Anaesthesia
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Review
General kinetic and dynamic principles and their application to continuous infusion anaesthesia.
The use of intravenous anaesthetic agents by continuous infusion requires knowledge of their pharmacokinetic properties. In this article, the general pharmacokinetic principles behind the use of infusions of intravenous agents are presented and the literature with regard to the individual drugs used in this way is reviewed.
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A review of the hypnotic, anticonvulsant and brain protective action of etomidate in animals shows that when given as a single injection in different animal species recovery from hypnosis is quick and that the safety margin is large. In dogs a bolus or infusion produces high amplitude theta activity on the electroencephalogram (EEG). During infusion burst suppression is seen. ⋯ Studies in various animal models show that etomidate might have brain resuscitative properties. In hypoxic-ischaemic conditions etomidate has some protective effects, where its anticonvulsant action is probably important. Lowering of the cerebral metabolic rate of oxygen consumption, and reducing the rise of intracranial pressure, coupled with immobilisation and prevention of hyperactivity enables animals to resist a hypoxic insult.
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Two groups of six patients who had undergone major maxillofacial surgery and who required intermittent positive pressure ventilation, analgesia and sedation for about 48 hours postoperatively were studied. Analgesia in the postoperative period was maintained by an infusion of fentanyl 0.034 micrograms/kg/minute. Sedation was maintained with an intravenous infusion of etomidate such that the patients slept but opened their eyes when addressed and obeyed commands. ⋯ The use of results obtained from the first group of six patients enabled a dosage regimen to be calculated that used a two stage infusion. This regimen enabled a reduction in the time taken to establish the appropriate degree of sedation in the second group of six patients. The two-stage infusion technique provides a means of rapid sedation and of maintaining a suitable clinical response for the prolonged periods that may be necessary when patients are transferred to an intensive therapy unit.
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A questionnaire was sent to senior registrars in General Medicine and Anaesthesia enquiring into the amount of training they received in Intensive Therapy and their attitudes to this in the light of their expectations for a consultant post. The results suggest that training is inadequate and that trainees are dissatisfied with the current situation.