Clinical Guideline for the Treatment of Hypokalaemia in Adults

Background information
Definition of hypokalaemia
Symptoms of hypokalaemia
Causes of hypokalaemia
Cautions and contraindications of potassium use
Treatment summary diagram
Oral potassium administration
Intravenous potassium administration
Other routes of administration
Monitoring
Adverse drug reactions
Interactions of note

Background Information

Potassium is the most abundant cation in intracellular fluids; 98% of potassium is found in the intracellular fluid compartment.

Low serum potassium is an electrolyte abnormality commonly encountered in clinical practice. Hypokalaemia is found in over 20% of hospitalised patients. Chronic hypokalaemia indicates a profound deficit in total body potassium and replacement may take several days.

Hypokalaemia is usually well tolerated in otherwise healthy people but it can be life threatening when severe. Even mild or moderate hypokalaemia increases the risk of morbidity and mortality in patients with cardiovascular disease. As a result, when hypokalaemia is identified, the underlying cause should be identified and treated. Hypokalaemia can be exacerbated by speed of onset.

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Definition of hypokalaemia

The reference range for serum potassium used at the Leeds Teaching Hospitals NHS Trust is 3.5-5.3 mmol/L

For the purposes of this guideline, hypokalaemia is defined as a serum concentration of less than 3.5 mmol/L

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Symptoms

Hypokalaemia is usually asymptomatic unless serum potassium concentrations fall below 3.0 mmol/L.  

Table 1: Clinical features of hypokalaemia and corresponding serum potassium concentrations. 

Hypokalaemia seriously increases the risk of digoxin toxicity and its arrhythmogenic potential.

It is recommended that all patients with hypokalaemia have an ECG done to assess for the presence of arrhythmias.

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Causes of Hypokalaemia

True hypokalaemia is almost always the result of potassium depletion due to renal or intestinal losses and decreased oral intake. Renal losses are most frequently due to metabolic alkalosis whereas intestinal losses are due to diarrhoea. Catecholamine release after myocardial infarction may induce hypokalaemia. Diuretics have been found to cause up to 41% of hypokalaemias. Occasionally drugs are responsible for an acute shift from extra- to intra-cellular spaces. Magnesium deficiency may also lead to hypokalaemia.

For further details of investigations into hypokalaemia see the LTHT pathology website (LTHT Internal Only)

Medicines that are known to cause hypokalaemia include:

• Thiazide diuretics (e.g. bendroflumethiazide)
• Loop diuretics (e.g. furosemide)
• Amphotericin, cisplatin, foscarnet
• Aminoglycosides
• Beta-agonists (e.g. salbutamol, terbutaline)
• Insulin treatment (e.g. in the treatment of diabetic ketoacidosis)
• Corticosteroids and mineralocorticoids
• Caffeine, theophylline
• Adrenaline, pseudoephedrine
• High dose penicillins
• Non-potassium containing fluids in patients with no oral intake

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Treatment Options

Cautions and Contraindications

• Potassium supplements should be used with extreme caution and frequent monitoring in severe renal impairment.
• Caution should be used in patients with renal insufficiency or when ACE inhibitors or potassium-sparing diuretics are being administered concomitantly.
• Administering potassium intravenously carries a significant clinical risk. Appropriate monitoring should therefore be undertaken. See link for monitoring requirements.
• Intravenous potassium is very irritant and rapid administration can be harmful. Administration guidance (see below) should be followed to minimise risks.
• Replace with caution in patients with significant tissue damage (e.g.severe burns, post-surgery) that may result in hyperkalaemia

Note: failure to correct hypokalaemia despite appropriate treatment may be due to underlying hypomagnesaemia. Serum magnesium concentration should be checked and corrected if appropriate. If appropriate, refer to the hypomagnesaemia guideline for further information (LINK)

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Treatment

This monograph aims to provide guidance only. The dose of potassium to correct hypokalaemia must be established on an individual patient basis.

Treatment Summary Diagram

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Oral potassium administration

Oral potassium supplementation is considered first line therapy in asymptomatic patients with a serum potassium concentration of 2.5 - 3.5 mmol/L. 

Table 2: Suggested oral replacement of potassium

• The dose and duration of treatment depends on the existing potassium deficit and whether there are continuing losses. Review the prescription daily and stop oral potassium as soon as appropriate. Ensure a review date is stated on the prescription chart; this should be at least 3 days (or more frequent). 
• A liquid oral potassium preparation is also available. Contact Pharmacy for advice if your patient is unable to take Sando K.   
• Larger doses of potassium may be required in patients with digitoxicity or diabetic ketoacidosis. Advice is available from the acute medical team or Clinical Biochemistry in this situation. Please refer to the diabetic ketoacidosis guideline (LINK) if applicable to your patient. 
• If the cause of hypokalaemia remains unexplained, further investigations may be needed. Advice may be obtained from the acute medical team or Clinical Biochemistry.

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Intravenous potassium administration

Intravenous potassium administration is indicated in the following situations:

• Patients with serum potassium concentration of less than 2.5 mmol/L 
• Patients with symptoms of hypokalaemia 
• Patients who are nil by mouth  
• Patients who are unable to tolerate oral administration  
• Patients who are unlikely to absorb oral potassium. 

The dose and rate of infusion of potassium is dependent on the patient’s serum potassium concentration and clinical picture, renal function and whether the cause for hypokalaemia has been addressed.

• As a guide, adult patients should receive 40-80 mmol potassium per day to meet normal maintenance requirements 
• A recommended maximum is 2-3mmol/kg of potassium in 24 hours 
• The rate of intravenous infusion of potassium should not normally exceed 20 mmol/hour
• The maximum concentration of potassium that can normally be infused via a peripheral venous catheter is 40 mmol/L
• Only ready-made bags or products made in pharmacy must be used in all non intensive care clinical areas.

Table 3: Suggested initial intravenous replacement of potassium 

For details of ready-made infusion bags containing potassium that are available at LTHT.

Concentrated potassium products may only be used in approved clinical areas. If a concentrated solution is required, contact Medicines Information on ext 65377 in working hours or the on-call pharmacist out of hours for advice.

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Other routes of administration

Potassium can be administered by subcutaneous infusion in solution at low concentrations for long term fluid dependent patients with no venous access. For more information please see link to the subcutaneous fluids guideline or contact Medicines Information on ext 65377.

Potassium must not be administered by the IM route.

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Monitoring

Continuous ECG monitoring should be undertaken in patients receiving intravenous potassium at rates exceeding 20mmol/hour, concentrations in excess of 40 mmol/L or if the patient has a cardiac history or renal impairment.

For patients receiving IV potassium therapy, serum potassium concentrations should be monitored at least daily.

For patients receiving oral potassium supplementation, serum potassium concentrations should be monitored according to the schedule outlined in the treatment section above (LINK).

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Adverse Drug Reactions

Excessive doses of potassium may lead to the development of hyperkalaemia, especially in patients with renal impairment.

          Symptoms of hyperkalaemia include:

• paraesthesia of the extremities
• muscle weakness
• paralysis
• cardiac arrhythmias*
• heart block*
• cardiac arrest*
• confusion

          *Cardiac toxicity is of particular concern after intravenous dosage.

Refer to the hyperkalaemia guideline (LINK) for further information and treatment options.

Pain, phlebitis or serious injury may occur when given intravenously via peripheral veins, particularly at higher concentrations.

The following adverse reactions have been reported with oral potassium salts

• nausea
• vomiting
• diarrhoea
• abdominal cramps

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Interactions of note

This is not an exhaustive list - consult product literature for further information. Potassium supplements should be used with caution, if at all, in patients receiving drugs that increase serum potassium concentrations. These include

• potassium-sparing diuretics (e.g. spironolactone, amiloride, triamterene, co-amilofruse & co-amilozide)
• ACE inhibitors (e.g. ramipril, lisinopril)
• angiotensin II receptor antagonists (e.g. irbesartan, losartan, candesartan)
• tacrolimus
• ciclosporin
• drugs that contain potassium such as the potassium salts of penicillin
• drospironone-containing contraceptives or HRT

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