Hyperkalaemia is defined as a serum potassium of greater than 5.5 mmol/l (may vary depending on local reference ranges), and whilst usually asymptomatic at relatively low levels, it is important to identify and treat the condition early due to cardiac and other complications that may arise


The most common causes of hyperkalaemia in the post-operative patient are:

  • Repeated blood transfusions
  • Drugs:
    • Potassium-Sparing Diuretics
    • Spironolactone
    • ACEi or ARBs
  • Excessive potassium treatment


A patient may commonly be asymptomatic; symptoms are rare in patients with a potassium serum concentration of less than 7.0mmol/l.

Any symptoms of hyperkalaemia that may present include non-specific pains, paraesthesia, muscle weakness, nausea and vomiting, and palpitations.

Assessment and Investigations

The assessment of any patient with hyperkalaemia needs to be timely and is often performed simultaneously with treatment. The initial investigations required are:

  • Bloods (FBC, U&Es CRP)
  • Venous blood gas (VBG)
    • A VBG will provide a quick check result of the patient’s potassium levels
  • ECG (as below)
  • Catheterisation if necessary (for fluid status)

The patients observations and fluid status should be reviewed, as well as their medication (identifying any precipitants of hyperkalaemia).

ECG Changes in Hyperkalaemia

Fig 1 - ECG findings in the precordial leads in hyperkalaemia

Fig 1 – ECG findings in the precordial leads in hyperkalaemia

The ECG is vital in the assessment of hyperkalaemia, ECG findings progressing with increasing serum levels.

Whilst the ECG findings generally can be correlated to the serum potassium concentration, potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalaemia.

  • Mild (5.5-6.5mmol)
    • Tall ‘tented’ T waves (seen across the precordial leads)
      Prolonged PR segment
  • Moderate (6.5-7.5mmol)
    • Decreased or ‘flattened’ P wave
      Prolonged QRS complex
  • Severe (>7.5mmol)
    • Progressive widening of the QRS complex
      Axial deviation and Bundle Branch Blocks

The progressively widened QRS eventually merges with the T wave, forming a sine wave pattern. Subsequent Ventricular Fibrillation (VF) or asystole may then follow.


The management of a hyperkalaemic patient can be considered in three parts:

  • Stabilisation of the myocardium
  • Reduction of serum potassium
  • Reduction of total body potassium

Whilst the rationale for the first and second management strategies may be self-evident, it is important to consider that the underlying cause for the hyperkalaemia must also be addressed.

Early and repeated blood testing is vital and any ECG changes warrant urgent treatment. Alert a senior to any complications developing.

Stabilisation of the Myocardium

A stat dose of IV Calcium Gluconate or Calcium Chloride (typically 10ml of 10%, dependent on local guidelines) should be started, instigated as soon as ECG changes are demonstrated.

Continuous cardiac monitoring is then required following this stabilisation treatment.

Reduction of Serum Potassium

Salbutamol nebulisers and / or variable rate insulin with dextrose infusion should be started (typically 200ml of 20% glucose with 10U of insulin over 30mins, yet dependent on local guidelines), acting to increase cellular uptake of potassium and thus reduce serum concentration.

These measures are only short term, as the potassium will leave the cells within 30-60 minutes, therefore repeated doses may be required.

Reduction of Total Body Potassium

Oral calcium resonium can be given to reduce total body potassium. However, this step is more complex and specialist input should be sought early. Any reversible underlying cause should be identified and appropriately managed.

Referral to renal physicians may be warranted. This may involve temporary haemodialysis or specialised potassium binding treatment.

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