What are the causes of acute confusion in geriatric patients, particularly those with a history of dementia or chronic medical conditions?

Causes of Acute Confusion in Geriatric Patients

Acute confusion (delirium) in geriatric patients is most commonly caused by infections (particularly urinary tract infections and pneumonia), medications (especially anticholinergics and benzodiazepines), and metabolic derangements, with the evaluation requiring immediate assessment for reversible life-threatening causes. 1, 2

Most Common Infectious Causes

• Urinary tract infections and pneumonia are the two most common infectious precipitants of delirium in elderly patients. 1, 2
• Over 80% of patients with bacteremia demonstrate neurological symptoms ranging from lethargy to coma. 2
• Any acute infection can trigger delirium, particularly in patients with underlying dementia or chronic medical conditions. 3, 4

Medication-Related Causes (Critical Priority)

Medications represent one of the most important and reversible causes of acute confusion in the elderly. 1, 5, 6

High-Risk Medication Classes:

• Anticholinergic medications (including antihistamines like cyclizine) are among the highest-risk drugs and should be discontinued immediately. 1, 2, 6
• Benzodiazepines are potent precipitants of delirium and must be discontinued unless treating alcohol or benzodiazepine withdrawal. 2
• Opioids, particularly in patients with renal impairment, accumulate toxic metabolites. 2
• Antipsychotics, sedative/hypnotics, vasodilators, and diuretics all contribute to delirium risk. 1
• The total anticholinergic burden from multiple medications may be more important than any single agent. 6

Metabolic and Electrolyte Disorders

• Hypoglycemia and hyperglycemia require immediate point-of-care glucose testing. 5
• Dehydration is a common precipitant that may not be apparent on initial laboratory examination. 2
• Hyponatremia due to SIADH may require specific testing beyond basic metabolic panels. 2
• Hypercalcemia should be suspected even with indolent symptoms, as delirium from hypercalcemia is reversible in 40% of cases. 2
• Electrolyte abnormalities detected through complete blood count and standard electrolyte panels are essential to evaluate. 1

Cardiovascular and Respiratory Causes

• Hypoxia from respiratory causes must be assessed immediately with oxygen saturation monitoring. 5
• Acute myocardial infarction can present atypically with altered mental status in elderly women without chest pain. 5
• Congestive heart failure is a common precipitant, particularly in patients admitted with confusion. 4
• Orthostatic hypotension should be evaluated with lying and standing blood pressure measurements. 5

Neurological Causes

• Cerebrovascular disease, including stroke and traumatic brain injury, can trigger acute mental status changes. 2
• Subdural hematoma from unrecognized trauma, especially in patients on anticoagulation, must be considered. 5
• Nonconvulsive seizures require EEG evaluation, not just imaging. 2, 5
• Less frequent causes include status epilepticus, intracranial mass effect, chronic subarachnoid hemorrhage, meningitis, encephalitis, and hydrocephalus. 2

Environmental and Physiological Factors

• Sleep deprivation is both a symptom and a factor that prolongs delirium. 2
• Visual and hearing impairments contribute significantly—patients should use their glasses and hearing aids. 2
• Pain, constipation, and pressure ulcers are often-overlooked physical factors. 2
• Hypothermia can precipitate delirium and requires core temperature assessment. 5

Iatrogenic Causes

• Iatrogenic disease is more common in patients who develop confusion after hospitalization rather than those admitted with confusion. 4
• Physical restraints can worsen delirium and should be avoided. 2, 7
• Polypharmacy is a major contributor, particularly in nursing home residents. 5, 6

Critical Clinical Context

Delirium represents a medical emergency with mortality rates twice as high when the diagnosis is missed. 2, 7, 5 The overall mortality in elderly patients with altered mental status is approximately 8.1%, and delirium occurs in 25% of hospitalized geriatric patients. 1, 2 Consequences include increased morbidity, extended hospital length of stay, lasting functional decline, and increased need for nursing home placement. 1

Essential Diagnostic Workup

Upon identifying acute confusion, obtain the following immediately:

• Point-of-care glucose testing 5
• Vital signs including oxygen saturation and orthostatic measurements 5
• Core temperature 5
• EKG to assess for myocardial ischemia 1, 5
• Complete blood count 1, 5
• Comprehensive metabolic panel (sodium, glucose, renal function, calcium) 1, 5
• Thyroid function (TSH) and vitamin B12 levels 1
• Measurable medication levels when applicable 1
• Urinalysis and chest imaging when infection suspected 1, 2

Common Pitfalls to Avoid

• Do not attribute acute confusion to known dementia without investigating for reversible causes. 7
• Hypoactive delirium is the most commonly missed subtype and carries higher mortality risk than hyperactive delirium. 7
• Do not overlook medication reconciliation—elderly patients often take multiple interacting medications. 5, 6
• Do not assume "no stroke" without proper evaluation, as small vessel disease may not present with obvious focal deficits. 5
• Recognize that almost any acute illness can cause delirium in vulnerable elderly patients. 3, 8