The quick machine--a mathematical model for the extrinsic activation of coagulation.

The present paper describes a mathematical model of the kinetics of the extrinsic coagulation cascade in vitro. The coagulation factors FI, FII, FV, FVII, FX, heparin and antithrombin III (ATIII) as well as soluble fibrin polymers are considered. The effect of single-factor deficiencies of the factors II, V, VII and X, diseases like hypo- and dysfibrinogenaemia, hepatic insufficiency, inhibited polymerisation by degradation products, heparin therapy with and without ATIII deficiency and coumarin therapy on prothrombin time can be portrayed. Physiology of coagulation is represented in a dynamic mathematical model as a differential equation system. The model is based on three reaction types: enzymatic cleavage, complex formation and polymerisation. The model was implemented in a continuous simulation program on a personal computer using the Pascal programming language. Unknown rate constants were estimated by chi 2 fit. Prothrombin time calculated by the model was compared to the training set of 20 plasma samples. In most but not all cases the model harmonized quite well with the coagulometric data.

[Lidocaine elimination and MEGX formation after oral lidocaine administration--a practicable test for assessment of quantitative liver function]. / Lidocainelimination und MEGX-Bildung nach oraler Lidocainbelastung--Ein praktikabler Test zur Abschätzung der quantitativen Leberfunktion.

Oral load with 200 mg Lidocain was performed in 370 patients with chronic liver disease. The 120- and 240-minute Lidocain plasma concentrations as well as the 30- and 60-minute MEGX plasma concentrations, main metabolite of Lidocain, were measured by means of gas chromatography and with the commercial TDX test from the firm Abbott. No side effects caused by the load were observed and all of the patients resorbed Lidocain. Peak concentrations were found both for Lidocain and for MEGX in the 60-minute tests. Patients with liver cirrhosis of different aetiology showed significantly higher Lidocain plasma concentrations and lower MEGX values than patients with chronic non-cirrhotic liver disease. The differentiation of these two groups of patients was most successful via the determination of the 240-minute Lidocain plasma concentration. Oral load with 200 mg Lidocain has turned out to be a practicable and meaningful test for the estimation of the Cytochrom P450-dependent liver function.

[Diagnostic strategies for detection of the von Willebrand syndrome]. / Diagnostische Strategien zur Erkennung des von-Willebrand-Syndroms.

The von Willebrand disease (vWD) is the most severe coagulopathy. Because of the complex biochemical structure of the von Willebrand factor (vWF), a great number of types and subtypes of the vWD were found. A screening of vWD can only be done by examining the bleeding time, the ristocetin cofactor activity (risto) and by an immunological determination of the vWF concentration. Examinations of 200 patients with a bleeding tendency showed that the ratio vWF/risto < 0.7 indicates a high probability for an abnormal multimeric structure of vWF. The exact determination of the vWD subtype then has to be done by a SDS-agarose gel electrophoresis. In 16.8% of our patients we found a decreased vWF concentration in the platelets. These patients showed normal plasmatic coagulation factors, but a bleeding tendency and a prolonged bleeding time. For diagnosis of vWD the bleeding time, immunological determination of the vWF and the risto should be done first. If a ratio vWF/risto < 0.7 or a prolonged bleeding time with a bleeding tendency is found, the separation of the vWF multimers into plasma and platelets and the determination of the vWF concentration in platelets should be carried out for an exact diagnosis of vWD.