Subsyndromal delirium (SSD) is a condition characterized by a less severe cognitive impairment in comparison to delirium. To date there is no published consensus on SSD definitions and has been commonly reported as an intermediate stage between delirium and normal mental states.

SSD encompasses some of the delirium symptoms, and has been diagnosed with Intensive Care Delirium Screening Checklist scale (ICDSC) and Confusion Assessment Method-ICU (CAM-ICU).

The objective of this study is to identify subsyndromal delirium prevalence, the association between SSD and clinical outcomes and understanding the relationship between SSD and conversion to delirium.

The relevance of this study is understanding of subsyndromal delirium in ICU, namely the importance of early presentations of acute brain dysfunction in the patients outcome.

SubSynD is a prospective, observational, multicenter clinical study, involving 400 patients in Intensive Care Units, to assess subsyndromal delirium.

A systematic screening for delirium and subsyndromal delirium (SSD) is done with Intensive Care Delirium Screening Checklist (ICDSC) and Confusion Assessment Method-ICU (CAM-ICU). Scales are applied once per day until ICU discharge or for up to 14 days of being in ICU.

The investigators access three different groups of patients: non-delirium, delirium and subsyndromal delirium. It is intended that either ICDSC or CAM-ICU, paired with a Richmond Agitation and Sedation Scale (RASS) be administered once per day (i.e. with first assessment in the morning). All patients with abnormal CAM-ICU or ICDSC features, beside the underlying cause of delirium and SSD are included. In addition, data regarding baseline demographic and clinical characteristics will be collected as well as data regarding the procedure performed (see Case Report Form (CRF)).

Inclusion Criteria:

1. Age ≥ 18 years;
2. Admission in Intensive care Unit

Exclusion Criteria:

1. Primary neurological diagnosis, with Glasgow Coma Scale (GCS) <14 on ICU admission or in previous days;
2. Blindness or deafness;
3. Aphasia;
4. Inability to communicate in the native language of the country where the study is enrolled;
5. Death during the first 24 hours;
6. Limitation of therapeutic efforts in the Intensive Care Unit admission;
7. Refusal to participate;
8. Previous diagnosis of dementia or psychiatric illness;
9. Readmission in ICU;

Intensive Care Unit patients