Diuretics Flashcards
What does the glomerulus do
filtration
What does the proximal tubule do
reabsorption (mostly NaCL)
- also secretes hydrogen, foreign substances, organic anions and cations
- isotonic
Carbonic Anhydrase Inhibitors and osmotic diuretics work here
What does the loop of Henle do
concentrates urine
-isotonic, hypertonic, hypotonic
Descending Loop: NaCl diffuses in, water reabsorbed
Ascending Loop: NaCl actively reabsorbed, water stays in
Loop diuretics work here
What does the distal tubule do
Reabsorption of Nacl, water (ADH required), bicarb
- isotonic or hypotonic
Thiazides work here
This is where blood pressure changes are made - thiazides work here and they work on decreasing pressure…WHERE THE RAAS system begins
What does the collecting duct do
final concentration
- reabsorbs water (ADH required), NaCL
What is the GFR for CKD diagnosis
less than 60 for over 3 months with/without kidney damage
Are longer intervals between HD and surgery associated with a higher risk of post-op mortality?
YES
What BUN/SCR is dehydration?
BUN/SCR > 20
Where does each group of diuretic work?
Proximal tubule - Carbonic anhydrase inhibitors AND osmotic diuretics
Loop of Henle - Loop diuretics
Distal Tubule - Thiazides
Distal tubule / collecting duct - potassium sparing
Are carbonic anhydrase inhibitors used as diuretics these days?
Not really - Acetazolamide (Diamox) is used off label for metabolic alkalosis (commonly happens when “over-diuresing” CHF patients)
What is an interesting use for Acetazolamide?
Altitude sickness
What do carbonic anhydrase inhibitors do?
Inhibit CA which inhibits H+ secretion in the proximal tubule. Bicarb and sodium are blocked from reabsorption
Do carbonic anhydrase inhibitors cross the BBB?
YES
What do osmotic diuretics do (mannitol and urea)
Uncouples Na and H2O reabsorption by increasing the osmotic gradient in the proximal tubule. Na reabsorption initially, but H2O is not, leading to decreased Na reabsorption distally.
They “pull water” and increase intravascular volume.
Osmotic diuretics primarily inhibit water reabsorption in the proximal convoluted tubule and the thin descending loop of Henle and collecting duct, regions of the kidney that are highly permeable to water.
Osmotic diuretics also extract water from intracellular compartments, increasing extracellular fluid volume. Overall, urine flow increases with a relatively small loss of Na+. In fact, urine osmolarity actually decreases.
What are Mannitol’s different uses?
Prophylaxis against acute renal failure (ARF)…loop diuretics are too
Differential diagnosis of acute oliguria (if the patient responds to mannitol, they are just dehydrated…if not, they have actual renal damage)
Treatment of increased intracranial pressure (ICP)
Decreasing intraocular pressure (IOP)
Is mannitol REALLY nephroprotective? What does current research say about it?
NOPE.
No better than plain saline pre-radiocontrast dye
EXCEPT: renal transplant surgery
Do you need an intact BBB when using mannitol?
YES
If not, it will pull water into the brain and increase ICP, which is the opposite of what we want
What are dangerous side effects of mannitol?
Pulmonary edema, hypovolemia, hypernatremia
electrolyte disturbances, plasma hyperosmolarity d/t water and NaCl secretion (hypernatremia)
