British journal of anaesthesia
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A study of controlled hypotension was undertaken in 50 major surgical patients using labetalol, a drug with both alpha- and beta-adrenoceptor blocking activity. The patients were such that difficulty in achieving controlled hypotension could be anticipated: the young, the anxious and those for whom halothane was contraindicated. The administration of labetalol quickly induced hypotension which was controlled easily and was rapidly antagonized.
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Ten patients with intracranial lesions, anaesthetized with thiopentone and nitrous oxide (70%) in oxygen (30%) received etomidate 0.2 mg kg-1 i.v. Ventilation was controlled in each patient. Intracranial pressure (i.c.p.) and mean arterial pressure (m.a.p.) were recorded. ⋯ M.a.p. decreased in most patients, but the decrease was statistically significant only at 3 and 4 min after the administration of etomidate (0.05 greater than P greater than 0.02). The changes in cerebral perfusion pressure (c.p.p.) and heart rate were not clinically or statistically significant. We conclude that etomidate can be used for the induction of anaesthesia in patients with intracranial space-occupying lesions without increasing i.c.p. or seriously reducing c.p.p.
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We have evaluated a new method for measuring the oxygenated mixed venous PCO2 (PVCO2) in patients undergoing general anaesthesia. The lungs were inflated with a gas mixture containing 0% carbon dioxide and then 12% carbon dioxide and the expired gas was analysed both before and after a brief period of breath-holding. PVCO2 was estimated from the differences in carbon dioxide concentration before and after the apnoeic period. ⋯ The range of PaCO2 studied was 3.2--6.13 kPa. The relationship between mixed venous and arterial PCO2 was found to be PaCO2 = 0.87 PVCO2--0.44 (r = 0.91). We conclude that this method for measuring PVCO2 can be used during anaesthesia allowing PaCO2 to be estimated with considerable accuracy.