Pressure Blood & Cardiovascular Center
Laura, Jessica, Michelle and Tigest
Problem
A
47- year old teacher goes to her physician complaining of dizziness, fainting, and shortness of breath. Objective evaluation reveals: HR 70 supine, 68 sitting, and 68 standing; BP 120/74 supine, 98/54 sitting, 84/48 standing. Heart and lungs sounds are normal. General neurologic exam is normal. Routine labs are normal.
Questions
What is abnormal about her examination? How does this information help explain her symptoms. List all the functional locations within cardiovascular regulation where pathology could lead to these changes. Further tests were performed in an attempt to identify the pathology:
1) Administration of atropine did not result in any changes in heart rate. 2) Administration of isoproterenol resulted in increase in heart rate from 60 to 118 bpm.
Are these responses normal? Where do you think the pathology lies?
The Reflex Arc
Which of these components is the source of the problem?
Abnormal
Heart and blood vessels are not responding: diastolic pressure is going down and systolic is not going up. HR 70 supine, 68 sitting, and 68 standing; BP 120/74 supine, 98/54 sitting, 84/48 standing You need an increase MAP so that blood can go to the brain. SNS to the heart and blood vessels should increase cardiac output (raising systolic pressure), and increase vasoconstriction (increasing venous return and raising diastolic pressure) Her heart cant efficiently pump blood against the gravity, causing dizziness and fainting.
Atropine
An
anti-parasympathetic drug Parasympathetic antagonist Should leave sympathetic input without the balancing of effect the parasympathetic input This should raise the heart rate The teacher had no reaction to Atropine
Isoproterenol
It
is a specific Beta1 agonist (receptors only found in the heart and kidneys) When it is administered, isoproterenol stimulates these sympathetic receptors (as NE would) and increases heart rate When isoproterenol was given to our teacher, her heart rate increased from 60 to 118 bpm which leads us to believe that the receptors for NE at her heart are not the cause of her poor blood pressure regulation
Autonomic Cardiovascular Regulation
http://www.usc.edu/hsc/pharmacy/ced/autonomic/HeartBlowUp.html
Where does the pathology lie?
By
administering atropine and isoproterenol, it helped identify that the pathology is in the nervous system, but where?
Baroreceptors Afferent
nerves Cardiovascular Center in the medulla Efferent nerves
Analogy
Atropine and Isoproterenol should both deliver a message that says increase HR
While you are out, someone calls and ...