ANSWER 75
This young man has been brought in unconscious having been well less than 24 h previ-
ously. The most likely diagnoses are related to drugs or a neurological event. The first part
of the care should be to ensure that he is stable from a cardiac and respiratory point of view.
His respiratory rate is a little high. Blood gases should be measured to monitor the oxy-
genation and ensure that the carbon dioxide level is not high, suggesting hypoventilation.
The family history of diabetes raises the possibility that his problem is related to this.
However, the speed of onset makes hyperglycaemic coma unlikely. One would expect a
slower development with a history of thirst and polyuria over the last day or so. However,
the blood sugar should certainly be checked. Hypoglycaemia comes on faster but would
not occur as a new event in diabetes mellitus. It might occur as a manifestation of a rare
condition such as an insulinoma. Other metabolic causes of coma such as abnormal levels
of sodium or calcium should be checked.
A neurological problem such as a subarachnoid haemorrhage is possible as a sudden
unexpected event in a young person. Where the level of consciousness is so affected, some
localizing signs or subhyaloid haemorrhage in the fundi might be expected. If no other
cause is evident from the initial investigations, a computed tomography (CT) scan might
be indicated.
The most likely cause is that the loss of consciousness is drug related. Despite the lack of
any warning of intent beforehand, drug overdose is common and the question of avail-
ability of any medication should be explored further. This would be likely to be a sedative
drug. If there is any suspicion of this then levels of other drugs which might need treat-
ment should be measured, e.g. aspirin and paracetamol.
The other possibility in somebody brought in unconscious is that they are suffering from
carbon monoxide poisoning. The fact that it is winter and he was found in the bathroom
where a faulty gas-fired heater might be situated increases this possibility. Patients with
carbon monoxide poisoning are usually pale rather than the traditional cherry-red colour
associated with carboxyhaemoglobin. Papilloedema can occur in severe carbon monoxide
poisoning and might account for the swollen appearance of the optic discs on funduscopy.
Measurement of carboxyhaemoglobin showed a level of 32 per cent. He was treated with high
levels of inspired oxygen and made a slow but full recovery over the next 48 h. Mannitol for
cerebral oedema and hyperbaric oxygen are considerations in the management. The problem
was traced to a faulty gas water heater which had not been serviced for 4 years.
- Drug overdose is the commonest cause of unconsciousness in young people, but other
diagnoses must always be considered. - Carboxyhaemoglobin levels should be measured in patients found unconscious indoors
or in vehicles and after known exposure to smoke. - In carbon monoxide poisoning marked hypoxia may be present in the absence of
cyanosis.