Regulation & Disorders of Salt and Water - Gyamlani Flashcards
What overall concept regulates water balance?
Plasma Osmolality (sr. na+)
In the ecf, where is hte majority of na found?
in the venous blood system
What is a surrogate marker for serum osmolality?
serum sodium
What is synonymous with ECFV and regulated by changes in EABV?
Total Body Sodium
What is the formula for Posm?
2[na] + Gluc/18 + BUN/2.8
What is the bigger factor when determines sodium concentration: water or amount of sodium?
Water (TBW)
In a normal person, when EABV goes up, does ECFV go up or down?
Up, they should go together in a healthy individual
In a person with CHF, a person with decreased EABV will have high or low ECFV?
Increased
What causes the low EABV in a patient with CHF?
Decreased Cardiac Output
In a person with cirrhosis of the liver, will they have increased or decreased EABV?
Low
In a person with cirrhosis of the liver,w ill they have increased or decreased ECFV?
High
What are the effectors for osmoregulation?
adh and thirst
What are the major effectors for volume regulation
adh
In response to what, the juxtaglomerular cells secrete renin?
In response to low blood volume
Explain the renin-angiotensin-aldosterone pathway.
Decreased Na levels/Decreased ECF volume/Decreased arterial pressure lead to renin secretion from JG cells. This raises angiotensin I which is converted to Angiotensin II (which causes vasoconstriction and increased Na reabsorption by PCT). Angiotensin II also activates aldosterone, increased K secretion and increased Na reabsorption
What is the opposite of Renin-Aldoseterone pathway?
Atrial Natriuretic Peptide
What are the effects of ANP?
Increased Na excretion and Increased K absorption. Also, afferent arteriolar vasodilation
What specifically triggers renal sodium rentention in CHF?
Renin-angiotensin activation due to decreased EABV
What leads to edema formation in cirrhosis?
decreased osmotic pressure (low albumin) leads to increased hydrostatic pressure in portal circulation which promotes the movement of plasma to ISF
What receptors are stimulated when there is hypertonicity?
Hypothalamic receptors
What effects do the hypothalamic receptors have in response to hypertonicity?
Increased thirst, increased water intake leading to isotonicity
Increased AVP release leading to renal water retention
What is the opposite of the hypertonicity of the hypothalamic pathway?
The opposite but still leading to isotonicity
Where is the thirst center located?
third ventricle
What is the stimulus of the thirst center?
increased ECF osmolarity, volume depletionm angiotensin II, pain nausea and vomiting. Leads to ADH
How does ADH effect AQP-2
Increased sr osm increased AVP/ADH. This opesn AQP2 CD and INcreased H20 reabsorption. This increased U osm and Decreasing serum osmolarity
What are the three general categories of hyponatremia?
Hypovolemic Euvolemic, Hpervolemic
In hypervolemic hyponatremia, what do TBW and TB Na do?
TBW decreases. TB Na decreases even more.
What will the urine Na be in hyponatremia
less than 20 meq/l
what is a common cause of hypovolemic hyponatremia
vomiting and diarrhea
What are clinical recognition signs of sodium depletino?
reduction in bp
poor skin turger, absence of dependent edema
disproportionate increase in BUN to creatinine
Reduced urine sodium excretion except in cases with renal losses of Na
In Euvolemic Hyponatremia, what do the TBW and TB Na do?
TBW increases while TB Na stays the same
What are causes of euvolemic hyponatremia?
pulmonary disorders, cns disorders and cancer, antipsycho drugs
What conditions must be ruled out to ensure a euvolemic hyponatremia?
glucocorticoid deficiency
hypothyroidism
What is SIADH
it’s an inappropriate release of ADH, allowing aqps to reabsorp more water. na excreition remains the same but concentration thus increases. there is an inhibition of raas because that’s activated by arterial pressure, which is the same because of all the extra water
What is hypervolemic hyponatremia?
retention of both sodium and water in which the latter increases enough to still call hyponatremia
What are teh causes of hypervolemic hyponatremia?
CHF, hepatic cirrhosis nephrotic syndrome renal disease
what are symptoms of hyponatremia?
nausea, malaise, headache, lethargy, obtundation, seizures, coma
How does the brain adapt to hyponatremia?
following hyponatremia, h20 moves down its osmotic gradient producing cerebral edema. in response the brain loses extracellular and intracellular osmolytes. h20 losses then accompany the osmolytes and the brain volume decreases back to normal in chronic hyponatremia
What can happen if you correct hyponatremai too quickly?
cerebral demyelination syndromew
what is cerebral demyelination syndrome?
caused by excessive rate or amount of correction of serum Na. can lead to paraplegia, permanent or fatal
What is the big test for hypernatremia?
Uosm
If you had a Uosm under 300, what does it mean?
Central nephrogenic water diuresis
If you have a Uosm greater than 500, what does it mean
extra-renal water loss OR osmotic diuresis
In treating euvolemic hypernatremia, how much should you replace over the first 24 hours?
1/2
