How do you diagnose delirium in an elderly patient presenting with confusion at night?

How to Diagnose Delirium in an Elderly Patient with Nighttime Confusion

Delirium is a clinical diagnosis that requires establishing acute onset and fluctuating course through informant interview, documenting inattention on bedside testing, and using a validated tool like the Confusion Assessment Method (CAM) to confirm the diagnosis. 1

Establish the Three Essential Diagnostic Features

1. Obtain Collateral History from a Knowledgeable Informant

• Determine the patient's baseline cognitive function, behavior, and functional abilities before this episode 1
• Document the exact timeline: when did the confusion start (hours to days, not weeks to months) 1
• Ask specifically about fluctuations: does the confusion vary throughout the day, worsening at night (sundowning pattern) 1
• Identify potential precipitants: new medications, recent infections, hospitalizations, falls, or changes in medical status 2, 3

2. Perform Bedside Cognitive Assessment

• Test attention directly by asking the patient to recite months of the year backwards (MOTYB) or perform serial 7s 1
• Assess level of consciousness: is the patient hyperalert, drowsy, or fluctuating between states 1
• Evaluate for disorganized thinking: ask simple questions like "Will a stone float on water?" or "Are there fish in the sea?" 1
• Repeat assessments every 8-12 hours (at least once per shift) because cognitive status fluctuates substantially within a day 2

3. Apply the Confusion Assessment Method (CAM)

The CAM requires ALL of the following: 1

• (1) Acute onset and fluctuating course (from informant history)
• (2) Inattention (demonstrated on bedside testing)
• PLUS either (3) Disorganized thinking OR (4) Altered level of consciousness

The CAM has 82% sensitivity and 99% specificity when properly administered 1

Critical Pitfall: Recognize Hypoactive Delirium

Hypoactive delirium is the most commonly missed subtype, especially in elderly patients presenting with nighttime confusion 1, 2

• Patients appear sedated, withdrawn, or "quietly confused" rather than agitated 1
• This subtype is frequently mistaken for depression, fatigue, or simply "normal aging" 2
• Hypoactive delirium carries higher mortality risk than hyperactive delirium 1
• Look for cognitive slowing, reduced motor activity, and decreased responsiveness rather than agitation 1

Simultaneously Investigate Underlying Causes

While establishing the diagnosis, immediately evaluate for precipitants: 1, 2

• Point-of-care glucose (hypoglycemia/hyperglycemia)
• Vital signs including oxygen saturation (hypoxia, fever suggesting infection)
• Medication review focusing on recent additions or dose changes: anticholinergics, sedatives, opioids, vasodilators, diuretics 2, 3
• Urinalysis and chest X-ray (UTI and pneumonia are the most common infectious precipitants) 2
• Comprehensive metabolic panel (electrolyte disturbances, renal dysfunction, hepatic encephalopathy) 2, 3
• Complete blood count (infection, anemia) 3
• Thyroid function tests and vitamin B12 (especially in patients with underlying cognitive impairment) 1

Differentiate from Dementia

The time course distinguishes delirium from dementia: 1

• Delirium: hours to days onset, fluctuating throughout the day
• Dementia: months to years onset, stable throughout the day
• Delirium commonly occurs superimposed on pre-existing dementia—do not attribute acute confusion to known dementia without investigating for reversible causes 1, 2

Alternative Validated Tools for Specific Settings

If CAM is not feasible: 2, 4, 5

• 3-Minute Diagnostic CAM (3D-CAM): streamlined version for busy clinical settings
• Delirium Triage Screen (DTS) followed by Brief CAM (bCAM): two-step approach with 98% sensitivity for DTS and 96% specificity for bCAM 5
• 4AT tool: rapid assessment requiring no special training
• CAM-ICU: specifically designed for intubated or critically ill patients 2

Document Delirium as a Medical Emergency

Delirium represents a medical emergency with mortality rates twice as high when the diagnosis is missed 2, 3

• Without validated screening tools, clinicians fail to recognize delirium in approximately 75% of cases 4, 5
• Initiate non-pharmacological interventions immediately: reorientation, sleep-wake cycle optimization, mobilization, sensory aids (glasses, hearing aids), hydration 1
• Measure and document delirium severity over time to ensure appropriate response and resolution 1