Sympathomimetic- Phenylephrine Flashcards
Is a 3-hydroxyphenylethylamine and a synthetic noncatecholamine. Differs from epinephrine in that it lacks a 4-hydroxyl group on the benzene ring
Phenylephrine
phenylephrine mimics effects of NE -how is potency and duration different
less potent than NE and longer lasting then NE
which receptor does phenylephrine directly stimulate
alpha-1 adrenergic receptors
which receptor does phenylephrine indirectly stimulate
beta adrenergic receptors
phenylephrine dose to stimulate alpha 1 receptors vs alpha 2 receptors
smaller doses stimulate alpha 1 than the dose to stimulate alpha 2
CNS stimulation for phenylephrine
minimal
IV bolus dose for phenylephrine
50-200mcg iv
name two type of patient conditions phenylephrine is beneficial to
patients with CAD and AS
why is phenylephrine good for patients with CAD and AS
it increases coronary perfusion pressure without chronotropic side effects- unlike most sympathomimetics
what is the primary effect of phenleyphrine
vasoconstriction
what is the continuous infusion dose of phenlyephrine
20-100mcg/min
how is phenylephrine used for SVT
reflex vagal effects are used to slow HR
when phenylephrine is used with nitric oxide what is the effect
can improve arterial oxygenation
what is the effect of rapid administration of 1mg/kg to anesthetized patients with cad
transient impairment of lv global function
oral clonidine premedication plus phenylephrine create what response
auguemtns the pressor response to phenylephrine presumably due to clonidine induced potentiation of alpha 1 mediated vasoconstricito
Rapid IV injection of phenlyphrine to patients with CAD produce what effects to the heart
vasoconstriction, increase BP, decreased CO
why does phenlephrine create a decrease in CO
due to increased after load - likely due to baroreceptor mediated bradycardia in response to increases in DBP
phenylephrine increases blood flow in these two places
coronary blood flow
pulmonary artery pressure
phenylephrine decreases blood flow in these three places
renal
splanchnic
cutaneous blood flow
which receptor disrupts the potassium load from shifting into the cells while phenylephrine is infusing
alpha
what is the result of phenylephrine infusion and potassium infusion.
increased serum potassium because potassium is unable to shift into the cells
in the absence of acute potassium load- does phenylephrine affect plasma potassium concentration
no
phenylephrine 3 things seen with overdose
HTN
tachycardia
baroreceptor medicated Bradycardia
which medication is appropriate to treat phenylephrine toxicity
phentolamine- alpha 1 antagonist
vascular absorption of phenlyphrine when used as a topical or injected vasconstrictors in the surgical field COULD result in what complication
overdose
where does blood pool in phenlyphrine overdose
pulmonary vascular beds
the natural protection of pulmonary vascular overload is to maintain what function
CO
can we beta block a patient with phenylephrine overdose
Since Beta-1 receptor blockades reduces CO treatment of phenylephrine induced hypertensive crisis with Beta adrenergic blocking drugs is CONTRAINDICATED can cause cardiac collapse
which medication do we administer to help with phenylephrine overdose
NTG and phentolamine
do we always treat phenylephrine overdose
Systemic hypertension induced by IV administered administered alpha agonists may not require treatment. This is b/c duration of action of IV phenylephrine and epinephrine are brief and hypertension may resolve spontaneously
Severe hypertension treatment must not decrease the ability of the stressed myocardium to increase contractility and HR. Thus vasodilating drugs such as nitroprusside or NTG maybe helpful (as well as phentolamine)
Explain phenylephrine’s indirect acting action:
its ability to evoke the release of norepinephrine
explain phenylephrine’s direct acting effect:
Principally stimulates alpha-1 adrenergic receptors
Is Phenylephrine primarily direct or indirect acting?
Direct
*stimulation of alpha 1
