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Coma and brain death
In a comatose patient first look for reversible causes (glucose, poisoning, seizures, infection) and examine the brainstem to separate a structural from a metabolic cause; brain death is the irreversible loss of all brain and brainstem function, determined by prerequisites, examination and an apnoea test.
Why it matters in the exam
Questions present an unconscious patient and ask about the first steps (sodium, glucose, thiamine, naloxone if opioids are suspected), the meaning of pupil findings (pinpoint pupils — opioids or a pontine lesion; one dilated pupil — herniation; reactive pupils with other reflexes absent — a metabolic cause), and the difference between coma and locked-in syndrome, in which the patient is awake and moves the eyes vertically. Questions on brain death check the prerequisites (body temperature, sedative drugs, metabolic disturbances, blood pressure), brainstem reflexes, and the apnoea test with a rise in PaCO2. In Israel determination follows the Brain-Respiratory Death Act. A common distractor is declaring brain death in a cooled or sedated patient.
Key points
- In coma start with reversible causes: glucose, thiamine, naloxone and seizures.
- Reactive pupils with other reflexes absent suggest a metabolic cause.
- Locked-in: awake, with vertical eye movements — not coma.
- Brain death requires prerequisites: temperature 36 degrees or more, systolic pressure 100 or more, no sedative drugs.
- Apnoea test: no breathing when PaCO2 reaches 60 or more and has risen by 20 or more.
Summary table
| Aspect | Finding or rule | Meaning |
|---|---|---|
| First steps | Airway (GCS 8 or less — consider intubation), glucose, thiamine, naloxone, CT | Then: electrolytes, liver and kidney function, ammonia, toxicology screen, blood gas, EEG |
| Pupils | Pinpoint — opioids or pontine lesion; one dilated — uncal herniation; mid-position and fixed — midbrain lesion | Reactive pupils with other reflexes absent suggest a metabolic or toxic cause |
| Coma mimics | Locked-in: awake, vertical eye movements and blinking preserved (ventral pontine lesion); vegetative state: eyes open without awareness | EEG if non-convulsive status is suspected |
| Prerequisites for brain death | A known irreversible cause; core temperature 36 degrees or more; systolic pressure 100 mmHg or more; no effect of sedative drugs or severe metabolic disturbance | Without these the examination must not be done |
| Examination and apnoea test | Unresponsive coma; absent reflexes: pupillary, corneal, oculocephalic, caloric, cough and gag; apnoea test: no breathing when PaCO2 reaches 60 mmHg or more and has risen by 20 or more | Ancillary test (cerebral blood flow) when the examination cannot be completed; in Israel — according to the law and regulations |
Free exam questions
מה מהממצאים הבאים ברישום EEG קשור בפרגונוזה טובה לאחר נזק אנוקסי? (the question as examined, in Hebrew)
- א. Alpha Coma
- ב. Burst Suppression
- ג. Periodic Patterns
- ד. Reactivity
איזו תופעה בהליכה שכיחה בחולי פרקינסון ולא בתסמונות פרקינסוניות אחרות? (the question as examined, in Hebrew)
- א. קיפאון
- ב. פסטינציה
- ג. צעדים קטנים ונמוכים
- ד. קומה שפופה
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Sources
- AAN/AAP/CNS/SCCM Consensus Practice Guideline: Pediatric and Adult Brain Death/Death by Neurologic Criteria Determination, 2023 — Prerequisites, examination and apnoea test
- Israel Brain-Respiratory Death Act and Ministry of Health Regulations, 2008 — Determination procedure
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.