DOSE REQUIREMENTS OF PROPOFOL BY INFUSION DURING NITROUS OXIDE ANAESTHESIA IN MAN: I: Patients Premedicated with Morphine Sulphate

The study was performed to determine the ED₅₀ and ED₉₅ of acontinuous infusion of the emulsion formulation of propofolduring 67% nitrous oxide anaestheisa in 57 patients premed-icatedwith morphine sulphate 0.15 mg kg^–1. Anaesthesia was inducedwith propofol 2 mg kg^–1, and maintained before incisionwith a fixed-rate infusion of propofol to supplement nitrousoxide. The response to the first surgical incision, made atleast 30 min after induction of anaesthesia, was observed. TheED₅₀; was 53.5 µg kg^–1 min^–1 and the ED₉₅was 112.2 µg kg^–1 min^–1. At the time of thefirst surgical incision, the venous whole blood concentrationsof propofol at the ED₅₀ and ED₉₅ infusion rates (EC₅₀and EC₉₅were 1.66 µg ml^–1 and 3.39 fig ml^–1 respectively.The satisfactory maintenance of anaesthesia provided by nitrousoxide supplemented with propofol was associated with stabilityand rapid, uncomplicated recovery.