General - Potassium

Question 1

1) Hyperkalemia is a serum potassium of what?
2) What effect does hyperkalemia have on the membrane potential?

Answer 1

1) >5.5mmol/L
2) Hyperkalaemia results in a decrease in the resting membrane potential, which decreases the threshold potential for an action potential which initially makes cells hyperexcitable

Question 2

1) Name 2 conditions that can cause hyperkalemia
2) Name 2 medications that can cause hyperkalemia

Answer 2

1) AKI, CKD, metabolic acidosis, rhabdomyolysis, adrenal insufficiency (Addison’s), tumour lysis syndrome
2) Aldosterone antagonists (spironolactone and eplerenone), ACE inhibitors, ARBs, NSAIDs, potassium supplements

Question 3

Name 2 ECG signs associated with hyperkalemia

Answer 3

• Tall, peaked T waves
• Flattening or absence of P waves
• Broad QRS complexes

Question 4

What is the main complication associated with hyperkalemia?

Answer 4

Cardiac arrhythmias such as ventricular fibrillation

Question 5

1) What is given to stabilise cardiac muscle cells?
2) What can be given to drive potassium into cells?
3) Name another option for lowering serum potassium

Answer 5

1) Calcium gluconate
2) Insulin, dextrose, nebulised salbutamol
3) IV fluids, oral calcium resonium, sodium bicarbonate, dialysis

Question 6

Hypokalaemia is defined as serum potassium concentration of what?

Answer 6

<3.5mmol/L

Question 7

1) Name a renal cause of hypokalemia
2) Name an extra-renal cause of hypokalemia

Answer 7

1) Diuretics, renal tubular acidosis, Bartter’s, Liddle’s and Gitelman’s syndromes, Conn’s syndrome (primary hyperaldosteronism), hypomagnesaemia
2) Inadequate oral intake, gut losses i.e. diarrhoea, vomiting, ileostomy, Zollinger-Ellison syndrome, re-distribution into cells i.e. beta agonists, insulin, theophylline, alkalosis