Table 1. Combination of Propofol–Remifentanil

(A ) With the exception of two volunteers (3,11; propofol only), every patient received a step up–down infusion of propofol, followed by a step up–down infusion of propofol in the presence of a constant concentration of remifentanil. The first concentration indicated refers to the highest concentration achieved during the respiratory depression phase (single drug administration), the second concentration indicated refers to the highest concentration achieved during the CNS depression–interaction phase (changing concentrations of the first drug and constant concentrations of the respective second drug). The concentration ranges were determined by pharmacodynamic considerations (see Methods). The remifentanil target for one patient (15) was erroneously set to 2 ng/ml instead of 1 ng/ml. (B ) With the exception of two volunteers (1,2; remifentanil only), every patient received a step up–down infusion of remifentanil, followed by a step up–down infusion of remifentanil in the presence of a constant concentration of propofol. The first concentration indicated refers to the highest concentration achieved during the respiratory depression phase (single drug administration), the second concentration indicated refers to the highest concentration achieved during the CNS depression–interaction phase (changing concentrations of the first drug and constant concentrations of the respective second drug). The concentration ranges were determined by pharmacodynamic considerations (see text).