Cardiac Preload and Afterload
- 0Feb 23, '03 by orca1Hi,
I need help from the professionals
I am being tested tomorrow on cardiac and was wondering if anyone in the critical care field can explain preload and afterload in student nurses terms
I am a bit confused and need a little clarification.
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- 16Feb 23, '03 by hoolahanThink of it like a garden hose.
Preload is about volume. If the watre pressure is low, the water output will be a trickle, not enough to water and sustain your pretty garden.
If the volume is too much, it will back up your plumbing system (Right-sided heart failure engorged liver, systemic edema, etc, or left-sided faiolure pulmonary edema.)
Afterload is about pressure or resistance. If there is a link or narrowing in your garden hose, the volume will back up AND the output will drop.
I can't really make a good analogy about the hose and low afterload, just less resistance, may end up w a relative hypovolemia ie use water glass and med cup analogy.
Fill a med cup (30cc) with water. Med cup is your normal vascular system, filled w normal blood volume. Pt becomes septic, results in massive vasodilation, which is like taking that 30cc of water, and pouring it into an 8-oz glass, it is a relative hypolvolemia, so most blood volume will be shunted to major organs, and periphery and kidneys will be sacrificed.
Just think in this way Preload = Volume
Afterload = Pressure/Resistance
- 16May 13, '07 by jaquelynneGross analogy, but works for me....
Thing about flushing a toilet......
you flush, and then flush again right away......nothing happens right? THis is because the tank doesn't have time to fill....PRELOAD is decreased in the tank.
What if the toilet is plugged up? When you flush, it backs up....this is too much afterload.
- 0Mar 26, '09 by hikingcolefunny thing, i am taking my cardiac classes right now. i asked the professor about preload and afterload today and she simply replied that i need to read the material over again. i do hate it when they won’t take a minute or two to explain anything and very glad that most of our professors are not like that.
i just want to see if i understand preload and afterload now that i have read the replies to the question. is it that preload is the blood in the heart and the pressure caused by this and the afterload is the blood in the arteries when it leaves the heart and the pressure exerted by such?
i am very interested in the heart and wish our cardiac professor knew more about it and was more interested in answering our questions. she has admitted not understanding much of the content in the powerpoints she has posted. there is much she simply does not cover and tells us we will have to learn it on our own. we shall see what happens.
i’m so glad someone else had posted about this. i have yet to figure out how to post on this site. i joined, got the confirmation e-mail but every time i click on the link, internet explorer closes. i finally gave up.
- 6Mar 26, '09 by Sarcolemmain student terms:
preload = pressure inside the heart during diastole (resting phase)
-starling curve. to a point, the more volume sitting in a chamber, the better a heart works
afterload = pressure the heart has to overcome to squirt blood out of the ventricle
-anything that causes resistance. from a malfunctioning valve to tight arteries to standing on your head.