Baseline-adjusted marginal means with 95% CI of the Δ values of all stimulus-by-remifentanil dose combinations as determined by mixed models. Values for differences in pupil diameter (ΔPD), heart rate (ΔHR), and bispectral index (ΔBIS) are based on back-transformation as: ΔPD = e(ΔPD′) + 3.50656, ΔHR = e(ΔHR′) − 2.70805, and ΔBIS = e(ΔBIS′) − 3.91202 (see Materials and Methods for transformation of variables). Red bars indicate tetanic stimulation, and blue bars indicate intracutaneous stimulation. P values are for the additive main effects of remifentanil dose, stimulus type, and the interaction effect of remifentanil dose × stimulus type. ANI = Analgesia Nociception Index; MAP = mean arterial blood pressure; SPI = Surgical Pleth Index.