 The purpose of this study is to assess whether peri-operative period in neonates and infants is associated with an increase in blood biomarkers, specific for neuronal injury, and to correlate them with clinical variables and sedativeanalgesic agents. Patients, who meet inclusion criteria and does not meet exclusion criteria, are enrolled. Blood samples for measurement serum concentrations of markers S100-B and Neuron-Specific Enolase NSE are drawn before surgery baseline and on the 1-st, 2-nd and 3-rd day after surgery. During surgery cerebral oxygenation rSO2 monitoring is continuously applied; rSO2, hemodynamic and respiratory values are simultaneously recorded every 5 minutes. Anesthesia, pre and postoperative treatment, including analgesia and sedation, are given as per standard of care. 