Renal: Potassium & Sodium

Question 1

What is the main complication of hyperkalaemia?

Answer 1

cardiac arrhythmias, such as ventricular fibrillation, which can lead to cardiac arrest.

Question 2

Define potassium levels:

1) normal

2) mild hyperkalaemia

3) mod hyperkalaemia

4) severe hyperkalaemia

Answer 2

1) 3.5 - 5.3 mmol/L

2) 5.4 - 6

3) 6 - 6.5

4) over 6.5

Question 3

Give 6 causes of hyperkalaemia

Answer 3

1) AKI
2) CKD (stage 4 or 5)
3) Drugs e.g. ACEi, spironolactone
4) Tumour lysis syndrome
5) Adrenal insufficiency (Addison’s)
6) Rhabdomyolysis
7) Massive blood transfusion

Question 4

How can adrenal insufficiency (Addison’s diseas) cause hyperkalaemia?

Answer 4

Deficiency of aldosterone results in potassium retention

(aldosterone causes sodium to be absorbed and potassium to be excreted)

Question 5

How does rhabdomyolysis cause hyperkalaemia?

Answer 5

Causes AKI: following damage to the muscular sarcolemma sheath, resulting in the leakage of myoglobin and other metabolites that cause kidney damage.

Question 6

What medications can cause hyperkalaemia?

Answer 6

1) Aldosterone antagonists e.g. spironolactone, eplerenone

2) ACEi e.g. ramipril

3) Angiotensin II receptor blockers (e.g., candesartan)

4) NSAIDs

Question 7

What can cause pseudohyperkalaemia during sampling?

Answer 7

Haemolysis (rupture of blood cells) during sampling –> recommend a repeat sample.

Question 8

Give 4 ECG changes in hyperkalaemia

Answer 8

1) Tall tented T waves

2) Broad QRS complexes

3) Prolonged PR interval

4) Flattening or absence of P Waves

Question 9

In what 2 situations do patients require urgent treatment for their hyperkalaemia?

Answer 9

1) ECG changes

2) Serum potassium above 6.5 mmol/L

Question 10

Management of hyperkalaemia below 6.5 mmol/L without ECG changes?

Answer 10

Aimed at the underlying cause, for example, treating acute kidney injury and stopping medications (e.g., spironolactone or ACE inhibitors).

Question 11

What is the mainstay of treatment in hyperkalaemia (needing treatment)?

Answer 11

1) Insulin and dextrose infusion

2) IV calcium gluconate

Question 12

Purpose of insulin in hyperkalaemia?

Answer 12

Insulin drives potassium from the extracellular space to the intracellular space

Question 13

What is given alongside insulin in hyperkalaemia?

Why?

Answer 13

Dextrose is required to prevent hypoglycaemia while on insulin

Question 14

Role of calcium gluconate in hyperkalaemia?

Answer 14

Calcium gluconate stabilises the cardiac muscle cells and reduces the risk of arrhythmias

Question 15

Give 4 other options for lowering serum potassium?

Answer 15

1) Nebulised salbutamol: temporarily drives potassium into cells

2) Oral calcium resonium: reduces potassium absorption in the GI tract (this is slow and causes constipation)

3) Sodium bicarbonate: (in acidotic patients on renal advice) drives potassium into cells as it corrects the acidosis

4) Haemodialysis: may be required in severe or persistent cases

Question 16

Is hyperkalaemia associated with acidosis or alkalosis?

Answer 16

Metabolic acidosis

Question 17

What are some foods that are high in potassium?

Answer 17

1) salt substitutes (i.e. Contain potassium rather than sodium)

2) bananas, oranges, kiwi fruit, avocado, spinach, tomatoes

Question 18

Beta blockers in renal failure?

Answer 18

Beta-blockers interfere with potassium transport into cells and can potentially cause hyperkalaemia in renal failure patients

Remember beta-agonists, e.g. Salbutamol, are sometimes used as emergency treatment

Question 19

In hyponatraemia causes, what 3 tests should be ordered?

Answer 19

1) Urine osmolality
2) Plasma osmolality
3) Urinary sodium

Question 20

Give some causes of hyponatraemia with urinary sodium >20 mmol/l?

Answer 20

1. Sodium depletion, renal loss (patient often hypovolaemic):
   a) diuretics: thiazides, loop diuretics
   b) Addison’s disease
   c) diuretic stage of renal failure
2. Patient often euvolaemic:
   a) SIADH (urine osmolality > 500 mmol/kg)
   b) hypothyroidism

Question 21

Give some causes of hyponatraemia with urinary sodium <20 mmol/l?

Answer 21

1. Sodium depletion, extra-renal loss:
   a) diarrhoea, vomiting, sweating
   b) burns, adenoma of rectum
2. Water excess (patient often hypervolaemic and oedematous)
   a) secondary hyperaldosteronism: heart failure, liver cirrhosis
   b) nephrotic syndrome
   c) IV dextrose
   d) psychogenic polydipsia

Question 22

Give 4 causes of hypernatraemia

Answer 22

1) dehydration

2) osmotic diuresis e.g. hyperosmolar non-ketotic diabetic coma

3) diabetes insipidus

4) excess IV saline

Question 23

Hypokalaemia can be associated with alkalosis of acidosis.

Give some causes of hypokalaemia with alkalosis

Answer 23

1) vomiting
2) thiazide and loop diuretics
3) Cushing’s syndrome
4) Conn’s syndrome (primary hyperaldosteronism)

Question 24

Give some causes of hypokalaemia with acidosis

Answer 24

1) diarrhoea
2) renal tubular acidosis
3) acetazolamide
4) partially treated diabetic ketoacidosis