 This is a study designed to explore Copeptin values in all kinds of critically ill paediatric patients. Patients with normal blood pressures will allow calculating Copeptin reference values for the ones requiring cardiovascular support. Therefore, all patients, irrespective of their medical condition e.g. medical or surgical, mildly or severely affected and their age neonates to adolescents admitted to the Intensive Care Unit of the Universitys Children Hospital Zurich will be eligible, as long as they fulfil the mentioned inclusion criteria. 