Vasopressors and Vasodilators Flashcards
What can sympathomimetic agents lacking B1 specificity cause?
-cause intense vasoconstriction
-reflex-mediated bradycardia–aka, the phenylephrine effect
What is the MOA of sympathomimetics?
-either directly or indirectly activate beta or alpha adrenergic G-protein coupled receptors
-Increases cAMP–enhances calcium influx to the cytosol (actin and myosin interact more forcefully)
Direct vs indirect acting sympathomimetics:
-direct: Epi, NE, Phenylephrine, Dopamine
-indirect: ephedrine is the main one! Evoke the release of NE from postganglionic sympathetic nerve endings—then the NE acts on the adrenergic receptor
(phenylephrine has a lil bit of a indirect action)
Epinephrine:
“the prototype catecholamine”
-Alpha and Beta sitm, increases CO the HR the MOST, no real effect on PVR
Dose of Epinephrine:
1-2 mcg IVP
Phenylephrine:
-alpha1 agonist, tx hypotension
-VERY useful in CAD and AS b/c NO TACHYCARDIA!!
-venous constriction> arterial constriction
-mimics NE, but less potent and longer-lasting
What’s a big thing to look out for with Phenylephrine?
-REFLEX BRADYCARDIA: more of this the higher the dose of Neo ya give!
Dose of Phenylephrine:
50-100 mcg IVP (on hand: 10 mg/mL)
What should you give if you want to increase CO without increasing HR?
Vasopressin (per Dr. Kane)
Ephedrine:
-indirect acting, released NE acts on agonist receptor
-BP response is less intense and lasts 10x longer than epi
-tachyphylaxis develops QUICK
-can give IM (50 mg) for longer effect (ex: spinal anesthesia)
Which sympathomimetic is DOC for women in labor?
-Ephedrine!
-tx hypotension d/t SAB
-NO effect on uterine blood flow! Doesn’t put the baby at risk
Dose of ephedrine:
5-10 mg (on hand: 50 mg/mL)
True or False: Ephedrine has a little positive effect on PVR
True!
Epinephrine has no effect, Ephedrine has a little effect, Phenylephrine has a huge effect, and Vasopressin is in between ephedrine and Phenylephrine
Vasopressin:
-stimulates vascular V1 receptors to cause ARTERIAL vasoconstriction
-also increases renal-collecting duct permeability, increases water absorption
Which sympathomimetic is effective in reversing catecholamine-resistant hypotension?
Vasopressin!
(also treats ACE-I resistant hypotension)
What are the side effects of Vasopressin?
-CV: coronary artery vasoconstriction (so DON’T give to CAD pts)
-GI: stimulate GI smooth muscle…abd pain, N&V
-decreases platelet counts and antibody formation
Vasopressin Dose:
1-2 units
Nitric Oxide:
-chemical messenger for cGMP: inhibits calcium entry into smooth muscle-increases uptake at endoplasmic reticulum (relaxes muscle tone)
What is the first line drug for pulmonary HTN in neonates?
Nitric Oxide!
What all is nitric oxide involved in?
-CV tone relaxation
-platelet regulation
-CNS neurotransmitter
-GI smooth muscle relaxation
-immune modulation
-pulmonary artery vasodilation
So how does NO release actually lower BP?
-decreases SVR: arterial vasodilators
-decrease venous return: venous vasodilators
Is sodium nitroprusside an arterial or venous vasodilator?
-arterial vasodilator > venous
Is Nitroglycerin an arterial or a venous vasodilator?
Venous vasodilator
Sodium nitroprusside:
-relaxes arteries more than veins, but still both
-immediate onset, transient duration-requires continuous administration
-REQUIRES invasive arterial monitoring!!
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