Clinical phenotypes of delirium in patients admitted to the cardiac intensive care unit

BACKGROUND: Limited data are available on clinical phenotype for delirium that occurs frequently among patients admitted to the cardiac intensive care unit (CICU). The objective of this study was to investigate the clinical pictures of delirium, and their association with clinical outcomes in CICU patients. METHODS: A total of 4,261 patients who were admitted to the CICU between September 1 2012 to December 31 2018 were retrospectively registered. Patients were excluded if they were admitted to the CICU for less than 24 hours or had missed data. Ultimately, 2,783 patients were included in the analysis. A day of delirium was defined as any day during which at least one CAM-ICU assessment was positive. The clinical risk factors of delirium were classified by the delirium phenotype, as follows; hypoxic, septic, sedative-associated, and metabolic delirium. RESULTS: The incidence of delirium was 24.4% at the index hospitalization in all CICU patients, and 22.6% within 7 days after CICU admission. The most common delirium phenotype was septic delirium (17.2%), followed by hypoxic delirium (16.8%). Multiple phenotypes were observed during most delirium days. Delirium most frequently occurred in patients with heart failure. Of all patients affected by delirium within 7 days, both ICU and hospital mortality significantly increased according to the combined number of delirium phenotypes. CONCLUSIONS: Delirium occurred in a quarter of patients admitted to the modern CICU and was associated with increased in-hospital mortality. Therefore, more efforts are needed to reduce the clinical risk factors of delirium, and to prevent it in order to improve clinical outcomes in the CICU.