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Disorders of Potassium Balance

Authors: Andrew Parfitt, Emma Townsend / Editors: Steve Fordham / Reviewer: Chris Gray / Codes: HAP10 / Published: 16/09/2019 / Review Date: 16/09/2022

Abnormal potassium levels are the most common electrolyte abnormalities encountered in the emergency department, and can be life threatening if not recognised and managed correctly. This is made all the more difficult as patients with hyper or hypokalaemia may be asymptomatic.

Disorders of potassium balance occur due to:

  • Abnormal intake
  • Abnormal distribution
  • Abnormal excretion

A normal serum potassium level is 3.5 – 5mmol/L, though this may change slightly dependent on your assays. Check with your local biochemistry department for the values you should use in your place of work.

A full history and examination, together with review of regular and other recent medications must be undertaken. Symptoms and signs of potassium disorders can be absent, subtle, or highly non-specific, such as lethargy and weakness, and therefore a serum potassium level is needed. Together with a serum potassium level, it is important to check:

  • Renal function as patients may have acute or chronic renal failure
  • Blood gases as potassium and hydrogen ion status are closely linked
  • ECG as high or low potassium levels can be associated with conduction defects or life-threatening arrhythmias

Its important to note that ECG changes only occur in around 50% of patients with hyperkalaemia, so dont rely on the ECG for diagnosis.

In patients with hyperkalaemia, it is also important to monitor the blood sugar, as insulin is often used to treat this, which could affect sugar levels.

In patients with hypokalaemia, it is also important to check serum magnesium levels, as low magnesium will need to be corrected first.

Together with a serum potassium level, it is important to check:

  • Renal function as patients may have acute or chronic renal failure
  • Blood gases as potassium and hydrogen ion status are closely linked
  • ECG as high or low potassium levels can be associated with conduction defects or life-threatening arrhythmias

Its important to note that ECG changes only occur in around 50% of patients with hyperkalaemia, so dont rely on the ECG for diagnosis.

In patients with hyperkalaemia, it is also important to monitor the blood sugar, as insulin is often used to treat this, which could affect sugar levels.

In patients with hypokalaemia, it is also important to check serum magnesium levels, as low magnesium will need to be corrected first.

Hyperkalaemia

  • Stabilise the myocardium if there are conduction abnormalities or arrhythmias, using calcium gluconate 10% 10-20ml over 5 minutes
  • Shift potassium back into the cells using 10 units of short acting insulin in 50ml 50% dextrose, and consider also giving 10-20ml nebulised salbutamol

Hypokalaemia

  • Correct any other underlying electrolyte abnormalities such as hypomagnesaemia
  • Administer potassium chloride in sodium chloride at a maximum rate of 20mmol/hour

For all patients, we need to identify and correct the underlying cause and consider fluid resuscitation with balanced crystalloid solution.

It is important to continue to monitor blood sugar levels, potassium levels, and acid-base balance for these patients.

If the hyperkalaemic patient does not respond to medical management, has renal failure, is acidotic, or is oligo/anuric, make an early referral to the intensivists or nephrologists for consideration of haemodialysis

For the fluid-overloaded patient needing electrolyte replacement, central venous access can allow you to give smaller volumes of fluid.

Dont forget:

  • The majority of patients are asymptomatic
  • The ECG does not always reflect the potassium level
  • Remember medications are common causes of potassium disturbance
  • Look for the underlying cause and try to correct that too
  • Remember to monitor glucose levels during treatment with insulin
  • Consider early intensive care involvement for complex patients with potassium abnormalities
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