Hypokalaemia and Hyperkalaemia

Question 1

What controls potassium concentration in the serum?

Answer 1

1. Acid-base balance primarily

2. Catecholamines and insulin

Question 2

What happens to the serum potassium in acidosis and alkalosis?

Answer 2

Acidosis - hyperkalaemia

Alkalosis - hypokalaemia

Question 3

At what point is urgent treatment required for hypokalaemia?

Answer 3

<2.5mmol/L

Question 4

What metabolic disturbance could be causing these signs and symptoms?
Muscle weakness, hypotonia, hyperreflexia, cramps, tetany, palpitations, arrhythmias, constipation.

Answer 4

Hypokalaemia

Question 5

What are the ECG findings in hypokalaemia?

Answer 5

1. Small or inverted T-waves
2. Prominent U waves (after T waves)
3. Long PR
4. Depressed ST

Question 6

What are the causes of hypokalaemia?

Answer 6

1. Diuretics (thiazide) (high bicarbonate indicates long-standing hypokalaemia), vomiting, diarrhoea
2. Cushing’s/steroids
3. Conn’s syndrome (HTN, hypokalaemia, alkalosis, not on diuretics)
4. Alkalosis

Question 7

What might the other metabolic disturbance be in hypokalaemia which would make it difficult to correct?

Answer 7

Hypomagnesaemia

Question 8

What is the management for mild hypokalaemia?

Answer 8

Oral K+ supplements (Sando-K, 2 tablets/8h)

Question 9

What is the management for severe hypokalaemia?

Answer 9

IV K+ cautiously, no more than 20mmol/h and if not oliguric.

Question 10

At what point does hyperkalaemia need urgent emergency assessment and treatment?

Answer 10

> 6.5mmol/L or if there are ECG changes

Question 11

What metabolic disturbance might be causing these signs and symptoms?
Fast, irregular pulse. Chest pain, weakness, palpitations are worrying.

Answer 11

Hyperkalaemia

Question 12

What are the ECG findings in hyperkalaemia?

Answer 12

1. Tall tented T-waves
2. Wide QRS
3. Flattened P-waves

Question 13

What are the causes of hyperkalaemia?

Answer 13

1. Oliguric renal failure
2. K-sparing diuretics
3. Rhabdomyolysis
4. Metabolic acidosis
5. Addison’s disease
6. Massive blood transfusions
7. Burns
8. Artefactual result - haemolysis, contamination with EDTA in FBC bottles, delayed analysis

Question 14

What is the management for hyperkalaemia (ECG abnormal/K+ >6.5)?

Answer 14

1. 10ml of 10% calcium chloride (30ml of 10% calcium gluconate) IV into big vein - cardioprotective
2. 10U of insulin in 50ml of 50% dextrose over 30 mins.
3. Definitive treatment requires K+ removal - discontinue ACEi, sodium bicarbonate if acidotic.