1.2.1 General considerations
Blackouts may occur due to a number of mechanisms including:
- vasovagal syncope or ‘faint’, which accounts for over 50 per cent of blackouts and may be due to factors such as hot weather, emotion or venepuncture but may also be due to more serious causes that may recur
- syncope due to other cardiovascular causes such as structural heart disease, arrhythmias or vascular disease
- epileptic seizure, which accounts for less than 10 per cent of blackouts
- other causes including metabolic (e.g. hypoglycaemia), drug intoxication or sleep disorder.
Determination of the mechanism of a blackout may be straightforward based on history, investigations and specialist referral, and the person may be managed as per the appropriate chapter. Alternatively, it may require extensive cardiovascular and neurological investigations and referral to several specialists. People should be advised not to drive until the mechanism is ascertained and the corresponding standard met.
Some drivers may attribute a crash or driving mishap to a ‘blackout’ in order to excuse an event that occurred for some other reason such as inattention or distraction (e.g. a mobile phone conversation). There will also be a small proportion of cases in which a clear cause cannot be established.