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-   -   Vagus Nerve Response? (https://www.adrsupport.org/forums/showthread.php?t=6664)

go*big*red 11-09-2006 07:27 AM

Morning

Yesterday I had a nerve root block at L3/4, 4/5 and 5/S1 trying to find the nerve root that is affecting the back of my right leg.

Let me just say that it was "injections from hell!" This was so painful like I just can't tell you. No IV or anything. These are not my first, but may very well be my last. By the time we were done, my nerves in my leg were screaming. He kept asking me where the pain was and at times was amazed at where it was. I wonder if my nerves are in different places.

ANYWAY - the reason for this post is that between the first (L3/4) and second (L4/5) injections, I felt like I was going to pass out.

I started sweating, my hear rate increased significantly and my blood pressure went from 125/80 to 158/109. Dr. P said it was a "vagus nerve response". I can't find anything about this - does anyone know anything about it?

Thx and hope all is doing well.

Justin 11-09-2006 08:04 AM

The Vagus Nerve is one of the twelve paired cranial nerves--it starts in the brain and travels through your neck, thorax and abdomen. The nerve "touches," or innervates, different muscles and organs as it travels down your body. One of its many functions in the body is to "slow things down" (this is called parasympathetic innervation [PI]).

Parasympathetic innervation is commonly referred to as anything that enables the body to "rest and digest." Thus, PI is involved in digestion, etc.

Another type of innervation is sympathetic innervation, which is commonly referred to as "fight or flight." Meaning this type of response is activated during activities like being chased by a bear--it increases heart rate, dialates bronchial passages in your lungs, etc. It can be thought of as the opposite of PI innervation, so digestion will be put on hold.

It is interesting that your doctor called this "vagus nerve response," as the vagus nerve is key in slowing heart rate (consequently lowering blood pressure).

From my uneducated perspective, it sounds like your blood pressure increased due to sympathetic innervation----your body was experiencing pain and was gearing up to "fight or flight."

I hope this makes sense and isn't too detailed.

Justin

thy aching doctor 11-09-2006 08:43 AM

A vasovagal response can occur with any unpleasant external stimulus. It is the same thing that makes people pass out when they see blood, get a shot, have emotional stress, fear, or many other things. The vagus nerve is one of 12 major nerves (cranial nerves) that come directly off the brain. It is the 10th one. It provides sensory function to the thoracic and abdominal organs and motor function for speech, swallowing, and the muscles of the thoracic/abdominal organs. It also carries sympathetic and parasympathetic outflow to these organs. Sympathetic and parasympathetic nervous function is involuntary (ie. you cannot control it), and causes things like sweating, goose bumps, changes in blood pressure, heart rate, movement of the bowels, and abdominal organ function. The vasovagal response is a very complex response, but in a nutshell, sudden stimulation of the sympathetic and parasympathetic portions of the nerve causes an episode of low blood pressure, low heart rate, and sweating (often preceded by high blood pressure, higher heart rate, and feeling hot), that makes you feel as if you are going to pass out. Actually, most people do pass out. Stimulation of the sympathic/parasympathetic system is very commonly seen with sudden severe pain and is a very common finding during myelograms. If you want more information, look up the terms vasodepressor, vasovagal, or neurocardiogenic syncope in a medical text or website. I hope that helps.

From thy aching doctor,

go*big*red 11-09-2006 09:58 AM

Thank you both of you!

Very good explanations. I do remember this happening in different times of my life. Most recently (aside from yesterday) was when I was in the hospital when I had the revision on my ACDF and at the same time hardware removal from my first PLIF. Was about 2 (?) years ago. I did pass out that time in the bathroom at the hospital - after I used the call button and had the whole floor in my bathroom in short order as it was about 2:30 am.

My blood pressure had been low all that evening but tok a dive to about 90/50 after that incident. They kept waking me up and having me drink water and assisting me in walking throughout the night.

What's interesting is that I don't remember anything at that time bringing it on. I do have a very high pain threshold so maybe there were pain receptors firing that I just didn't know about. I do remember itching horribly on my bum and legs all night long. Someone did say that's a pain response sometimes.

Anyway - I guess it's normal and nothing to worry about. I did tell them I thought I was going to pass out and they gave me oxygen and blew it on my face and tried to make me as comfortable as possible until it passed which seemed like an eternity.

Thanks again for your responses. I just hope this worked and will be my last time.

kappa5070 11-10-2006 10:36 AM

I thought the Vagus nerve is parasympathetic only to the thorax and abdomen. Wouldnt sympathetic stimulation come from nerves coming off the sympathetic trunk running down the lateral aspect of the spine? If something "shocked" the vagus nerve and temporarily interrupted its ability to provide parasympathetic stimulation, the heart would beat harder and faster because it would be under the influence of the SA node only. If the heart needs to beat harder under most conditions, the cardiac plexus provides the sympathetic innervation and sends nore-epinepherine to speed things up. That is my understanding, but I may need to brush up on my cardiac physiology.


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