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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Anaesthesist 44 (1995), S. 761-769 
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Spinalanästhesie ; Zwei-Kammer-Modell ; Liquorverlust ; Punktionstrauma ; Retraktion ; Key words Spinal anaesthesia ; Two-chamber-model ; Liquor leakage ; Post-dural-puncture trauma ; Retraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Various in vitro models have been introduced for comparative examinations of post-dural-puncture trauma and measurement of liquor leakage through puncture sites. These models allow simulation of subarachnoid, but not of peridural, pressure. A new two-chamber-model realizes the simulation of both subarachnoid and peridural pressure and allows observation of in vitro punctures with video-documentation. Frame grabbing and (computer-aided) image analysis show new aspects of spinal puncture effects. Therefore, post-dural-puncture trauma and retraction can be objectively visualized by this method, which has not previously been demonstrated. Methods. The two-chamber-model consists of two short aluminium cylinders. Native human dura patches (8×8 mm) from fresh cadavers are put (correctly oriented) between two special polyamide seals. Mounted between the upper and lower cylinder, these seals stretch the dura patch, which remains flexible and even in all directions. After filling of the lower (subarachnoid) and upper (peridural) chamber with Ringer lactate solution, positive or negative physiological pressure can be adjusted by way of two (Ringer lactate solution filled) infusion lines in each chamber. Puncturing is performed at an angle of 57° to the dura. The model allows examination with epi-illumination and transmitted (polarized) light. In vitro punctures are observed through an inverted camera lens with an CCD-Hi8 video camera (Canon UClHi) looking into the peridural chamber and documentated by means of an S-VHS video recorder (Panasonic NV-FS200EG). After true-colour frame grabbing by a video digitizer (Fast Screen Machine II), single video frames can be optimized and analysed with a 486-66 MHz computer and conventional software (Corel Draw 3.0, Photostyler 1.1a, DDL Aequitas 1.00b). Punctures demonstrated in this paper have been done under simulation of a transdural gradient of 20 cm water similar to the situation of a recumbent patient (15 cm water in the subarachnoid and –5 cm water in the peridural chamber). The punctures were followed by short-time observation for up to 10 minutes. Results. By making it possible to obtain a picture of the puncture site at 20-ms intervals (because of the PAL norm of 50 half-frames/s), video-documentation has become accepted as superior to conventional photography. When the Ringer lactate solution in the subarachnoid chamber is stained with methylene blue, transdural leakage can easily be observed. The results of this documentation technique demonstrate that no dural puncture can be atraumatic, when a 29-G Quincke needle is used. Calculation of the difference between a digitized video frame before and after the puncture clearly illustrates the dural trauma. Owing to their non-cutting tip, as expected, pencil-point needles leave diffuse changes across the dura patch, whereas a more local trauma was observed after puncturing with cutting-tip needles. The same computer calculation between two video frames allows examination of post-puncture-dural retraction of the puncture site. In this connection, we found that relevant dural retraction is a phenomenon limited to the first minute after puncture. Thin spinal needles with so-called modern tips (e.g. Whitacre, Atraucan) can minimize the post-dural-puncture trauma, whereas thicker, conventional, spinal needles (Quincke) leave considerable dural defects. Conclusions. The two-chamber-model presented allows easy simulation of physiological subarachnoid and peridural pressure. The Ringer lactate solution in the subarachnoid chamber corresponds to the liquor, whereas that in the peridural chamber corresponds to the intercellular (peridural) space. The tension of the dural patch between the polyamide seals is similar to the situation in an anatomical model observed by spinaloscopy (in an earlier study). With the video documentation and computer-aided analysis technique introduced, dural trauma and retraction on the puncture site can be examined and demonstrated precisely. This model can be regarded as the current experimental standard for comparative in vitro studies of different spinal needles.
    Notes: Zusammenfassung Es wird ein neues Zwei-Kammer-Modell zur Untersuchung und Demonstration transduraler Liquorverluste nach Spinalanästhesien vorgestellt. Mittels Videodokumentation und nachfolgender Bilddigitalisierung erstellte Einzelbildserien verschaffen einen unmittelbaren Eindruck von den Veränderungen an der Dura während und nach einer in vitro-Punktion; durch computergestützte Verrechnung dieser Bilder ist es möglich, einen bislang nicht gezeigten Aspekt der durch Spinalpunktionen entstehenden traumatischen Veränderungen wie auch der nach der Punktion stattfindenden Retraktionsvorgänge zu demonstrieren. Mit der Entwicklung dieses in vitro-Modells und der vorgestellten Dokumentations- und Auswertungsmethodik wird der Versuch unternommen, für den Vergleich heute vorhandener und zukünftiger Spinalnadeln einen experimentellen Standard zu schaffen.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 470 (1929), S. 275-283 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 113 (1938), S. 221-225 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 73 (1961), S. 334-338 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Während das Keten bei der Polymerisation ein einheitliches Dimeres ergibt, führt die kontinuierliche Polymerisation der Aldoketene zu neuen, einheitlichen, trimeren Verbindungen. Daneben entstehen nur geringe Mengen dimerer Produkte mit einer dem Diketen analogen Struktur. Auf Grund der Bildungsweise, der Abbaureaktionen und des Vergleichs der IR-Spektren der di- und trimeren Aldoketene konnte für letztere die Struktur von Dialkyl-cyclobutenolonacylaten bewiesen werden. Als Zwischenstufe treten dimere Aldoketene mit Dialkyl-cyclobutenolon-Struktur auf, was durch ihre Reaktion mit Keten und Diäthylketen bewiesen wurde, die gemischte Trimere ergibt. Zur Trimerisation sind lediglich die Aldoketene befähigt.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 63 (1930), S. 1635-1638 
    ISSN: 0365-9631
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 64 (1931), S. 791-797 
    ISSN: 0365-9631
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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