09 - Autonomic Nervous System II - Adrenergic Agonists Flashcards
The balance of adrenergic agonist activity can _____ at different doses
Shift
Adrenergic agonists have _____ selectivity/specificity for different adrenergic receptors. The activity can be
Varying
Overlapping
Phenylephrine (neosynephrine) is a predominantly
Direct a1 agonist (pure a)
The primary effect of phenylephrine is _______. It causes ______ venous return and stroke volume (preload)
Peripheral vasoconstriction
Increased
Cardiac output remains the same in most patients given phenylephrine because of
Reflex bradycardia (vagal reflex probably mediated through baroreceptors)
Phenylephrine causes _______ coronary blood flow
Increased
The vial concentration of phenylephrine?
1% (10 mg/ml)
What is the continuous infusion dose for phenylephrine? What can happen at higher doses?
0.25-1 mcg/kg/min (37.5-150 ml/hr)
Decreased renal perfusion at higher doses
T or F? Phenylephrine does not have tachyphylaxis.
False, phenylephrine requires upward titration of infusion but it is more common with ephedrine
Epinephrine is a ____________ that has variable peripheral effects in
Direct adrenergic agonist
a: skin, mucosa, kidney
b: skeletal muscle
Which receptors do epinephrine act on and what effects does it cause?
b1 - increased HR, contractility, and myocardial O2 demand, increased SBP
b2 - bronchodilation, skeletal muscle dilation (decreased DBP?)
a1 - decreased splanchnic/renal blood flow, increased coronary/cerebral blood flow
Epinephrine is used to treat?
Anaphylaxis
Ventricular fibrillation
Risks of epinephrine?
Cerebral hemorrhage
coronary ischemia
ventricular dysrhythmias
What should be used with caution in conjunction with epi? Why?
Volatile anesthetics, especially halothane
Potentiates dysrhythmias
What is the dose of epi for vfib?
1 mg = 1 ml of 1:1000
What is the dose of epi for anaphylaxis and shock?
50-100 mcg
What is the dose of epi for continuous infusion for improved contractility?
.01-.1 mcg/kg/min
Which adrenergic agonist can be applied topically or infiltration to decrease bleeding?
Epinephrine - causes vasoconstriction
How much epi is added to local anesthetic to prolong block?
1:200,000 - 1:600,000
Ephedrine is a ______ with similar effects to
Indirect (and direct) adrenergic agonist
Epinephrine
T or F. Ephedrine is a catecholamine that acts on a and b receptors.
False, ephedrine is a NONcatecholamine sympathomimetic
How does ephedrine cause tachyphylaxis?
It causes NE release, depleting the stores
How long does ephedrine last?
10x longer than epi
Ephedrine causes _____ venoconstriction than arteriolar constriction which redistributes _____ and _____ venous return (preload)
More
Centrally
Improves
Which adrenergic agonist may have anti emetic properties?
Ephedrine
What is the adrenergic agonist of choice in OB?
Ephedrine - thought to preserve uterine blood flow better than direct acting a agonists (evidence is lacking)
Phenylephrine - current data supports but consider reflex Brady in setting of sympathectomy
What is the dose of ephedrine?
5-10 mg IV
Norepinephrine (levophed) is a ______ without
Direct a1 agonist
b2 activity
Norepinephrine causes ______ BP due to intense arterial and venous
Increased
Vasoconstriction
Does norepinephrine cause reflex bradycardia?
Possible
Why isn’t norepinephrine a good first line treatment for cardio genic shock?
It causes decreased renal perfusion and increased myocardial O2 requirements
Ensure the pt has adequate volume resuscitation
Can see end organ ischemia/necrosis
Pulmonary vasoconstriction
What is the norepinephrine infusion dose and how is it administered?
.01-.1 mcg/kg/min
Central access only (extravasation->tissue necrosis)
Which adrenergic agonist is a dose related agonist to all adrenergic receptors?
Dopamine
The low dose of dopamine is _____ and stimulates ______
<2 mcg/kg/min
DA receptor
_________ of dopamine is considered outdated
Neal dose
The low does of dopamine causes
Renal vasodilation, diuresis
Inhibits renal/splanchnic NE release
The medium dose of dopamine is ______ and stimulates the
2-10 mcg/kg/min
b1 receptor
The medium dose of dopamine causes
Increased contractility, HR, CO
Myocardial O2 demand > O2 supply
High dose of dopamine is _____ and stimulates
10-20 mcg/kg/min
a1 receptor
What does of dopamine causes risk for dysrhythmias?
High
High doses of dopamine cause
Increased PVR, decreased renal perfusion
Coronary/pulm vasoconstriction
Increased PA pressures
Isoproterenol is a highly potent _______ with no
b1 and b2 agonist
No a activity
Isoproterenol was used as an ______ because it _______ HR and contractility
Inotrope
Increases
Risk for arrhythmia
Has been replaced by b1 specific agonist (dobutamine)
Used to increase HR in presence of a heart block until a place maker can be placed
Dobutamine
Which adrenergic agonists increase myocardial O2 demand?
Epinephrine Norepinephrine Dopamine (medium dose) Isoproterenol Dobutamine
Isoproterenol causes _______ which can lead to coronary steal
Coronary artery dilation
Isoproterenol was used as a _____ but has been replaced by b2 specific agonists
Bronchodilator
Used for bronchodilation and as an inotrope but has been replaced by more selective agonists
Isoproterenol
Isoproterenol decreases _____ due to peripheral vasodilation. The overall effect is increased ___ and decreased
SVR
SBP
DBP
Dobutamine is a _____ that increases CO due to contractility. It is also a weak
Selective b1 agonist
INOTROPE
Coronary vasodilation
Dobutamine has ____ b2 activity
Selective
Slightly increased and
Potential arrhythmias, esp at higher doses
Some pulmonary vasodilation
Systemic vasodilation -> decreased SVR (hypotension)
Dobutamine has some ____ activity that is unmasked when _____ leading to
a1
Beta blocker is given
Hypertension
What dose of dobutamine potentially causes arrhythmias?
> 10 mcg/kg/min
Dose of dobutamine?
2-20 mcg/kg/min
Fast onset and short acting adrenergic agonist?
Dobutamine
This adrenergic agonist is a selective phosphodiesterase (PDE) inhibitor
Milrinone (primacor)
How do PDE inhibitors facilitate the inward movement of calcium?
Inhibit PDE III -> increased myocardial cAMP, leading to influx of calcium
Which adrenergic agonist is an inodilator?
Mirinone
Positive inotropic effect + vascular/airway smooth muscle relaxation + pulmonary vasodilator
Milrinone has a ______ effect on SVR
Significant
Leads to hypotension
Dose of Milrinone
50 mcg/kg over ten min followed by .5 mcg/kg/min infusion
What is the onset of milrinone?
5-15 min
Slower onset and offset
What is the elimination half time of milrinone?
2.7 hr
Which adrenergic agonist should be used with caution in severe renal disease?
Milrinone
Clonidine is used to treat ______ because it is a
Hypertension
Selective a2 agonist (a2:a1 = 220:1)
Clonidine is not commonly administered by
IV
Administered PO, TD patch, IM
Side effects of clonidine
Brady
Hypotension
Dry mouth
Used as an adjunct for analgesia: added to local anesthetic or opioids for epidural/spinal/nerve block
Clonidine
Effective against post operative shivering? Dose?
Clonidine
.5-1 mcg/kg
Used as a sedative. What are the effects?
Clonidine
Anxiolytics, sedation, decreases MAC
Highly selective a2 agonist?
Dexmedetomidine
ADH is secreted from the
Pituitary gland
Non adrenergic sympathomimetic that activates smooth muscle V1 receptors
Vasopressin
Vasopressin is an _____ version of ADH
Exogenous
Used in the treatment of diabetes insipidus
Vasopressin
Because pt with DI lack ADH secretion
How is vasopressin used to support BP?
Induces re absorption of water from renal collecting ducts
Vasoconstriction
Ackles dose of vasopressin
40 units
Lactic acidosis may develop from use of
Vasopressin
Which adrenergic agonists have potential to cause arrhythmias?
Epinephrine, especially with halothane
High doses of dopamine
Dobutamine, more liekly with higher dose
Isoproterenol
