It has been proved that lithium carbonate can prolong slow wave sleep with few or no side-effects. The aim of the present study is to evaluate postoperative sleep quality of patients undergoing heart valve surgery with cardiopulmonary bypass taken 250mg lithium carbonate after surgery.

This study is a prospective, randomized, controlled (randomized, parallel group, concealed allocation), double-blinded trial. All patients undergoing heart valve surgery with cardiopulmonary bypass will be randomized 1:1 to the treatment intervention with lithium carbonate 250mg (Baoqing, Hunan, China) or calcium carbonate 500mg (Reneed, Beijing, China) after surgery. The objective of the trial is to evaluate the lithium carbonate 250mg on the postoperative night sleep quality. Duration of sleep was collected with polysomnography on second postoperative night. (from 20:00pm to 06:00. Mini-Mental State Examination (MMSE) score was performed on the seventh postoperative day

Inclusion Criteria:

• Ethnic Chinese;
• Age, 18 to 65 years old;
• Patients undergoing heart valve surgery with cardiopulmonary bypass

Exclusion Criteria:

• Preoperative Pittsburgh Sleep Quality Index global scores higher than 6
• Cognitive difficulties
• Partial or complete gastrectomy
• Previous esophageal surgery
• Previous treated by radiotherapy or surgery
• Inability to conform to the study's requirements
• Body mass index exceeding 30 kg/m2
• Deprivation of a right to decide by an administrative or juridical entity
• Ongoing participation or participation in another study <1 month ago
• Recent (< 3 months prior) use of antibiotics, probiotics, prebiotics, symbiotics, hormonal medication, laxatives, proton pump inhibitors, insulin sensitizers or traditional Chinese medicine