British journal of anaesthesia
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The speed of onset of anaesthesia with Althesin has been compared with that of other intravenous anaesthetics. Like thiopentone, Althesin appears to be a truly rapidly acting drug, producing sleep in one arm-brain circulation time. The relative potencies of the drugs studied were approximately Althesin 60 mulitre/kg equivalent to thiopentone 4 mg/kg, equivalent to methohexitone 1.2 mg/kg, although by some criteria Althesin 80 mulitre/kg is required to produce an effect equivalent to thiopentone 4 mg/kg.
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We evaluated the effects of ephedrine, mephentermine, metaraminol, phenylephrine, methoxamine, noradrenaline and adrenaline on halothane anaesthetic requirement (MAC) in dogs. MAC increased significantly only during ephedrine infusion (50%) although significance was approached with mephentermine (21%). ⋯ Arterial pressure was increased 50-100% with all agents. Our results support the hypothesis that anaesthetic requirement may be related, in part, to release of brain noradrenaline.
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RX 72601, a new and potent anticholinesterase, has been evaluated for its ability to reverse the neuromuscular blockade induced by non-depolarizing muscle relaxants. In rats RX 72601 10 mug/kg i.v. proved effective in reversing the effects of alcuronium gallamine, pancuronium or tubocurarine and the drug exhibited a wide margin of safety. ⋯ In dogs and cats, effective anti-curare doses had little action on the cardiovascular or respiratory systems. Overall the results obtained indicate that RX 72601 may be a safe antagonist of non-depolarizing muscle relaxants and that it will be possible to use RX 72601 without prior administration of atropine.
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Totally closed circuit anaesthesia has been used with nitrous oxide/oxygen gas mixtures, supplemented by halothane for spontaneous breathing, or by opiates for artificial ventilation. Oxygen expenditure averaged 227 ml/min, while nitrous oxide expenditure declined exponentially from an initial value of 462 ml/min to 110 ml/min after 2 hr. ⋯ Halothane expenditure average 3.5 ml (liquid) per hr. Halothane concentrations in the operating theatre atmosphere did not increase above 0.03 p.p.m.
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Brachial plexus block (axillary approach) has been compared with ulnar nerve block for the evaluation of local anaesthetic drugs. Duration of analgesia is the same in both techniques with the same drugs. Following axillary nerve block the median, ulnar and radial nerves are blocked for a different time. ⋯ Larger amounts of local anaesthetic solutions are necessary for plexus blockade and this may cause toxic effects. The volunteer's comfort is less after plexus block because of more widespread paralysis. Therefore, ulnar nerve block and extradural block are in many respects the most suitable techniques for evaluation of new local anaesthetic agents.