Hyperkalaemia

Question 1

Over what level is classed as:

• Mild
• Moderate
• Severe

Answer 1

> 5.5 mmol/L

> 6.0 mmol/L

> 6.5 mmol/L

Question 2

Hyperkalaemia means there is a reduced chemical gradient with the intracellular fluid (ICF).

This means there is less leakage of K from the ICF.

Why do cardiac and all muscle cells become more excitable initially?

What about later on?

Answer 2

Increased excitability

The early effect of mild hyperkalemia on myocyte function is to increase myocyte excitability by shifting the resting membrane potential to a less negative value and thus closer to threshold potential; but as potassium levels continue to rise, myocyte depression occurs and Vmax continues to decrease.

REMEMBER POTASSIUM IS +VE

In hyperkalemia, the resting membrane potential is decreased, and the membrane becomes partially depolarized. Initially, this increases membrane excitability. However, with prolonged depolarization, the cell membrane will become more refractory and less likely to fully depolarize.

Reduced excitability

https://www.youtube.com/watch?v=-32U9eU1hdM

Question 3

Causes:

Reduced potassium excretion:
- What type of organ failure causes this?

Why does acidosis cause hyperkalaemia?

Muscle breakdown can cause this. What is this called?

What type of diuretic causes this?

Answer 3

Kidney failure - AKI or CKD

A frequently cited mechanism for these findings is that acidosis causes potassium to move from cells to extracellular fluid (plasma) in exchange for hydrogen ions, and alkalosis causes the reverse movement of potassium and hydrogen ions

Rhabdomyolysis

K sparing diuretics

Question 4

S+S:

CV:

• They may be asymptomatic but have ECG changes!
• They get arrhythmias. What are some symptoms of this?

Neurological:
They have similar symptoms of having damage to a nerve. What 3 symptoms will they have?

Answer 4

Altered HR
Palpitations
Light-headed

Paraesthesia
Flaccid weakness
Hyporeflexia

Question 5

ECG changes:

Over what level do you get ECG changes?

What 3 core changes do you see? - think from P to T

Answer 5

> 6 mmol/L

Small P waves
Wide QRS waves
Tall tented T waves

Question 6

Investigations:

What would blood gas show?

What will be raised in rhabdomyolysis? - 2

Answer 6

Acidosis

A frequently cited mechanism for these findings is that acidosis causes potassium to move from cells to extracellular fluid (plasma) in exchange for hydrogen ions, and alkalosis causes the reverse movement of potassium and hydrogen ions

Calcium and CK

Question 7

Management:

What drugs should be stopped which could be causing it?

Mild to moderate:

• What is the patient advised?
• Calcium resonium can be given. What does it do?

Severe:

• At what level is severe?
• It is also classed as severe if there are ECG changes!
• What drug is given which is cardioprotective but will not resolve hyperkalaemia?
• Why are IV insulin and IV glucose given?
• What other resp drug can be used?
• What diuretic can be used, otherwise dialysis is needed?

Answer 7

ACEi
K-sparing diuretics
NSAIDs

Binds K in the gut and prevents absorption - brings it down in a few days

> 6.5 mmol/L

Calcium gluconate
Calcium chloride IV

Causes shift of K into cells

Salbutamol nebs - same mechanism as above!

Furosemide - all diuretics apart from potassium sparing!