Cardiac Question Help

Here.I.Stand, BSN, RN · Feb 15, 2014

What did they say the rationale was? I'm confused myself because the pt would at least need a pulmonary artery catheter to track that, and a pt admitted for GI issues is not going to have one of those. Actually I used to work in a CVICU and don't remember ever calculating a preload myself...we looked at cardiac output, stroke volume, cardiac index, SVR (again, not something that your GI pt is going to have such an invasive line to be able to track)...

I would have answered heart rate too. Out of those four parameters, that's the only one that you can "monitor more closely" in someone that's admitted to the floor for re-hydration and Zofran. Now all those other hemodynamic values will be affected too because your pt is clearly dry from all that vomiting and diarrhea, and therefore has less circulating volume. But again, he's not going to have a line that can tell you what any of those values are.

His heart rate will be a quick indicator of his fluid status in the medical floor setting; it will increase in someone who is dry. You'd expect BP to decrease also.

Someone please correct me if I'm wrong...if I am you can teach me something today too. :)

Esme12, ASN, BSN, RN · Feb 15, 2014

It is actually really simple......

Preload is stretch. The amount of volume being returned to the right side of the heart from systemic circulation.

Afterload is squeeze. The amount of resistance the left side of the heart has to overcome in order to eject blood.

Preload is about volume. If the water 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 failure 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. Think of it like a garden hose.........

A good analogy is that your hose has gone form a garden hose to a fire hose or developed huge leaks and it will either get more blood to the right places easier (decreasing afterload so the heart doesn't have to work as hard and will therefore work better) ...or you will not get the blood to where it need to go until you "patch it up" (constrict the blood vessels to a more normal size like the vasodilation that occurs with sepsis)or stop the bleeding by sealing the leak(the source of hemorrhage)....OR....

Gross analogy, but it works...Think 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.

Preload = Volume

Afterload = Pressure/Resistance

https://allnurses.com/nursing-student-assistance/preload-vs-afterload-887678.html

allnurses Guide · Feb 15, 2014

I need help understanding the rationale for this question. A patient is admitted with weight loss of 2.3 kg over 36 hours diarrhea, nausea, and vomiting. Based on this information, the nurse should assess which cardiovascular parameter more closely? A. Preload B. Afterload C. Stroke Volume D. Heart Rate I chose D, and so did most of the rest of my class, but the answer was A- Preload. Several of us asked why the answer would be A: Preload, and we were given a rationale, but it wasn't completely clear to me. While I'm waiting for an e-mail response, can anyone more experienced help me understand the rationale? Thanks :)[/quote']
Take the cardiac component out of the question for a moment: if you had a patient with a rapid weight loss with nausea, vomiting, and diarrhea, what would you be worried about?

Halcyonn · Feb 15, 2014

I would worry about fluid loss.

nurseprnRN, BSN, RN · Feb 15, 2014

And when you have big enough fluid loss, you have decreased BP, even if you have an attempt to compensate by increasing heart rate; and heart rate will not be able to keep up at some point. Why is that? Preload, that's why. Less venous return coming to the heart makes less coming out of the heart.

Sure, you might need a CVP line (at a minimum) to quantify preload with a number. But didn't you learn about jugular distension (and, in this case, lack thereof) in physical exam class? If someone has a fat jugular at 45 (or 30, 60, or 90) degrees, you know he has more preload going on than someone whose jugular is flat.

2.3 kg is 2.3 liters of fluid. That's a lot of juice missing. This guy is DRY.

Halcyonn · Feb 15, 2014

Gross analogy, but it works...Think 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.

Awesome analogy - this totally makes sense to me!

Lev, MSN, RN, NP · Feb 16, 2014

HR is affected by the preload, but it wouldn't be affected right away. A change in preload would come before any changes in HR related to volume gain or loss.

Stroke volume would not be an entirely accurate factor to look at, because it can be improved by changes in HR, even if the patient is hypovolemic.

The preload is the blood going back to the heart after it has gone through systemic circulation and after volume loss has occurred. Therefore, it makes sense to look at preload.

ChipNurse · Feb 17, 2014

Patient would have fluid volume deficit. Preload = volume. You don't NEED a PA to measure preload, you can transduce a central line to get a CVP.

nurseprnRN, BSN, RN · Feb 17, 2014

And if there's no big CVP line you look at JVD. Check your physical exam textbook or look that up.