After the induction of anaesthesia and before intubation the child receives one of the research drugs in a double-blind fashion: 0.1 mg/kg of oxycodone , 0.1 mg/kg of morphine, 0.5 mg/kg dexamethasone (max 24 mg), or placebo. All the research drugs are diluted into a dose of 10 ml with NaCl 0.9%, the placebo being solely the dilute.