Articles: anesthetics.
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Biophysical journal · Jul 1984
Mechanisms of use-dependent block of sodium channels in excitable membranes by local anesthetics.
Many local anesthetics promote reduction in sodium current during repetitive stimulation of excitable membranes. Use-, frequency-, and voltage-dependent responses describe patterns of peak INa when pulse width, pulse frequency, and pulse amplitude are varied. Such responses can be viewed as reflecting voltage-sensitive shifts in equilibrium between conducting, unblocked channels and nonconducting, blocked channels. ⋯ We develop analytical expressions characterizing guarded receptors as "apparently" variable-affinity binding sites and predicting shifts in "apparent" channel inactivation in the hyperpolarizing direction. These results were confirmed with computer simulations. Furthermore, these results are in quantitative agreement with recent investigations of lidocaine binding in cardiac sodium channels.
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We treated 72 patients, referred to a pain clinic for acute herpes zoster neuralgia, with local anesthetics administered by nerve block and infiltration. Only those patients with severe pain initially proved to be at risk for the development of chronic postherpetic neuralgia (defined as pain in the involved dermatomes lasting at least six months). Although local anesthetic injections effectively relieved the acute pain of active herpes zoster, they did not prevent the development of chronic postherpetic neuralgia.
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Studies with an emulsion formulation of ICI 35 868 (2,6- diisopropylphenol ) indicate that this new formulation has anaesthetic properties in rats and mice, and haemodynamic effects in the mini-pig which are similar to those of the previously available Cremophor formulation. Administration of the emulsion formulation to dogs produced no untoward effect, whereas the Cremophor formulation produced a marked increase in plasma histamine concentration. In the mini-pig, no adverse response was produced by the repeated administration of the emulsion formulation of ICI 35 868, whereas the Cremophor formulation produced anaphylactoid responses when a second injection was given 1 week after an uneventful first exposure to this formulation. Behavioural responses in the rat suggest that the emulsion formulation may produce less discomfort on i.v. injection.
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The new relaxants vecuronium (Norcuron) and atracurium (Tracrium) have been compared with pancuronium (Pavulon) with respect to onset and duration of action and intubating conditions under clinical situations. A variant of the balanced anaesthesia technique with flunitrazepam, fentanyl and N2O/O2 was used. The following doses were considered equipotent (mg/kg body weight): vecuronium 0.07/0.10; atracurium 0.35/0.50; pancuronium 0.08/0.115. ⋯ The early recovery phase (from 5% to 25% recovery) was 6.1 +/- 2.4 after vecuronium, 8.3 +/- 1.7 after atracurium, 17.2 +/- 10.8 after pancuronium. There is a good correlation between our semiquantitative results, using the train of four, and quantitative recordings of muscle contractions reported in the literature. Both drugs show no cumulative effect after five repeated administrations.(ABSTRACT TRUNCATED AT 250 WORDS)
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A 2-month-old infant developed severe methemoglobinemia following topical pharyngeal application of a common benzocaine containing agent ( Cetacaine ). Although a number of reports of this complication have appeared in recent years, this is apparently the first case reported in the Otolaryngology literature. The pathophysiology, pharmacology, and treatment of this condition are reviewed.