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The use of propofol for induction and maintenance of anaesthesia by intermittent bolus injection in 37 patients undergoing body surface operations is described. This technique gave good operating conditions in most of the patients in the series. With an induction dose of 2.5 mg/kg propofol, a dose of 11.25 mg/kg/h was found to be the median dose requirement for maintenance of anaesthesia in this study. This dose will be used to calculate infusion rates for future studies with the drug.

A standard method (fixed initial dose of 1.25 mg/kg followed by 10 mg every 15 s) for studying the induction dose of propofol showed a marked falling off in requirements in fit unpremedicated patients aged 60 y and over. With this slow technique of administration, side effects were rare, even in the elderly.

Two studies were carried out on 609 fit, unpremedicated patients to assess the influence of patient age on the response to the rapidly-acting hindered phenol, propofol, which is being evaluated for induction of anaesthesia. In the first study, 1.25 mg/kg was injected over 20 seconds followed by 10-mg increments every 15 seconds until loss of verbal contact. This showed a great individual variation in response to the drug. A reduction in the 'induction' dose was found in elderly patients, which became marked around 60 years. In the second (340), doses ranging from 1.5-3.0 mg/kg in patients under 60 years and 1.25-2.25 mg/kg in those over 60 years were injected as a bolus over 20 seconds. Doses of 2.25-2.5 mg/kg were required to induce anaesthesia in patients under 60 years, whilst 1.5-1.75 mg/kg was adequate in those over 60 years. Side effects were more marked with the rapid injection and doses in excess of 1.75 mg/kg caused significant hypotension and apnoea in the elderly. These studies reveal marked sensitivity to propofol in the elderly with respect to both induction dose and acute toxicity.

Changes in three recognized liver function tests are reported following the use of propofol in 30 fit, unpremedicated women in whom propofol was used as the main anaesthetic agent. Doses of 140 to 330 mg were given, together with nitrous oxide and oxygen. All patients were undergoing minor gynaecological operations and all conformed to Grade 1 physical status of American Society of Anesthesiologists Classification. In none of these patients was there hypoxia or hypercarbia at any time during or following anaesthesia and none of the patients received any other drugs until completion of the study. No significant changes in liver enzymes (aspartate transaminase and alanine transaminase) or in serum alkaline phosphatase were detected.