Anaesthesia
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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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Total intravenous anaesthesia is a feasible alternative to the use of inhalational agents and the rationale behind such a technique is presented. The various intravenous agents are discussed, particularly with regard to their suitability for this form of anaesthesia, and their physiological effects compared with those of the inhalational anaesthetics. Some of the problems associated with the use of total intravenous anaesthesia are mentioned.
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In six patients undergoing gynaecological surgery computer assisted total intravenous anaesthesia (CATIA) was performed using etomidate and alfentanil. Constant plasma levels of etomidate (0.3 microgram/ml) from the very beginning onwards were achieved using the so called B. ⋯ Alfentanil plasma concentrations of 0.45 microgram/ml were maintained by the same infusion scheme beginning with skin incision until 20 minutes prior to the end of surgery. The proposed concept of CATIA provided an adequate analgesic and hypnotic effect during anaesthesia for abdominal surgery with a recovery period of short duration.
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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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Randomized Controlled Trial Clinical Trial
Cardiovascular response to intubation. A comparative study of thiopentone and midazolam.
The cardiovascular response evoked by tracheal intubation was observed in 20 patients undergoing elective abdominal surgery in whom anaesthesia was induced with either midazolam 0.3 mg/kg or thiopentone 4.5 mg/kg followed by pancuronium 0.1 mg/kg. In the thiopentone group, intubation caused a mean rise in systolic arterial pressure from 141 to 193 mmHg (p less than 0.0005) and in the heart rate-systolic pressure product from 11101 to 21763 (p less than 0.05); 5 minutes later the mean values were still 173 mmHg and 19030 respectively. In the midazolam group systolic arterial pressure and the rate pressure product increased from 138 to 151 mmHg and 10960 to 14267 respectively in response to intubation. These values were significantly lower than the thiopentone group (p less than 0.005 in each case) and were relatively transient and returned to control values within 5 minutes.