The Autonomic Nervous System - Fight or Flight Response (article) Jun 15,2017

Medical ( Trauma - What you need to know prior to treating your first patient )

The Enemy of First Responders: 

The Autonomic Nervous System and

The Fight or Flight Reaction

Patrick O’Neil, PA


Don’t let the title scare you off.  This isn’t going to be a nerd-fest of mindboggling medical jargon that will put you to sleep within 5 minutes.  I’m going to keep this very basic and I assure you that you will fully understand it before I am done.  So let’s start off with the obvious question as to why this is even important?  Well, the problem in simple terms is that trauma is a stressful event.  I don’t care who you are, or how many trauma cases you have seen, the Autonomic Nervous System is going to reach out and touch every one of us from time to time.  For first responders, this is not a good thing.  At precisely the moment when we are expected to function in a cool, calm, and collected manner; our bodies are doing the exact opposite thing we want them to do.

The Autonomic Nervous System is divided into two parts:  The Sympathetic and Parasympathetic Nervous Systems.  Think of the Sympathetic Nervous System as a stimulator, or an “upper.”  The Parasympathetic Nervous System counteracts the Sympathetic.  It is the “downer” that helps overcome the Sympathetic effects.



When confronted with a stressful situation such as imminent danger, anxiety, fear or stress; it is the Sympathetic Nervous System that activates the “Fight or Flight” reaction.  I like to think of the Fight or Flight reaction as the body’s survival mechanism, and you will see why in a few moments.  This reaction has very predictable physical, emotional and cognitive (thinking) effects. 

When a stress event occurs the body is going to release a number of hormones, one of them being adrenaline.  There are others, but adrenaline is the one most people are familiar with.  Remember, Sympathetic is an “upper.”   The body is entering into survival mode and the predictable physical reactions include the following:

Pulse and Blood Pressure:  The heart rate increases as does the blood pressure.  The body is preparing for intense physical activity such as running or fighting.

Constriction of certain blood vessels:  Basically, the body is shutting down the blood supply to those areas that don’t need it during a Fight or Flight situation.  Skin, intestines, kidneys.  If the body can survive temporarily without blood supply to certain organs, it shuts them down to provide extra blood to vital areas.

Dilation of blood vessels for most muscles:  You need a lot of blood flow to the large muscles if you are going to run or fight. Think large muscles here:  Legs, chest, back, arms, and gluteus.  Small muscles don’t receive much blood supply.

Lungs:  The respirations are going to increase at a more rapid rate and the bronchioles are going to dilate.  This will allow more air into the lungs in preparation for a burst of physical activity.

Digestive Tract:  Not needed during Fight or Flight, so this is pretty much shut down

Increased energy production:  The liver makes more sugar and the body uses fat as an energy source. 

Eyesight:  The pupils are going to widen out.  This is to allow more light in during a nocturnal event.  However, it causes a negative effect on near vision.

Auditory:  Loss of hearing. 

Tunnel Vision:  You lose peripheral vision

Cognitive deficit:  This is the thinking part of the equation.  You can barely focus on one task at hand.  Multi-tasking is impossible.  Very common to see people fumbling from one task to another, never quite finishing the first task they started.  Some people will also describe the situation as moving in “slow motion” because their minds can only handle a minute amount of information at any given moment. 

Shaking:  a tremor develops in your hands or possibly the entire body if severe

Sweat Glands:  The body is going to start sweating more.  This is in preparation for a large burst of energy; to help keep the body cool during the physical activity.

As I mentioned previously, this Fight or Flight reaction is the enemy for any First Responder, or anyone put into a stressful situation.  Life and death situations are extremely stressful, yet this is when we are expected to perform at the peak of our abilities.

Think of it in these terms:  I have a trauma patient in front of me that is absolutely tore up and in a very bad way.  I need to remain calm so I can think clearly.  I need my hands to be steady.  I don’t want to have a rapid heart rate or breathing rate, because that affects my ability to work smoothly.  I need to concentrate and focus on the task at hand.  I have to think not just about what I am doing at the moment, but what I need to be doing in the next few minutes.  I don’t need to be dripping sweat onto my patient, having a problem opening up bandages because my hands are so sweaty.   I need my hearing to remain intact so I can understand what is going on around me.  I cannot afford to get tunnel vision and miss other injuries that I would normally see.  I need my pupils to remain normal size so I don’t lose my near vision.  I need to see what is in front of me.  I also do not need the blood going to my large muscles, I need it going into the small muscles of my hands so I can perform tasks that require fine manipulation. 

This will be the difficult task you will be faced with.  You must find a way to remain absolutely calm and prevent yourself from having a Sympathetic Nervous System response.  And while you are thinking about that, realize one more incredibly important detail:  You will be preparing for an event that very likely will involve one of your loved ones.  That always ratchets the stress factor up a few notches.  This is why doctors don’t treat their family members.  It is too stressful in emergency conditions.  But that is exactly what you will need to do. 

Think of the person you love the most in this world.  Now imagine that person with you as you have a blowout on a road.  The car rolls several times and hits a tree on your loved ones side of the car.  You get out and pull your aid bag out of the trunk.  They are moaning, bleeding, pleading for help.  You have no idea what you are going to see next.  How do you handle that?  How can you prepare yourself so you don’t enter into a Sympathetic Sensory overload?

The answer is in REALISTIC TRAINING.  The more you train, and the more realistic that training is, the better prepared you are.  If you know you are trained well, have practiced it multiple times, and have confidence in your abilities; it raises the threshold of when the Sympathetic System kicks in.  The more realistic the training, the more times you practice trauma scenarios, the more difficult you make those scenarios; all this will help you overcome any stressful situation you may find yourself facing.  Realistic Training enables you to walk around the side of the car, look at your loved one, and say, “I got you! You are going to be OK and help will be on its way soon.”


“Amateurs train until they get it right.  Professionals train until they can’t get it wrong!”


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