INFLUENCE OF VENTILATORY MODE ON TARGET CONCENTRATIONS REQUIRED FOR ANESTHESIA 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 fo r propofol) in 40 healthy, unpremedicated, adult patients undergoing k nee arthroscopy. All patients were given alfentanil (10 mu g.kg(-1)) a nd ketorolac (10 mg) immediately before induction and all received a 2 :1 mixture of nitrous oxide:oxygen. An initial target blood concentrat ion of propofol of 6.0 mu g.ml(-1) was used in most patients to induce anaesthesia. The blood target concentration required to produce accep table anaesthetic conditions was not significantly influenced by the m ode of ventilation. The mean maintenance target concentration for prop ofol was 3.9 (SD 0.83) mu g.ml(-1) in the ventilated group and 3.5 (SD 0.82) mu g.ml(-1) in the group of patients breathing spontaneously.