A 30-year-old man with severe traumatic brain injury (GCS 6) is being transferred to the operating theatre for evacuation of an extradural haematoma. During transfer his systolic blood pressure falls to 85 mmHg for 4 minutes before correction. Which statement BEST reflects the significance of this event?
- A A single episode of systolic pressure below 90 mmHg roughly doubles mortality and is among the strongest predictors of poor outcome ✓
- B It has little prognostic impact once corrected within minutes
- C It matters only if accompanied simultaneously by hypoxaemia
- D Its effect is fully offset by subsequent aggressive osmotherapy
Correct answer: A. A single episode of systolic pressure below 90 mmHg roughly doubles mortality and is among the strongest predictors of poor outcome
Explanation
In head injury, a single documented episode of hypotension defined as systolic blood pressure below 90 mmHg approximately doubles mortality, making it one of the most powerful secondary insults alongside hypoxaemia. Loss of autoregulation makes the injured brain perfusion-passive, so the fall directly cuts cerebral perfusion pressure. Correction later does not undo the ischaemic insult, and osmotherapy cannot offset it.
Reference: Brain Trauma Foundation Guidelines for the Management of Severe Traumatic Brain Injury, 4th ed.
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