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Picture this scene. You walk into an acute cubicle. “What’s going on here?”
“This 19 year old has come in with a severe allergic reaction. I am giving some adrenaline.”
The nurse plunges the full syringe into the IV.

“Prey tell,” you ask, “How much adrenaline have you just given?” Before you get an answer, the patient becomes grey and this is what happens on the monitor. “Oh, 100 micrograms.”

Let’s go to resus.

What would be a 19 year old’s maximum heart rate? 220-19= 201

Why does he go into VT? 

This is primarily related to a potassium shift. A rapid inward rush of potassium depolarises the membrane quickly. This leads to the arrhythmia.

What to do?

Remember that adrenaline has a relatively short half life (in arrests we need to give it every 2-3 minutes), so all should come back to normal unless the patient has an ischaemic episode. In a young person, this is exactly what happened. All normalised quickly and the patient was well.

You did keep him overnight for observation and did consult with cardiology.

Phew!! So be careful about those adrenaline doses. Give 10-30 micrograms at the most in aliquots and see what the patient does. Don’t give 100 micrograms at once.

I always give it myself. Then I know what is being given.


  • Judi gearon says:

    When you say maximum heart rate for a 19year old (220-19=201) does this equation relate to any age? And when you say maximum heart rate what does this Imply? Anything above 201 is pre arrest? How long is safe to maintain this rate?

  • admin says:

    Hi Judi
    Maximum heart I am referring to is, maximum sinus heart rate. It applies to all age groups. For example a 3 year old may have a higher maximal sinus rate than a person of 80plus years.
    The amount of time that it can be maintained depends on the patient and their level of heart disease or fitness.
    In terms of heart rate in tachyarrhythmia, the maximal heart rate generally accepted is about 300 beats per minute. Above this and the heart tends to go into Vfib.

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