British journal of anaesthesia
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Five patients who underwent thoracic operations had an extradural catheter placed in the paravertebral space. X-ray contrast was injected through the catheters. ⋯ In one patient, contrast appears to have entered the extradural space and, in another who had no detectable analgesia, the contrast was probably dispersed intrapleurally. The significance of these findings is discussed.
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Alcuronium 0.2 mg kg-1 was given to six patients to investigate the simultaneous recovery of breathing and peripheral neuromuscular function. Anaesthesia was maintained with 66% nitrous oxide in oxygen supplemented with 0.5% halothane, and the patients were ventilated to normocarbia. Patients were disconnected from the ventilator after the reappearance of the tetanic response. ⋯ Spontaneous breathing returned at a mean time of 23.6 min after the injection of alcuronium. Sixty minutes after the administration of alcuronium, respiratory exchange was judged adequate, and at that time neuromuscular function was still markedly depressed with a tetanic height less than 25% of control. It was concluded that, because of the slow recovery of neuromuscular function, alcuronium should be reserved for the longer surgical procedure.
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The arterial to end-tidal PCO2 difference (PaCO2-PE'CO2) was measured in five anaesthetized dogs during controlled ventilation at 0.25 Hz (15 b.p.m.) and during high frequency jet ventilation at 1, 3 and 5 Hz. Because of the slow response of the infra-red carbon dioxide analyser, satisfactory recordings of end-tidal carbon dioxide could not be obtained at frequencies greater than 1 Hz. The interruption of high frequency jet ventilation by conventional ventilation resulted in approximately equal arterial and end-tidal PCO2 values during the first breath, and restoration of the normal arterial to end-tidal PCO2 difference by the third breath. It is concluded that, when high frequency jet ventilation at 1, 3 or 5 Hz is interrupted with normal tidal volumes at low frequencies, the arterial PCO2 can be estimated from recordings of the end-tidal PCO2.
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Opioids were available in clinical practice since before the birth of modern anaesthesia--Setürner isolated morphine in 1806. They have a record of safety which is reflected in their high therapeutic ratios, especially the synthetic opioids introduced recently (table III). The most serious immediate adverse effect, respiratory depression, is a predictable effect related closely to analgesia. It is fortunate for anaesthetists who use opioids regularly, that recognition and treatment of respiratory problems are an integral part of their craft and that opioid antagonists are effective in reversing respiratory depression.
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Complications of local anaesthesia in general have been considered in so far as they may be confused with adverse effects of local anaesthetic drugs. Local anaesthetics may give rise to adverse reactions by a number of mechanisms. They affect nerve conduction and vasculature at the site of injection: a local effect; but is it unlikely that they ever produce an irreversible noxious effect on nerve fibres. ⋯ Ignorance or carelessness are frequently causative factors in serious reactions. Adequate oxygenation is vital in prophylaxis and immediate treatment of systemic toxicity, while resuscitative skill and equipment must always be to hand. Idiosyncrasy or allergy can only rarely be an excuse for adverse reactions to local anaesthesia.