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The combination of propofol and alfentanil was administered to 20 patients for total intravenous anaesthesia during general surgery. The infusion rates for both drugs were controlled by microprocessors in order to institute constant blood levels adapted to the patients' varying needs. The mean blood level of propofol required for adequate hypnosis during anaesthesia was 2.42 micrograms/ml (SD 0.43). Awakening occurred 7.9 minutes (SD 3.4) after the end of the infusion, at a propofol blood level of 1.59 micrograms/ml (SD 0.34). The plasma level of alfentanil was 285 ng/ml (SD 72) during major noxious stimulation and 148 ng/ml (SD 56) during minor stimulation. The computer-assisted infusions showed a measured/predicted ratio of 1.01 (SD 0.28) for alfentanil and 0.88 (SD 0.22) for propofol. This indicates that the administration device used in this study is reasonably reliable. The technique of total intravenous anaesthesia was characterised by a smooth induction without significant haemodynamic alterations, by good control during anaesthesia and by a very fast recovery without major side effects.
Schüttler et al. (Tue,) studied this question.