British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Intradermal study of a new local anaesthetic agent aptocaine.
In a double-blind trial in 28 human volunteers, a new local anaesthetic agent, aptocaine, was compared intradermally at 1, 2 and 3% concentrations with lignocaine 2% and bupivacaine 0.5%. In a second trial in 27 subjects, 1% aptocaine was compared with mepivacaine and prilocaine, both 1, 2 and 3%. In terms of activity as determined by area of anaesthesia, and of duration of action, aptocaine was similar to mepivacaine and more active and long-lasting than lignocaine and prilocaine. ⋯ Duration of action was unaffected by concentration. Aptocaine had marked vasoconstrictor activity, which was maximal at 1%. These local anaesthetic properties suggest that aptocaine merits clinical trials, especially in dentistry.
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The effect of the physical characteristics of the carrier gas on the output of automatic plenum vaporizers was studied. The Vapor and Fluomatic halothane output at all dial settings was highest with oxygen as the carrier gas, as compared with helium and nitrous oxide and was a function of carrier gas viscosity at all dial settings. The output of the Fluotec Mark 2 at the 0.5 and 1% settings was highest with nitrous oxide as the carrier gas, but at 2, 3 and 4% settings it was highest with oxygen; at the 0.5% and 1% dial settings it was a function of carrier gas density, but at 2%, 3% and 4% it was a function of carrier gas viscosity.
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A young patient with a head injury inhaled a dental plate 60 hr after injury.
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Porcine malignant hyperthermia was studied in seven Pietrain pigs under standardized experimental conditions. In five animals malignant hyperthermia was triggered with suxamethonium and halothane, but in two pigs suxamethonium alone was used. Characteristic metabolic and physiological changes were found and these are discussed with regard to a possible mechanism to explain the malignant nature of the syndrome.
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The contributions of aerobic and anaerobic muscle metabolism to the heat produced in porcine malignant hyperthermia were studied in seven Pietrain pigs. Oxygen consumption measurements were used to calculate the increase in muscle temperature as a result of aerobic metabolism and this was compared with the observed muscle temperature. The results show that in the initial stage of porcine malignant hyperthermia heat production is largely aerobic in origin. Terminally, aerobic metabolism can account for about half the observed temperature increase.