CIS #1 Flashcards
hyponatremia
sodium < 135
induces fluid movement into cells
hypernatremia
sodium > 145
induces fluid movement out of cells
main cause of hyponatremia?
inability to excrete water
inability to suppress ADH
exception polydipsia
-drink a ton of water
pseudohyponatremia
not caused by change in water balance
other substances in plasma that make measurement of sodium inaccurate
hyper: protein, lipid, cholesterol
or unmeasured osmol
sodium concentration not changed**
-just inaccurate
true hyponatremia
dilute urine, low ADH:
reset osmostat (pregnancy)
psychogenic polydipsia
concentrated urine, high ADH:
decreased effective circulating volume
SIADH
hyponatremia leads to ?
cell swelling
hyponatremia in DM patient?
glucose pulls water to vascular space and dilutes plasma sodium concentration
anion gap
Na - Cl + HCO3
plasma osmolality
2xNa + glucose/18 + BUN/2.8
used in osmolar gap
osmolar gap
difference between calculated and lab osmolality
large difference in two may suggest another substance pressure that exerts osmotic effect**
reset osmostat
pregnancy
-volume expanded
-reset to new lower level
polydipsia
hyponatremia
lots of dilute urine
U-osm:P-osm
ratio of how concentrated urine is
SIADH
lung cancer
TB
lithium treatment
damages kidney and can’t concentrate urine
can lead to hypernatremia
may lead to nephrogenic diabetes insipidus
nephrogenic DI
high ADH but can’t respond
also high osmolality
neurogenic DI
low ADH levels
also high osmolality
desmopresin
exogenous ADH
can give via inhalation
-should work unless nephrogenic DI
extrarenal water loss?
sweating, fever, diarrhea, vomiting
-urine output low, circulating AVP high
hypernatremia
renal water loss
central or nephrogenic DI
hypernatremia
lithium mechanism?
inhibits V2 receptors
-no aquaporins in collecting duct
nephrogenic DI
hypercalcemia and hyperkalemia
also associated with nephrogenic DI
common causes of central DI?
head trauma
postpartum hypophysitis (can give steroids)
hypothalamus/pituitary tumor
other causes of SIADH?
TB CHF CNS issues intubation drugs
CHF?
initial hypovolemia
- activate RAAS and increased ADH
- ANP also high (senses high pressure)
- net effect: decreases excretion of Na and water
- RAAS and ADH overcome ANP
two more cases
look at them
