renal 4 Flashcards
what is diuresis
excessive urine output
what is a diuretic
a drug that increases urine output due to action in th ekidney (increase water out and excretion of others)
why use diuretics
congestive heart failure
hypertension
why use a diuretic for congestive heart failure
heart weakens decreased Cardiac output decreased GFR increase aldosterone increased Na and H2O reabsorption increased ECV and edema
why use a diuretic for hypertension
increased ECV
increased plasma volume
increased Blood pressure
how to diuretics gain access to tubules
Filtration
secretion
where do osmotic diuretics work
in water permeable segments of the nephron (PT and descending loop of henle
where do Ca inhibitors act
proximal tubule
what are loop diuretics
inhibit Na reabsorption via the NaK2Cl symporter
where do loop diuretics work
act in the thick ascnending limb
what is the action of Thiazides
block NaCl symptoer
where do thiazides work
early distal tubule
what are the types of K sparing diuretics
Aldosterone Antagonists
ENaC Blockers
where do K Sparing diuretics work
late distal tubule
cortical collecting duct
what is the action of K sparing diuretics
inhibit sodium reabsortpion and Potassium secretion
what are Aquaretics
ADH antagonists
what is the action of Osmotic diuretics
increase osmotic pressure in tubular fluid, therefore impairing Na reabsorption
what are examples of osmotic diuretics
mannitol
Pathologicallyy elevated glucose
how do osmotic diuretics get into the tubule
via glomerular filtration and are poorly reabsorbed
where do osmotic diuretics have an effect
in tubule freely permeable to water
where do osmotic diuretics tend to get reabsorbed
PT and DL
- rest reabsorbed downstream
what happens when Osmotic diuretics are reabsorbed downstream
results in excretion of 10% of filtered Na
what is the effect on Ca due to osmotic diuretics
decrease Ca reabsorption from a decreased solvent drag
what is the action of Carbonic Anhydrase inhibitors
reduce Na reabsorption by inhibiting Ca
- reduces H available for Na/H antiporter
what is a CA inhibitor
Acetazolamide
how do Ca Inhibitors gain access to the proximal tubule
secretion
why does CA inhibitors affect mostly the proximal tubule
1/3 of Na reabsortpion relies on the Na/H antiporter there
how large of an effect does CA inhibitors have on excreteion
not large
- increase Na excretion to 5-10% filtered load
why does CA inhibitors have not a large effect downstream
downstream segments increase Na reabsoprtion when tubular Na increases
what is the most powerful diuretic
Loop diuretics
what is the action of loop diuretics
inhibit Na reabsoprtion
- inhibit NaK2CL symptorer in thick ascending limb creating not dilute urine
- no osmotic gradient estabilished in the medulla interstitum so water is not reabsorbed along collecting duct
where do loop diuretics work
in the loop of henle
how does the urine change in loop diuretics
starts out not dilute, but then very diluted
- increases Na excretion to 25% of filtered load because Na reabsorption capacity is limited downstream
can ADH compensate for loop diuretisc
Nope
what is a type of Thiazide diuretic
Chlorothiazine
where are thiazide diuretics secreted
into the proximal tubules
where do thiazide diuretics act
in the early distal tubule
what is the action of thiazide diuretics
block the NaCl transporter
- the kidneys ability to dilute urine is dimished
net effect of thiazide diuretics
reabsorption of water in collecting duct occures
- 5-20% of filtered Na is excreted
where do K sparing diuretics work
act where K is normally secred into tubular fluid by principal cells
what is the action of aldosterone antagonists
blok aldosterone’s ability to increase Na transporters in principal cells
where must aldosterone antagonists go
must get inside tubular cells to block aldosterone receptors
what is an examples of an aldosterone antagnoists
spironolactone
what do ENaC blockers do
block Na reabsorption across the apical membrane
how do ENaC blockers get to their target
act on membrane protein so gain acess by secretion into proximal tubule
what happens to the effectiveness of Diuretics over time
become less effective due to volume contraction counteracting the effects of the diuretics
how does increased sympathetic activty in response to reduced blood pressure from diurestics manifest
decrease GFR
increase PT reabsorption and increased renin
what does secretion of renin from juxtaglomerular apparatus manifest as
increase angiotensin II and aldosterone
- decrease Na excretion
what is the diuretic braking phnomenon
the body’s response to lots of diuretics that decrease their effectiveness
what are the secondary effects of diuretics
Diuretic braking phenomenon: - increased sympa in response to reduced BP - decreased natriuretic peptides - secrete renin - stimulate ADH release Increased excreteion of K Disrutpion of acid-base balance disrupt calcium homeostasis
why does the use of diretics increase Excretion of K
- diuretics increase flow of tubular fluid, stimulating K secretion
- Diuretics reduce ECV-> increase aldosterone-> stimulate K secretion
what is used to stop the increased excretion of K from prolonged diuretics
K sparing diuretics
what does CA inhibitors do to acid base balance
metabolic acidosis
what does Loop and Thiazide diuretics do to acid base balance
reduced ECV
metabolic alkalosis
what do K sparing diuretics do to acid-base balance
metabolic acidosis due to H secretion in distal tubule and cortical collectin duct is inhibited
what diuretic doesn’t affect calcium homeostasis
K sparing diuretics
what do osmotic and Ca inhibitors do to Ca homeostasis
reduce reabsorption of CA in the proximal tubule
what do loop diuretics do to Ca homeostasis
increase CA excretion by affecting transepithelial voltage that normally is the driving force fro transprot of calcium
what do Thiazide diuretics do to Ca Homeostatis
stimulate Ca reabsorption in the distal tubule and reduce excretion
how Much Ca does the distal tubule usually reabsorb
9% of filtered calcum via active transportretion
what is hemodialysis
removal of waste produces from the blood when kidney function has been impaired
is the need for hemodialysis/transplant increasing
Yes
how is hemodialysis done in a kidney failure patient
blood briefly removed from the body to be circulated through a dialyzer
how does a dialysizer work
A cylindrical bundle of fibers that allows small modcules to diffuse into dialysis fluid
what direction do the fluid and blood move in a dialyzer
in countercurrent direction to remove nitrogenous and other waste
- adjust osmolarity before blood is returned to the body
what is the concentration of NaCL in dialysis fluid
Similar to that of plasma
what diffuses from the blood into dialysis fluid
urea
Potassium
Phosphate
what flows from dialysis fluid to the blood
Bicarbonate
how often is dialysis done
3-4 hours 3 times per week
side effects of hemodilaysis
- Vascular access problems
- short term: Fatigue, chest pain, cramps, nausea, headaches (dialysis hangover)
- long term: sepsis, endocarditis, osteomyelitis (sec infections)
- amyloid deposites in joints
what causes a dialysis hangover
Acute, dramatic changes in blood chem
what causes amyloid depsoites in joints from hemodialsis
build up of trace minerals in dialysis fliud
why do patients with chronic renal failure get anemia
Inadequate secretion of EPO and loss of erythrocytes
what cells produce EPO
Interstitial fibroblasts in the renal cortex
where is EPO production control
Transcriptional level
what stimulates EPO production
PO2 is low
how do Transcription factors work for EPO
Hypoxia inducible factors are continually produced but are targeted for degradation when O2 is normal
