Delirium in Intensive Care Unit: Phenomenology, Subtypes, and Factor Structure of Symptoms

AIM: This study aimed to explore the phenomenology, motor subtypes, and factor structure of symptom profile of delirium in patients admitted to the intensive care unit (ICU). METHODS: Consecutive patients aged ≥16 years admitted in an ICU were screened daily for delirium using confusion assessment method-ICU. Patients diagnosed to have delirium as per Diagnostic and Statistical Manual fourth revision, text revision (DSM-IVTR) criteria were assessed with Delirium Rating Scale-Revised 98 (DRS-R 98) and Memorial Delirium Assessment Scale (MDAS). Motor subtypes of delirium were assessed with amended Delirium Motor Symptom Scale. RESULTS: Sixty-six patients were evaluated for delirium, of which 45 (68%) patients developed delirium at point of their ICU stay. All patients had sleep-wake cycle disturbances, followed by motor symptoms (retardation - 80%; agitation - 73.3%). As per MDAS assessment, all the subjects had disturbances in the consciousness and sleep-wake cycle disturbances, and a substantial majority also had attention difficulties (93.3%) and motor symptoms (93.3%). Hypoactive subtype (47%) was the most common motoric subtype of delirium. Factor analysis revealed three-factor model for DRS-R 98, MDAS, and combining items of the two. CONCLUSION: Phenomenology of delirium in ICU setting is similar to that of the non-ICU settings. The factor analysis consistently demonstrated a three factor solution, with a robust attention-arousal factor, and overlapping cognitive (core vs. non-core) motor factors.