Electrolytes

Question 1

Normal serum potassium

Answer 1

3.5 - 5.5

Question 2

Approach to hyponatraemia?

Answer 2

Do serum osmolality

low < 280: hypotonic hypo Na

• check volume status - is patient dehydrated?

→ yes, hypovolaemic: do urine sodium
> Una <10 = extrarenal salt loss: dehydration, diarrhoea, vomiting, burus
> Una > 20 = renal salt loss: diuretics, ace I, nephropathy, Addisons,

→ no, euvolaemic
> siadh
> hypothyroid
> exercise.

→ no, oedematous, hypervolaemic
> heart failure
> liver disease
> nephrotic syndrome, advanced kidney disease

Normal 280 - 295 = isotonic hypo Na

• hyper proteinaemia
• hyper lipidaemia

High > 295 = hypertonic hypo Na,

• hyperglycaemia
• mannitol, sorbitol, glycerol, maltose,
• radio contrast agents