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)
What electrolyte abnormality can mannitol create?
Hypernatremia from excess water loss
What negative side-effect is urea associated with?
Venous thrombosis and tissue necrosis after extravasation (not seen with mannitol)
What is loop diuretics MOA?
Inhibits Na and Cl reabsorption in the ascending loop and to a lesser extent in the proximal tubule
Which two diuretics are nephroprotective?
mannitol (osmotic) and loop diuretics (furosemide)
What are loop diuretics clinical uses?
Mobilization of edema fluid due to renal, hepatic, or cardiac dysfunction
Treatment of increased ICP
Treatment of hypercalcemia
Differential diagnosis of acute oliguria
What happens when you take NSAIDS while on a loop diuretic?
Furosemide-induced increases in renal blood flow are inhibited by NSAIDs resulting in an attenuated diuretic effect
What is braking phenomenom?
Acute Tolerance (Braking Phenomenon) – ceiling effect with diuretic where giving more doesn’t increase outcome but can increase side effects.
Associated with loop diuretics
Loop diuretics electrolyte side-effects
All low basically
Hypokalemia
Hypochloremia
Hyponatremia
Hypomagnesemia
Hypokalemic Metabolic alkalosis (thiazides also cause this)
Which diuretic can cause deafness?
Loop diuretics
Which type of medication are loop diuretics cross-sensitive to?
Sulfa antibiotics, sulfonylureas, thiazide diuretics
Do antibiotics increase the chance of nephrotoxicity when using loop diuretics?
YES, for aminoglycosides and cephalosporins
- penicillins and furosemide together are associated with allergic interstitial nephritis
What is thiazides (chlorothiazide, hydrochlorothiazide) MOA?
Compete for the Na-Cl cotransporter in the distal tubule to inhibit reabsorption. Inhibit only urinary diluting capacity, not concentrating capacity.
Which electrolyte do thiazide diuretics INCREASE?
calcium (increased calcium reabsorption)
What are thiazides clinical uses?
hypertension and mobilization of edema
Thiazides electrolyte side-effects
Hyperglycemia
Hyperuricemia
Hypercalcemia
Decreased renal or hepatic function
Decreased intravascular volume
metabolic alkalosis with chronic administration
Are thiazides associated with hyper or hypo blood sugar and uric acid?
HYPERglycemia and HYPERuricemia
Do potassium-sparing diuretics cause hyperglycemia and hyperuricemia like thiazides?
NOPE
What are the MOA of potassium-sparing diuretics?
Amiloride and Triamterene: inhibit Na reabsoprtion induced by aldosterone. Inhibit active counter transport of Na and K in the collecting duct. MESS UP THE the Na-K-ATPase pump
Spironolactone and Eplerenone: competes for aldosterone receptor sites in the distal tubule to block Na reabsorption and K secretion. Competitive inhibitors of aldosterone
What is the main side-effect of potassium-sparing diuretics and what makes this issue worse?
HYPERKALEMIA
Made worse when also taking NSAIDs, Ace inhibitors (i.e. lisinopril), Beta-blockers
Which two diuretics cause hypokalemic, hyperchloremic metabolic alkolosis?
Thiazides and loop diuretics
EKG changes with hyperkalemia
Tall peaked T wave
Loss of P wave
Widened QRS with tall T wave
Why do we give calcium when correcting hyperkalemia?
Stabilizes the heart and lowers the threshold potential of the myocardium.
Caution in patients who are on digoxin – calcium has been reported to worsen the myocardial effects of digoxin toxicity..could use Mg as an alternative to stabilize the myocardium
Treatment for hyperkalemia
C = Calcium (cardiac stabilizer)
B = inhaled beta2 agonists (intracellular shift)
I = Insulin (followed by..)
G = Glucose (given with insulin)
K = Kayexalate (mainly chronic RF)
D = Diuretics (renal elimination)
ROP = Renal unit for dialysis Of Patient
What are some causes of hyponatremia?
Loss of body fluid, thiazides, loops, CHF, SSRIs, Carbamazepine, Lithium, Liver disease
Hyponatremia correction rates
Severe symptomatic hyponatremia: 6-12 mEq/L in the first 24 hrs and 18 mEq/L or less in 48 hrs
Chronic hyponatremia: 0.5 mEq/L/hr with max change of 8-10 mEq/L in a 24 hr period
What is calcium dependent on?
Albumin
What are some causes of hypercalcemia?
Hyperparathyroidism
Chronic renal failure or vitamin D deficiency
Vitamin D intoxication
Malignancy
Diuretics (usually mild)
What antibiotics can cause nephrotoxicity when using with loop diuretics?
Aminoglycosides and cephalosporins
