Sketchy Pharm: Loop Diuretics

Question 1

What percent of the filtered sodium is reabsorbed in the ascending loop of Henle?

Answer 1

25%

Question 2

Just like in the proximal convoluted tubule, the basolateral side of the loop of Henle also _________________.

Answer 2

absorbs sodium via a Na/K antiported (like the mom taking her kid’s peanuts and giving him a banana)

Question 3

The apical membrane of the loop of Henle actively absorbs what electrolytes?

Answer 3

•Na
•K
* 2 Cl

(Think of the kid passing peanuts, banana, and two chloride packets to the attendant.)

Question 4

True or false: water is passively absorbed in the lower ascending loop.

Answer 4

False. The ascending loop is impermeable to water.

(Think of the water bottles stuck in each car of the roller coaster.)

This is why the loop of Henle is referred to as the diluting segment.

Question 5

Loop diuretics indirectly block the absorption of which two electrolytes?

Answer 5

Magnesium and calcium

The Na/K/2Cl protein creates a gradient that pulls Ca and Mg into the cell. When this gradient is destroyed, Mg and Ca remain in the lumen and are excreted.

(Think of the kid clinging to his ice cream and magnet necklace which then spill out of the car.)

Question 6

Explain the role of prostaglandins at the loop of Henle (which I don’t recall learning in CVPR)?

Answer 6

Prostaglandins have been shown to inhibit the absorption of sodium in the loop of Henle AND increase the renal blood flow by dilating the afferent arteriole. As such, prostaglandins potentiate the effects of loop diuretics.

In contrast, NSAIDs reverse both of these effects and oppose the effect of loop diuretics.

(Think of the kid with the Pro-Slugger bat pushing open a path to the afferent arteriole.)

Question 7

What are some common indications for loop diuretic use?

Answer 7

• CHF (dad with deflated balloon)
• Pulmonary edema (dad with lung-shaped life preserver)
• Ascites (mom with yellow pool floaty around her abdomen)
• Hypertension (steam pipes beneath roller coaster)

Question 8

Why do loop diuretics cause hypokalemia?

Answer 8

First, loop diuretics block the protein that actively absorbs potassium. Second, when the excess sodium reaches the collecting duct, it is absorbed in exchange for potassium which further exacerbates hypokalemia.

Question 9

Other than the electrolyte abnormalities mentioned in other cards, what are some side effects of furosemide?

Answer 9

• Ototoxicity (like the tinnitus gong being rung)
• Sulfur allergy (eggs thrown at kids)
• Interstitial nephritis (like the kidney-shaped container with the little blue tickets –blue because that’s how the lymphocytic infiltrate will look)
• Hyperuricemia due to enhanced uric acid reabsorption (woman knitting)
• Contraction alkalosis due to enhanced aldosterone action (OH bottle being squeezed out)