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Approach to coma and altered consciousness
In a comatose patient, stabilise ABC, check glucose and give thiamine and naloxone as needed, then separate a structural cause (lateralising signs, unequal pupils — CT at once) from a metabolic, toxic or infectious one — and treat herniation and infection without waiting for every test.
Why it matters in the exam
Questions present an unconscious patient brought to the emergency department and test the first step: almost always bedside glucose, and in a malnourished or alcoholic patient thiamine 100 mg before or together with glucose so as not to provoke Wernicke encephalopathy. Naloxone is given when there are small pupils and slow breathing.
Reading the neurological examination is also tested: a dilated, unreactive pupil on one side suggests uncal herniation; pinpoint pupils — opioids or pontine haemorrhage; fixed mid-position pupils — midbrain injury. The Cushing triad (hypertension, bradycardia and irregular breathing) signals raised intracranial pressure. A GCS of 8 or less usually requires a definitive airway.
Further work-up: non-contrast head CT, then sodium, calcium, kidney and liver function, ammonia, blood gas, toxicology and thyroid function. When meningitis or encephalitis is suspected, antibiotics and aciclovir are given at once, before CT and lumbar puncture. A confused patient who does not wake without an explanation needs an EEG to exclude non-convulsive status epilepticus. In herniation, raise the head to 30 degrees, give osmotic therapy (mannitol 0.5–1 g/kg, or alternatively hypertonic saline) and keep hyperventilation short, only as a bridge.
Key points
- ABC, glucose, thiamine and naloxone — before anything else.
- Lateralising signs or one dilated pupil — CT at once.
- Cushing triad — raised intracranial pressure.
- Suspected infection — antibiotics and aciclovir before CT.
- Unexplained confusion — EEG to exclude non-convulsive status.
Summary table
| Type | Clues | Deciding test | Immediate treatment |
|---|---|---|---|
| Structural (bleed, infarct, tumour) | Lateralising signs, one dilated pupil, Cushing triad | Head CT | Neurosurgery; treat herniation |
| Metabolic | No lateralising signs, asterixis, reactive pupils | Glucose, sodium, calcium, ammonia, blood gas | Correct the disturbance |
| Toxic | Toxidrome, small or large pupils | History and examination, levels | Naloxone, specific antidotes, support |
| Infectious | Fever, neck stiffness, rash | Lumbar puncture after CT as needed | Antibiotics and aciclovir at once |
| Non-convulsive seizures | Persistent unexplained confusion, subtle twitching | EEG | Benzodiazepines and antiseizure drugs |
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Sources
- Plum and Posner's Diagnosis and Treatment of Stupor and Coma, 5th edition (2019) — Approach to the patient in coma
- Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th edition (2020) — Altered mental status and coma
- Brain Trauma Foundation / Neurocritical Care Society, Emergency Neurological Life Support, 2023 — Coma and intracranial hypertension
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.