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K Storck

Publications and source records attributed to K Storck.

9 recordsLinked to original sources
PubMed1996

Heat transfer evaluation of the nasal thermistor technique.

When analyzing transvalvular and venous flow velocity patterns, it is important to relate them to respiration. An accurate recording of respiratory phase can be carried out with different methods. One of these methods is the use of a thermistor, which reacts to the variation in air temperature, placed in the noise of the patient. The thermistor used has a diameter for 1.0 mm and is of standard bead type. Although small, it has a considerable long time-constant and a long time-delay. The high time-constant gives a low cutoff frequency, well below the respiratory frequency and thereby causing a large phase difference. The thermistor was analyzed with the lumped heat capacity method, where it was easy to study the influence from design parameters, time-dependent air temperature, and velocity. The analysis was extended using the finite element method and the temperature field in the thermistor and the probe was calculated as a function of space and time. These calculations confirmed the result from the lumped model. The result showed that timing of respiration was not accurately obtained with the thermistor analyzed. To improve the timing, it was necessary either to change the measuring method or to use signal processing in order to achieve faster response.

Blood Flow Velocity↗
PubMed1995

Quality control of platelet concentrates by the Thrombostat 4000.

Quality control of platelet concentrates (PC) is an important prerequisite for good transfusion praxis. However, direct measurement of platelet function is complex, since available methods (e.g. aggregometry, serotonin release) are time consuming and require special equipment. Therefore a test system is needed, which is easy to handle, fast, and achieves reliable results. The present paper compares the results of conventional platelet function tests with those of a modified in-vitro bleeding test (IVBT) (Thrombostat 4000) in liquid-stored and cryopreserved PCs. A high correlation between aggregometry, serotonin release, GMP 140 expression upon stimulation, and IVBT was demonstrated. Therefore IVBT seems to be a good alternative to the conventional platelet function tests for quality control of PCs. In addition, a good correlation between the results of IVBT of patients' blood after PC transfusion and IVBT of patients blood before transfusion supplemented with platelets of the respective PC could be found. Therefore IVBT seems to be able to predict PC transfusion success. However, since these data were obtained in a small sample undergoing bone marrow transplantation, further studies are needed to verify this hypothesis.

Bleeding Time↗
PubMed1993

[Quality control of platelet concentrates. Functional assessment of stored platelets in vitro].

Platelet concentrates transfused for correction of thrombocytopenia or reduced platelet function do not consistently improve primary haemostasis in the recipient. Insufficient therapeutic effects may be caused by impaired donor platelet function and by unfavourable donation and storage conditions, as well as by immunological interactions with the recipient blood. The present study was designed to investigate whether the effect of platelet transfusion on recipient platelet function can be predicted by in vitro methods. METHODS. Blood samples were taken from 12 thrombocytopenic patients before (20 ml, P0) and after (10 ml, P(vivo)) transfusion of one unit of platelets previously stored for 24-120 h in acid citrate dextrose. An additional sample was taken from the platelet concentrate (TK) immediately before transfusion. P0 was divided into two specimens and TK platelets were added to one of them (P(vitro) in order to obtain a platelet count similar to that in P(vivo). Bleeding time (BT) and bleeding volume (BV) of the samples P0, P(vivo) and P(vitro) were measured using the method of Kratzer and Born (Fig. 2); mean values were calculated for each sample from six measurements. Aggregability of TK platelets was determined in addition by aggregometry. In contrast to previous studies, physiological Ca2+ concentrations were restored and secondary haemostasis was inhibited by low-molecular-weight heparin (Fragmin P, Pfrimmer Kabi GmbH und Co. KG, Erlangen) in the platelet-rich plasma used for aggregometry. RESULTS. Platelet counts increased in all patients after transfusion (P(vivo) vs P0, Table 1) and were nearly identical in P(vitro) and P(vivo) (r = 0.94, P < 0.001; Fig. 3). Parameters of primary haemostasis were significantly improved by addition of platelets to P0 in vitro (BT P < 0.05, BV P < 0.01) as well as by platelet transfusion (BT P < 0.05, BV P < 0.01). Direct comparison of P(vitro) and P(vivo) yielded a very close correlation of BT (r = 0.88, P < 0.001) and BV (r = 0.89, P < 0.01) in both samples. Although aggregometry revealed decreasing platelet function with increased storage time, aggregability was considerably higher compared to previous studies of platelet concentrates stored for 2-5 days. CONCLUSION. A new technique has been developed which allows reliable prediction of the effect of platelet concentrates on primary haemostasis of the recipient by in vitro measurement of bleeding time and bleeding volume prior to transfusion using the method of Kratzer and Born.

Blood Platelets↗
PubMedDate not supplied

Prediction of the transfusion effect of platelet concentrates as measured by a model of primary hemostasis ex vivo.

A method to determine primary hemostasis ex vivo (Thrombostat) was modified to monitor the transfusion effect of platelet concentrates (PC) in 12 patients with thrombocytopenia following bone marrow transplantation. It was possible to measure platelet function in patients with a platelet count lower than 2 x 10(10)/l. In addition, the platelet aggregometer (Born) was adapted to determine cell function in PC anticoagulated with acid citrate dextrose of citrate phosphate dextrose. It was possible to make a prediction (r = 0.89) of the effect of a given PC on a patient's ex vivo primary hemostasis parameters. Platelet aggregation following addition of 20 muM ADP to PC, obtained from 12 single donors, resulted in an average maximal light transmission (light transmission/age of concentrate in days) of 61%/1 day and 37%/5 days, respectively. The same experiment gave only 39%/1 day and 13%/4 days for pooled platelets. To avoid possible immunization and bleeding complications, a reliable monitoring of platelet transfusion seems highly desirable.

Bone Marrow Transplantation↗