Blood Pressure Question

 

Mr. L has developed an anaphylactic allergic response to an anesthetic used during surgery. His peripheral blood vessels have dilated and his bronchioles have constricted; his blood pressure is too low to measure and he is having difficulty breathing. The doctor has called for an emergency injection of epinephrine. What will the epinephrine do? Is it the proper treatment?

 

When you check Mr. L’s chart, you discover that he has high blood pressure and is on beta-blockers. How will this affect the usefulness of epinephrine in this emergency?

 

List of stuff we know:

·        Man’s peripheral blood vessels dilated and his BP is low

·        Difficulty breathing

·        Bronchioles are constricted

·        Allergic response to anesthetic

 

The question asks:

They gave him epinephrine.  What will it do, and is it the proper treatment?

 

To answer:

 

  1. Identify the relevant concept – epinephrine is a neurotransmitter binding to receptor sites; sympathetic nervous system
  2. What do you know about the SNS and epinephrine?

SNS is fight or flight system

Epinephrine = adrenalin, produced in adrenal cortex

Epinephrine binds to adrenergic receptors:

Alpha-1 – cause blood vessels to constrict in skin, guts, and kidneys

Alpha-2 – stops the SNS when enough epinephrine has been released

Beta-1 – increase heart rate and strength

Beta-2 – dilates bronchioles

 

  1. How does this information relate to the question?

His blood vessels are dilated now. Epinephrine would attach to alpha-1 receptors and constrict them and fix this problem.

 

His bronchioles are constricted. Epinephrine would attach to the beta-2 receptors and dilate them and fix this problem.  This will also fix his problems with breathing.

 

He has low BP. Epinephrine will attach to beta-1 receptors and increase heart rate and strength and fix this problem.  Constricting blood vessels by attaching to alpha-1 receptors will also help raise BP by sending more blood to the heart.

 

  1. What exactly did the question ask, and have you answered that?

 

What will epinephrine do?  -- answered above.

Is it the proper treatment – yes, because when it binds to the receptors it reverses the problems and improves his condition.

How will his taking beta-blockers affect the usefulness of epinephrine in this emergency? – the beta blockers will stop the beta-1 and beta-2 receptors from responding to epinephrine. If those don’t respond, then:  the beta-2 receptors won’t dilate the bronchioles so they will remain constricted and the beta-1 receptors won’t raise the heart rate so it will remain low.

 

The alpha receptors aren’t blocked, so epinephrine can still attach to alpha-1 receptors to constrict blood vessels in the skin, gut, and kidneys and alpha-2 receptors can still shut off the SNS.

 

The epinephrine will be much less effective. It will raise BP a little, by constricting the blood vessels using the alpha-1 receptors. It won’t be able to raise blood pressure very well because it can’t make the heart beat faster, and it won’t dilate the bronchioles so his breathing problems will not be solved.