[Endo] Hyponatraemia

Question 1

for pts in hospital, what is any degree of hyponatraemia associated with?

Answer 1

increased mortality

Question 2

what is the 1st line ix for hyponatraemia?

Answer 2

paired osmolalities (serum and urinary)

Question 3

what should be tested to confirm true hyponatraemia?

Answer 3

paired osmolalities and blood glucose

Question 4

what is the largest cause of hyponatraemia and so, what should be done?

Answer 4

drugs → medication reviews should be taken out

Question 5

what directs the likely cause of hyponatraemia?

Answer 5

the fluid status of the pt

• hypovolaemia
• euvolaemia
• hypervolaemia

Question 6

what are the hypovolaemic causes leading to hyponatraemia?

Answer 6

• medication related

- hypovolaemia from poor intake or increased insensible losses

Question 7

what are the euvolaemic causes leading to hyponatraemia?

Answer 7

SIADH

Question 8

what are the hypervolaemic causes leading to hyponatraemia?

Answer 8

heart, liver and kidney failure

Question 9

what are the sx of hyponatraemia?

Answer 9

• confusion
• altered GCS
• headaches
• seizures
• encephalopathy

Question 10

you find that the pt has serum sodium <130mmol/L, what do you do next?

Answer 10

stop any sodium lowering drugs (diuretics, SSRIs, ACEi)

Question 11

pt has serum sodium <130mmol/L, presenting acutely + symptomatic. what do you do next?

Answer 11

3% hypertonic saline

under higher level care with 6 hourly sodium monitoring

Question 12

pt has serum sodium <130mmol/L, but not presenting acutely and not symptomatic. what do you do next?

Answer 12

assess fluid status

Question 13

after assessing fluid status you find that the pt is hypovolaemic. what do you do next?

Answer 13

normal saline infusion

Question 14

after assessing fluid status you find that the pt is euvolaemic. what do you do next?

Answer 14

check urinary sodium

Question 15

after checking urinary sodium on the euvolaemic pt, you find that the urinary sodium is >20. what do you do next?

Answer 15

fluid restriction

Question 16

after checking urinary sodium on the euvolaemic pt, you find that the urinary sodium is <20 (normal). what do you do next?

Answer 16

re-assess fluid status and consult endocrinology

Question 17

after assessing fluid status you find that the pt is hypervolaemic. what do you do next?

Answer 17

treat underlying cause (cardiac, liver or renal failure)

Question 18

what is SIADH caused by?

Answer 18

overproduction of ADH in the posterior pituitary

Question 19

what happens in SIADH?

Answer 19

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

Question 20

what are the causes of SIADH?

Answer 20

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)

Question 21

what is a normal urinary sodium level?

Answer 21

<20 mmol/L

Question 22

what do high urinary sodium levels diagnosed in euvolaemic pts represent?

Answer 22

high renal losses of sodium

Question 23

how do you treat SIADH?

Answer 23

fluid restriction for rx

and daily U+Es to monitor overcorrection

Question 24

what can be considered for refractory cases of SIADH under specialist guidance?

Answer 24

Tolvaptan, a selective ADH receptor 2 antagonist

Question 25

sudden decline in GCS after correcting hyponatraemia. dx?

Answer 25

osmotic demyelination syndrome

Question 26

polydipsia, normal glucose and high end of normal sodium. dx?

Answer 26

diabetes insipidus

Question 27

large hands and jaw, bitemporal hemianopia. dx?

Answer 27

pituitary tumour with acromegaly

Question 28

what should be given if the pt is acutely symptomatic from hyponatraemia?

Answer 28

hypertonic saline in higher level care is 1st line

Question 29

how is SIADH treated?

Answer 29

treating the underlying causes whilst fluid restricting the pt