Fig. 5. Urinary free cortisol. The total excretion of urinary free cortisol (mean ± SD) from 10:30 pm until 7:00 am reveals a significant decrease in cortisol excretion in the remifentanil–placebo (Remi) group. *  P = 0.004. Mel = saline–melatonin; Remi/mel = remifentanil–melatonin; Saline = saline–placebo.