Chapter 55: Delirium
1. Chapter Overview
Delirium is an acute, typically reversible syndrome of cerebral insufficiency characterized by a rapid decline in attention and cognition with a fluctuating course over the day. It is extremely common among hospitalized older adults (especially in ICUs and post-operatively) and serves as an independent, high-risk predictor of prolonged hospital stays, long-term functional decline, institutionalization, and mortality. The chapter emphasizes that delirium is not merely a symptom but a medical emergency, signaling severe underlying physiological stress.
2. Pathophysiology and Risk Factors
Pathophysiology: While the exact mechanisms remain partially elusive, prevailing theories point to neuroendocrine imbalance (centrally, acetylcholine deficiency and dopamine excess), systemic inflammation (pro-inflammatory cytokines crossing the blood-brain barrier causing neuroinflammation), and impaired cerebral oxidative metabolism.
Two-Factor Model: Delirium results from the complex interplay between "Predisposing Factors" (vulnerability) and "Precipitating Factors" (insults).
Predisposing Factors: Advanced age, pre-existing dementia (the strongest independent risk factor), multimorbidity, sensory impairments (vision/hearing loss), and severe frailty.
Precipitating Factors: Acute infections (e.g., pneumonia, UTIs), polypharmacy (especially anticholinergics and sedatives), severe pain, electrolyte imbalances, surgical stress, and sleep deprivation. In highly vulnerable, frail older adults, even a trivial insult (like constipation or a room change) can trigger delirium.
3. Clinical Subtypes and Diagnosis
Delirium manifests in three primary motor subtypes:
Hyperactive: Characterized by restlessness, extreme agitation, hallucinations, and combative behavior. This type is most easily recognized.
Hypoactive: Characterized by lethargy, apathy, psychomotor retardation, and sluggish responsiveness. This is the most common yet most frequently missed subtype, and it generally carries a worse prognosis.
Mixed: Patients fluctuate between hyperactive and hypoactive states.
Diagnostic Tools: The chapter strongly recommends the Confusion Assessment Method (CAM) for rapid clinical diagnosis. Its four core features are: (1) acute onset and fluctuating course, (2) inattention, (3) disorganized thinking, and (4) altered level of consciousness. A positive diagnosis requires the presence of 1 and 2, plus either 3 or 4.
4. Prevention and Non-Pharmacological Management
Non-pharmacological multicomponent interventions are the gold standard for both the prevention and treatment of delirium. Programs like the Hospital Elder Life Program (HELP) significantly reduce delirium incidence. Core strategies include:
Frequent reorientation (communicating time, place, and person).
Early mobilization and strict avoidance of physical restraints and urinary catheters.
Promoting sleep hygiene by optimizing the nighttime ward environment (reducing noise and light).
Correcting sensory deprivation (ensuring the use of eyeglasses and hearing aids).
Ensuring adequate hydration and nutritional intake.
5. Limitations of Pharmacotherapy
Currently, there are no FDA-approved medications specifically for treating delirium. Pharmacological interventions (such as low-dose haloperidol or atypical antipsychotics) should be used strictly as a last resort, and only when a patient exhibits severe hallucinations or extreme agitation that poses an imminent physical threat to themselves or others, or impedes life-saving medical therapies. Sedatives must never be used for hypoactive delirium, as they will only exacerbate the condition.
—Brocklehurst’s Textbook of Geriatric Medicine and Gerontology