Altered Mental Status and Coma

Diffuse metabolic/toxic (bilateral hemispheric depression, brainstem reflexes preserved)

• Glucose derangement: hypoglycemia (insulin, sulfonylureas, alcohol-associated glycogen depletion) deprives neurons of their obligate substrate; DKA and hyperosmolar hyperglycemic state cause osmotic shifts
• Organ failure: uremic encephalopathy, hepatic encephalopathy (ammonia → astrocyte glutamine accumulation → cerebral edema, per AASLD), hypercarbic respiratory failure, hypoxemia
• Electrolyte/endocrine: hyponatremia, hypernatremia, hypercalcemia, myxedema coma, adrenal crisis
• Toxins: opioids, benzodiazepines/alcohol (GABA), anticholinergics, salicylates, carbon monoxide, toxic alcohols; withdrawal states are equally common

Non-modifiable risk factors

• Advanced age and baseline cognitive impairment: dementia is the single strongest predisposing factor for delirium; reduced cognitive reserve means a small insult produces large decompensation
• Prior stroke, Parkinson disease, sensory impairment (vision/hearing), male sex, and severe comorbidity

Modifiable risk factors

• Polypharmacy: anticholinergics, benzodiazepines, opioids, sedative-hypnotics — the AGS Beers Criteria specifically flag these as potentially inappropriate in older adults
• Alcohol and substance use disorder, including withdrawal risk quantified with CIWA-Ar
• Precipitants targeted by SCCM PADIS-guideline prevention bundles: untreated pain, immobility, physical restraints, indwelling catheters, sleep deprivation, dehydration, hypoxia, and untreated infection

• Diffuse cerebral dysfunction: Metabolic encephalopathy from hypoxia, hypoglycemia, uremia, hepatic dysfunction, hypercarbia, or electrolyte abnormalities impairs neuronal metabolism globally; toxins (alcohol, opioids, anticholinergics) directly depress neural function
• Brainstem/RAS injury: Structural damage to upper pons/midbrain (from hemorrhage, infarction, herniation, mass effect) directly eliminates arousal capacity; even small lesions here cause profound coma while large hemispheric lesions may spare consciousness
• Increased intracranial pressure (ICP): Space-occupying lesions (tumor, hematoma, abscess, edema) increase ICP, reducing cerebral perfusion pressure (CPP = MAP – ICP) and causing ischemia; herniation through tentorial opening compresses brainstem, causing irreversible coma
• Seizure activity: Prolonged seizures or status epilepticus deplete neuronal energy stores and cause persistent altered mental status even after electrical activity ceases (postictal state); convulsive or non-convulsive variants both cause coma
• Neurotransmitter dysfunction: GABA agonists (benzodiazepines, alcohol, barbiturates) and opioids enhance inhibitory neurotransmission; anticholinergics block acetylcholine; dopamine depletion occurs in Parkinson's disease and neuroleptic malignant syndrome

• Mild altered mental status: Disorientation, confusion, difficulty with attention/concentration, inappropriate behavior, slurred speech; patient arousable with normal or delayed response; retain some purposeful movement
• Delirium (acute confusional state): Acute onset with fluctuating course, inattention as core feature, disorganized thinking, autonomic hyperactivity (tachycardia, hypertension, hyperthermia), hallucinations; highly agitated or withdrawn; common in ICU, sepsis, intoxication
• Lethargy/obtundation: Decreased alertness, delayed responses, easily falls back asleep, requires repeated or vigorous stimulation; responds appropriately when aroused
• Stupor: Only responds to vigorous or painful stimulation; minimal purposeful response; cannot be easily aroused to conversation
• Coma: No eye-opening, no verbal response, no purposeful motor response to stimuli; brainstem reflexes may be intact (corneal, gag, pupillary) or absent depending on severity
• Glasgow Coma Scale (GCS): Essential bedside tool; score 3–8 = coma, 9–12 = severe impairment, 13–14 = mild impairment, 15 = normal; each point drop is clinically significant
• Posturing: Decorticate (flexion of arms, extension of legs) indicates supratentorial lesion; decerebrate (extension of all limbs) indicates brainstem involvement; absence of response (flaccidity) may indicate deepest coma or spinal cord injury
• Pupillary findings: Pinpoint pupils suggest opioid toxicity or pontine hemorrhage; dilated fixed pupils indicate brainstem death or anticholinergic toxicity; sluggish pupils suggest metabolic encephalopathy; anisocoria (unequal pupils) raises concern for ipsilateral mass causing herniation
• Important clinical pearl: A metabolic patient typically preserves brainstem reflexes (pupils reactive, corneal reflex present) while a structural patient may lose them; this distinction guides imaging urgently

• Clinical assessment: Obtain collateral history from family/friends regarding acute vs. chronic onset, medication/substance access, prior psychiatric history, trauma, fever, headache; vital signs are crucial—fever suggests infection (meningitis, encephalitis, UTI, aspiration pneumonia), hypothermia suggests intoxication or sepsis, hypertension may indicate stroke or hypertensive emergency
• Physical examination beyond mental status: Complete neurologic exam assessing symmetry of motor/sensory function (asymmetry = structural lesion), reflexes, meningeal signs (neck stiffness, Kernig/Brudzinski signs = meningitis), focal deficits, fundoscopy for papilledema (elevated ICP), skin for rashes (petechiae in meningococcemia), odor of breath (ketones in DKA, fruity in methanol poisoning)
• Laboratory studies (STAT): Serum glucose (hypoglycemia is medical emergency—give dextrose empirically if no contraindication), electrolytes (hyponatremia, hypernatremia, hypercalcemia), BUN/creatinine, liver function tests, ammonia (if hepatic encephalopathy suspected), arterial blood gas (acidosis, hypercarbia, hypoxia), complete blood count (infection, anemia), urinalysis and urine drug screen, blood cultures if sepsis suspected, toxicology screen (alcohol level, acetaminophen, salicylates), lactate (tissue hypoperfusion)
• Neuroimaging: CT head (non-contrast) is first-line to rule out acute intracranial hemorrhage, mass effect, herniation before LP; if LP needed (suspected meningitis), CT should be obtained first to exclude mass effect unless LP cannot be delayed (clinical evidence of meningitis + antibiotics must not wait); MRI provides better detail for ischemic stroke, subtle hemorrhage, and metabolic/demyelinating disease but takes too long in acute setting
• Lumbar puncture (LP): Indicated if meningitis/encephalitis suspected; obtain opening pressure, cell counts, protein, glucose (blood glucose simultaneously), Gram stain, culture, and consider viral PCR (HSV, VZV, enterovirus) and fungal stain if risk factors; contraindications: papilledema, focal neurologic deficits, mass on imaging
• EEG: Identify non-convulsive seizures (absence or petit mal-like activity that may not show obvious motor seizure); useful in suspected status epilepticus, encephalitis (characteristic findings), metabolic encephalopathy; triphasic waves classically seen in hepatic encephalopathy
• Additional studies based on clinical suspicion: Carboxyhemoglobin (CO poisoning), ammonia level, lactate, chest X-ray (aspiration, pneumonia, pulmonary edema), ECG (arrhythmia causing hypoperfusion), thermoregulation assessment
• Important diagnostic consideration: Always consider hypoglycemia as it is rapidly reversible and catastrophic if missed; give dextrose empirically in undifferentiated coma if blood glucose cannot be checked immediately; also consider opioid overdose (give naloxone empirically if opioid toxidrome present) and status epilepticus (may be non-convulsive)

• Airway/Breathing/Circulation: Protect airway with intubation if GCS ≤ 8 or unable to protect airway; maintain normoxia (SpO₂ > 94%) and normocarbia (avoid hyperventilation unless herniation suspected, as it transiently improves ICP but worsens ischemia); establish IV access, place on continuous cardiac monitoring, maintain systolic BP > 90 mmHg (hypotension worsens cerebral ischemia)
• Empiric therapy for reversible causes (do not wait for diagnostic confirmation):
• Dextrose: 50 mL of D50W IV bolus for any altered

Complications of the underlying disease

• Airway loss and aspiration pneumonitis/pneumonia (emergency): obtunded patients lose protective gag and cough; signals are new hypoxemia, gurgling respirations, and a dependent-segment infiltrate. Intubation for GCS ≤ 8 is preventive, not therapeutic
• Cerebral herniation (emergency): expanding mass or edema shifts brain across dural boundaries; heralded by anisocoria with a fixed dilated pupil (uncal/CN III compression), progressive posturing, and the Cushing reflex (hypertension, bradycardia, irregular respirations). Requires head-of-bed elevation, hyperosmolar therapy (mannitol or hypertonic saline), and immediate neurosurgical consultation per Brain Trauma Foundation principles
• Non-convulsive status epilepticus (emergency): persistent coma disproportionate to the insult with no motor activity; only EEG reveals it
• Secondary hypoxic-ischemic injury: hypotension or hypoxemia lowers cerebral perfusion pressure (CPP = MAP − ICP) in an already injured brain
• Immobility sequelae: venous thromboembolism, pressure injury, rhabdomyolysis with myoglobinuric acute kidney injury (markedly elevated CK), contractures

Complications of treatment

• Naloxone-precipitated withdrawal: abrupt opioid receptor reversal causes agitation, vomiting (aspiration risk) and, rarely, flash pulmonary edema; because naloxone's half-life is shorter than methadone's or extended-release opioids', re-sedation after initial response is the classic trap — observe and consider infusion
• Flumazenil-induced seizures (emergency): unmasking of GABAergic tone in chronic benzodiazepine users or co-ingested TCA overdose; largely avoided in undifferentiated coma
• Osmotic demyelination syndrome: over-rapid correction of chronic hyponatremia produces delayed quadriparesis, dysarthria, and locked-in syndrome days later; correction rate must be capped
• Wernicke encephalopathy: glucose administration in a thiamine-deficient patient can precipitate the confusion–ophthalmoplegia–ataxia triad; give thiamine with or before dextrose
• Antipsychotics for agitation: QT prolongation with torsades, extrapyramidal effects, neuroleptic malignant syndrome; SCCM PADIS guidelines do not support routine haloperidol to treat or prevent delirium
• Benzodiazepines: deepen delirium except in alcohol/benzodiazepine withdrawal, where CIWA-Ar–triggered dosing is standard

• Check a fingerstick glucose in every altered patient — before imaging, before the tox screen. Hypoglycemia is instantly reversible and is the most commonly missed cause on exams; ADA Standards of Care support IV dextrose when the patient cannot take oral carbohydrate
• Thiamine with or before glucose in malnourished or alcohol-using patients. The stem gives you ophthalmoplegia, ataxia, confusion — that is Wernicke encephalopathy, and glucose alone can precipitate it. Korsakoff (confabulation, anterograde amnesia) is the irreversible sequela
• Pinpoint pupils + hypoventilation + depressed consciousness = opioid toxidrome; the single best next step is naloxone, not intubation, and certainly not a CT scan first. Watch for re-sedation once naloxone wears off
• Metabolic versus structural is decided at the bedside by symmetry and brainstem reflexes. Symmetric exam with reactive pupils favors metabolic/toxic; anisocoria, focal deficits, or lost corneal/oculocephalic reflexes mandate emergent non-contrast head CT
• A blown pupil with contralateral hemiparesis is uncal herniation compressing CN III — the answer is hyperosmolar therapy plus neurosurgery, not "obtain MRI"
• Do not delay antibiotics for the CT or LP in suspected bacterial meningitis. IDSA guidance is blood cultures, then dexamethasone with or just before the first antibiotic dose, then imaging/LP
• Coma that persists without motor activity after a seizure is non-convulsive status until EEG proves otherwise; triphasic waves instead point to hepatic encephalopathy
• Distractors to avoid: flumazenil in undifferentiated coma (seizure risk); calling a patient with intact vertical gaze and blinking "comatose" when the answer is locked-in syndrome from a ventral pontine lesion; and treating agitated delirium with benzodiazepines — per SCCM PADIS guidelines, benzodiazepines are reserved for alcohol or benzodiazepine withdrawal, where dosing is guided by CIWA-Ar
• Intubate for GCS ≤ 8 or inability to protect the airway; the GCS motor score carries the most prognostic weight