[Endo] Hyponatraemia Flashcards
(29 cards)
for pts in hospital, what is any degree of hyponatraemia associated with?
increased mortality
what is the 1st line ix for hyponatraemia?
paired osmolalities (serum and urinary)
what should be tested to confirm true hyponatraemia?
paired osmolalities and blood glucose
what is the largest cause of hyponatraemia and so, what should be done?
drugs → medication reviews should be taken out
what directs the likely cause of hyponatraemia?
the fluid status of the pt
- hypovolaemia
- euvolaemia
- hypervolaemia
what are the hypovolaemic causes leading to hyponatraemia?
- medication related
- hypovolaemia from poor intake or increased insensible losses
what are the euvolaemic causes leading to hyponatraemia?
SIADH
what are the hypervolaemic causes leading to hyponatraemia?
heart, liver and kidney failure
what are the sx of hyponatraemia?
- confusion
- altered GCS
- headaches
- seizures
- encephalopathy
you find that the pt has serum sodium <130mmol/L, what do you do next?
stop any sodium lowering drugs (diuretics, SSRIs, ACEi)
pt has serum sodium <130mmol/L, presenting acutely + symptomatic. what do you do next?
3% hypertonic saline
under higher level care with 6 hourly sodium monitoring
pt has serum sodium <130mmol/L, but not presenting acutely and not symptomatic. what do you do next?
assess fluid status
after assessing fluid status you find that the pt is hypovolaemic. what do you do next?
normal saline infusion
after assessing fluid status you find that the pt is euvolaemic. what do you do next?
check urinary sodium
after checking urinary sodium on the euvolaemic pt, you find that the urinary sodium is >20. what do you do next?
fluid restriction
after checking urinary sodium on the euvolaemic pt, you find that the urinary sodium is <20 (normal). what do you do next?
re-assess fluid status and consult endocrinology
after assessing fluid status you find that the pt is hypervolaemic. what do you do next?
treat underlying cause (cardiac, liver or renal failure)
what is SIADH caused by?
overproduction of ADH in the posterior pituitary
what happens in SIADH?
overproduction of ADH → increases free water retention in the collecting ducts via aquaporins → dilutes blood → increases blood volume → reduces RAAS activation → increased excretion of sodium by the kidneys
what are the causes of SIADH?
SIADH:
S - surgery (unknown pathophysiology)
I - infection (lung / brain)
A - any brain pathology (haemorrhages, strokes)
D - drugs (PPIs, carbamezapine, SSRIs, anti-psychotics)
H - hormones (ectopic/paraneoplastic ADH secretion, hypothyroidism)
what is a normal urinary sodium level?
<20 mmol/L
what do high urinary sodium levels diagnosed in euvolaemic pts represent?
high renal losses of sodium
how do you treat SIADH?
fluid restriction for rx
and daily U+Es to monitor overcorrection
what can be considered for refractory cases of SIADH under specialist guidance?
Tolvaptan, a selective ADH receptor 2 antagonist
