Vagal nerve syncope

The vagus nerve helps regulate heart rate and blood pressure. In a syncope episode, a trigger such as pain, fear, heat, prolonged standing, dehydration, or straining can produce an exaggerated reflex. The heart may slow while blood vessels relax, reducing blood flow to the brain for a short time. Dizziness, nausea, sweating, a feeling of warmth, grey or tunnel vision, and weakness may come before loss of consciousness. A clear trigger can support this explanation, but fainting can also arise from anaemia, low blood sugar, dehydration, or a heart-rhythm problem.

At the first warning, lie down and raise your legs. If you cannot lie down, sit immediately and place your head low. Tell someone nearby, avoid walking, and wait until you feel completely clear before standing gradually. Sip fluids after recovery if you are awake and swallowing normally; do not drink while faint or confused. Record the trigger, position, warning symptoms, medicines, and recovery time. A clinician can use this account to decide whether an examination, ECG, or blood tests are appropriate.

Seek emergency care for fainting during exercise, while lying down, or without warning, and for chest pain, breathlessness, severe palpitations, prolonged confusion, seizure-like activity, or a serious fall. New one-sided weakness or difficulty speaking is also an emergency. Do not assume a faint is vagal when recovery is slow, episodes recur, or there is a known heart condition. Emergency responders should assess anyone who remains unconscious or is not breathing normally.

Ask whether your story fits reflex syncope, whether medicines or fluid loss could contribute, and whether heart-rhythm monitoring is needed. Discuss safe return to work, driving, exercise, and ways to avoid a known trigger.