Flashcards in Cardiovascular Effects of Autonomic Agents Deck (41):
Name an indirect parasympathetic agonist
What is edrophonium?
Short lasting ACh-esterase inhibitor that stimulates strong parasympathetic discharge for about 30 seconds
Side effects of edrophonium?
Profound abdominal cramping by stim smooth muscle contractions in GI
What are the clinical uses of edrophonium?
Used to inc AV refractoriness for brief periods
-Diagnose supravent tachyc
-Breaks supravent tachycs
What is a muscarinic agonist?
Agonist for parasympathetic NS (ACh)
List 3 adrenergic endogenous agonists
Epineph, norepi, dopamine
List 3 sympathetic adrenergic agonists
Phenylephrine, dobutamine, isoproterenol
Alpha 1: locations and actions
Vasc smooth m--constriction (mainly at skin, kidney, GI where they are most densely populated and also at large veins)
Genitourinary smooth m---constriction
Alpha 2: locations and actions
Vasc smooth m--constrict
Beta 1: locations and actions
Heart--inc in inotropy and chronotropy (inc in HR, velocity of impulse, metabolic rate, inotropy, dec in refractoriness)
Beta 2: locations and actions
Vasc smooth m---vasodilation (arteriolar vasodilation)
Airway smooth m--dilation
What receptors does epinephrine work on?
It is a mixed alpha, beta 1 and beta 2 agonist
What does epinephrine do to the SVR?
Stays the same because alpha constricts, but beta vasodilates
What does epinephrine do to the HR?
Increases it because beta 1 activity overrides baroreceptor mediated slowing which was stimulated due to inc in BP-->increase in inotropy
What does epinephrine do to the CO?
Increases CO which is redistributed away from skin, GI, kidney due to alpha mediated vasoconstriction
What does epinephrine do to the BP?
Increased CO leads to inc in BP=CO X SVR
What receptors does norepi work on?
Mixed alpha and beta 1 with little beta 2 activity
What does norepinephrine do to the SVR?
Increases it due to alpha 1 vasoconstriction and lack of beta 2 offsetting vasodilation
What does norepinephrine do to the HR?
Decrease it due to activation of baroreceptor reflex. SVR increase is so profound, that beta 1 cannot offset the baroreceptor reflex.
What does norepinephrine do to the CO?
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
What does norepinephrine do to the MAP?
Increased due to inc SVR
What receptors does dopamine work on?
Mixed alpha, beta 1 agonist with little beta 2 activity
What is special about the way dopamine works?
Its effects depend on its dosages
Dopamine actions at low dose
Produces predominantly renal vasodilation
Dopamine at intermediate dose
Beta 1 action combines with dopaminergic action (ie inc renal vasodilation) to inc CO with minimal effect of systemic vascular resistance
Dopamine at high dose
Alpha action overwhelms dopaminergic action and the effect is similar to norepi with lots of vasoconstriction
What do we use dopamine clinically for?
It is a good presser and at low to medium doses, does not reduce renal blood flow
What is Phenylephrine?
Synthetic adrenergic agonist that is a predominant alpha agonist with little beta activity
What does Phenylephrine do to the SVR?
What does Phenylephrine do to the HR?
Decrease: activation of baroreceptors causes vagal discharge
What does Phenylephrine do to the CO?
Small decrease due to increase in afterload
What does Phenylephrine do to the MAP?
What is Isoproterenol?
Synthetic beta agonist
What does Isoproterenol do to the SVR?
What does Isoproterenol do to the HR?
Increase due to beta 1 chronotropic stimulation
What does Isoproterenol do to the CO?
Increases due to inc in LV contractility and dec in SVR
What does Isoproterenol do to the MAP?
Possible slight dec
What is Dobutamine?
Synthetic predominant beta 1 agonist with modest beta 2 activity. PRedominant inotropic with moderate chronotropic activity
What does Dobutamine do to the BP?
Little effect because of modest beta 2 activity
When do we use Dobutamine?
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