Potassium and Electrolytes

Question 1

What is the serum concentration for normal potassium?

Answer 1

3.5-5 mmol/L

Question 2

What is potassium regulated by?

Answer 2

Angiotensin II and aldosterone

Question 3

What does aldosterone contribute in terms of electrolyte balance?

Answer 3

Aldosterone is stimulated by Angiotensin II and K+

Aldoesterone causes resorption of sodium and the excretion of K+ in the urine

Question 4

What are the main causes for hyperkalaemia?

Answer 4

Renal failure: Reduced GFR resulting in excretion of K+ and thus increased K+. Also hyponatreamia because less water excretion.

Decreased Renin

ACE Inhibitor: Less conversion

Angiotensin II Receptor Blocker e.g. Losartan- leading to less aldosterone release.

Addison’s Disease: Next is damage to the adrenal gland e.g. Addison’s.

Aldosterone antagonist e.g. Spironolactone.

Rhabdomyolysis

Acidosis

Question 5

What are the main causes of hyperkalaemia?

Answer 5

Renal impairement – reduced renal excretion

Drugs: ACE inhibitors, ARBS, spironolactone

Low aldosterone: Addison’s disease, Type 4 renal tubular acidosis (low renin, low aldosterone), release from cells e.g. rhabdomyolysis, acidosis

Question 6

What are ECG changes with hyperkalaemia?

Answer 6

peaked T waves, broad QRS due to hyperkalaemia

Question 7

What is the treatment for hyperkalaemia?

Answer 7

No treatment until ECG changes and K+ is above 6.5

Treat underlying cause

10ml 10 % calcium gluconate to stabilise cardiac myocardium

100ml 20% dextrose with 10 units insulin bolus

(Nebulized salbutamol)

Question 8

What are causes of hypokalaemia?

Answer 8

GI loss e.g. vomiting

Renal Loss: Diuretics, High Aldosterone and excess cortisol e.g. Cushings, Increased sodium delivery to distal nephron, Osmotic diuresis e.g. diabetes

Redistribution into the cells: Insulin, beta agonsits, alkalosis

Rare causes: Renal tubular cidosis type 1 % 2, hympomagnesaemia.

Question 9

What are the clinical features of hypokalaemia?

Answer 9

Nephrogenic diabetes insipidus- resistant to ADH-
polyuria and polydipsia.

Muscle weakness

Arrhythmia

Question 10

How do you manage hypokalaemia?

Answer 10

Serum potassium 3.0-3.5 mmol/L: Oral potassium chloride (two SandoK tablets tds for 48 hrs)

Recheck serum potassium

Serum potassium < 3.0 mmol/L: IV potassium chloride, maximum rate 10 mmol per hour (Rates > 20 mmol per hour are highly irritating to peripheral
veins)

Treat the underlying cause e.g. spironolactone

Question 11

Which drug can cause hyperkalaemia?

Answer 11

Ramipril

Question 12

Which drug can cause hypokalaemia?

Answer 12

Furosemide