Cardiovascular Effects of Autonomic Agents

Question 1

Name an indirect parasympathetic agonist

Answer 1

Edrophonium

Question 2

What is edrophonium?

Answer 2

Short lasting ACh-esterase inhibitor that stimulates strong parasympathetic discharge for about 30 seconds

Question 3

Side effects of edrophonium?

Answer 3

Profound abdominal cramping by stim smooth muscle contractions in GI

Question 4

What are the clinical uses of edrophonium?

Answer 4

Used to inc AV refractoriness for brief periods

• Diagnose supravent tachyc
• Breaks supravent tachycs

Question 5

What is a muscarinic agonist?

Answer 5

Agonist for parasympathetic NS (ACh)

Question 6

List 3 adrenergic endogenous agonists

Answer 6

Epineph, norepi, dopamine

Question 7

List 3 sympathetic adrenergic agonists

Answer 7

Phenylephrine, dobutamine, isoproterenol

Question 8

Alpha 1: locations and actions

Answer 8

Vasc smooth m–constriction (mainly at skin, kidney, GI where they are most densely populated and also at large veins)

Genitourinary smooth m—constriction

Question 9

Alpha 2: locations and actions

Answer 9

Vasc smooth m–constrict

Platelet aggregation

Question 10

Beta 1: locations and actions

Answer 10

Heart–inc in inotropy and chronotropy (inc in HR, velocity of impulse, metabolic rate, inotropy, dec in refractoriness)

Kidney–renin secretion

Question 11

Beta 2: locations and actions

Answer 11

Vasc smooth m—vasodilation (arteriolar vasodilation)

Airway smooth m–dilation

Question 12

What receptors does epinephrine work on?

Answer 12

It is a mixed alpha, beta 1 and beta 2 agonist

Question 13

What does epinephrine do to the SVR?

Answer 13

Stays the same because alpha constricts, but beta vasodilates

Question 14

What does epinephrine do to the HR?

Answer 14

Increases it because beta 1 activity overrides baroreceptor mediated slowing which was stimulated due to inc in BP–>increase in inotropy

Question 15

What does epinephrine do to the CO?

Answer 15

Increases CO which is redistributed away from skin, GI, kidney due to alpha mediated vasoconstriction

Question 16

What does epinephrine do to the BP?

Answer 16

Increased CO leads to inc in BP=CO X SVR

Question 17

What receptors does norepi work on?

Answer 17

Mixed alpha and beta 1 with little beta 2 activity

Question 18

What does norepinephrine do to the SVR?

Answer 18

Increases it due to alpha 1 vasoconstriction and lack of beta 2 offsetting vasodilation

Question 19

What does norepinephrine do to the HR?

Answer 19

Decrease it due to activation of baroreceptor reflex. SVR increase is so profound, that beta 1 cannot offset the baroreceptor reflex.

Question 20

What does norepinephrine do to the CO?

Answer 20

Unchanged or slight decrease. SVR increases LV afterload offsetting some of the inotropy (which would have inc SV). In addition, HR is going down due to the baroreceptor reflex.

Beta 1 activity opposed by the strong alpha activation on SVR and vagal discharge. CO is shunted away from kidneys, GI, skin

Question 21

What does norepinephrine do to the MAP?

Answer 21

Increased due to inc SVR

Question 22

What receptors does dopamine work on?

Answer 22

Mixed alpha, beta 1 agonist with little beta 2 activity

Question 23

What is special about the way dopamine works?

Answer 23

Its effects depend on its dosages

Question 24

Dopamine actions at low dose

Answer 24

Produces predominantly renal vasodilation

Question 25

Dopamine at intermediate dose

Answer 25

Beta 1 action combines with dopaminergic action (ie inc renal vasodilation) to inc CO with minimal effect of systemic vascular resistance

Question 26

Dopamine at high dose

Answer 26

Alpha action overwhelms dopaminergic action and the effect is similar to norepi with lots of vasoconstriction

Question 27

What do we use dopamine clinically for?

Answer 27

It is a good presser and at low to medium doses, does not reduce renal blood flow

Question 28

What is Phenylephrine?

Answer 28

Synthetic adrenergic agonist that is a predominant alpha agonist with little beta activity

Question 29

What does Phenylephrine do to the SVR?

Answer 29

Increase

Question 30

What does Phenylephrine do to the HR?

Answer 30

Decrease: activation of baroreceptors causes vagal discharge

Question 31

What does Phenylephrine do to the CO?

Answer 31

Small decrease due to increase in afterload

Question 32

What does Phenylephrine do to the MAP?

Answer 32

Increase

Question 33

What is Isoproterenol?

Answer 33

Synthetic beta agonist

Question 34

What does Isoproterenol do to the SVR?

Answer 34

Decrease

Question 35

What does Isoproterenol do to the HR?

Answer 35

Increase due to beta 1 chronotropic stimulation

Question 36

What does Isoproterenol do to the CO?

Answer 36

Increases due to inc in LV contractility and dec in SVR

Question 37

What does Isoproterenol do to the MAP?

Answer 37

Possible slight dec

Question 38

What is Dobutamine?

Answer 38

Synthetic predominant beta 1 agonist with modest beta 2 activity. PRedominant inotropic with moderate chronotropic activity

Question 39

What does Dobutamine do to the BP?

Answer 39

Little effect because of modest beta 2 activity

Question 40

When do we use Dobutamine?

Answer 40

Effective for circulatory support in severe congestive HF because it is a relatively pure myocardial inotrope with modest effect on HR and little effect on peripheral circulation

Question 41

When should you clinically use adrenergic agonists?

Answer 41

As an adjunctive therapy to support a pt hemodynamically while they are in shock