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emergency & critical carescoring tool

Glasgow Coma Scale (GCS)

The Glasgow Coma Scale quantifies level of consciousness across three components: eye opening, verbal response, and motor response. Total score ranges from 3 (deep coma) to 15 (fully alert). It is the most widely used consciousness assessment tool in acute and trauma care worldwide.

inputs

✓ when to use

Use for any patient with altered consciousness, traumatic brain injury, post-cardiac arrest, stroke, infection with altered mental status, or any acute neurological presentation requiring serial monitoring. Applicable across ED, ICU, ward, and pre-hospital settings. The GCS is a core component of trauma primary survey (ATLS), NEWS2, and multiple prognostic scores (APACHE II, SOFA).

✗ when not to use

GCS is unreliable in intubated or sedated patients (verbal component cannot be assessed — record as 'T' for tube and report component scores separately, e.g., E3VTM5). Limited in pre-verbal children (use paediatric GCS modification). Does not assess brainstem reflexes or respiratory pattern — consider the FOUR score in neurocritical care when these are needed. A GCS of 15 does not exclude significant intracranial pathology.

clinical pearls

  • Always report component scores (e.g., E3V4M5 = 12), not just the total. Two patients with GCS 8 can have very different neurological states — E2V2M4 vs E1V1M6 carry different prognostic and management implications.
  • The motor score is the single most prognostic component. If you can only assess one component, motor response alone correlates most strongly with outcome.
  • GCS ≤8 is the classic threshold for considering intubation ('GCS 8, intubate'), but this should not be applied rigidly — clinical context matters. A patient with GCS 9 who is deteriorating may need intubation sooner than a stable patient at GCS 7.
  • In intubated patients, do not assign V1 — record as VT (tube) and use the E + M components. Alternatively, use the FOUR score which was designed for this situation.
  • A lucid interval (initial GCS 15 followed by rapid deterioration) is a classic presentation of extradural haematoma — serial GCS monitoring is essential in all head injuries, even those initially appearing minor.

related tools

four-scoreAlternative coma assessment (includes brainstem reflexes)news2GCS is a component of NEWS2canadian-ct-headGCS is a criterion in the Canadian CT Head RulepecarnGCS used in paediatric head injury assessment