Inclusion Criteria:  18 years and older ASA Physical Status 1-3 Admitted to the ICU after surgery with a predicted length of stay for more than 48 h MMSE ≥ 20 (to exclude dementia)  Exclusion Criteria:  Refused to participate Patients with severe visual or auditory disorder/handicaps or endotracheal intubation which might impede communication Presence of a major psychiatric condition such as bipolar disorder, major depression, schizophrenia, Alzheimer or dementia, Parkinsonism Deep sedation or coma ASA physical status IV or V