Electrolyte abnormalities

Question 1

Hyperkalaemia is defined as what?

Answer 1

When blood potassium levels are >5.5mmol/L.

Question 2

Name 5 causes of hyperkalaemia.

Answer 2

1) Spurious: sample haemolysed or taken from limb with IVI containing Potassium.
2) Reduced renal excretion: AKI, patients with CKD, patients on dialysis with K+ load, potassium sparing diuretics.
3) Cell injury: crush injury, causes of rhabdomyolysis, burns, tumour cell necrosis, large or incompatible blood transfusion.
4) K+ cellular shifts: acidosis from any cause (e.g. DKA) or drugs (suxamethonium/ beta blockers).
5) Hypoaldosteronism: Addison’s disease or drug induced (NSAIDs/ ACE inhibitors).

Question 3

Give 4 clinical features of hyperkalaemia.

Answer 3

1) Weakness/ cramps
2) Paraesthesiae
3) Hypotonia
4) Focal neurological deficits

**Dangerous hyperkalaemia can be asymptomatic.

Question 4

Give 4 ECG changes which can occur as a result of hyperkalaemia.

Answer 4

1) Tall tented (peaked) T waves
2) Small, broad or absent P waves.
3) Widening QRS complex
4) Sine wave pattern
5) AV dissociation or VT/VF.

Question 5

What three methods of management should be used for a patient with severe hyperkalaemia or moderate hyperkalaemia with ECG changes?

Answer 5

1) 10mL or 10% Calcium Chloride/ Calcium gluconate slowly IV (over 5 mins).
2) 10 units short acting human soluble insulin with 50mL 50% glucose IV.
3) 5mg nebuliser salbutamol, repeated once as necessary.

**Look for and treat underlying cause.

Question 6

1) In which patients does calcium gluconate/ calcium chloride need to be given more slowly?
2) How should volume deficits or acidosis associated with hyperkalaemia be treated?

Answer 6

1) Patients taking digoxin. Give over 30 minutes instead as hypercalaemia could potentiate digoxin toxicity in these patients.
2) IV fluids and sodium bicarbonate.

Question 7

What management is required for a patient with moderately severe hyperkalaemia, without ECG changes?

Answer 7

10 units of short-acting human soluble insulin in 50mL of 50% glucose IV over 15-30 minutes.

**Look for and treat underlying cause. Consider diuretics or dialysis.

Question 8

How should mild hyperkalaemia be managed?

Answer 8

Treat underlying cause and any associated hypovolaemia.

Question 9

Give the ranges for the following severities of hyperkalaemia:

a) severe
b) moderate
c) mild

Answer 9

a) >7.0 mmol/L
b) 6.1 - 6.9 mmol/L
c) 5.5 - 6 mmol/L

Question 10

1) What is hypokalaemia defined as?
2) What can moderate hypokalaemia result in?
3) What can severe hypokalaemia cause (K+ <2.5mmol/L)?
4) What ECG changes can be seen in patients with hypokalaemia?

Answer 10

1) K+ <3.5mmol/L
2) Lethargy, weakness and leg cramps.
3) Rhabdomyolysis and respiratory difficulties.
4) Prominent U waves and flattened T waves.

Question 11

1) What is the maximum recommended infusion rate of Potassium?
2) What should more rapid rates of Potassium infusion (20mmol over 20-30 minutes) be reserved for?
3) Many patients with Potassium deficiency are also usually deficient in what?

Answer 11

1) 20mmol/ hour.
2) For patients who have unstable arrhythmias where cardiac arrest is imminent (senior, expert help should be obtained).
3) Magnesium (consider replacing Mg in patients with severe hypokalaemia).