Vagus syncope: what it means and what to do

The vagus nerve helps coordinate heart rate, blood vessel tone and digestion. A trigger such as fear, pain, heat, prolonged standing, seeing blood or straining can cause the reflex to become too strong. Blood pressure falls and the brain briefly receives less blood. People may notice nausea, sweating, warmth, pallor, tunnel vision or ringing in the ears before losing consciousness. These features support a reflex pattern, but fainting has other causes, including dehydration, anaemia, low blood sugar and heart-rhythm problems. A clinical assessment is needed when the cause is uncertain.

Lie flat promptly and raise your legs, or sit and place your head between your knees if lying down is not possible. Move away from heat and ask someone to stay with you. After recovery, drink fluids if safe and rise gradually. Learning your triggers, keeping hydrated and using physical counter-pressure such as tensing leg muscles may reduce episodes for some people. Do not drive, climb or bathe alone until a clinician has reviewed an unexplained faint.

Call emergency services for chest pain, breathing difficulty, severe injury, seizure-like activity, confusion, a new irregular heartbeat or delayed recovery. Urgent assessment is also needed when fainting occurs during exercise, while lying down, without warning or repeatedly. A clinician can review the trigger, medicines, blood pressure and heart rhythm, and may check for dehydration, anaemia or low glucose.

Does my story fit reflex syncope? Should I have an ECG, blood tests or blood-pressure monitoring? Which warning signs and activities should guide my safety plan?