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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 51 (1996), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We examined the effect of high frequency transcutaneous electrical nerve stimulation on the onset of brachial plexus block. Three groups of patients scheduled for surgery of the hand had a local anaesthetic block performed with 40 ml mepivacaine 1.5% using the axillary approach. After injection of the local anaesthetic transcutaneous electrical nerve stimulation was applied for 15 min either to the median nerve or the ulnar nerve; no stimulation was applied in the control group. Before and for 45 min after, the injection of local anaesthetic touch perception, pin prick, motor strength andskin temperature were tested by a blinded investigator in the areas supplied by the median, musculocutaneous, radial and ulnar nerves. There were no differences in the onset of block between the groups. Thus, the frequency-dependent action of local anaesthetics could not be demonstrated.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Chronopharmakologie ; Bupivacain ; Nervenaktivität ; Kaninchen ; Key words Bupivacaine ; Chronopharmacology ; Nerve activity ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract To test the hypothesis that the efficacy of local anaesthetics to block nerve conduction is related the time of day (TOD) of drug application, we retrospectively analysed data from previous experiments on tachyphylaxis. During the course of these experiments, as a measure of drug efficacy we determined the minimal blocking concentration (cm) of bupivacaine in rabbit aortic nerves at several TODs. The special in situ preparation used permitted study of local anaesthetic pharmacodynamics without the influence of pharmacokinetics, making it possible to investigate the chronopharmacodynamics of these drugs by relating cms to the respective TODs of their measurement. Methods: In 43 New Zealand rabbits anaesthetised with urethane, the aortic nerve was dissected and partly placed in a double-lumen perfusion chamber (Fig. 1A), which was continuously perfused with tyrode solution or bupivacaine. Spike activity was continuously recorded by bipolar platinum-iridium electrodes caudad to the chamber for control and cephalad for registration of blocking effects. As a measure of drug efficacy, by increasing the bupivacaine concen- tration stepwise we determined the smallest concentration that blocks spike activity, i.e., cm. After each determination bupivacaine was rinsed off to confirm intact nerve function (Fig. 1B). Results: Forty-nine determinations of bupivacaine cm were performed between 12:25 p.m. and 2:35 a.m. Data were pooled into groups of 2 h (Fig. 2). There was no significant difference between groups (ANOVA). In particular, cm at 3:00 p.m. was not lower than at 11:00 p.m., times at which local anaesthetics have been found to be most and least effective, respectively. Conclusions: The cm of bupivacaine, and thus its efficacy to block nerve conduction, does not depend on TOD of drug application. Therefore, it is suggested that chronopharmacodynamics does not play an important role in the well-known circadian rhythm of the action of bupivacaine and probably of local anaesthetics in general.
    Notes: Zusammenfassung Um die Frage zu beantworten, ob die zirkadiane Rhythmik in der Wirksamkeit von Lokalanästhetika durch tageszeitabhängige Änderungen ihrer Pharmakodynamik verursacht wird, haben wir Daten aus früheren Untersuchungen über Tachyphylaxie retrospektiv analysiert. Methoden: Bei diesen Untersuchungen wurde die Wirksamkeit von Bupivacain in situ am N. Depressor des Kaninchens wiederholt und zu verschiedenen Tageszeiten bestimmt. Durch die spezielle in situ-Präparation war es möglich, die Wirksamkeit der Lokalanästhetika unabhängig vom Einfluß pharmakokinetischer Variablen zu untersuchen. Als Maß der Wirksamkeit wurde die minimale Blockierungskonzentration bestimmt, d.h. die niedrigste die Nervenleitung blockierende Lokalanästhetikumkonzentration. Ergebnisse: In insgesamt 49 Bestimmungen der minimalen Blockierungskonzentration zeigten sich keine tageszeitabhängigen Änderungen der Wirksamkeit von Bupivacain am Nerven, insbesondere fanden sich weder nachmittags noch nachts gerichtete Änderungen, Zeiten, zu denen Lokalanästhetika besonders lange bzw. kurz wirken. Schlußfolgerung: Demnach beruht die zirkadiane Rhythmik der Lokalanästhetikawirkung eher auf Änderungen ihrer Pharmakokinetik als auf Änderungen ihrer Pharmakodynamik.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Doppellumentubus: Komplikation ; Einlungenbeatmung: Komplikation ; Kreislauf: Pneumothorax ; Lunge: Pneumothorax ; Key words Double lumen tube ; One-lung ventilation ; Pneumothorax ; Vascular surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract The authors report a rare, recently diagnosed and atypical mishap during one-lung ventilation (OLV) via a double lumen tube (DLT) and left-sided thoracotomy: an ipsilateral pneumothorax during ventilation of the right lung. This occurred in a 63-year-old patient with chronic obstructive airway disease who was scheduled for urgent repair of a descending thoracic aortic aneurysm. Anaesthesia and surgery were uneventful until aortic cross-clamping release. The common presentation of increased intrathoracic extrapleural pressure owing to a pneumothorax in patients with mechanically ventilated lungs is a rapid decrease in oxygen saturation, followed or paralleled by haemodynamic deterioration. Although the above presentation could be seen in this case, the diagnosis of a tension pneumothorax was delayed twice. First, symptoms were initially obscured by haemodynamic changes resulting from a head-down tilt and aortic declamping. Second, since the lack of consolidation after aortic declamping focused attention on the airway problems, complications resulting from the use of a DLT were primarily considered. In particular, since breathing sounds were detectable initially, malposition or torsion of the DLT had to be excluded by fibre-optic bronchoscopy, which involved a further delay. Finally, two observations led to the diagnosis of a right-sided tension pneumothorax: (1) bullae of the contralateral lung, detected during thoracotomy; (2) the finding that ventilation of both lungs and the left lung subsequently increased arterial (SaO2) and mixed venous oxygen saturation (SvO2) and the circulatory status, but ventilation of the right lung caused a deterioration. Chest radiography and insertion of a chest tube with drainage of air, thereafter, validated our hypothesis. The time course of oxygen desaturation during OLV and tension pneumothorax was as severe as expected; the time course of haemodynamic deterioration, however, appeared quicker and had more impact than expected. Assuming that mediastinal deviation was not hindered by contralateral intrathoracic pressure during thoracotomy, we believed that circulation should be depressed later or to a lesser extent in patients with an intraoperative pneumothorax. Yet, during thoracotomy, decrease in cardiac filling and output during tension pneumothorax in OLV obviously results primarily from the immovability of the mediastinum owing to mediastinal fixation and is at least as decisive as the contralateral intrathoracic pressure in closed-chest patients. In summary, a tension pneumothorax during one-lung ventilation and thoracotomy is a rare, but disastrous complication during the use of a DLT, which has not, to our knowledge, been reported previously. We recommend that tension pneumothorax be added to the list of complications and problems during OLV by the use of a DLT, especially in patients with structural lung diseases.
    Notes: Zusammenfassung Die Verwendung von Doppellumentuben zur Einlungenbeatmung bei Eingriffen an der thorakalen Aorta hat die Inzidenz von Lungentraumen gesenkt und die Operationsbedingungen verbessert. Intubationsschwierigkeiten des linken Hauptbronchus, insbesondere bei großen Aortenaneurysmen, und Beatmungsprobleme infolge Dislokation während der Operation sind bekannte Verfahrensnachteile. Im vorliegenden Fallbericht wird über einen ipsilateralen Pneumothorax bei Einlungenbeatmung berichtet, dessen Diagnose und definitive Therapie verzögert wurde durch einen operationsspezifischen Blutdruck- und Sauerstoffsättigungsabfall infolge Aortenfreigabe und durch ein verfahrensspezifisches Problemlösungsverhalten (Bronchoskopie bei vermeintlicher Tubusfehllage). Eine für den Patienten kritische Hypoxämie konnte durch Beatmung der anderen Lunge verhindert werden.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Der Anaesthesist 45 (1996), S. 533-537 
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Leitungsanästhesien ; Lokalanästhetika ; Bupivacain ; frequenzabhängige Blockade ; elektrische Stimulation ; Key words Conduction block ; Anaesthetics ; local ; Bupivacaine ; Frequency-dependent block ; Electrical stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract The action of local anaesthetics on isolated nerves is enhanced by high stimulation frequencies. The aim of our study was to investigate whether high-frequency stimulation enhances regional anaesthesia in man. Methods. Seven healthy volunteers underwent three ulnar nerve blocks while non-noxious electrical stimulation with high (10, 50 Hz) or low (0.2 Hz) frequencies was applied via a widespread cutaneous electrode in the area supplied by the ulnar nerve. Perception was monitored continuously by means of a visual analogue scale. Skin temperature (infrared telethermometry) was evaluated every minute as an indicator of vasomotor block. After complete loss of perception or after 45 min, the spread of anaesthesia was determined by sharp-dull discrimination. The nerve block was preceded by a control stimulation of 45 min under otherwise identical conditions. Results. During stimulation with 10 and 50 Hz, perception was lost significantly earlier than with 0.2 Hz. The spread of sensory block at the end of the experiments was also enhanced by stimulation with high frequencies, whereas the onset of vasomotor block (rise in skin tempeature) remained unaltered. Conclusion. Non-oxious electrical stimulation with high frequencies significantly accelerates the onset of anaesthesia and extends the spread of sensory block.
    Notes: Zusammenfassung Die Wirkung von Lokalanästhestika am isolierten Nerven ist abhängig von der Aktionspotentialfrequenz, d.h. die Wirkung des Lokalanästhetikums wird durch hohe Aktionspotentialfrequenzen verstärkt. Ob dieses Prinzip auch bei Leitungsblockaden am Menschen gilt, ist jedoch unbekannt. An sieben gesunden Probanden wurden deshalb drei Ulnarisblockaden durchgeführt, während eine Elektrostimulation mit verschiedenen Frequenzen (0,2; 10 und 50 Hz) über eine Flächenelektrode im Versorgungsgebiet des Nerven an der Hand appliziert wurde. Die Probanden gaben die Empfindungsintensität kontinuierlich auf einer visuellen Analogskala an. Die Hauttemperatur wurde mittels Infrarot-Telethermometrie bestimmt. Nach komplettem Empfindungsverlust, höchstens aber nach 45 min wurde die Ausbreitung der Leitungsblockade mittels Spitz-Stumpf-Diskrimination bestimmt. Zur Kontrolle wurde vor jeder Untersuchung die Empfindungsintensität bei 45minütiger Stimulation ohne Leitungsblockade für jede Stimulationsfrequenzen ermittelt. Bei Leitungsblockaden unter hohen Stimulationsfrequenzen (10 bzw. 50 Hz) trat der Empfindungsverlust signifikant eher ein als bei der niedrigen Frequenz (0,2 Hz). Auch die Ausbreitung der sensiblen Blockade am Ende der Untersuchung wurde durch die hochfrequente Stimulation verbessert, hingegen blieb der Beginn der vasomotorischen Blockade (Anstieg der Hauttemperatur) unverändert. Nicht schmerzhafte, elektrische Stimulation mit hohen Frequenzen beschleunigt also Anschlagzeit und Ausdehnung einer Leitungsblockade des N. ulnaris.
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  • 5
    ISSN: 1432-1106
    Keywords: Triethyldodecylammoniumbromide ; Local anesthetics ; Neurotoxins ; Conduction block ; Wallerian degeneration ; Blood-nerve barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The blocking effect of triethyldodecylammoniumbromide (TEA-C12), applied locally to the sciatic nerve, was studied in 28 adult BDF1 mice. Clinical parameters, electrophysiological recordings of muscle action potentials evoked by stimulation at the sciatic notch, and morphological aspects are presented. Our results show that both the minimal blocking concentration and half the minimal blocking concentration induce flaccid paresis of the treated hind-limb. There was a complete, long-lasting nerve conduction block due to Wallerian degeneration of the myelinated nerve fibers. In contrast, pain sensation was abolished only on day 4 after application of the minimal blocking concentration, but was preserved during the rest of the time that nerve conduction block was observed. This corresponded to the electron microscopic finding of preservation of unmyelinated nerve fibers. Recovery of nerve conduction was characterized electrophysiologically by occurrence of minute polyphasic regeneration potentials between day 18 and 21, clinically by advanced restitution of muscle force on day 64, and morphologically by nerve regeneration. TEA-C12 also induced a disturbance of the blood-nerve barrier, demonstrated using an intraperitoneally administered biotinylated IgG tracer in the endoneurial space. The morphological features of the acute axonal changes of the myelinated nerve fibers including the degeneration of the axonal mitochondria suggest that the neurotoxic effect of TEA-C12 is possibly mediated by interference with the axonal energy supply. The selective affection of myelinated nerve fibers separates TEA-C12 from other neurotoxins that induce changes of the axonal microorganelles or complete Wallerian degeneration of myelinated and unmyelinated nerve fibers. The selectivity for myelinated nerve fibers and the supposed pathogenetic mechanism exhibit some similarities with the human polyneuropathy caused by acute arsenic acid intoxication.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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