Safety concerns

The National Patient Safety Alert (NPSA) aims to reduce the risk of accidental overdose of intravenous (IV) potassium arising from high strength potassium chloride.

Potassium overdose can be fatal. Incorrect administration of IV potassium chloride increases the risk of arrhythmias and cardiac arrest.

Administering IV potassium should be in a hospital setting where appropriate monitoring is available.

Organisational actions

Organisations should have measures in place to prevent errors occurring from the use of IV potassium.

Restrict and control the storage and handling of potassium chloride concentrate solutions to pharmacy departments and critical care areas for urgent use.

Ensure all staff groups administering medicines undergo training relevant to their role and be subject to robust governance procedures.

Causes of hypokalaemia

Hypokalaemia can occur in patients due to:

• decreased intake of potassium
• intestinal loss such as diarrhoea
• magnesium depletion
• medication side effects
• renal loss such as metabolic alkalosis
• transcellular shift

Consider reviewing medicines that can cause hypokalaemia such as:

• aminoglycosides
• beta-agonists
• insulin
• loop diuretics
• theophylline
• thiazide diuretics

Classification of hypokalaemia

Hypokalaemia is defined as less than 3.5mmol/L of serum potassium.

Mild

3.0 to 3.5mmol/L serum potassium.

Clinical signs

No symptoms.

Moderate

2.5 to 2.9 mmol/L serum potassium.

Clinical signs

Generalised weakness, lethargy and constipation, cardiac arrhythmias.

Severe

Less than 2.5mmol/L serum potassium.

Clinical signs

Muscle necrosis and cardiac arrhythmias.

Management of hypokalaemia

The reference range for serum potassium and dosing recommendations may vary locally. Healthcare professionals should work in line with the organisation’s medicines policy.

Identify and treat the underlying causes of hypokalaemia.

The dose, dosing schedule and duration of treatment will depend on your patient’s serum potassium level and symptoms.

Lower doses may be required in renal impairment due to the risk of hyperkalaemia.

Mild

Use oral potassium replacement.

Dose

Give an oral dose of 24mmol of potassium up to 2 to 3 times a day.

Give an initial IV dose of 20 to 40mmol/L of potassium in patients who cannot receive treatment via the oral or enteral route.

Moderate

Use oral potassium replacement.

Dose

Give an oral dose of 24 to 36mmol of potassium up to 3 to 4 times a day.

Give an initial IV dose of 20 to 40mmol/L of potassium in patients who cannot receive treatment via the oral or enteral route.

Repeat doses depending on serum potassium level.

Severe

IV potassium chloride should be given in a hospital setting.

Give an initial dose of 40mmol/L of potassium for severe or symptomatic hypokalaemia.

Repeat doses depending on serum potassium level.

The maximum dose of potassium in 24 hours is 2 to 3mmol/Kg.

Choice of oral potassium replacement

Oral potassium is well absorbed, but large doses are limited by nausea and vomiting.

Oral potassium should be given with or after food.

Modified-release (MR) tablets are considered less suitable for NHS prescribing due to gastrointestinal side effects resulting in poor compliance.

Oral preparations of potassium chloride available in the UK are:

• effervescent tablets (each tablet of Sando K contains 12mmol of potassium from potassium chloride and potassium bicarbonate).
• an oral solution (each ml of the 7.5% syrup contains 1mmol of potassium).
• MR tablets (each tablets contains 8mmol of potassium).

Oral potassium may not be suitable for patients who:

• have severe hypokalaemia.
• are nil by mouth.
• have no or limited gastrointestinal absorption.
• are unable to tolerate oral medicines.
• require immediate correction of potassium blood levels.

Choice of intravenous potassium replacement

Consider the following when you are choosing IV potassium products.

High strength versus ready-to-use

High strength potassium chloride solutions are defined as 10% potassium chloride (1gram potassium in 10ml) or more.

Prescribe and use commercially available ready-to-use diluted solutions of potassium where possible

Using commercially available diluted solutions of potassium reduced the risk of fatalities from potassium overdose.

A full list of IV potassium preparations are in the BNF.

Infusion fluid

Use premixed infusions during replacement where possible. These should be glucose-free because glucose can cause a further decrease in the serum-potassium.

Concentration

Do not exceed a concentration of 40mmol/L of IV potassium through a peripheral line.

Higher strengths can cause inflammation of the vein near the skin and pain at the injection site.

Higher concentrations have been given in severe cases of hypokalaemia and require a central line and infusion pump control.

Rate

The rate of IV potassium should not normally exceed 10mmol/hour. Administration rates above 20mmol/hour require cardiac monitoring due to the risk of arrhythmias.

Monitoring 

The monitoring parameters during potassium replacement should include:

• serum potassium
• serum magnesium
• renal function
• ECG monitoring with high concentration potassium

Other parameters will depend on individual patient circumstances.