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!!
**
What is the dose of sodium nitroprusside?
-0.3 mcg/kg/min, titrated to 2 mcg/kg/min
What are types of surgeries sodium nitroprusside is good or?
-pheochromocytoma
-case where you need immediate response b/c don’t wanna rupture an aortic suture line! (aortic surgery)
-spine surgery
Which vasodilator can cause cyanide toxicity?
Sodium nitroprusside
-with higher doses-CN accumulates due to insufficient amount of sulfur donors/methemoglobin exhaustion
When to worry about CN poisoning?
-when tachyphylaxis is developing with sodium nitroprusside and giving larger doses
-increased mixed venous sats
-metabolic acidosis
-CNS dysfunction, change in LOC
STOP DRUG!!
Nitroglycerin:
-acts on venous capacitance vessels
(mostly) and large coronary arteries as well
-causes venous pooling: decreases CO b/c of decreases preload
When can you hit tachyphylaxis with nitroglycerin?
60-100 mcg/min
dose dependent and duration dependent (within 24 hours) limits vasodilation
Initial dose of nitroglycerin:
5-10 mcg/min infusion and titrate up d/t tachyphylaxis
What are common uses for nitroglycerin?
-acute MI: relieves pulmonary congestion, decreases O2 requirements, limits MI size
-sphincter of Oddi spasm: give after glucagon!
-retained placenta: inhibits calcium release-placenta turns loose of the uterus
Hydralazine:
-direct, systemic arterial vasodilator
-decreases ITP, decreases Calcium release
-causes EXTREME hypotension, rebound tachycardia
What is the onset of hydralazine?
peak plasma concentration at 1 hr
What is the initial dose of hydralazine?
2.5 mg IV
1/2 life of Hydralazine:
3-7 hours**
slow starting but long-lasting!
What are the different types of calcium channel blockeres?
-phenyl alkylamines: selective for AV node
-benzothiazepines: selective for AV node
-dihydropyrimidines: selective for arterial beds**the ones that cause vasodilation!!!
How do CCB’s work? (MOA)
bind to receptors on voltage-gated calcium ion channels (L type, main pathway) and decrease calcium influx…inhibits excitation-contraction coupling
What 2 things are decreased with CCB’s?
-decreased vascular smooth muscle contractility (decreased SVR and systemic blood pressure, increased coronary blood flow)
-decreased speed of conduction through the AV node
Nicardipine:
-aka Cardene
-greatest at coronary artery dilation!!
-short term control of hypertension
-great effects with minimal side effects
-NO change in HR!
Dose of Nicardipine:
5 mg/hr, can increase by 2.5 mg/hr 4 times, MAX dose of 15 mg/hr
True or False: Nicardipine is a quick onset and offset drug
True!
50% drug decrease 30 minutes after D/C
Which vasodilator can worsen PaO2?
Sodium Nitroprusside d/t affected hemoglobin
Which drug would be the first intervention for HTN post-CEA?
cardene drip b/w won’t increase HR and causes arterial dilation
