HealthLingo: Vagal Nerve and Syncope

Q: My dad recently had major surgery and when I first saw him in intensive care with all the medical equipment, I got very lightheaded and nearly passed out. The same feeling came over me when I saw someone bleeding heavily from a cut. A friend said it could be connected to my vagal nerve. I never heard the term before. Can you help?

A: Sure, but first a short anatomy lesson.

The vagus, or vagal (VAY-gul), nerve is an important part of what’s known as your autonomic nervous system and it controls the things you do without thinking, such as breathing or digesting your food. The vagus starts at the base of your brain, then splits into branches that run through your neck and down both sides of your body to the vital organs in your abdomen.

What you describe is an example of a condition called vasovagal syncope. Let’s break down the term. The vaso (VAY-zoh) in vasovagal refers to blood vessels and vagal is the nerve we’re discussing. Syncope (SING-kuh-pee) is a medical term for fainting. What you describe is near syncope, or almost fainting.

Vasovagal syncope happens when your body overreacts to certain triggers, such as blood or emotional stress. This causes your blood pressure to drop like a rock and your heart rate slows. That reduces blood flow to your brain, making you feel dizzy or causing you to faint. Heat exposure, standing for extended periods of time and having blood drawn also can trigger vasovagal syncope.

Such episodes are usually brief and harmless, but you should always check with your doctor, who’ll likely want to make sure you’re not feeling that way because of a more serious reason, such as a heart condition or other medical problem.