Causes

• overdose ^b
• trauma ^d
• shock ^c
• cardiac arrest ^c
• stroke or cerebral haemorrhage ^c
• hepatic encephalopathy ^c
• hypoglycaemia

• infection ^c
• brain tumours ^c
• uraemia and other metabolic disorders
• psychogenic 

Why?

Hypoxia- ischaemia , cardiac arrest or stroke are common causes of non-traumatic coma

Causes of non-traumatic coma	% (95% CI)
hypoxia- ischaemia c	42% (38% to 46%)
cardiac arrest	30% (26% to 34%)
brain infarct	15% (12% to 18%)
brain haemorrhage	13% (10% to 16%)
hepatic encephalopathy	10% (7.5% to 13%)
subarachnoid haemorrhage	7.6% (5.3% to 9.9%)
other metabolic disturbances	3.8% (2.1% to 5.5%)
infection	3.2% (1.7% to 4.7%)
isolated disorders like hypoglycaemia	2.4% (1.1% to 3.7%)
mass lesions	2.2% (0.9% to 3.5%)

• 10% of patients with an altered level of consciousness have an opiate overdose: 10% (95% CI: 6.4% to 14%) ^b