NE, Dopamine, Isoproterenol, Dobut, Ephedrine and Phenylephrine. Flashcards
What is the dose for NE for hypotension?
4-16mcg/min
Where is NE most potent?
Alphas and B1
What receptor does NE have a minimal effect on?
B2
Because NE has minimal B2 effects what four events result?
- Intense vasoconstriction of the skeletal muscles, liver, kidneys, cutaneous tissue (at risk for metabolic acidosis)
- Increased SBP, DBP, MAP
- Baroreceptors are activated which DECREASES HR and decrease respiration in a patient breathing for themselves
- Decreased venous return, CO, HR (despite B1 effect)
Dopamine is the endogenous precursor of?
NE
Which receptors does DA stimulate?
Same potency?
In what other way can it work?
- All adrenergic including DA receptors.
- Not at the same potency
- Also works by increasing the release of NE from vesicular stores.
At what dose of DA are we mainly stimulating D1 receptors?
1-3mcg/kg/min
At what dose of DA are we mainly stimulating B1 receptors?
3-10mcg/kg/min
At what dose of DA are we mainly stimulating Alpha receptors?
> 10mcg/kg/min
Are dosing ranges a reliable predictor of expected plasma concentration of DA?
No.
Can DA be given PIV?
Dangerous if it infiltrates.
What six things does DA increase?
- Myocardial contractility
- Renal blood flow
- Urine output
- GFR
- Endogenous release of NE
- IOP
What drug can be used with DA to synergistically reduce afterload and improve cardiac output?
Dobut
Where is DA inhibitory?
What will the patient have an altered response to?
- Carotid bodies
2. Hypoxia.
At which receptors does Isoproterenol act?
Selective B1 and B2 agonist. Pretty much equally.
What does Isoproterenol do to HR, contractility, SVR, SBP, DBP and MAP?
Increased HR, contractility and SBP (B1)
Decreases SVR, DBP and MAP (B2)
What is the dose of isoproterenol and when is it used?
1-5mcg/min for HB and bradydysrhythmias. At doses higher than this we would have supply vs. demand issues.
How is isopproterenol metabolized?
It is a synthetic catecholamine so by COMT. Need an infusion.
What kind of patient is at risk with use of isoproterenol?
CAD
What is the dose range for dobutamine?
2-10 mcg/kg/min
Under 5mcg/kg/min where is dobutamine selective?
B1! However, weak activity at the SA node gives us an assist with contractility without a huge increase in HR.
Over 5 mcg/kg/min where will dobutamine have weak stimulation?
Alpha 1
Why do we like dobutamine in CHF?
Improves CO without increasing HR or BP substantially.
Where dose dobutamine vasodilate?
The coronary arteries.
How and where does ephedrine work?
Indirect and direct agonist at alpha and beta receptors. All four receptors.
How is ephedrine given?
IV, PO or IM
What is the dose of ephedrine IV? and IM?
- 10-25mg IV
2. 10-50IM
What do we see with repeated dosing of ephedrine?
Tachyphylaxis tolerance because of NE depletion. Receptor occupation because of a long half life.
How is ephedrine metabolized and excreted? Half life?
- Non-catecholamine so metabolized by MAO, conjugated in liver and 40% excreted unchanged in the urine.
- 3 hours.
Why can’t ephedrine have direct B2 effects?
Because NE has minimal action at the B2 receptor.
What kind of a stimulant is phenylephrine?
Primarily an alpha 1 adrenergic receptor stimulant.
Where do we see the most constriction resulting from phenylephrine?
Venoconstriction more than arterial constriction giving us a nice boost in preload.
Compare potency and DOA of phenylephrine to NE.
Phenylephrine is less potent but longer acting.
What is the typical bolus IV dose of phenylephrine?
50-200mcg IV
What is the typical infusion rate of phenylephrine?
20-50mcg/min
How long does it take for phenylephrine to take effect?
1 minute
Do we see an increase or decrease in HR with phenylephrine and why?
Decrease because of baroreceptor activity.
What kind of an effect does phenylephrine have on MAP, SBP, DBP, SVR and CO?
Increases Map, SBP, DBP, SVR and decreases CO.
