The investigators are going to conduct a prospective observational cohort study in pediatric patients aged 28 days to 14 years old scheduled for elective cardiac surgery with cardiopulmonary bypass. The primary purpose of this study is to explore the effect of preoperative sleep disturbance on the incidence of postoperative delirium. Sleep status will be assessed using the Brief Infant Sleep Questionnaire(BISQ) and Children's Sleep Habits Questionnaire (CSHQ), and postoperative delirium status will be evaluated by Cornell assessment of pediatric delirium(CAPD). During the peri-operative period, children will wear actigraphs to record their sleep parameters.

Inclusion Criteria:

• Aged more than 28 days and less than 14 years old；
• Scheduled to undergo elective corrective surgery for congenital heart disease under cardiopulmonary bypass.

Exclusion Criteria:

• Emergency surgery;
• Combined with severe hepatic and renal dysfunction (with a diagnosis of acute or chronic renal insufficiency or requiring renal replacement therapy; with a diagnosis of acute or chronic hepatic insufficiency or requiring artificial liver treatment);
• Combined with non-cardiac malformations (adenoidal hypertrophy, tracheobronchial stenosis and ocular disorders);
• History of preoperative cerebral ischemia or haemorrhage;
• Refuse to sign the informed consent form or the child has poor compliance.

Pediatric patients aged more than 28 days and less than 14 years old who are scheduled to undergo elective corrective surgery for congenital heart disease under cardiopulmonary bypass.