Severe vasovagal syncope: what to know

A vasovagal episode can follow a trigger such as prolonged standing, heat, pain, fear, seeing blood or a medical procedure. The body briefly lowers blood pressure and heart rate, reducing blood flow to the brain. Light-headedness, nausea, sweating, warmth, blurred vision or ringing in the ears may come first, followed by a short loss of consciousness and tiredness afterwards. Fainting is not always vasovagal. Anaemia, dehydration, low blood sugar and heart-rhythm problems such as [Atrial Fibrillation](/conditions/atrial-fibrillation/) can also need consideration. The pattern and recovery matter.

If warning symptoms begin, lie flat and raise your legs, or sit with your head lowered if lying down is not possible. Loosen tight clothing, move away from heat and do not stand quickly after recovery. Someone with you should protect your head, check breathing and place you on your side if you are vomiting or remain drowsy. Do not give food or drink until you are fully alert. Arrange medical review after a first faint, repeated fainting, an unexplained episode or any injury. Mention possible [Dehydration](/conditions/dehydration/) or [Hypoglycaemia](/conditions/hypoglycaemia/) to the clinician.

Call emergency services if the person is not breathing normally, does not wake promptly, has chest pain, severe breathlessness, a new neurological problem, a serious injury, seizure-like movements, fainting during exertion, or palpitations before the episode. Emergency assessment is also needed when fainting occurs without warning, while lying down, or with ongoing confusion. Do not assume a severe episode is harmless because a familiar trigger was present.

Ask what trigger and warning pattern suggest vasovagal syncope, whether your medicines or fluid intake contribute, whether you need an ECG or blood tests, how to avoid injury, and when you can safely drive, work at height or exercise.