Secondary hypertension | Circulatory System and Disease | NCLEX-RN | Khan Academy

Secondary hypertension | Circulatory System and Disease | NCLEX-RN | Khan Academy


– [Voiceover] With primary hypertension you’ve got this high blood pressure. And well, ultimately the
cause is unknown, right. We’ve got this big laundry
list of risk factors that might contribute. But really we don’t know
exactly what did it. With secondary hypertension, the difference is we know exactly what’s causing your
blood pressure to rise. And we can pinpoint this
other medical condition. So the hypertension happens secondary to some other disease. This form of hypertension
accounts for only about 10% of hypertension cases. And so it’s not that common, right, whereas the other 90%
have primary hypertension. So let’s sort of just
dive right in to some of the common diseases that
can lead to hypertension. All right, so renal diseases
tend to be big time culprits for secondary hypertension. Where when we say renal, we’re
referring to the kidneys. With these, the kidneys don’t
function as they normally do. So since they’re such huge players in regulating blood pressure through water and sodium regulation, if you’ve got some kind of
underlying kidney problem, it can result in this inability
to get rid of some fluid. And so more fluid in your body leads to higher plasma and blood volume and so higher blood pressure, because remember, flow and
resistance in the blood vessels is directly related to blood pressure. So if you increase flow,
you increase blood pressure. And one potential culprit
for kidney diseases is polycystic kidney disease. By looking at poly, we know
that that means many, right. And cystic refers to cysts which are like these fluid-filled sacs. So this is an inherited condition where you develop these fluid-filled sacs all around your kidneys. And if these guys get too big
or there are too many of them, they can start to damage or
disrupt your kidney’s function, which can cause you to
hold on to more fluid, and this will increase
your blood pressure. Another renal disease
is glomerular disease. And your glomeruli in your kidneys are like these filters for
waste and salt or sodium. If these filters get swollen or just aren’t working
like they normally do, this can also increase your plasma volume and increase your blood pressure. Finally, you’ve got
renovascular hypertension, where reno refers to your kidneys, right, and vascular are like the arteries that supply your kidneys with blood. So renovascular
hypertension is usually due to some kind of narrowing of your arteries that supply your kidneys with blood. If and when these get narrow, they can’t supply the kidneys
with enough blood, right. When this happens, your kidneys think that there’s not a lot
of blood in your body and that maybe you’re just
dehydrated or something. And then they respond by trying to hold on to more fluid instead, which, as we know, causes
your blood pressure to go up. Okay, so those were all having
to do with your kidneys. But it doesn’t always
stem from the kidneys. Cushing syndrome, for example, has been known to cause
secondary hypertension as well. With Cushing syndrome,
you’ve got these high levels of circulating glucocorticoids, which are like these steroid hormones made by your adrenal cortex. So you’ve got all these glucocorticoids floating around in your bloodstream. And these facilitate
sodium and water retention, which increases your plasma
volume and your blood pressure. Another disease is called
primary aldosteronism. This is where some factor, some thing, maybe like a tumor,
causes your adrenal gland to release too much aldosterone. So this time you’ve got
all this aldosterone circulating around your bloodstream. And what does that do? Well, it heads straight
over to the kidneys and tells them to hold
on to sodium and water. As we know all too well by now, this increases your plasma volume and so your blood pressure. The next one’s a bit of a mouthful. It’s pheochromocytoma. And this one again is a tumor that grows in the adrenal glands, which are also responsible
for releasing hormones like norepinephrine and epinephrine which regulate your
fight or flight response and can temporarily raise
your blood pressure. Another one that’s pretty important that you should be aware
of is actually sleep apnea. Seems a little weird, right. Well, with sleep apnea,
your breathing keeps like starting and
stopping while you sleep. If you do this over and over
and over again all night long, you end up not getting very much oxygen. When you don’t get enough oxygen, your heart tries to pump
harder and deliver more oxygen, which tends to sort of
increase your flow at night, and therefore your blood pressure. So it’s not uncommon to see a
higher blood pressure at night for patients with sleep apnea. Obesity, though, it’s also a risk factor for primary hypertension, can be a lone cause of
secondary hypertension as well, since as your body weight increases, so does the amount of blood
circulating around your body. This added plasma volume
increases your flow and therefore increases
your blood pressure. And finally, there’s brain
tumors and encephalitis. Both of these brain tumors and the inflammation of the
brain or a/k/a encephalitis cause an increased pressure in your skull. This tends to decrease your blood delivery to parts of the skull, like
your brain, pretty important. And since your brain is so important, your body tries to increase
your blood pressure as well to sort of overcome this
pressure in the skull and force more blood up into
the skull and into the brain.