Re: Cardiac Preload and Afterload

Thanks so much for the explanation. It's making more sense all the time. I have a week before my next exam on cardiac but have two exams and clinical during that week so I want to KNOW this and not just "get it" long enough to pass the exam. I was actually thinking about it when I woke up this morning. I think I know this one now.

Gale

Re: Cardiac Preload and Afterload

Think of preload in relation to a rubber band. If you remember back to Anatomy and Physiology class, there is an optimal point in which you can stretch a muscle fiber and it will have the most effiency. I belive its 120% of the orginal length of the muscle fiber. Sooooo..........think of a rubber band. You stretch it a little and let go and it barely moves. You pull it back farther and farther it really starts to snap back hard. You pull it back unti you cant pull it anymore and it snaps the strongest. This is the same concept as preload............you are Preloading the cardiac muscle sarcomere (muscle fibers) by giving volume we stretch the heart far enough that we get a good snap from the heart. Afterload is the resistance that the heart pumps against when it ejects the blood. Its actually the measurement of Left ventricular wall tension during systole. SO, we preload the heart with a certain volume and then we eject it. Now, afterload will be high if we have to eject that volume through something the size of a coffee stirer. Afterload will be low if we eject the volume through a vessel the size of a car tire. On a extra note, CHF is similar to us stretching that rubber band sooooo far that it loses its optimal stretch. We stretch it out so far that it is beyond that 120% point and is too lose and streched out to recoil well. That is CHF in essence.

Re: Cardiac Preload and Afterload

What a great explanation. Thanks! I just took that exam a few weeks ago and the second half Thursday. I did well on the first half and even better on Thursday's exam. Coming in here for the info on preload and afterload made a WORLD of difference. I'm sure future students are going to get a GREAT deal of understanding from the explanations we see in here.

We all appreciate the help all of you give us here. Thanks again!

Sandra Gale

Re: Cardiac Preload and Afterload

Are there any sites where you can get quizzed on hemodynamic monitoring-?

Re: Cardiac Preload and Afterload

Originally Posted by belahaven

Are there any sites where you can get quizzed on hemodynamic monitoring-?

www.pacep.org has an entire hemodynamic quiz/education program. Im not sure if the administrators will allow you to view a link to another website in this reply, but if so check it out. Its very informative.

Re: Cardiac Preload and Afterload

Quick and easy:

Preload= stretch (the amount the ventricle has to stretch during diastole to accomodate volume)
Afterload = resistance (the amount of resistance the ventricle has to overcome to push blood through the aortic valve)

Re: Cardiac Preload and Afterload

Originally Posted by jaquelynne

Gross 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.

I love this analogy....no mistake...everyone can relate to this!

Re: Cardiac Preload and Afterload

WHat great explanations to difficult concepts; will use them for my new nurses in ICU/CCU. Hikingcole should inform director of nursing dept of the professors' responses to questions and inability and indifference to questions in this area. Makes all educators look bad. Perhaps another faculty member should be teaching that class

Re: Cardiac Preload and Afterload

Originally Posted by jmca26

Hi,

I am a student nurse and I need help from a professional
I want to know why hypertension or high blood pressure is common in patient with diabetes mellitus how is this happen?

thanks!

One of the factors affecting blood pressure is the relaxation and contraction of the smooth muscle inside the blood vessels. Other factors are blood volume, heart rate, and contractility of the heart muscle. Diabetes stimulates the sympathetic nervous system and the renin-angiotensin-aldosterone system causing a constriction of these smooth muscles, a retention of sodium, and an inability to excrete excess water. As this cycle progresses the heart muscle becomes altered so that it loses it's abilty to stretch, the kidneys lose their abilty to filter blood ( more angiotensin released) and more water is retained. More volume in a constricted vessel equals high pressure.