3D CAM into Turkish validity and reliability on postoperative delirium will be test as a prospective diagnostic study. After approval by Dr. Edward R. Marcantonio, (15) will translation and back-translation. The original 3D-CAM will translate into Turkish by two medical doctor .The two translational versions will be discussed and merged into a final version. Back translation will performed in regardless of any information from its original version by another two medical doctor. Both the translated and back translated versions will sent to Dr. Marcantonio for approval. Eligibility and the documentation of consent will be confirmed at the preoperative visit. During this visit, patients will provide demographic and historical medical information, including information regarding medication usage. The Mini-Mental State Exam (MMSE) will be performed.

Delirium assessment

Delirium assessment with the 3D-CAM Before the study period, all researchers will participate online training program on 3D CAM. Delirium will be evaluated using the 3D CAM every each morning and evening (18:00-20:00) for postoperative 3 days.

Delirium assessment with the DSM-5 The psychiatrist investigator who was blinded to the 3D-CAM assessment results, will evaluate the patients according to the criteria of DSM-5 within 3 min after the 3D-CAM assessment.

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