What is the appropriate work‑up (delirium panel) for a patient with suspected hypoactive delirium?

Hypoactive Delirium Work-Up Panel

The appropriate delirium panel for suspected hypoactive delirium should include: complete metabolic panel (electrolytes, renal function, glucose), complete blood count, urinalysis with culture, chest radiograph, oxygen saturation, point-of-care glucose, medication review focusing on anticholinergics/sedatives/opioids, and assessment for dehydration. 1, 2, 3

Core Laboratory Studies

The essential laboratory work-up targets the most common reversible precipitants:

• Complete metabolic panel to identify electrolyte disturbances (particularly hyponatremia), renal failure, hepatic dysfunction, and glucose abnormalities 1, 4
• Complete blood count to detect infection, anemia, or hematologic abnormalities 1
• Urinalysis with culture since urinary tract infections are among the most common precipitating factors for delirium 5, 3
• Chest radiograph to evaluate for pneumonia, which along with UTI represents the most frequent infectious trigger 5
• Point-of-care glucose and oxygen saturation as immediate bedside tests for hypoglycemia, hyperglycemia, and hypoxia 1, 2

Critical Clinical Assessments

Beyond laboratory studies, the work-up must include:

• Comprehensive medication review with particular attention to recent additions or dose changes of anticholinergic drugs, sedatives, narcotics, and polypharmacy (≥5 medications) 5, 1, 4
• Hydration status assessment since dehydration is a common and readily reversible precipitant in older adults 1, 4
• Vital signs including temperature to identify sepsis, hypothermia, or acute myocardial infarction 5, 6

Additional Investigations Based on Clinical Context

Selective additional testing should be guided by specific clinical findings:

• Thyroid function tests and cortisol if clinical features suggest endocrine dysfunction (bradycardia, hypotension, hypothermia) 6
• Electroencephalogram (EEG) to rule out non-convulsive status epilepticus when delirium mimics are suspected 1
• Brain imaging (CT or MRI) is NOT routinely indicated for new-onset delirium unless there are focal neurologic deficits, head trauma, suspected stroke, seizure, or headache 5

Critical Pitfall: Hypoactive Delirium Recognition

Hypoactive delirium is the most commonly missed subtype and carries higher mortality risk than hyperactive delirium. 2, 4, 7 This presentation manifests as:

• Paucity of speech, slow or absent movement, unresponsiveness 5, 1
• Withdrawn appearance with decreased motor activity 5, 7
• Often misattributed to dementia or depression rather than recognized as a medical emergency 5, 2

The work-up must be initiated urgently because mortality is twice as high when delirium diagnosis is missed, and hypoactive presentations are frequently unrecognized in up to 35% of cases. 5, 2, 4

Practical Implementation Algorithm

1. Immediate bedside assessment: Point-of-care glucose, vital signs including oxygen saturation, medication list review 1, 2
2. Stat laboratory panel: Complete metabolic panel, complete blood count, urinalysis 1, 3
3. Infection screening: Chest radiograph, urine culture 5, 3
4. Identify and eliminate delirium-inducing medications: Steroids, anticholinergics, benzodiazepines, opioids 5, 4
5. Assess hydration status and correct deficits 1, 4
6. Reserve advanced testing (thyroid function, EEG, neuroimaging) for cases with specific clinical indicators 5, 1, 6

The work-up should proceed simultaneously with diagnostic confirmation using validated tools like the Confusion Assessment Method (CAM) and immediate implementation of non-pharmacological interventions, as delirium represents a medical emergency requiring urgent evaluation and treatment of underlying causes. 5, 1, 2