Anaesthesia
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Randomized Controlled Trial Clinical Trial
Influence of ventilatory mode on target concentrations required for anaesthesia using a 'Diprifusor' TCI system.
This study examined the influence of mode of ventilation (spontaneous or controlled) on the target blood concentrations required to maintain anaesthesia with 'Diprifusor' (a target controlled infusion system for propofol) in 40 healthy, unpremedicated, adult patients undergoing knee arthroscopy. All patients were given alfentanil (10 micrograms.kg-1) and ketorolac (10 mg) immediately before induction and all received a 2:1 mixture of nitrous oxide:oxygen. ⋯ The blood target concentration required to produce acceptable anaesthetic conditions was not significantly influenced by the mode of ventilation. The mean maintenance target concentration for propofol was 3.9 (SD 0.83) micrograms.ml-1 in the ventilated group and 3.5 (SD 0.82) micrograms.ml-1 in the group of patients breathing spontaneously.
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Randomized Controlled Trial Clinical Trial
Influence of pre-anaesthetic medication on target propofol concentration using a 'Diprifusor' TCI system during ambulatory surgery.
The effects of pre-anaesthetic medication on target propofol concentration, induction dose, time to induction, and discomfort on infusion were studied in 45 female patients undergoing ambulatory gynaecological procedures using 'Diprifusor' target controlled infusion of propofol. The patients were randomly allocated to receive either no premedication (group 1) or premedication with diazepam alone (group 2) or in combination with alfentanil (group 3). ⋯ There were no significant between-group differences in discomfort on infusion or target concentration during maintenance. For short ambulatory procedures, the recommended initial target concentration of propofol is 4 micrograms.ml-1 in premedicated and 6 micrograms.ml-1 in unpremedicated patients.
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There has recently been much debate about pre-operative fasting for paediatric anaesthesia. There is no consensus about the optimum fasting times for children undergoing elective surgery. ⋯ The results show that the following guidelines for duration of fast are acceptable to the majority of respondents-neonates: 2 h for clear fluids, 4 h for breast and formula milk; infants: 2 h for clear fluids, 4 h for breast milk, 6 h for formula milk and solids; children: 2 h for clear fluids, 6 h for milk and solids. We suggest that these times be used as guidelines and audited for pre-operative fasting in paediatric anaesthesia.
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The predictive performance of a 'Diprifusor' target controlled infusion system for propofol was examined in 46 patients undergoing major surgery, divided into three age groups (18-40, 41-55 and 56-80 years). Measured arterial propofol concentrations were compared with values calculated (predicted) by the target controlled infusion system. Performance indices (median performance error and median absolute performance error) were similar in the three age groups, with study medians of 16.2% and 24.1%, respectively. ⋯ Measured concentrations tended to be higher than calculated concentrations, particularly following induction or an increase in target concentration. The mean (SD) propofol target concentration of 3.5 (0.7) micrograms.ml-1 during maintenance was lower in older patients, compared with higher target concentrations of 4.2 (0.6) and 4.3 (0.7) micrograms.ml-1 in the two younger age groups, respectively. The control of depth of anaesthesia was good in all patients and the predictive performance of the 'Diprifusor' target controlled infusion system was considered acceptable for clinical purposes.