Diuretics Flashcards
Define the following
a) natriuresis
b) kaliuresis
c) aquaretics
a) Increased sodium excretion
b) Increased K+ excretion
c) Substances that cause increased net excretion of water
How does aldosterone increase the resorption of water and Na+?
Increases expression of Na/K ATPase, ENaC channels, and K+ channels
What kinds of diuretics can you use on the PCT, LOH, DCT and CT?
PCT: carbonic anhydrase inhibitors, osmotic diuretics
LOH: loop diuretics; furosemide
DCT: Thiazide diuretics; metolazone
CT: Amiloride; blocks ENaC channels
Aldosterone antagonists
Give an example of a carbonic anhydrase inhibitor and their mechanism of action
Acetazolamide:
No H+ and HCO3 produced - no H+ into filtrate and HCO3 into blood
What is one consequence of carbonic anhydrase inhibitors?
Reduced amount of bicarbonate production
-> metabolic acidosis
What do osmotic diuretics do and name one example
Mannitol:
Increases plasma osmolarity by drawing fluid out of tissues/cells -> solutes filtered at glomerulus but not reabsorbed -> ions lost in the urine
How does a loop diuretic impact other ions? What is the mechanism of loop diuretics?
Inhibits Na/K/2Cl cotransporter on luminal LOH:
Less K+ in filtrate (ROMK) - filtrate more -ve -> ca2+ and Mg2+ less likely to leave filtrate -> more water/solutes are excreted
What is the mechanism of thiazide diuretics? What are two consequences?
Targets luminal NCC channels: Na+, Cl- and water stay in filtrate
Basolateral Na+/Ca2+ exchanger: pumps more Na+ into cell and reabsorbs more Ca2+ = hypercalcemia
Less Cl- reabsorption means less K+ follows = hypokalemia
Describe the mechanism of action of aldosterone antagonists and K+ sparing diuretics do.
Are they potent? Name one example of an aldosterone antagonist
Mild diuretics:
Aldosterone antagonists, i.e spironolactone: Less Na reabsorption -> less NA/K ATPase action on basolateral
K+ sparing diuretics, i.e amiloride: decrease ENac channels
=hyperkalemia for both!
Why would diuretics be used in congestive heart failure? Which diuretics would you prescribe?
High systemic venous pressure leads to edema, hypotension activates RAAS -> more retention of Na+ and water - need diuretic to reduce extra volume
1st choice: LOOP diuretics
Thiazide diuretics used alongside
What is the primary goal of diuretics other than losing more fluid?
Symptomatic relief
What happens in nephrotic syndrome and which diuretics should you use?
Hydrostatic>oncotic
- protein in the urine (gets pushed out)
- edema
- Lower circulating volume: Reduced CO
- RAAS:
Loop diuretics with thiazide diuretics
Why do you need diuretics in liver cirrhosis?
Less albumin produced - reduces oncotic pressure
Hydrostatic>oncotic
Two clinical scenarios where you might use spironolactone (aldosterone inhibitor)
Portal hypertension:
*increased venous pressure -> ascites -> reduced CO and worsening RAAS
Primary aldosteronism/Conn’s syndrome
What comprises the splanchnic circulation?
GI circulation, superior and inferior mesenteric artery
When would you prescribe mannitol?
Cerebral edema
Which diuretic works best for glaucoma? Why?
Carbonic anhydrase inhibitors, (decrease intraocular pressure)
Which diuretics can lead to hypokalemia?
Thiazide diuretics: Less cl- being resorbed means K+ unlikely to follow
LOOP: Inhibiting Na/K/Cl- cotransporter means K+ stays in the filtrate
Which diuretic can lead to hypovolemia? How would you monitor this?
LOOP diuretics are most potent and can therefore lead to excessive water and ion loss,
*monitor weight, BP, postural drop
Which diuretic can give you erectile dysfunction?
Thiazide diuretics
Explain how alcohol and coffee can have a diuretic effect
Alcohol: inhibits ADH
Coffee: Increases GFR and lowers Na+ resorption
How can diuretics lead to gout?
Diuretics concentrate blood, (can crystallize solutes and increase the concentration of uric acid)
What’s the difference between diabetes insipidus and Mellitus? How do they have a diuretic effect?
Mellitus: insulin intolerance or deficiency -> glucose in filtrate (draws water in)
Insipidus: decreased production of ADH (retain less water/ions and pee more)
What are the two types of diabetes insipidus?
Cranial: reduced ADH secretion from posterior pituitary
Nephrogenic: CTs have a poor response to ADH (aquaporins)
Which diuretics can lead to hyperkalemia?
Aldosterone antagonists and K+ sparing diuretics, as both increase Na+ excretion and K+ resorption
Which part of the kidney is most targeted by aldosterone antagonists
Principal cells in DCT and CT
