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SummaryThe 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. Mean values for 'divergence' and 'wobble' were ¹7.6%.h ¹1 and 21.9%, 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) mg.ml ¹1 during maintenance was lower in older patients, compared with higher target concentrations of 4.2 (0.6) and 4.3 (0.7) mg.ml ¹1 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.

The incidence of myocardial ischaemia during tracheal intubation and extubation was compared using ambulatory ECG monitoring in 60 patients undergoing a variety of different surgical operations. Seven patients had myocardial ischaemia after tracheal intubation and seven patients during tracheal extubation. The patients who developed myocardial ischaemia during tracheal extubation had significantly greater rate-pressure products immediately before tracheal extubation (P < 0.05) and 1 min after tracheal extubation (P < 0.01) compared with those patients who did not develop myocardial ischaemia during extubation.

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