Vasodepressor syncope: what to know

A trigger such as prolonged standing, heat, pain, fear, or seeing blood can cause blood vessels to relax. Blood pressure then falls briefly, reducing blood flow to the brain and causing light-headedness or loss of consciousness. Nausea, sweating, warmth, blurred vision, or ringing in the ears may come first.

Fainting can have other causes, including dehydration, anaemia, low blood sugar, or an abnormal heart rhythm such as atrial fibrillation. A careful history, examination, blood pressure checks, and sometimes heart testing help separate these possibilities.

If warning symptoms begin, lie flat and raise your legs if possible. Loosen tight clothing, move away from heat, and do not stand quickly. If someone has fainted, check breathing, protect them from injury, and place them on their side if they are breathing but remain unresponsive. Do not give food or drink until they are fully alert.

After recovery, arrange a review if this was a first episode, happened during exercise, caused injury, or keeps recurring. Regular fluids and gradual position changes may help when suitable for your health.

Call emergency services for fainting with chest pain, severe breathlessness, palpitations, seizure-like movements, serious injury, pregnancy, or prolonged confusion. Urgent assessment is also needed if the episode occurred during exercise, without warning, or while lying down.

Ask what trigger was most plausible, whether medicines or dehydration may lower your pressure, whether you need an ECG or blood tests, and how to reduce falls. Ask whether driving, swimming alone, or climbing should be restricted until review.