The unconscious patient

Prolonged loss of consciousness (coma, defined as a Glasgow Coma Score of 8 or less) is seen commonly: (1) following head injury, (2) after an overdose of sedating drugs, and (3) in the situation of ‘nontraumatic coma’, where there are many possible diagnoses, but the most common are postanoxic, postischaemic, systemic infection, and metabolic derangement, e.g. hypoglycaemia.

Clinical approach

Urgent assessment is required to identify and, where possible, correct the pathological cause, and protect the brain from the development of irreversible damage. Key issues are to (1) ensure adequate protection of the airway and adequate ventilation; (2) immediately exclude (and treat) rapidly reversible causes, in particular hypoglycaemia and opioid toxicity; and then (3) consider a wide range of differential diagnoses—even in ‘nontraumatic coma’ the patient may be harbouring delayed effects of head injury such as subdural haematomas, or meningitis arising from a basal skull fracture.

Investigations

After performing resuscitation, obtaining a history (from a witness if necessary), physical examination and bedside tests (e.g. fingerprick blood glucose), further investigation depends on the clinical context: (1) coma with focal signs or evidence of head injury—urgent brain imaging by CT or MRI; (2) coma with meningeal irritation but without focal signs—urgent brain imaging and/or lumbar puncture is required; treat before investigation if clinical suspicion of e.g. meningitis is high; (3) coma without focal lateralizing neurological signs and without meningismus—the probability of finding a focal abnormality is low; haematological/biochemical tests or a toxin screen are most likely to provide the diagnosis.

Prognosis

Brainstem reflexes are the most important clinical signs in defining prognosis: in the absence of sedative drugs, the absence for 24 h of corneal or pupillary reflexes, or of oculovestibular responses, is almost incompatible with recovery to independence, whatever the cause of coma.

Treatment

Specific treatment (if any) will depend upon the particular cause of coma, but—whatever the cause—long-term attention is required to the patient’s respiration, skin, circulation, and bladder and bowel function, seizures must be controlled, and the level of consciousness should be regularly assessed and monitored. In patients in whom the prognosis is hopeless, the institution and continuation of resuscitative measures is inappropriate and will serve only to prolong the anguish of relatives and carers (see Chapter 17.8).