U+E

Question 1

Causes of hyponatraemia

Answer 1

Hypovolaemic causes: thiazide diuretics, Addion’s, vomiting, diarrhoea.
Euvolaemic causes: SIADH, hypothyroidism, fluid replacement therapy e.g. 5% dextrose, AKI.
Hypervolaemic causes: heart failure, nephrotic syndrome, cirrhosis –> ascites.

Question 2

Low sodium, low potassium differentials.

Answer 2

Vomiting, diarrhoea.

Question 3

Low sodium, high potassium differentials

Answer 3

Addisonian crisis.

Congenital adrenal hyperplasia / salt wasting crisis.

Question 4

Other tests to consider if cause of hyponatraemia is SIADH

Answer 4

Urine osmolality (high)
Urine sodium (high)
Plasma osmolality (low)
Visual field testing.

Question 5

Causes of hyperkalaemia

Answer 5

Renal causes: Addisonian crisis, congenital adrenal hyperplasia + salt wasting crisis, AKI, chronic kidney disease.
Medication: Spironolactone, ARB, ACE inhibitors, digoxin.
Non-renal causes: DKA, tumour lysis syndrome, metabolic acidosis, rhabdomyolysis.

Question 6

Electrolyte abnormalities in tumour lysis syndrome

Answer 6

Low calcium
High phosphate
High potassium
High urea

Question 7

ECG of hyperkalaemia

Answer 7

Peaked T waves
Absent P eaves
Broad QRS
Sine wave pattern
VT

Question 8

Cause of hypokalaemia

Answer 8

Renal: Conn’s (hyperaldosteronism), secondary hyperaldosteronism from renal artery stenosis, ectopic renin, oedematous state/ascites, renal tubular acidosis.
Non-renal causes: vomiting, diarrhoea, low magnesium, DKA.
Meds: Loop diuretics.

Question 9

What would you see on ABG of Conn’s and why?

Answer 9

Metabolic alkalosis.
Aldosterone increases water retention. Efflux of K+ from intracellular to extracellular space in exchange for H+, increases pH and H+ secretion in the kidney in order to enable more K+ reabsorption.

Question 10

Dehydration clues

Answer 10

urea raised more than creatinine

Question 11

What does the urine osmolality tell us about renal function

Answer 11

Whether they are able to concentrate urine and effectively re-absorb and secrete ions.