Diagnosis of hypertension | Circulatory System and Disease | NCLEX-RN | Khan Academy
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Diagnosis of hypertension | Circulatory System and Disease | NCLEX-RN | Khan Academy

September 2, 2019

– [Voiceover] Probably the most common way your blood pressure might
be measured is through direct physical measurement. This is also probably the one that you’re most familiar with, right? It’s with the inflatable arm cuff. So usually the clinician
will put this like deflated cuff around your arm and then pump it up
until it’s really tight. Like tight enough to stop the blood flow in your blood vessels in your arm. Then, as it slowly deflates again, they can measure at what point
your blood pressure is enough to start pushing blood
through the vessels again. As this happens, the cuff
will be attached to this gauge that tells them the pressure reading in millimeters of mercury. They’ll then use this number to figure out where in the spectrum of
hypertension you would fall. Whether it’s normal or prehypertension, stage one, or stage two. They’ll also probably take
two or three measurements over the course of several visits, though before making an actual diagnosis. Since your blood pressure
fluctuates throughout the day, it might be the case that you came in during a short period of higher pressure. If your blood pressure is measured and it turns out to be
really high, then what? Well, we need to figure out why. To do that we might take
a look at a blood test. And these are diagnostic tests where we take a sample of blood and look at what’s floating around. Depending on what’s there, we can start to try and understand the extent that an organ’s
been damaged by hypertension or to help us pinpoint the
cause of secondary hypertension. Two super important things we might measure in a blood sample are blood urea nitrogen or BUN for short, and creatinine. The levels of both of these taken together help us figure out how well
the kidneys are functioning. The blood urea nitrogen
measures how much nitrogen is cruising around in your bloodstream. Which comes from the waste product urea. And this little guy is formed in the liver from the metabolism of protein. And since it’s a waste
product, we don’t want it. And it gets sent down the
bloodstream to the kidneys where they get rid of it. But what happens if your
kidneys aren’t working? Well, they won’t be getting
rid of the urea, right? And your blood urea
nitrogen levels might go up since you have more of
this urea floating around. And in renal disease, your
blood urea nitrogen levels might be over 10 to 20
milligrams per deciliter. Or, if we’re talking international units, over two point five to
eight millimoles per liter. But, it’s really important to remember that there are a lot of
things besides kidney function that can influence your
blood urea nitrogen levels. So it’s always looked at
alongside your creatinine levels which look like this
and are normally around zero point five to one
milligrams per deciliter or 44 to 88 micromoles per liter. Creatinine is also a waste product and is produced from muscle metabolism and released into your
bloodstream at this constant rate. And then it’s removed
entirely by your kidneys. And because of this, it’s
generally a pretty solid estimate of kidney function. Just like blood urea
nitrogen levels though, if your kidneys aren’t functioning right, this creatinine is gonna build up and you’re gonna have more
than these normal levels. When your creatinine is elevated, along with elevated blood
urea nitrogen levels, we can start to understand
the current level of dysfunction of the kidneys
and also get a clue as to why blood pressure might be high. Another thing we can look at are the amount of
glucocorticoids in the blood. If these are elevated,
it can give us a hint toward Cushing’s Syndrome
as a potential cause. Since Cushing’s Syndrome directly elevates the blood
levels of glucocorticoids. Blood glucose levels can be also a really good thing to look at because they can help us determine whether diabetes is present or not. Which can often accelerate
the development of either hypertension or heart disease. And finally, we might
look at your lipid profile which could be elevated because elevated lipids in the bloodstream can also accelerate
hypertension and heart disease. Now blood tests and pressure cuffs aren’t the only diagnostic
tools that we have. You might get something called
an electrocardiogram or ECG or, for the Germans out there, EKG. This test records and displays the electrical activity of your heart and it’ll often pop up
as its characteristic PQRST complex. Which looks a little something like this. And something that the
physician might look for is this tall R-wave which is this guy right here. This is often seen with
left ventricular hypertrophy which can happen when your blood pressure is elevated for a long, long time. These aren’t always the
most sensitive tests though, so sometimes it’s valuable
to look at something else in addition to that, like a chest X-ray. Sometimes if the patient has
an enlarged left ventricle, the doctor will be able to actually see that on a chest x-ray. And, used together, along
with these other tests, the doctor can start to understand if hypertension is present. And if it is, understand how it got there in the first place.

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