The study aims to include all children from birth to 15 years old scheduled for an elective or urgent diagnostic or surgical procedure under sedation or general anaesthesia with or without regional analgesia or under regional anaesthesia. This represents the denominator dataset for calculation of the incidence of severe critical events, which is the primary aim of the study. The anaesthesiologist in charge will record the occurrence of selected severe critical events during and up to 60 minutes after anaesthesia or sedation AND requiring immediate intervention. These severe critical incidents include: Laryngospasm, Bronchospasm, Pulmonary aspiration, Drug error, Anaphylaxis, Cardiovascular instability, Neurological damage, Perianaesthetic cardiac arrest and postanaesthetic Stridor. The secondary endpoint is represented by the risk factors and the consequences for the occurrence of these severe critical events including in-hospital mortality established up to 30 days or at discharge. Relevant aspects of the child's medical and family history will be recorded.