DOSE REQUIREMENTS OF PROPOFOL BY INFUSION DURING NITROUS OXIDE ANAESTHESIA IN MAN

Abstract

The study was performed to determine the ED₅₀ and ED₉₅ of a continuous infusion of the emulsion formulation of propofol during 67% nitrous oxide anaestheisa in 57 patients premed-icated with morphine sulphate 0.15 mg kg⁻¹. Anaesthesia was induced with propofol 2 mg kg⁻¹, and maintained before incision with a fixed-rate infusion of propofol to supplement nitrous oxide. The response to the first surgical incision, made at least 30 min after induction of anaesthesia, was observed. The ED₅₀; was 53.5 μg kg⁻¹ min⁻¹ and the ED₉₅ was 112.2 μg kg⁻¹ min⁻¹. At the time of the first surgical incision, the venous whole blood concentrations of propofol at the ED₅₀ and ED₉₅ infusion rates (EC₅₀and EC₉₅ were 1.66 μg ml⁻¹ and 3.39 fig ml⁻¹ respectively. The satisfactory maintenance of anaesthesia provided by nitrous oxide supplemented with propofol was associated with stability and rapid, uncomplicated recovery.