Nagelhout 13 Flashcards
3 naturally occurring catecholamines
Epinephrine
Norepinephrine
Dopamine
The duration of action of ephedrine is longer than that of epinephrine bc
It Lacks is a basic catechol structure making it resistant to metabolism by monoamine oxidase
Ephedrine onset is
Immmediate
Duration of ephedrine is (5-25mg)
15 mins to 1.5 hrs
Depending on dose
Ephedrine should be used with caution i what type of patient ?
Patient with questionable coronary perfusion
Bc
It increases myo O2 demand
Dose depends changes by ephedrine are
Increased BP HR SVR CO
Which is preferred in obstetrics : ephedrine or phenylephrine? Why?
Phenylephrine.
Ephedrine causes fetal acidosis by increasing fetal metabolic rate via b stimulation
List the b2 agonists
Albuterol : proventil , ventolin;
Levalbuterol : Xopenex
Salmeterol :serevent
Pirbuterol: Maxair
Long acting beta 2nagonist are
ForMOTEROL and SaleMETEROL
Are b2 agonist completely selective ?
No, bc tachycardia caused by these are due to lower incidence of B1 agonist
B2 agonists have increased duration of action bc
Their non catecholamine structure make it hard for COMT to break them down
What can occur with chronic use of b2 agonists
1) Tachyphylaxis secondary to down regulation of b receptors
2) increased hyper responsiveness
What is the block box warning for long acting beta 2
Asthma related death
Safer to give them in a combination with inhaled corticosteroids
Why are B2 tocolytic ?
Bc they increase cAMP which will DECREASE intracellular calcium levels and diminish the level of actin-myosin coupling
What is the beta 3 agonist used to inhibit destructor muscle and treat overactive bladder
Mirabegron ( Myrbetriq)
Presynaptic agonist
Clonidine
How does clonidine decrease BP ?
1) By acting on peripheral A2 = inhibits catecholamine release + vasodilation
2 by acting on central A2 = antihypertensive mechanism bc it diminishes sympathetic outflow => decreased amount of circulating catecholamines and renin activity
What is a major concern with clonidine ?
Rebound hypertension after abrupt discontinuation ( bc the catecholamines return with a vengeance ) tachycardia + HTN
Important to continue it pre op
Can even give a patch which releases med for 1 week
What are all the uses of clonidine ?
1) premedication sedative
2) analgesia with opioids for epidural tx of severe pain aka Duraclon
3) suppression of alcohol withdrawal
4) to suppress catecholamine in dx f pheochromocytoma
What are the properties of precedes ?
Dose dependent Sedation Analgesia Sympatholysis Anxiolytsis ** without respiratory depression ++
The side effects fo precedex are predictable . What are they ?
Hypotension
Bradycardia
Oversedation
Delayed recovery
What are A receptor antagonist used for ?
HTN BPH Pheochromocytoma Raynaud Phenomenon Ergot Alkaloid toxicity
What are the common side effects of A antagonist?
Orthostatic Hypotension
Baroreceptor reflex tachycardia
Dibenzyline
Phenoxybenzamine is a halo ally among with BOTH A1 and A2 blocking . NONCOMPETIVETIVE and IRREVERSIBLY
How is the action of Pjhenoxybenzamine terminated ?
Either by getting metabolized or generation of new A receptors
How long before preop is phenoxybenzamine started ?
1- 3 weeks
What is epi reversal ?
Phenoxybenzamine plus epinephrine will lead to enhanced B2 response with a worsening of hypotension and tachycardia
Besides orthostatic BP what other side effect frequently reported with phenoxybenzamine ?
Nasal stuffiness
Dose of phetolamine
1 to 5 mg by slow IV push
5 to 10 mg of phentolamine with ____ml of NS injected _____to treat _______.
5- 10 mg of phentolamoine 10 ml of NS injected in site of infiltration to treat infiltration of vasoconstricting agents
