In LPN School and needing help on understanding BPeffect on HR!

[baker09]

I am in LPN school, my 2nd year to be exact. I am having trouble understanding how the BP is low, the HR will be high! I don't understand how that is. I'd like to know a explanation of how they are opposite. I always thought if you had HIGH BP you would also have HIGH HR?

[THELIVINGWORST, ASN, RN]

If there is less volume in the vascular space, there is less resistance and therefore, low BP.

The hr is high because the heart is trying to maintain adequate cardiac out put.

Stroke volume(how much blood is pumped with each heart beat) x HR= cardiac output.

[springchick1, ADN, RN]

If you have low blood volume, your heart is going to have to work harder to get the blood to where it needs to go. This may sound crazy but think of your heart as a shampoo bottle and the blood as the shampoo. When the bottle is full, you barely have to squeeze it to get the shampoo to come out. When the bottle is empty, you are having to work harder to get it out of the bottle. Same with the heart. If you have a low blood volume, you have to work harder to get the blood out.

[KelRN215, BSN, RN]

BP and HR are not always opposite. It depends on the reason behind what's going on. If your BP is high because of something like stress, chances are your HR will also be high. If you're an Olympic athlete, you may have a baseline HR of 40-50 and a baseline BP of 90/50.

[pookyp, LPN]

If you have low blood volume your heart is going to have to work harder to get the blood to where it needs to go. This may sound crazy but think of your heart as a shampoo bottle and the blood as the shampoo. When the bottle is full, you barely have to squeeze it to get the shampoo to come out. When the bottle is empty, you are having to work harder to get it out of the bottle. Same with the heart. If you have a low blood volume, you have to work harder to get the blood out.[/quote']

I like this. :)

[nurseprnRN, BSN, RN]

A really low heart rate can cause a low BP (except in an athlete, for whom it is normal and makes a normal BP).

A high heart rate can cause a high BP, as a normal person gets when he runs up a flight of stairs; the higher BP supports the higher oxygen needs of the muscles for the extra work.

Also, the same chemicals that your body puts out when you are watching a scary movie and Freddie jumps out of the closet, BOO! will increase your heart rate and your BP.

But when someone is hypovolemic (low blood volume) the pressure in the blood vessels is low (think of a balloon with a lot of air in it and one with a little air in it-- which once has higher pressure?). Therefore the body is not happy about being shorted on blood flow, and sends chemical signals to the regulatory system telling it to step things up. The fastest way to do that is to increase heart rate.

What's happening is that every heartbeat pushes blood out into the arterial system. If you had a pressure monitoring device in that artery, you would see a spike in the pressure when the heartbeat happens. In between beats, the blood runs off into the body and into the capillary bed lowering pressure in the vessel, and you would see the spike fall off, lower and lower as time passes between beats. So when the heart rate is really slow, the pressure falls lower and lower. If the rate is fast, though, the new spike comes along before the pressure gets very low, so it stays higher.

There are a lot of things that influence heart rate; this is just a really superficial summary. It's great to hear you wondering about that, so if you want more, the book for you is the Physiology Coloring Book, not a gag, but a real nifty book to explain this and other useful concepts. The Physiology Coloring Book (2nd Edition) by Wynn Kapit, Robert I. Macey and Esmail Meisami

[na-na]

If you have low blood volume, your heart is going to have to work harder to get the blood to where it needs to go. This may sound crazy but think of your heart as a shampoo bottle and the blood as the shampoo. When the bottle is full, you barely have to squeeze it to get the shampoo to come out. When the bottle is empty, you are having to work harder to get it out of the bottle. Same with the heart. If you have a low blood volume, you have to work harder to get the blood out.

I am not in LPN school yet, start in January but this is a pretty good example and I would like to remember it hen I start.