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R39209 (Alfentanyl), a new narcotic analgesic with a uniquely short duration of effect, was used to supplement nitrous oxide and oxygen for the maintenance of anaesthesia. Twenty-two patients undergoing minor surgery were studied. Clinical anaesthesia was excellent or good in most (16) of the patients, and recovery was excellent or good in 18 patients, waking time being less than one minute in 15 patients. However the incidence of complications and side-effects, mainly movement, apnoea, difficulty in assisting ventilation, nausea and vomiting was high. Intravenous administration of R39209 during anaesthesia induced significant depression of respiratory rate and minute volume during the second, third and fourth minutes after injection. There was an unexplained significant rise in respiratory rate and minute volume in the first 30 seconds after the first injection. The first administration of R39209 also caused an unexplained, significant reduction in cardiac rate. An insignificant rise in mean systolic blood pressure followed injection of the drug. The transient effect of R39209 was confirmed in clinical practice, and the drug exhibited the features of a typical narcotic analgesic. It is concluded that R39209 will have a useful place in anaesthetic practice, and that better clinical results will be obtained with more experience of the drug, and better selection of indications for its use.

The use of mass spectrometers for total gas monitoring during anesthesia presents a number of problems which stem from the Cracking Pattern of the gases present, inlet design, viscosity variations, water vapour and machine deterioration. Some of these have been adequately solved, by making mechanical modifications to the inlet system, and by using more complex electronic circuitry to process the signals obtained. Remaining problems, however, still limit accuracy and ease of operation. CO2 measurements are particularly prone to error, especially when sampling halothane-containing gas which leads to significant internal production CO2. A study of the principal sources of error remaining in the machine suggests that the only definitive solution is to develop a microprocessor system which could cope with complex Cracking Patterns and non-linearities, and which would allow complete automation of the calibration procedure.