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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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.
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Carbon dioxide clearance during high frequency jet ventilation. Effect of deadspace in a lung model.
The effects of the volume and length of deadspace on the clearance of carbon dioxide from a lung model have been investigated during high frequency jet ventilation (HFJV) at 1, 3 and 5 Hz. At 1 Hz, increasing the volume of the deadspace without changing the length caused a reduction in the clearance of carbon dioxide. ⋯ Furthermore, the clearance of carbon dioxide at 5 Hz was very inefficient compared with that at 1 Hz. It is concluded that, during HFJV, carbon dioxide is cleared most efficiently when the frequency is low enough for the delivered tidal volume to be greater than the volume of the morphological deadspace.