First aid: Syncope
BMJ 2005; 330 doi: https://doi.org/10.1136/sbmj.0505183 (Published 01 May 2005) Cite this as: BMJ 2005;330:0505183
- Samena Chaudhry, senior house officer in cardiothoracic surgery1,
- Magnus Harrison, consultant in emergency medicine1
- 1University Hospital North Staffordshire, Stoke-On-Trent
Many of us will have fainted or seen someone else faint - in medicine, this is called syncope. Syncope is defined as a transient loss of consciousness associated with a decrease in cerebral blood flow.1 Differentiating true syncope from other “non-syncopal” conditions causing a loss of consciousness is important because the mechanisms of syncope range from nearly normal (physiological) to abnormal and life threatening.
In syncope, bradycardia (a slow heart rate), hypotension, and a weak thready pulse are common. Unconsciousness results in muscular relaxation and may cause the tongue to fall into the oropharynx, obstructing or partially obstructing the airway - this itself is life threatening.2 Although many causes of syncope exist, we will briefly focus on the commonest causes seen in the emergency department.
Presyncope
Presyncope is the period of time when inadequate cerebral circulation and the resulting lack of nutrition and oxygen start to take effect. Early manifestations include pale skin colour that may be cool and moist (“a cold sweat”). Some people say they feel bad, or that everything is going dark just before losing consciousness. By recognising presyncope, you can prevent a person from falling.
Causes of syncope
The causes of syncope can be grouped into cardiac and non-cardiac causes (box 1). Cardiac syncope is associated with increased mortality and may lead to sudden death. Syncope affects 30% of adults at some point in their lives and is a common problem in people presenting at emergency departments.1 One reason postulated for syncope being so common reflects our incomplete evolutionary adaptation to the upright body position as standing upright requires blood pressure regulation to drive blood against gravity up to the head.3
Box 1: Causes of syncope
Non-cardiac causes of syncope
Vasovagal syncope
Situational syncope
Urinating (micturition syncope)
Defecating …
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