10 - ANS III Flashcards
The side affects of a1 receptor blockage are
Hypotension, orthostatic hypotension, tachycardia
(Worse with hypovolemia, standing position)
Other side effects: miosis, nasal stuffiness, diarrhea
Vessels with higher initial tone have a _____ response to alpha 1 blockade, which causes
Greater
Smooth muscle relaxation
What happens with chronic alpha antagonist use?
Phenylephrine?
Norepi?
Epi?
Blunted sympathetic response
Phenyl: response completely blocked
Norepi: tachycardia due to b1 activation
Epi: tachy and sever hypotension due to b2 mediated vasodilation
Why does a2 receptor blockade lead to more NE release? What does this cause?
It eliminates negative feedback
Tachycardia
Two nonselective a receptor antagonists are
Phentolamine
Phenoxybenzamine
What is chemical sympathectomy? What drugs are used for this?
Removal of pain by increasing blood flow to an area through vasodilation
Nonselective alpha antagonists
Complete offset of the effects of nonselective alpha antagonists must be accomplished by
Synthesis of new receptors
Phentolamine and phenoxybenzamine are almost exclusively used for the treatment of
Pheochromocytoma
Why is alpha blockade before beta blockade necessary in management of pheochromocytoma?
I opposed alpha stimulation can lead to hypertensive crisis - heart pumping against constricted vessels
Nonselective alpha antagonists have _____ that can be treated with atropine
Cholinomimetic activity
Phentolamine binds _____ to the alpha receptor and phenoxybenzamine binds
Reversibly
Irreversibly
What is the dose of IV phentolamine?
5 mg bolus
Can also be used as an infusion
What are other uses (due to vasodilation) of phentolamine aside from management of pheochromocytoma?
Intercavernosal injection for treatment of impotence
Injection of treatment of norepi extravasation
Reversal of local anesthetic injection
How is phenoxybenzamine taken for preop management?
Orally
Phenoxybenzamine overdose is treated with
Norepi (some receptors are still free)
Prazosin is an ____ antagonist
Alpha 1 selective
What is used for the treatment of hypertension and benign prostatic hypertrophy (BPH) as well pheochromocytoma?
Alpha 1 selective antagonist
Prazosin
______ cause less tachycardia than nonselective alpha antagonists, but still some orthostatic hypotension
Alpha 1 selective antagonists
Drugs similar to prazosin
Terazosin
Doxazosin
Tamulosin
First generation beta antagonists are _____ and second generation beta antagonists are
Nonselective
Selective
Beta antagonists reduce _____ in patients with heart failure!reduce incidence of perioperative ____, and control
Mortality
MI
Tachydysrhythmias
Nonselective beta antagonist that lowers BP
Propranolol (inderal)
How does propranolol lower BP, reduce myocardial O2 demand, and slow ventricular response to SVT and VT?
Decreasing myocardial contractility, HR, and releasing renin
Propranolol may help treat the symptoms of ______ and _____ but should only be used after
Thyrotoxicosis (thyroid storm), pheochromocytoma
After alpha blockade
Side effects of propranolol (inderal)
Bronchospasm, CHF, bradycardia, AV heart block
Why does propranolol cause ______ after being stopped?
Withdrawal syndrome (rebound HTN, tachy, angina) Because of upregulation of beta receptors
Good choice in patients with reactive airway disease
Beta 1 selective antagonists
Metoprolol, atenolol
What is the IV dose of metoprolol?
2-5 mg bolus
How is metoprolol (lopressor) metabolized and what is its elimination half life?
Hepatic
3-4 h
How is atenolol (tenormin) excreted and what is its elimination half life?
Renally
6-7 hours
Esmolol (breviblock) is a _____ abut also causes ____ at high doses
Beta 1 selective antagonist
Beta 2 antagonism
Used to prevent tachy/HTN during intubation, emergence, and electroconvulsive therapy (ECT)
Esmolol
Esmolol is eliminated by
Ester hydrolysis (9 min)
Not plasma cholinesterase
What is the dose of Esmolol?
Bolus - .25-.5 mg/kg IV
Infusion: 50-200 mcg/kg/min
Mixed alpha and beta receptor antagonist?
Labetalol
Why doesn’t Labetelol cause reflex tachycardia?
alpha is mostly alpha 1
Beta is nonselective
What is the ratio of alpha to beta antagonism in Labetelol taken orally? By IV?
Orally - 1:3
IV- 1:7
Is bronchospasm a common complication when using Labetelol?
No, despite beta being nonselective
Common drug of choice for intraoperative HTN?
Labetelol
How does Labetelol decrease HTN?
Decreases peripheral vascular resistance and renin
Also some decrease in HR
What is the initial bolus does of Labetelol?
2.5-10 mg IV - works in minutes
Why should Labetelol be used in caution as an infusion?
It is a long acting agent
What is the hepatic elimination half life of Labetelol?
5-6 hours
What is another nonselective beta antagonist and alpha 1 antagonist aside from Labetelol? What is it used for?
Carvedilol (coreg)
Oral medication used for managing heart failure, left ventricular dysfunction after MI, and HTN
