Clinical meaning
Delirium is an acute, fluctuating disturbance in attention and cognition caused by an underlying medical condition. The pathophysiology involves a complex interplay of neurotransmitter dysfunction: acetylcholine deficiency (the primary neurotransmitter implicated, explaining why anticholinergic medications are a major risk factor), dopamine excess (explaining the efficacy of low-dose antipsychotics), serotonin and GABA imbalance, and neuroinflammation (elevated IL-6, IL-8, TNF-alpha). The cholinergic deficit theory explains why elderly patients (who have age-related cholinergic decline) are most susceptible. Precipitating factors such as infection, metabolic disturbance, medications, or surgery act on a vulnerable brain (reduced cognitive reserve from aging, dementia, or neurodegeneration). Delirium is classified as hyperactive (agitation, hallucinations), hypoactive (lethargy, withdrawal, reduced responsiveness - often missed), or mixed (fluctuating between both). Hypoactive delirium has the worst prognosis because it is frequently unrecognized.
Diagnosis & workup
Diagnostics & workup: - Screen with Confusion Assessment Method (CAM): acute onset + fluctuating course + inattention + EITHER disorganized thinking OR altered level of consciousness - Assess attention using digit span, serial 7s, or months backward - Obtain comprehensive metabolic panel, CBC, urinalysis, blood culture - Check thyroid function, B12, ammonia level if appropriate - Order chest X-ray if pneumonia suspected - Review medication list for deliriogenic agents - Order CT head if focal deficits, history of fall, or anticoagulation