67 Adrenaline / Epinephrine

KYJ 67 - Adrenaline /Epinephrine

In Knowing Your Jargon (KYJ) posts, you never know where the next topic will come from.  I was teaching a trauma course today and the topic of adrenaline (the hormone) came up, which generated questions about what is does.  So here we go.

Adrenaline or epinephrine as it is also known, is a hormone.  It is made in the Adrenal gland and is one of a number of chemicals that are collectively called catecholamines.

Catecholamines are hormones that excite certain biological processes in the body.

Epinephrine is a neuromodulator which means it modulates a nerve response, specifically the sympathetic nervous system.

So to fully grasp what epinephrine does, we must understand what the sympathetic nervous system does, because epinephrine is an SNS stimulator.

You've heard of "flight or fight"? That primitive response that if attacked or threatened, a person will respond with a neurohormonal surge of chemicals from many glands to prepare to stand and fight or flee the threat.  Either way there is a phenomenon of superhuman strength, speed and endurance.

The sympathetic nervous system effects do the following:


Increase mental alertness.
Increase heart rate (chronotropy).
Increase strength of contraction (inotropy).
Increase electrical nerve transmission speed (dromotropy).
Relax bronchiole smooth muscles- opening the lungs for greater gas exchange.
Open iris to let in more light.
Constricts veins to push more blood into arterial circulation (perfuses tissues/muscles, and increases BP).
Stimulates the breakdown of glycogen in the muscles and the liver, into glucose (we increase our blood sugar).

So, given these effects are all typical of the SNS; and, given that epinephrine modulates this response, it is also correct to say that epinephrine (adrenaline) causes these symptoms.  It is therefore called an Adrenergic response.
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Now consider these effects. And think of why or when we'd desire stimulating these effects...
... Can u see that we would want to give epinephrine to patients at a time that we wanted to :
manage slow heart beats,
Or  raise low BPs
Or  cause vasoconstriction in tissues that are swollen.
Or open up constricted airways or lungs.

In cardiac arrest, adrenaline is used for three reasons:
First:  peripheral vaso constriction. Pushing volume into the central vessels making CPR more effective
Second: to cause a fine undetectable cardiac electrical rhythm to become faster and coarser, so it may respond to defibrillation.
Third: to attempt to stimulate some cardiac activity.  A slim hope that the SNS might miraculously initiate an electrical stimulus.

In croup or upper airway oedema, the administration of adrenaline constricts blood vessels thereby reducing plasma leakage into tissues (oedema). And dries up salivary secretions.

As an additive in local anaesthetic (Lignocaine with Adrenaline), the profound vasoconstriction aids in bloodless incisions or suture lines.

As a soak on nose packing gauze, the vasoconstrictive effect assists with severe epistaxis (nose bleeding).

As an IV infusion, adrenaline is used to increase heart rate and force of contraction of the heart (inotropy).  This therefor maintains cardiac output and subsequently, increases BP in patients in shock.

As an IM or SC injection, (EpiPen) is used to reverse the life threatening cascade in anaphylactic shock (allergic reaction).  It reduces airway oedema, and assists to redistribute venous blood to improve arterial perfusion.

In nurses and paramedics it is a hormone surge that many of is crave.  That buzz you get is the best rush on Mother Earth. You get that call - the Red phone goes off. Your breathing rate increases, your pupils dilate, your heart races, and you feel it pounding in your chest.  Your mouth goes dry.  You feel super alert, clear of thought, senses are hyperalert, and you are super strong physically.
All hunger you had disappears, and those sore feet you've been on for hours, or that nursing back pain that seems persistent seems to have disappeared.

You are on the high of your life time... Whoa what a ride.  Then someone yells ..."MVA rollover...ETA 3 mins!!"
And you are high as a kite thinking ....."yeah..... Bring it on"
...
That is flight or fight!!!
That my friends is the nectar of the Gods.
That is Adrenaline!!!