How can I differentiate delirium from altered mental status in hospitalized older adults?

MAGNITUDE OF PROBLEM, COSTS OF MISSED DELIRIUM

Delirium is substantially underdiagnosed in geriatric patients. In a study that included 2,115 hospitalized patients age 70 to 74, the incidence of delirium based on retrospective chart review was more than 9 times higher than the incidence based on discharge coding.³

Missed delirium increases downstream utilization and costs, with excess intensive care costs of $17,838 per patient within 30 days and an estimated annual national burden exceeding $164 billion.^2,4

About 18% of the US population is 65 or older, and this proportion is projected to exceed 20% by 2030.^5,6 Geriatric patients are particularly susceptible to delirium due to age-related reductions in cholinergic neurotransmission, underlying microstructural brain changes, and impaired cerebral autoregulation.² Data indicate that 8% to 17% of geriatric patients in emergency departments and 40% of nursing home residents experience delirium.²

Delirium is misdiagnosed as psychiatric illness in up to 65% of cases,⁷ delaying treatment of reversible causes and increasing mortality (associated mortality rate 10%–65%) and cognitive decline.⁸ Hypoactive and fluctuating presentations further contribute to missed delirium cases in the emergency department, with a prospective study finding a 30.8% increase in 6-month mortality in patients whose delirium was not detected.⁹

Other studies show that untreated delirium is associated with increased morbidity and mortality, with mortality 5.23 times higher during admission, 2.72 times higher at 12 months, and 3.34 times higher at 5 years.¹⁰ Patients with delirium have longer hospital stays and ventilator time, higher rates of complications, and increased likelihood of discharge to long-term-care facilities.² On the other hand, prompt recognition and treatment of delirium reduces morbidity, mortality, and healthcare costs.¹¹

DIFFERENTIAL DIAGNOSIS

Delirium has an acute onset with fluctuating impairments in consciousness, attention, and cognition, often triggered by illness or hospitalization.^1,11 In contrast, dementia develops insidiously, attention and orientation generally are preserved in depression and psychosis, metabolic encephalopathy lacks characteristic fluctuation, substance-related altered mental status follows a predictable set of symptoms, and central nervous system insults produce focal deficits.^1,2,7

Table 1 summarizes key differences between delirium and other types of altered mental status.^1,7,11,12 Figure 1 presents a practical bedside approach to rapidly and cost-effectively assessing older adults for delirium in emergency, hospital, or intensive-care settings.^1,11,13–18

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Figure 1

Flowchart to efficiently distinguish delirium from other forms of altered mental status.

CAM = Confusion Assessment Method; CAM-ICU = Confusion Assessment Method for the Intensive Care Unit; DRS-R-98 = Delirium Rating–Scale Revised-98; IQCODE = Informant Questionnaire on Cognitive Decline in the Elderly

Based on information from references 1, 11, and 13–18.

INITIAL WORKUP

Etiologies of delirium and other forms of altered mental status may overlap, so a basic workup should include a detailed history and physical examination, complete blood cell count, comprehensive metabolic panel including renal and liver panels, urinalysis, and electrocardiography.¹ These tests yield results quickly, allowing for earlier intervention. A basic workup typically costs between $10 and $60 per individual; however, bundled emergency department workups may exceed $100 to $200.¹⁹

A thorough review of recent medication changes, including prescription and over-the-counter drugs, should be conducted to quickly identify triggers or exacerbating factors for altered mental status.^1,11 Detailed substance use history from corroborating sources must be completed to evaluate all possible causes of altered mental status and guide effective intervention.^1,11

Imaging usually is an unnecessary expense, but computed tomography of the head is indicated when there is trauma history or new focal deficits are present. Median costs are estimated at $400 to $450, but there is substantial variability driven by facility-related charges.^1,11,20

SCREENING FOR DELIRIUM

When delirium is suspected, the course of changes in consciousness, attention, and cognition should be assessed (Figure 1).

THE BOTTOM LINE

GCS and RASS provide reliable and cost-efficient assessment of consciousness and sedation status, helping identify patients appropriate for delirium screening. Brief, low-cost attention tasks, particularly MOTYB combined with clinical judgment during brief conversation, can rapidly and cost-efficiently identify delirium. CAM-ICU enables rapid identification of acute delirium in the intensive-care setting, while IQCODE and DRS-R-98 help distinguish baseline dementia and quantify delirium severity.

Standardized, ongoing assessment is essential once delirium is identified. In the intensive-care setting, daily use of tools such as CAM-ICU is recommended to guide management,²⁴ while in non–intensive-care settings brief attention tasks (standard CAM and MOTYB), repeated clinical assessment of attention and cognition, or the DRS-R-98 for delirium severity should be used to ensure timely recognition of clinical changes.

DISCLOSURES

The authors report no relevant financial relationships which, in the context of their contributions, could be perceived as a potential conflict of interest.