Name:
A 16-Year-Old with Hypokalemia
Description:
A 16-Year-Old with Hypokalemia
Thumbnail URL:
https://cadmoremediastorage.blob.core.windows.net/c1316b41-2c4c-4072-91e9-61df5d91a228/thumbnails/c1316b41-2c4c-4072-91e9-61df5d91a228.jpg?sv=2019-02-02&sr=c&sig=gxvNZIPCZrXWIQs4v1fNUiwo%2FFx8iU0sfHkUO6qogBU%3D&st=2024-05-02T04%3A23%3A52Z&se=2024-05-02T08%3A28%3A52Z&sp=r
Duration:
T00H05M06S
Embed URL:
https://stream.cadmore.media/player/c1316b41-2c4c-4072-91e9-61df5d91a228
Content URL:
https://cadmoreoriginalmedia.blob.core.windows.net/c1316b41-2c4c-4072-91e9-61df5d91a228/16437843.mp3?sv=2019-02-02&sr=c&sig=KrUDkKkyO8u1g5Bv38s8ccA1jEalIKBtP7CAvYSbXL0%3D&st=2024-05-02T04%3A23%3A52Z&se=2024-05-02T06%3A28%3A52Z&sp=r
Upload Date:
2022-02-28T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
♪ (music) ♪
CATHY: Hi, welcome to Harrison's Podclass where we discuss important concepts in internal medicine. I'm Cathy Handy. And I'm Charlie Wiener, and we're coming to you from the Johns Hopkins School of Medicine. Welcome to Harrison's Podclass. Today is Episode 4: A 16-Year-Old Woman with Hypokalemia. I will read the question. A 16-year-old star female gymnast presents to your office complaining of fatigue, diffuse weakness, and muscle cramps.
CATHY: She has no previous medical history and denies tobacco, alcohol, or illicit drug use. There is no significant family history. Examination shows a thin female with a normal blood pressure. Body mass index, or BMI, is 18 kg/m². Her oral examination shows poor dentition. Muscle tone is normal and the neurological exam is normal also. Her potassium is 2.7 mEq/L. Cathy, what are your initial thoughts?
CATHY: The main points that I take away from this case presentation so far is that the patient is a young 16-year-old. She's a highly competitive athlete too, and that can be associated with physical or emotional stressors that you wouldn't necessarily otherwise find in 16-year-olds. The important points from the exam are that she has poor dentition and a low BMI, so to me that suggests that she might have an eating disorder or excessive vomiting. You tell me that she has hypokalemia, but I would really want to also know the rest of the labs, especially the renal function and acid-base status.
CHARLIE: Okay, the additional laboratory study shows that her hematocrit is 38.5%, her creatinine is 0.6 mg/dL, and she has a serum bicarbonate of 30 mEq/L. The rest of the serum electrolytes are normal. The question then asks: Further evaluation should include which of the following? Option A is a plasma renin and aldosterone level; option B is a serum magnesium level; option C is a urinalysis and urine culture; option D is a urine toxicology screen for diuretics; and option E is a urine toxicology screen for opiates.
CHARLIE: So, Cathy, looking at those answer choices, what strikes you and what do you want to do next?
CATHY: Well, based on the labs you mentioned, she's not anemic and she has normal renal function. She has profound hypokalemia and an elevated serum bicarbonate level, so she has hypokalemia and a metabolic alkalosis. And we also heard that she doesn't have any other significant lab abnormalities. So, in general, when I hear about hypokalemia and metabolic alkalosis together, the main things that I'm thinking about are diuretics or vomiting. Vomiting is not in any of the answer choices, but diuretics is listed there, and someone who has the warning signs that we heard about above, like the poor dentition and the low BMI, I would be most concerned about surreptitious diuretic use.
CATHY: So, therefore, I'd go with option D to check the urine toxicology screen for diuretics.
CHARLIE: Okay, that sounds good. What are some other causes of hypokalemia and metabolic alkalosis though?
CATHY: So, like I mentioned before, vomiting is definitely high on the list. Low magnesium is something that I think about, too because in that case, the sodium-potassium ATPase is inhibited. You also need to remember when you're treating patients with low magnesium is that you have to replace the magnesium in addition to the potassium. That would be a reasonable choice in this case, but really not before excluding diuretic use. The other things I think about are Liddle syndrome, which is an autosomal dominant disorder.
CATHY: In that case, someone would present with severe hypertension and hypokalemia. Plasma renin and aldosterone would be helpful. And the other thing, too is Bartter syndrome which usually presents with polyuria, polydipsia, and nocturia. Again, plasma renin and aldosterone would be helpful in this case-- it would be high in Liddle syndrome, it would be undetectable.
CHARLIE: So, the plasma aldosterone and renin studies would be useful when you suspect kind of one of the more uncommon genetic causes of hypokalemia and metabolic alkalosis, right?
CATHY: That's right, but the case presentation doesn't match either of those syndromes, so those would be very low on the list here.
CHARLIE: Let's just round out the other answers that were not helpful in this case. A urine culture would not help you distinguish hypokalemia and metabolic alkalosis. And more important, in this case, there are no symptoms to suggest a UTI. Additionally, while you could suspect opioid use in a patient such as this, opioids typically do not cause hypokalemia and a metabolic alkalosis, so neither of those would have been helpful in that case either. So, the differential diagnosis of hypokalemia and a metabolic alkalosis includes the use of diuretics, and common causes of vomiting-- which in this case could have included bulimia.
CHARLIE: It also includes hypomagnesemia, and some less common genetic causes of hypokalemia. To learn more about potassium disorders and hypokalemia, you can read more in Harrison's chapter on disorders in the kidney and the urinary tract.
CHARLIE: Thank you.