Delirium in a general hospital psychiatric consultation service: Referral patterns, etiology, phenomenologic subtypes and prognosis

Ninety-six patients with delirium in a general hospital psychiatric consultation service were studied. The patients were followed daily by an attending psychiatrist with a symptom checklist. All information including clinical interview, medical records, and reports from staff and family were used for analysis. The most frequent etiologic factors were electrolyte imbalance and infection. Duration of delirium ranged from half a day to 23 days, with a mean of 9.24 +/- 5.29 days. In-hospital mortality rate was 11.5%. Six-month mortality rate was 19.8%. Sixty-six cases (68.8%) were classified as hyperactive type, 13 cases (13.5%) as hypoactive, and 17 cases (17.7%) as mixed type. Patients of the hyperactive group showed a shorter duration and lower mortality rate than patients of the hypoactive and mixed types. The mixed type had the highest in-hospital mortality rate. A longer duration may foretell a poorer outcome, especially for the hyperactive and the mixed types. Only 12 cases (12.5%) were correctly diagnosed as delirium by the referring doctors. To enhance understanding of delirium, the definition and pathophysiology of subtypes should be further investigated.