Hyperkalaemia

Question 1

What is hyperkalaemia?

Answer 1

Hyperkalaemia is defined as a serum potassium level greater than 5.5 mmol/L. It is a medical emergency due to the risk of life-threatening arrhythmias.

Question 2

What are the common causes of hyperkalaemia?

Answer 2

Common causes include renal impairment (acute or chronic), medications (e.g., ACE inhibitors, potassium-sparing diuretics), tissue damage (e.g., burns, rhabdomyolysis), metabolic acidosis (e.g., diabetic ketoacidosis), and endocrine disorders (e.g., Addison’s disease).

Question 3

What are the typical symptoms of hyperkalaemia?

Answer 3

Symptoms may include palpitations, muscle weakness, fatigue, and in severe cases, cardiac arrhythmias. However, hyperkalaemia can often be asymptomatic and detected incidentally on blood tests.

Question 4

How is hyperkalaemia diagnosed?

Answer 4

Diagnosis is based on serum potassium levels greater than 5.5 mmol/L. An electrocardiogram (ECG) is essential to assess for characteristic changes associated with hyperkalaemia.

Question 5

What ECG changes are associated with hyperkalaemia?

Answer 5

ECG changes may include tall, tented T waves, prolonged PR interval, widened QRS complexes, and in severe cases, a sine wave pattern leading to ventricular fibrillation or asystole.

Question 6

What is the initial management of severe hyperkalaemia?

Answer 6

Immediate management includes stabilising the myocardium with intravenous calcium gluconate, shifting potassium intracellularly using insulin with dextrose, and considering nebulised salbutamol.

Question 7

How does insulin with dextrose help in hyperkalaemia?

Answer 7

Insulin facilitates the uptake of glucose into cells, bringing potassium along with it, thereby reducing serum potassium levels. Dextrose is administered to prevent hypoglycaemia.

Question 8

What role does salbutamol play in treating hyperkalaemia?

Answer 8

Salbutamol, a β2-adrenergic agonist, stimulates cellular uptake of potassium, lowering serum potassium levels. It is typically administered via nebuliser.

Question 9

Why is it important to identify and treat the underlying cause of hyperkalaemia?

Answer 9

Addressing the underlying cause is crucial to prevent recurrence and to manage any associated conditions contributing to hyperkalaemia.

Question 10

What medications should be reviewed or discontinued in hyperkalaemia?

Answer 10

Medications that can increase serum potassium, such as ACE inhibitors, angiotensin II receptor blockers, potassium-sparing diuretics, and NSAIDs, should be reviewed and discontinued if appropriate.

Question 11

How is mild hyperkalaemia managed?

Answer 11

In mild cases without ECG changes, management includes dietary potassium restriction, correction of underlying causes, and the use of potassium-binding resins if necessary.

Question 12

What is the role of sodium bicarbonate in hyperkalaemia management?

Answer 12

Sodium bicarbonate may be considered in cases of hyperkalaemia associated with metabolic acidosis, as it can help shift potassium into cells. However, its use is controversial and should be guided by clinical judgment.

Question 13

How does renal impairment contribute to hyperkalaemia?

Answer 13

The kidneys are responsible for potassium excretion. Renal impairment reduces this ability, leading to accumulation of potassium in the blood.

Question 14

What dietary advice should be given to patients with hyperkalaemia?

Answer 14

Patients should be advised to limit intake of high-potassium foods, such as bananas, oranges, tomatoes, and potatoes, to help manage serum potassium levels.

Question 15

Why is hyperkalaemia considered a medical emergency?

Answer 15

Hyperkalaemia can lead to life-threatening cardiac arrhythmias, making prompt recognition and treatment essential.

Question 16

What is pseudohyperkalaemia, and how is it identified?

Answer 16

Pseudohyperkalaemia is a falsely elevated serum potassium level, often due to haemolysis during blood sample collection. It is identified by the absence of clinical signs and symptoms of hyperkalaemia and normal repeat potassium levels with proper sampling techniques.

Question 17

How does metabolic acidosis lead to hyperkalaemia?

Answer 17

In metabolic acidosis, hydrogen ions enter cells in exchange for potassium ions, leading to an increase in serum potassium levels.

Question 18

What is the significance of tall, tented T waves on an ECG?

Answer 18

Tall, tented T waves are an early ECG sign of hyperkalaemia, indicating increased potassium levels affecting cardiac conduction.

Question 19

How can hyperkalaemia be prevented in at-risk patients?

Answer 19

Prevention strategies include regular monitoring of serum potassium levels, cautious use of potassium-elevating medications, dietary modifications, and management of underlying conditions such as renal impairment.

Question 20

What is the role of dialysis in hyperkalaemia management?

Answer 20

Dialysis is considered in severe or refractory hyperkalaemia, especially in patients with renal failure, to rapidly remove potassium from the bloodstream.

Question 21

How does Addison’s disease cause hyperkalaemia?

Answer 21

Addison’s disease involves adrenal insufficiency, leading to decreased aldosterone production. Aldosterone promotes renal potassium excretion; thus, its deficiency results in hyperkalaemia.

Question 22

What are potassium-binding resins, and when are they used?

Answer 22

Potassium-binding resins, such as sodium polystyrene sulfonate, bind potassium in the gastrointestinal tract, facilitating its excretion. They are used in the management of hyperkalaemia, particularly when other measures are insufficient.

Question 23

How does rhabdomyolysis lead to hyperkalaemia?

Answer 23

Rhabdomyolysis involves the breakdown of muscle tissue, releasing intracellular potassium into the bloodstream, leading to hyperkalaemia.

Question 24

What is the significance of a widened QRS complex in hyperkalaemia?

Answer 24

A widened QRS complex on an ECG indicates more severe hyperkalaemia and an increased risk of progressing to ventricular arrhythmias or asystole.

Question 25

Why should calcium administration be used cautiously in digoxin toxicity with hyperkalaemia?

Answer 25

In digoxin toxicity, calcium administration can exacerbate myocardial instability, potentially leading to “stone heart” or asystole. Therefore, it should be used with caution, and alternative treatments should be considered.