preeclampsia and HELLP syndrome were treated in our ICU. The HELLP syndrome is defined as preeclampsia complicated by thrombocytopenia, hemolysis and disturbed liver function. 3 patients developed a severe DIC with consumption of hemostatic potential. One patient died in multiorgan failure having a consumption coagulopathy, liver rupture and renal failure. To prevent severe hemostatic complications, it is essential to start therapy of DIC as soon as possible by inhibition of the activated coagulation system. Bleeding caused by blood coagulation disorders can occur spontaneously and during operative treatment. Epidural or spinal anaesthesia should be avoided in patients with HELLP syndrome. Because of severe complications such as respiratory failure, diffuse bleeding caused by DIC and progressive deterioration of the renal and liver function in most of the cases, patients with HELLP syndrome require a close cooperation between obstetrics and anesthesist.

Development of a computer-aided reference system for differential diagnostics support.

In a situation of uncertain diagnosis, physicians may spend valuable time consulting relevant literature, often with unsatisfactory results. Therefore, our aim was to develop a computer system which supports differential diagnostics via rapid and comprehensive searches through information in literature. Based on entered signs and symptoms our prototype is able to offer probable diagnoses. Subsequently, further examinations and tests are suggested to confirm or exclude a certain disease. Thus, the final diagnosis is made gradually by differentiation of possible diseases. Our first attempt consisted in representing knowledge in a rule-based PROLOG system. However, because nearly all information for a sign-oriented differential diagnosis can be represented with very few relations only, we turned to a fact-oriented representation of signs and diseases. Access was possible via PROLOG or an imperative programming language. The index-sequential access on a fact-oriented representation of knowledge was suitable to manage a large knowledge base, which is necessary for a thorough differential diagnosis. A pointer structure was recently examined in order to handle different object-to-object relations. Efficient information processing is now possible which provides short response times using even broad knowledge bases.

[Comparison of 4 procedures in plasmapheresis: studies of modifying the hemostasis potential]. / Vergleich von 4 Verfahren der Plasmapherese: Untersuchungen zur Beeinflussung des Hämostase-Potentials.

The separation of plasma using the systems "Plasmapur Monitor" (Fa. Organon), "Autopheresis-C" (Fa. Baxter) and "PCS" (Fa. Haemonetics) was compared with the conventional blood bag centrifugation. In 16 apheresis per method, several parameters with the main focus on blood coagulation were examined in addition to other criteria. Compared to conventional centrifugation of blood bags, the plasma separation machines led to an only slight activation of the coagulation system, which seems to be negligible for donors as well as recipients. Furthermore, a decrease of coagulation factors and inhibitors in the collected plasma was most pronounced using bag centrifugation. Beyond this, particularly in apheresis systems with plasma filtration the low number of remaining cells meets the aim to reach a high quality of transfused plasma.

[Diagnosis of disseminated intravascular coagulation: the value of soluble fibrin, D-dimers and fibrin(ogen) split products]. / Diagnostik der disseminierten intravasalen Gerinnung: Aussagekraft von löslichem Fibrin, D-Dimeren und Fibrin(ogen)-Spaltprodukten.

The validity of the fibrin(ogen) derivatives 'soluble fibrin, D-dimers and fibrin(ogen) degradation products' was compared with other parameters in early and sensitive diagnosing of disseminated intravascular coagulation (DIC). In a clinical study 900 patients' samples from separate, defined groups were examined, including course observations of intensive care patients (n = 38) and patients with acute pancreatitis. The fibrin(ogen) derivatives correlated very well with the degree of blood coagulation disturbances: in particular, D-dimers and soluble fibrin proved to be more sensitive in early diagnosis of DIC than other parameters. The SF-PS-turbidimetry demonstrated a good validity and practicality in the quantitative determination of soluble fibrin, but a suitable analyzer is essential. Determination of D-dimers is preferable to that of fibrin(ogen) degradation products (both in the latex-agglutination test) because of the better sensitivity and practicality; even more sensitive results were provided by the D-dimer-ELISA, which is, however, not practical in acute diagnostics. The decrease in protein C was at least equally sensitive as the antithrombin III-levels in indicating the consumption of the hemostatic potential. The decrease of thrombocyte counts and fibrinogen levels could first be detected in a later stage of DIC. In conclusion, D-dimers and soluble fibrin can improve the DIC diagnostics, making them more reliable; additionally, antithrombin III and possibly protein C deserve further consideration, although the fibrin(ogen) derivatives are apparently of greater importance.