The current study aims to find the most appropriate dose of propofol for newborns of different gestational ages and of different post-natal ages. We will use propofol in different doses and after each 5 included patients per age group we will analyze whether the dose needs to be increased or decreased. The effect of the propofol will be extensively monitored and we will study the level of sedation, the quality of intubation, the stability of the patient en the occurrence of side effects.