Clinical Question

Is it possible to predict the likelihood of delirium and overall prognosis in hospitalized older patients?

Evidence Summary

Delirium is a common complication in hospitalized older patients, particularly in those in the intensive care unit.¹ Several interventions can prevent delirium or reduce its duration in at-risk patients. These interventions are aimed at reducing cognitive impairment, sleep deprivation, immobility, visual and hearing impairment, and dehydration.²

The first step in preventing delirium is identifying at-risk patients; therefore, researchers have tried to determine the risk factors for the condition. Inouye and colleagues studied 107 consecutive hospitalized patients older than 70 years who had no signs of delirium at admission; the average age of patients was 79 years.³ Patients with severe dementia were excluded, although those with mild-to-moderate dementia were considered for inclusion. About one fourth of patients in the study were diagnosed with delirium during their hospitalization. The Confusion Assessment Method questionnaire, which was administered by a single physician within 24 hours of onset of suspected delirium, was the reference standard for diagnosis. Four independent predictors of delirium were identified,³ making up a simple four-point clinical decision rule (see part I of the accompanying encounter form).^4–6

The rule was validated in a prospective group of 171 inpatients at the same hospital as the original cohort.³ Although the rule includes the APACHE II (Acute Physiology and Chronic Health Evaluation) score,⁴ a nurse's assessment of severe illness can be substituted. The rule was also prospectively validated in a group of more than 600 Dutch patients older than 70 years who were undergoing hip surgery. In this group, the rule performed almost identically to the original cohort.⁵

Inouye and colleagues noted that a significant percentage of patients had persistent delirium at hospital discharge, which was an important risk factor for death or nursing home placement.³ Therefore, they developed and validated a second clinical decision rule to predict persistent delirium at hospital discharge.⁷

This second rule was developed in a group of 491 consecutively hospitalized patients 70 years or older who did not have delirium at admission. Five risk factors for persistent delirium were identified. The five-point rule (see part II of the accompanying encounter form^7,8) was prospectively validated in a second group of 461 hospitalized patients older than 70 years. Sixty-three patients (14 percent) developed delirium during hospitalization, and 6 percent had delirium that persisted to discharge.⁷

Applying the Evidence

A 78-year-old woman is hospitalized for hip surgery. She has moderate cognitive impairment, a blood urea nitrogen (BUN)/creatinine ratio of 30, and moderate visual impairment (20/80); however, the admitting nurse determines that she is not severely ill. The patient needs assistance cleaning her home and preparing meals, but has no significant comorbidities. What is the likelihood that she will develop delirium during this hospitalization?

Answer: Using part I of the accompanying encounter form,^4–6 she receives 3 points (one point each for visual impairment, BUN/creatinine ratio, and cognitive impairment). This gives her a 37 percent risk of delirium during this hospitalization. Despite preventive measures, she develops delirium, but restraints are not used. Using part II of the accompanying encounter form,^7,8 you assess her risk of persistent delirium at hospital discharge. She receives 3 points (one point each for visual impairment, dementia, and impairment in activities of daily living), giving her a 14 percent risk.