sodium disorders Flashcards
what are the predominant symptoms associated with hypo and hypernatremia ?
associated with the brain
low sodium means low osmotic pressure and the brain swells
high sodium means high plasma osmolality and then the brain shrinks
what are the symptoms of hyponatremia ?
malaise
stupor
coma
nausea
what are the key diagnostic tests associated with sodium problems ?
plasma osmolality
urinary sodium
urinary osmolality
what is the plasma osmolality test ?
measures the amount of solutes present in the plasma
the key soluet is sodium
what is the osmolality in hyponatremia ?
osmolality should be LOW in hyponatremia
what are the situations associated with hyponatraemia and high osmolality ?
hyperglycemia or mannitol
this draws water out of the cells hence the hyponatremia
what are the causes of hyponatremia with normal osmolality ?
1- artifcats in serum potassium
2- hyperlipidemia
3- hyperproteinemia ( multipl myeloma )
4- pseudohyponatremia
what is the urine osmolality like in associated with the ADH levels ?
1- decreased ADH is associated with low urine osmolality
2- increased ADH is associated with increased urine osmolality
generally speaking under normal conditions what is the appropriate response of the urine to hyponatremia ?
urine should be diluted , ADH should be low, urine osmolarity should also be low
if the urine is not diluted, that means the kidneys are not responding well , fee ADH keteer when it should be low
what are the causes of hyponatremia ?
generally :
heart failure and cirrhosis
kidneys bayza
high ADH
psychogenic polydypsia / dietary
what are the features associated with heart failure and cirrohsis and what are the ADH levels ?
1- there is a decrease in effective circulating volume
2- but an increase in total body water
3- bas ADH is high
and because the ADH is high the urine will be concentrated
what are the sodium disorders associated with kidney disease ?
there is decreased ability to excrete water , leading to more water retention and dilution of sodium, usually always hyponatremia
what are the body fluid status associated with hyponatremia in kidney disease ?
can be associated with hyovolemic or euvolemic
if i have an increased urine osmolarity in renal failure what does this usually indicate ?
that means that the ADH levels are high hence the high urine osmolarity
when it should be low due to hyponatremia
this means there is an external stimulus of ADH
this indicates an abnormal response to sodium
what drugs are associated with hyponatremia ?
diuretics - especially thiazide diuretics where they cause both sodium and water loss
how do you diagnose hyponatremia in association with duretic use ?
monitoring the response to discontinuation of drugs
what type of diuretic is associated with a higher chance of developing hyponatremia ?
thiazide diuretics
what happens in the medullary gradients in loop diuretics vs in thiazide diuretics ?
loop diuretics diminish the medullary gradient
thiazide diuretics keep the medullary gradient intact
what happens to ADH levels in dehydration ?
higher levels of ADH
the sodium levels depend on the water intake
free water intake is associayted with hyponatremia
what are the mechanisms of high ADH that cause hyponatremia ?
adrenal insufficiency
hypothyroidism
SIADH
what is the pathology associated with SIADH ?
too much ADH - causing hyponatremia , with high urinary sodium and high urine osmolality
what are the oter causes of high ADH that must be excluded first before a diagnosis of SIADH is made ?
heart failure
cirrohsis
dehydration
thyroid/adrenal disease
what are the causes of SIADH ?
central SIADH - associated with head trauma, cancer and meningitis
Ectopic SIADH - small cell lung carcinoma
Drug induced SIADH - carbamezapine
what is the volume status of SIADH ?
normal fluid status euvolemic
dilutional hyponatremia with euvolemia
due to suppression of the RAAs system
