Potassium

Question 1

What is the normal range for potassium?

Answer 1

3.5-5.3 mmol/l

Question 2

What hormones are released after a high potassium load?

Answer 2

Aldosterone –> Increases renal excretion

Catecholamine (including beta agonists) –> Uptake into cells via NA/K ATPase (skeletal muscle)

Insulin –> Uptake into cells via NA/K ATPase (skeletal muscle, liver, adipose tissue)

Question 3

Over active RAAS leads to hypokalaemia.

What elevated hormone do each of these conditions produce to lead to over active RAAS…

1) Conn’s
2) Cushing’s
3) Renal artery stenosis

Answer 3

1) Aldosterone
2) Cortisol (acts as a mineralcorticoid)
3) Renin (1st responder to under-perfusion)

Question 4

Under active RAAS leads to hyperkalaemia.

What things can cause this?

Answer 4

1) Adrenal insufficiency (addison’s)
2) ACE inhibitors
3) Spironolactone

Question 5

What does hyperkalaemia occur in a metabolic acidosis?

Answer 5

EXTRA-RENAL –> Hydrogen and potassium ions compete for the intracellular movement (i.e. via H/Na pump and K/Na pump).
Body prioritises acid/base homeostasis over potassium homeostasis.

RENAL –> Hydrogen ions block potassium excretion therefore ECF potassium rises (i.e. K is NOT excreted in urine)

Question 6

What are the ECG changes of hyperkalaemia?

Answer 6

Tall T waves
Loss of P wave
Broad QRS complex
Prolonged PR interval

Question 7

What are some causes of hyperkalaemia?

Answer 7

Renal Failure (CKD)
Mineralocorticoid deficiency (Addison's) 
Acidosis
Insulin deficiency
Crush injury, haemolysis tumour lysis
ACEi, ARBs
Potassium-sparing diuretics

Question 8

What is the acute management of hyperkalaemia?

Answer 8

1) Calcium gluconate –> Cardioprotection
2) Redistribution –> Glucose + insulin, b-agonist, bicarbonate
3) Removal –> Loop diuretic (eg furosemide, bumetanide), ion-exchange resins, dialysis/haemofiltration

Question 9

What are the causes of hypokalaemia?

Answer 9

Fistula
Diarrhoea
Loop diuretics
Renal tubular acidosis
Mineralocorticoid excess (Conn's and Cushing's)
Insulin
Alkalosis
Salbutamol

Question 10

What are the ECG changes of hypokalaemia?

Answer 10

1) Flattened T wave becoming T wave inversion
2) ST depression
3) Prominent P wave and prolonged PR interval
4) U waves V2-4
5) Torsades de points

Question 11

What happens to potassium concentration in the following situations….

1) Diabetic ketoacidosis
2) Primary hyperaldosteronism
3) Adrenal insufficiency
4) Renal tubular acidosis

Answer 11

1) DKA –> Increases
2) Primary hyperaldosteronism –> Decreases, Na decreases too
3) Adrenal insufficiency –> Increases
4) RTA –> Decreases

Question 12

What happens to potassium concentration in the following situations….

1) Salbutamol infusion
2) Rhabdomyolysis
3) Delayed arrival (>8h) of sample to laboratory

Answer 12

1) Salbutamol infusion –> Decreases
2) Rhabdomyolysis –> Increases (Due to myoglobin in blood causing kidney damage)
3) Delayed arrival (>8h) of sample to laboratory –> Increases