Central diabetes insipidus (CDI),a disease caused by the decrease of AVP (a hormone involved in the control of water-electrolyte balance ) secretion and characerized by polyuria, is a common complication after neurosurgerical intervention and there is a lack of diagnostic criteria.Since the surgry casuses damage to patients' AVP-secreting neuronal cells, transient CDI (t-CDI) usually occurs 24-48h postoperatively and gradually resolves in about 10 days.However,permanent CDI (p-CDI) occurs in a small percentage of patients.Copeptin is a fragment of AVP, which has been shown to response the secretion of AVP.Multiple international studies have identified clinical applications for the use of copeptin to differentially diagnose adults with CDI , to assess electrolyte disturbances associated with AVP regulation, and to predict postoperative CDI after pituitary surgery.This study aims to investigate the trend of serum copeptin levels and its clinical value for postoperative CDI in pediatric patients after neurosurgerical intervention in ICU.