Lecture 4 Natremias Flashcards
the body controls tonicity by controlling ____
Na
an acute decrease in plasma osmolality causes water to move where?
into the cell (cell swelling)
what part of the body is most susceptible to increases in cell size?
brain (encased in skull)
ADH is secreted in response to ____ or ____
increased plasma osmolarity or decreased blood volume
is hyponatremia usually due to an excess of water or a deficit in Na?
excess of water (due to defect in renal excretion usually)
pseuodhyponatremia can be due to a marked elevation in ____ or ____
protein (ie multiple myeloma), lipids
an increase in glucose can cause ____natremia by causing osmotic translocation of water to plasma
hypo
symptoms of acute hyponatremia:
cerebral ____, seizures, coma, respiratory _____, pulm edema
swelling, arrest
SIADH is characterised by excessive free water _____. this causes a euvolemic ____natremia with continued urinary ___ excretion
retention;
hypo;
Na+
SIADH:
urine osmol is _____ than plasma osmol
greater (ADH causes reabsorption)
Most common cause of ectopic ADH?
small cell carcinoma
Other causes of SIADH:
____ trauma, ____ disease, and drugs such as ____ and SSRIs
head;
pulmonary,
cyclophosphamide
increasing serum Na too fast in treatment of SIADH can cause what
osmotic demyelination syndrome aka central pontine meylinolysis
ie dysarthria, dysphagia, quadriparesis, coma, seizure
conivaptan and tolvaptan are ____
ADH antagonists
which receptors do ADH antagonists bind to? where are these located?
V2;
collecting duct
mainstay of treatment of SIADH:
fluid restriction
3 general causes of polyuria
primary polydipsia (psychogenic), central DI, Nephrogenic DI
central DI:
ADH levels?
2 most common causes?
low;
pituitary tumor or trauma
also autoimmune, surgery
Nephrogenic DI:
ADH levels?
what 2 drugs can cause it?
normal or high; problem is V2 receptor
lithium (Most commonly) or demeclocycline
how do you distinguish between Central DI and Nephrogenic DI?
water deprivation test
do most patients with hypernatremia have a water deficit or an excess of Na?
water deficit
the neuronal response to hypernatremia is to release new osmoles into the ___, preventing a rapid reduction in ____
cell, cell volume
should acute hypernatremia be corrected quickly or gradually?
quickly ie within 24-35 hours
this condition is rare tho
should chronic hypernatremia be corrected quickly or gradually?
gradually to reduce risk of cerebral edema
