Hyperkalaemia

This is what happens when a body of water becomes incredibly hyperkalaemic very rapidly. Well, if you chuck a big enough block of potassium at a body of water of any significant size.

Definition

Serum potassium >5mmol/L, >6.5mmol/L is severe

Epidemiology

Pathophysiology

Your potassium goes up. The most important cause is oliguric acute renal failure where potassium is not filtered out properly. Other causes:

• Burns
• Excess K⁺ therapy
• Potassium-sparing diuretics
• Addison's disease
• Rhabdomyolysis
• Metabolic acidosis
• Massive blood transfusion
• Drugs - ACEi, suxamethonium

Also, remember that it can be an artefact from haemolysed blood, particularly if there's a delay. Don't go whacking calcium gluconate and insulin into people where you've just left the blood on the side for a bit too long. Muppet.

Clinical Features

The key ones is arrhythmias which can lead to sudden death. It's important. Don't led people suddenly die. That's bad.

Investigations

• U+E - hopefully, you've done this already
• ECG - the arrhythmias can cause death so it's important to be able to interpret an ECG that suggests hyperkalaemia.
  • Tall tented T waves
  • small P wave
  • wide QRS (possibly sinusoidal i.e. S-shaped)
  • VF

Management

Generally, you need to treat the underlying cause. However, if their hyperkalaemia is severe (K⁺ >6.5mmol/L), you need to start doing emergency treatment.

Severe hyperkalaemia

Medical Emergency - Severe hyperkalaemia can lead to VF so treat it!

These things need to be done in this order as this list is in order of importance.

1. Calcium gluconate 10ml (10%) iv 2min - it is cardioprotective but does not effect serum potassium
2. Insulin + glucose - e.g. 20 units soluble insulin + 50ml glucose 50% iv. The insulin moves K⁺ into cells and out of plasm
3. Nebulised salbutamol - this also moves K⁺ into cells.

Then, there's some slightly less important stuff:

• Polystyrene sulfonate resin - Calcium Resonium 15g/8h in water
• Dialysis