disorders of sodium balance Flashcards
volume status is dictated by the _____ in the body
content of sodium
volume contraction is a disorder of
sodium depletion
volume expansion is a disorder of
sodium overload
kidneys modify sodium handing according to the
perceived volume status- effective circulating volume
sodium retention occurs under circumstancces of
volume depletion
sodium excretion occurs under circumstances of
volume overload
sodium balance affects
volume status
water balance affects
plasma osmolality and sodium concentration
sensors that assess volume status
- afferent arteriole
- macula densa
- carotid/ aortic bodies
- cardiac chambers
blood pressure fall leads to the activation of
RAAS system
factors that stimulate renin secretion from JG
- decreased chl- delivery to macula densa
- decreased perfusion of JGA
- B1 sympathetic stimulationof JGA
actions of angiotensin II
- vasoconstriction of the systemic arterioles and efferent arterioles
- aldosterone release
- renal sodium retention through direct stimulation of sodium reabsorption in the PCT and enhancing sodium reabs. in CT mediated by aldosterone
factos stimulating aldosterone synthesis
- Angiotensin II
2. hyperkalemia
actions of aldosterone at the renal cortical collecting tubule
- increased sodium reabs
- enhanced potassium secretion
- increased hydrogen secretion
factors that stimulate SNS
decreased pressure at nerve plexi bodies in carotid arteries and aortic arch
actions of SNS
- sympathetic vasoconstriction
- renal sodium retention- direct stimulation pf PCT Na reabs
- efferent arteriolar vasoconstriction
- stimulation of renin release
factos that stimulate ANP from atria
increased atrial stretch
actions of ANP
- increased renal Na excretion- direct on CT
2. at higher doses is a vasodilator and can increase RPF and GFR
blood pressure is associated with which pressure
Pgc
in volume overload, where there is a higher GFR and thus a faster tubular flow rate what happens?
there is a shorter tubular transit time thus reabs of Na decreases and there is more loss of it in the urine
the whole purpose it to correct volume overload
volume depletion is diagnosed by
clinical symptoms!!!!!!!!
- decreased BP
- tachy
- decreased skin turgor
- orthostasis
- decresed JVP
characteristic lab and urine tests in volume depletion
- reduced GFR
- low urine Na
- increased BUN/Cr ration
- low Fractional Excretion of Na (FENa)
what is FENa?
excreted load of Na / filtered load of sodium
when do we expect to see a low FENa?
at times of volume depletion and there is an activation
true or false:
host response to ineffective perfusion is the same as the response to volume depletion
yep
true or false:
we can measure the effective circulating volume
nope
volume overload diagnosis made by
clinical symptoms!!!!!
- pulmonary edema
- peripheral edema
characteristics we see with volume overload
- elevated BNP
- high urine Na+
- high FENa
which diseases are associated with volume overload but there is still stimulus for sodium retention
- heart failure
- cirrhosis
- Nephrotic syndrome
underfill hypothesis 1
movement of fluid into intersittium triggers retention (via RAAS and SNS) in attempt to expand extracellular volume and restore tissue perfusion
overflow hypothesis 2
sodium retention by the kidney leads to expanded extracellular volume and results in fluid movement out of capillaries and into interstitium
edema formation is from 4 mechanisms
- increased capillary pressure due to increased venous pressure either by venous obstruction or expanded venous blood volume
- decreased plasma oncotic pressure such as in hypoalbuminemia
- increased capillary permeability
- lymphatic obstruction
how do we treat cirrhosis
treating the hemodynamic dysregulation and splanchnic vasodilation adn reducing extracellular volume
nephrotic syndrome
poorly characterized impairment of sodium excretion precedes the underfilled state due to heavy albumin loss in the urine
treatment of nephrotic syndrome
decreased Pgc with ACEi and AII blockers
ineffective circulating volume leads to inadequate renal perfusion which causes sodium rentetion by the kidney leading to an overall volume overload
this is the common pathway where these four diseases/states converge
- Heart failure- low cardiac output
- marathon- true volume depletion
- cirrhosis- Drop in SVR
- Nephrotic syndrome- hypoalbunemia resulting in extra-vascular pooling
treatment of volume disorders require
managing sodium balance and renal perfusion
FeNa is often a good indicator of the ______ as the kidney retains Na when it is underperfused and released Na when it is well perfused
effective circulating volume
HF results in volume overload by
reducing cardiac output, lowering renal perfusion, and stimulating Na retention.
Cirrhosis results in volume overload by
dropping plasma oncotic pressure (through impaired albumin synthesis).
Arteriovenous malformations in cirrhosis also drop SVR and BP, leading to
renal underperfusion and Na retention.
In nephrotic syndrome, protein loss in the urine lowers plasma oncotic pressure and intravascular volume, stimulating .
renal Na retention
Volume overload is sensed by the cardiac chambers which release atrial __________ to block sodium reabsorption in the CT.
natriuretic peptide (ANP)
