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Diagnosis of hypertension

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Tanner Marshall.

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Video transcript

- [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.