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Effects of Liver and Renal Failure on the Urea Cycle (Nursing)

by Rhonda Lawes

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    00:01 So take a look at this, look at this graphic that is pretty cool.

    00:04 You see the urea travels from your liver to your kidneys through the bloodstream Then our kidneys will filter that, send it out of the body through your urine.

    00:14 So let's do a quick review. First we've got ammonia.

    00:18 Now remember, where does ammonia come from? Right! from the breakdown of protein.

    00:26 Now here's what I want you to add to your notes so make sure you've got that.

    00:29 Protein can come from dietary or GI bleeding.

    00:34 Remember, red blood cells are a source of protein because of all the hemoglobin, so if someone has GI bleeding they've got a high source of protein because of that hemoglobin.

    00:46 Next, urea cycle.

    00:48 That the liver transforms the ammonia into urea which travels through the bloodstream down to the kidneys to be excreted because the kidneys will excrete the urea in the urine, why? because it's water-soluble Cool, you did a great job tracking with me.

    01:05 So here are the normal values again, you got that 7-20 (mg/dL) use lots of repetition help yourself memorize those lab values but now take a look at the BUN greater than 20 (mg/dL), this should start making more sense to you.

    01:19 Liver or renal dysfunction, ask yourself why would this tell me about liver or renal dysfunction? Well because I need the liver to break apart the protein, I need the kidneys to excrete it.

    01:30 Why would upper GI bleeding cause an elevated BUN? because blood has hemoglobin and hemoglobin is protein, and excess protein could lead to excess ammonia.

    01:42 Cool, what about high protein intake? Same thing like upper GI bleeding that's extra protein that my body has to process And last, significant dehydration is the third major category of causing an elevated BUN.

    01:58 Alright now let's have some fun, I know it's kind of nerd fun but it really is fun.

    02:02 Let's think about the impact of liver failure if you're taking care of a patient whose liver was not doing well, what change would you expect in their BUN level? So pause the video, think through what you know and what changes would you expect in a patient's BUN level who's liver failure.

    02:25 Alright welcome back, hopefully you're taking a chance to study along with us and pausing and seeing if you can come up with that answer yourself.

    02:33 We'll always come back and give you the right answer but it'll stick with you a lot more if you try and do that struggle of understanding as we go.

    02:41 So the patient is in liver failure, think about what the liver does.

    02:45 It breaks down that protein, right and helps convert ammonia into something called urea.

    02:52 Right, that's all familiar to you.

    02:54 So if a patient has liver failure, their BUN is going to be decreased.

    02:59 They'll have elevated ammonia and decreased BUN.

    03:03 So I want to take just a minute here because we're talking about how all your hard work and studying pays off in actually becoming an excellent nurse.

    03:12 I want to hit that ammonia level again remember it's neurotoxic, it'll go after your central nervous system.

    03:19 So anyone who has an impaired liver can end up with elevated ammonia levels or NH3.

    03:25 So you want to keep an eye on your patients whose liver is struggling, watch that ammonia level and it also explains why we sometimes limit dietary intake of protein in patients whose livers are struggling.

    03:38 Alright, you wrapped up your liver, let's take a look at the kidneys.

    03:42 So what change in the BUN would you expect with renal failure? Go ahead, try it by yourself first.

    03:54 Okay cool, welcome back.

    03:55 With renal failure, you're going to see an increased the BUN.

    04:01 Okay, so think that through, why do I have elevated BUN if the kidneys aren't functioning? Well the liver's doing it's job - it's breaking down protein, it ends up with ammonia, it turns it into urea.

    04:15 But if the kidneys can't filter appropriately, that's just gonna to build up in the body instead of being excreted if the kidneys were able to handle that Okay, so liver functioning - breaking down ammonia, I end up with urea, everything should be fine but once it makes it way down to the kidneys, if the kidneys are struggling, they can't get that out of the body into your urine.

    04:37 That's why you'll see the BUN level rise when the kidneys are struggling.


    About the Lecture

    The lecture Effects of Liver and Renal Failure on the Urea Cycle (Nursing) by Rhonda Lawes is from the course Blood Urea Nitrogen (BUN) – Renal Assessment (Nursing).


    Included Quiz Questions

    1. Urea is produced by the liver and is excreted by the kidneys
    2. Ammonia is a product of protein metabolism
    3. The kidneys can excrete urea as it is water-soluble
    4. Ammonia is produced by the liver and directly excreted through the kidneys
    5. The liver directly converted protein into urea to be excreted in urine
    1. Increased ammonia levels
    2. Increased in both the ammonia and blood urea nitrogen levels
    3. Elevated blood urea nitrogen levels
    4. Decreased ammonia levels
    5. Decreased blood urea nitrogen levels

    Author of lecture Effects of Liver and Renal Failure on the Urea Cycle (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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