Hyponatraemia

Question 1

does hyponatraemia imply Na+ depletion?

Answer 1

Not necessarily as hyponatraemia may be due to sodium depletion or wter excess

Question 2

how do you diagnose hyponatraemia?

Answer 2

combination of urinary sodium and osmolality levels

Question 3

what is plasma Na controlled by?

Answer 3

Plasma water

Question 4

what is plasma water controlled by?

Answer 4

ADH

Question 5

where is ADH released?

Answer 5

posterior pituitary

Question 6

what symptoms do you get with severe hyponatraemia

why do you get these symptoms?

Answer 6

headache
confusion
reduced GCS
seizures

low Na –> wet brain –> ^ICP –> these symptoms

Question 7

Causes of hyponatraemia can be wet or dry

wet - hypervolaemic - water excess - examples?

dry - hypovolaemic - dehydrated/Na depletion - examples?

Answer 7

wet - HF/liver failure/kidney failure/

dry - D&V/diuretics/addison’s

Question 8

what is addison’s

Answer 8

hypovolaemic and dehydrated

non-production of cortisol/aldosterone

hyper-pigmentation of skin

Question 9

Tx of Hyponatraemia - in terms of fluids - what do you give the following?

if chronic,asymptomatic?

if acute, symptomatic?

Answer 9

chronic = low and slow using resus fluid 10mM/day

acute = 1mM/hr of normal 0.9% saline

resus fluid contains more concentrated Na and CL - which would be dangerous in acute setting as you don’t want to replace too quickly.

Question 10

Tx of Hyponatraemia

1) Chronic Asymptomatic Hyponatraemia
- if fluid restriction isn’t sufficient, what else can be given?

2) Acute Symptomatic Hyponatraemia
a) if due to Na depletion?
b) if due to water excess?

Answer 10

1) Demeclocycline (ADH antagonist)
2) a) dry (D&V) cautious rehydration with 0.9% saline - don’t correct too quickly due to central pontine myelinolysis complication
b) water excess (HF) - give furosemide to prevent fluid overload

give furosemide over thiazides as furosemide works on loop of henle so causes mainly water loss but thiazide work on distal tubule so cause Na loss as well.

Question 11

when can you give Vaptans (vasopressor receptor antagonists) in hyponatraemia?

Answer 11

if hypervolaemic or euvolaemic as promote water excretion without loss of electrolytes

Question 12

in emergency setting (seizures/coma) what is the Tx?

aim for gradual increase but beware of?

Answer 12

hypertonic saline (1.8% saline) w/ furosemide

• Aim for gradual increase but beware of heart failure and central pontine myelinolysis.

Question 13

what is central pontine myelinolysis?

reversible?

when does it occur?

Dx?

Symptoms?

Answer 13

demyelination syndrome caused by rapid correction of hyponatraemia

irreversible

occurs 2-6 days after Na changes are made

Dx = MRI brain

Present with quadriparesis + bulbar palsy