Preventing vasovagal syncope

Vasovagal syncope is a brief loss of consciousness caused by a reflex that lowers blood pressure and may slow the heart rate. Heat, prolonged standing, pain, needles, emotional distress, dehydration or missing food can trigger it. Warning symptoms may include nausea, sweating, warmth, light-headedness, blurred vision or muffled hearing.

Not every faint is vasovagal. Anaemia, hypoglycaemia, dehydration and heart rhythm problems such as atrial fibrillation can also cause collapse or similar symptoms, so repeated or unexplained episodes deserve assessment.

Stop what you are doing and lie flat with your legs raised if possible. If lying down is unsafe, sit and lower your head. Tighten the muscles in your legs, arms and abdomen for short periods while waiting for the feeling to pass. Rise gradually, drink fluids if you can swallow safely, and keep a record of the trigger and warning symptoms.

Avoid standing still for long periods, overheating and skipping meals. Discuss prevention with a clinician if episodes recur, occur during exercise, or happen without warning.

Call for urgent help if fainting occurs during exercise, causes a serious injury, follows chest pain or severe breathlessness, or is accompanied by seizure-like movements, persistent confusion or palpitations. Seek prompt assessment for a first faint, repeated episodes, or a collapse without the usual warning symptoms.

Ask whether your episode fits a vasovagal pattern, whether medicines or dehydration contributed, and whether you need checks for anaemia, blood glucose or heart rhythm. Ask which activities are safe while the cause is being clarified.