Potassium imbalance

Question 1

Normal range of potassium

Answer 1

3.5-5.3

Question 2

Aetiology of hyperkalaemia

Answer 2

Renal impairment (reduced renal excretion)
Drugs: ACEi, ARBs, spironolactone, NSAIDs
Low aldosterone
- Addison’s disease
- T4 renal tubular acidosis (low renin, low aldosterone)
Release from cells: rhabdomyolysis, acidosis

Question 3

Investigations for hyperkalaemia

Answer 3

ECG:
1. Peaked T waves
2. Broad QRS
3. Flat P-wave
4. Prolonged PR + bradycardia
5. Sine wave, Torsades de pointes

VBG, U&Es

Question 4

Management for hyperkalaemia

Answer 4

1. 10ml 10% calcium gluconate (stabilise the heart)
2. 100ml of 20% dextrose (Previously 50ml 50% dextrose) (must be given together)
3. 10U insulin (must be given together)
4. Nebulised salbutamol - drives potassium into the cell
5. Bicarbonate infusion to correct any acidosis
6. Potassium exchange resin (calcium resonium/zirconium)
7. Dialysis
8. Treat the underlying cause

Monitor bloods every 30-40mins

Question 5

Aetiology of hypokalaemia

Answer 5

GI losses (diarrhoea, vomiting, fistulas)
Renal loss
- Conn’s (Hyperaldosteronism), Cushing’s
- Bartter syndrome, thiazide/loop diuretics (increased Na+ delivery to DCT)
- Hyperglycaemia (osmotic diuresis)
Redistribution into cells
- Insulin/insulinomas
- beta-agonists
- Alkalosis
Rare causes
- Hypomagnesaemia
- Renal tubular acidosis T1, T2

Question 6

Clinical features of hypokalaemia

Answer 6

Muscle weakness
Cardiac arrhythmias
Polyuria and polydipsia (nephrogenic DI from low K+ or a high Ca2+)

Question 7

Investigations for hypokalaemia

Answer 7

ECG: ST depression, flat T-waves, U waves
Aldosterone: Renin ratio (High in Conn’s)
VBG, U&Es

Question 8

Management for mild hypokalaemia

Answer 8

> 3
Oral KCl: 2 SandoK tablets, TDS, 48 hours
Recheck K+

Question 9

Management for severe hypokalaemia

Answer 9

<3
IV KCl
Maximum rate 10mmol/hour (rate >20mmol/hour → irritate peripheral veins)