Renin-angiotensin-aldosterone System (RAAS) (Nursing)

00:00 Now when we've talked about hormones, right, we talked about the structure and function changes first in the kidney, then we came to hormones. The first two we discussed were ADH and ANH. Now, I want to take a look at the RAAS. We briefly introduced it at the beginning of this series but I want to kind of walk you through it. So, what I asked you to do is either put your finger on the screen or use your pen, but I want you to kind of follow it through this diagram because they did an amazing job on creating this diagram for you. So start with the kidneys. When your body experiences a drop in blood pressure or a drop in fluid volume, you end up with renin being excreted. Now, renin hooks up with angiotensinogen. Thank you to our liver. You end up with angiotensin I. Still with me? Okay. Now, after angiotensin I connects with ACE, angiotensin-converting enzyme, that comes from the lungs, it was in the vasculature there, you end up with angiotensin II.

01:09 This is a killer one. Right? So, what I want you to do is put a big fatty box around angiotensin II because it is a bad ____. It is a potent vasoconstrictor. So see, angiotensin II follow that arrow up. Those vessels clamp down like your body makes a vasoconstrictor better than we can create synthetically. It's pretty amazing. Now the other thing, angiotensin II, is right a potent vasoconstrictor but you also end up with the release of aldosterone. Now follow aldosterone around. So when the adrenal gland pumps that out, what happens? Ohhh, that tells my body or my kidneys to hang on to more sodium and wherever sodium goes, water follows. So how the RAAS works, body picks up. I need a higher blood pressure for whatever reason. So, it kicks in to this RAAS since starting with renin. End-product, angiotensin II gives me a tight vasoconstriction and you have volume expansion because I have the potent vasoconstriction from the angiotensin II. I also have the stimulation of aldosterone and aldosterone tells my kidneys to hang on to sodium and wherever sodium goes, water follows and that's why I have more volume on-board. When I have more volume in my intravascular space, my blood pressure will raise. Now, as Jose ages, here's the deal.

02:53 There is less aldosterone. Okay, so this kind of slows down his ability to reabsorb sodium in the Loop of Henle because that's where it works, in the kidney. So, as Jose ages he's going to have less aldosterone available so that way he is not going to be able to hang on to much sodium as he could when he was younger. So, less sodium reabsorb leads to a lower serum sodium level. Because I want to let that set in for just a minute.

03:26 Remember in seniors, this isn't for you, this is for our earlier nursing students, be kind to them. When you draw a lab work, when we say serum sodium, lab tech comes or the nurse will do it and they will draw a lab sample from a vein and they will check the sodium level of your blood. Right? It's really hard to get a kneel into a cell to check out what the intracellular sodium level is. So when you're looking at lab work, that's what you're looking at. You're looking at the sodium level of the blood in the intravascular space. In older person when you look at their lab values could likely have, and I'm talking about healthy normal changes, their serum sodium, their blood sodium level or Na as you see it represented, will be lower than they would have been as a young adult. So we've got Jose here right in the salt shaker because this is why elderly have relatively, okay, relatively lower serum sodium levels because I hear you, I hear you coming for me because what you tell me is "Well my grandpa has to be on a low sodium diet." Ahh but I would ask you "Does your grandpa have hypertension, history of cardiovascular disease? What else would your grandpa have going on? Because Jose, he has been age healthy, normal experience, that's his journey has been that without cardiovascular disease. That's why he is likely to have relatively lower serum sodium levels. So, in the healthy elderly, we're pretty sure could be estimated around 7% of them have a serum sodium concentration of 137 or less. Now see if you can remember what is the normal serum sodium level? Good deal. So now you can see why he is definitely on the lower end of that scale. Now keeping in mind in the healthy elderly individual, these serum sodium levels we're talking about are independent of their volume status.