[An attempt to determine optimum dosage of fentanyl in neurolept analgesia (author's transl)].

In a retrospective study a comparison was made of the doses of Fentanyl used by anaesthetists to induce and maintain neurolept analgesia for a variety of surgical operations (158 cases). Dosages differed widely both for different surgical procedures and for different anaesthetists. A method, based on pharmacokinetic considerations, was developed for calculating Fentanyl requirements during any stage of anaesthesia. The dose/time relation, as represented by y = At + B (1--e-kt) makes it possible to calculate the required doses of Fentanyl; this enables the anaesthetist to maintain a stable level of anaesthesia and makes antagonization of Fentanyl unnecessary. Methods for determining the coefficients of the dose-time equation are described. Simulation by an analogue computer showed that by using the suggested procedure substantial variations of Fentanyl concentration in the brain and other body compartments can be avoided.