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CDHB

Altered Level of Consciousness

See also: Stupor and Coma.

In general terms decreased level of consciousness and coma is caused by either intracranial or extracranial abnormalities. Use the GCS or AVPU score to ascertain the level of consciousness.

Initial assessment and resuscitation

Note that supportive care with attention to the ABCs is paramount while the diagnostic possibilities are being considered. Once a diagnosis is reached, definitive management can be undertaken.

• Airway (commonly impaired by altered level of consciousness), breathing, circulation.
• Consider the "three coma antidotes":
  • Thiamine 100 mg IV or IM, if there is the possibility of Wernicke's encephalopathy. Give before glucose.
  • Glucose - check capillary blood glucose, if hypoglycaemia confirmed give 50 mL of 50% glucose (dextrose) solution IV.
  • Naloxone 0.2-0.4 mg IV and repeat at 2-3 minute intervals as necessary. If no response and narcotic overdose suspected give naloxone up to a maximum of 4 mg. Higher doses can be given, but in this situation, review the diagnosis of narcotic overdose before giving more than 4 mg. (2 mg may be required to reverse methadone overdose.) Flumazenil is available for benzodiazepine reversal but is rarely indicated in the emergency setting.

Definitive Management

According to the cause.

Extracranial causes

Rarely have focal neurology and often gradual onset.

• A Airway compromise.
• B Breathing abnormalities (hypoxia and hypercapnia).
• C Circulation abnormalities (hypo- and hypertension).
• D Drugs (sedatives, ethanol, tricyclic antidepressants, opiates etc.).
• E Endocrine and metabolic abnormalities.
  • Consider glucose, sodium and calcium abnormalities, hepatic encephalopathy, renal failure, hypo- and hyperthermia, hypo- and hyperthyroidism and Wernicke's encephalopathy.
  • Attention to and correction of any ABC abnormalities, along with specific treatment for toxic ingestions and metabolic abnormalities, is required.

Intracranial causes

Often have focal neurology and often abrupt onset. Will need an urgent CT head and referral to Neurosurgery if any suspicion of a focal lesion as it may be amenable to operative treatment.

• Trauma - extradural, subdural, subarachnoid, or intraparenchymal bleeds or diffuse axonal injury.
• Seizures and post ictal states:
  • Benzodiazepines, phenytoin and valproate as indicated.
• Infective - meningitis or encephalitis:
  • CT should precede lumbar puncture, but where meningitis is suspected early antibiotics are mandatory.
• Vascular - intracranial bleed or brain stem infarct.
• Mass lesion e.g., bleed into tumour or subdural haematoma:
  • Urgent referral to Neurosurgery as indicated.
• Hysterical coma (psychogenic altered level of consciousness):
  • Diagnosis of exclusion.
• Assess the Glasgow Coma Scale.

Topic Code: 1268