Coma in the Elderly

Coma in the Elderly Source note: Coma is addressed across chapters in the uploaded textbooks (Glasgow Coma Scale and prognosis in the subdural haematoma chapter, level-of-consciousness grading within the Confusion Assessment Method, hyperosmolar non-ketotic coma, myxoedema coma, hypothermia and hyperthermia) rather than in a single dedicated chapter. Points below integrate these with current peer-reviewed neurocritical care literature.

Coma is a state of unarousable unresponsiveness — no eye opening, no comprehensible speech and no purposeful motor response even to noxious stimuli; operationally GCS ≤8.

Consciousness has two components: arousal (ascending reticular activating system in the brainstem tegmentum and thalamus) and awareness (cerebral cortex). Coma requires damage to the ARAS or to both hemispheres.

Spectrum of impaired consciousness (as graded in the CAM): alert → vigilant → lethargic (drowsy, easily aroused) → stupor (difficult to arouse) → coma (unarousable).

Distinguish from delirium (acute onset, fluctuating, inattention, disorganised thinking — CAM), vegetative state / unresponsive wakefulness, minimally conscious state, akinetic mutism, locked-in syndrome (ventral pontine lesion; preserved vertical eye movement and blinking) and psychogenic unresponsiveness.

Ageing predisposes to coma: reduced cerebral reserve, brain atrophy (facilitating subdural haematoma), impaired drug clearance, polypharmacy, multimorbidity, blunted febrile and thirst responses, and atypical presentation.

Supratentorial structural: large hemispheric infarct with oedema, intracerebral haemorrhage, subdural haematoma (bridging vein tear after trivial or unremembered trauma — the classic elderly cause), extradural haematoma, tumour, abscess, hydrocephalus.

Infratentorial structural: brainstem infarct or haemorrhage, basilar artery occlusion, cerebellar haemorrhage or infarct with brainstem compression, central pontine myelinolysis.

Diffuse / metabolic-toxic (commonest group in the elderly): hypoglycaemia, hyperosmolar hyperglycaemic state (increased incidence in older adults), DKA, hyponatraemia, hypercalcaemia, uraemia, hepatic encephalopathy, hypoxia and hypercapnia, myxoedema coma, adrenal crisis, hypothermia, heat stroke, sepsis, Wernicke's encephalopathy.

Drugs and poisons: opioids, benzodiazepines, anticholinergics, antipsychotics, lithium, alcohol, carbon monoxide. In India, organophosphate and aluminium phosphide poisoning remain important.

Seizure-related: prolonged postictal state and non-convulsive status epilepticus — a reversible and frequently missed cause; have a low threshold for urgent EEG.

Infective: meningitis, encephalitis, cerebral malaria, neurocysticercosis, tuberculous meningitis (all endemic considerations in India).

ABC first: airway, breathing, circulation; check capillary blood glucose immediately; give thiamine before glucose if alcohol use or malnutrition is possible.

Obtain a collateral history: tempo of onset, trauma (even trivial), anticoagulants, drug and alcohol history, preceding headache, fever, seizures, and baseline cognitive and functional state.

Glasgow Coma Scale (E4 V5 M6, total 3–15) quantifies depth. Limitations in the elderly: dysphasia, hearing and visual impairment, intubation, and pre-existing dementia. The FOUR score (eye, motor, brainstem, respiration) is preferred in intubated patients.

Pupils: pinpoint reactive → pontine lesion or opioids; unilateral fixed dilated → uncal herniation compressing CN III; mid-position fixed → midbrain; preserved pupillary reactivity with deep coma strongly suggests a metabolic cause.

Brainstem reflexes: corneal, oculocephalic (doll's eye — not if cervical injury), oculovestibular (cold caloric), gag and cough. Respiratory pattern: Cheyne–Stokes (bihemispheric/diencephalic), central neurogenic hyperventilation, apneustic (pons), ataxic/Biot (medulla).

Motor: asymmetry indicates a structural lesion; decorticate (flexor) posturing implies a lesion above the red nucleus, decerebrate (extensor) posturing a brainstem lesion. Multifocal myoclonus and asterixis point to a metabolic cause.

Also examine: fundi (papilloedema, subhyaloid haemorrhage), neck stiffness, skin (rash, needle marks, jaundice, cyanosis, hot dry skin of heat stroke), temperature, and evidence of head or cervical injury.

Blood glucose, sodium, calcium, urea and creatinine, LFT, ammonia, ABG, CK, TSH, cortisol, blood and urine cultures, toxicology, ECG, chest X-ray.

Non-contrast CT head is the first-line imaging; MRI (with DWI) for posterior fossa, brainstem and basilar occlusion. Lumbar puncture after imaging if meningoencephalitis is suspected. EEG if NCSE is suspected.

Immediate reversal agents: 25–50 mL of 50% dextrose for hypoglycaemia; thiamine 100 mg IV; naloxone for opioids; flumazenil used cautiously (may precipitate seizures in chronic benzodiazepine use or mixed overdose).

Airway protection if GCS ≤8. Maintain oxygenation and normocapnia, treat hypotension, nurse head-up 30°, avoid hypotonic fluids.

Raised intracranial pressure: mannitol or hypertonic saline, controlled ventilation, urgent neurosurgical referral for subdural haematoma, intracerebral haemorrhage, cerebellar haemorrhage or hydrocephalus.

Correct hyponatraemia cautiously — Pathy's recommends raising serum sodium by only 6–8 mEq/L in 24 hours; a 100 mL bolus of 3% saline restores the GCS faster than a slow 20 mL/h infusion and had a lower mortality trend. Over-rapid correction risks osmotic demyelination.

Treat the cause: sepsis bundle and empirical antibiotics ± aciclovir; antiepileptics for NCSE; levothyroxine and hydrocortisone for myxoedema coma; rapid cooling for heat stroke; rewarming for hypothermia.

Supportive care: pressure-area care, VTE prophylaxis, aspiration precautions and nil by mouth, eye care to prevent exposure keratopathy, bladder and bowel care, nutrition, and prevention of contractures.

Prognosis depends entirely on cause. Metabolic and toxic causes are largely reversible; structural and hypoxic-ischaemic causes carry a poor outcome. In the elderly, early goals-of-care discussion and review of advance directives are an essential part of management, not an afterthought.