The Glasgow Coma Scale (GCS) is used to objectively describe the extent of impaired consciousness in all types of acute medical and trauma patients. The Glasgow Coma Scale (GCS) is the most common scoring system. GCS was used to assess a person's level of consciousness after a head injury, and the scale is now used by emergency medical services, nurses, and. Severe Head Injury----GCS score of 8 or less. The Glasgow Coma Scale (GCS) is used to describe the general level of consciousness in patients with traumatic brain injury (TBI) and to.