Hypokalaemia

  • See also

    Intravenous fluids Guideline
    Hyperkalaemia Guideline
    Diabetic Ketoacidosis (DKA) Guideline  

    Key points

    1. Oral/enteral is the preferred route of potassium administration.
    2. Intravenous potassium replacement carries risks of inadvertent hyperkalaemia, fluid overload, and peripheral vein extravasation/thrombophlebitis. Rapid intravenous administration or overdose may cause cardiac arrest.
    3. Monitoring of clinical/fluid status and electrolytes is important in children receiving potassium supplementation.
    4. Specialist advice should be sought for critical or symptomatic hypokalaemia.

    Background

    Hypokalaemia is defined as a plasma potassium level less than 3.5mmol/L. 

    Serum potassium (mmol/L) Severity
    3.0 - 3.4 Mild
    2.5 - 3.0 Moderate
    2.0 - 2.4 Severe
    < 2.0 Critical


    The goals of treating hypokalaemia are to:

    • prevent life threatening complications: arrhythmias, paralysis, rhabdomyolysis, diaphragmatic weakness
    • replace potassium deficit
    • correct the underlying cause

    Causes 

    Decreased intake Increased losses Transcellular shifts Medicines Spurious

    Illness

     

    Fasting

     

    Prolonged IV fluids not containing potassium

     

    Eating disorder

    Gastrointestinal

    • Vomiting
    • Diarrhoea
    • Fistula
     

    Renal

    • Diuretics
    • Osmotic diuresis
    • Aldosterone excess
    • Mineralocorticoid excess
    • Congenital disorders
    • Renal artery stenosis
     

    Alkalosis

     

    Hypomagnesaemia

     

    Hypernatraemia

     

    Glucose/insulin infusion

     

    Diabetic ketoacidosis

     

    Refeeding syndrome

     

    Loop diuretics (e.g.  frusemide)

    Thiazide diuretics

     

    Amphotericin

    Cisplatin

     

    Insulin

    Salbutamol

    Adrenaline  

    Sampling error
    • Recent line flush
    • IV fluids near sampling site
         

    Prevention

    In general, children eating a variety of foods will meet their daily potassium requirements.

    Consider the addition of potassium to maintenance fluids (see Statewide Intravenous Fluids Guideline) for children who are:

    • nil by mouth/enterally for prolonged periods (particularly if increased losses)
    • at risk of hypokalaemia (see table above, Causes) 

    Assessment 

    History and examination

    Identify underlying cause and correct where possible

    Assess for signs/symptoms of hypokalaemia

    • muscle weakness, cramps, paralysis
    • hyporeflexia
    • constipation, ileus
    • lethargy, confusion
    • rhabdomyolysis (rare)

    Assess fluid status as a baseline 

    Investigations

    Consider:

    • repeat electrolytes to verify the initial result

    Note: serum potassium level can be falsely elevated in haemolysed/finger prick samples, so a venous sample should be taken if clinical suspicion of hypokalaemia

    • baseline renal function
    • blood gas if concerns regarding acid-base status
    • serum magnesium level, especially if hypokalaemia is refractory to treatment (hypomagnesaemia promotes potassium wasting) 

    Perform ECG if signs/symptoms of hypokalaemia, risk of cardiac arrhythmia, or serum potassium <3mmol/L.

    • Look for wide flat T waves, ST depression, T wave inversion, tall wide P waves, prolonged PR segment, U waves, apparent prolonged QT (fusion of T and U waves), prolonged QRS, arrhythmia. 

    Management

    Replacement

    Potassium replacement is indicated if:

    • serum potassium <3.0 mmol/L or
    • serum potassium <3.5 mmol/L with symptoms/signs/ECG changes

    If serum potassium is 3.0 mmol/L - 3.4 mmol/L in a well child, it is reasonable to either:

    • monitor electrolytes,
    • increase maintenance potassium dose, or
    • replace potassium depending on the clinical situation  

    In children with stable hemodynamics and no ECG changes, aim for a gradual correction over 24-48 hours.

    Correct serum magnesium as necessary.

    Choice of dosing route 

    Oral/enteral is the preferred route of administration

    • Oral potassium is well absorbed from the gastrointestinal tract.
    • Best taken with or soon after food to reduce gastrointestinal irritation.

    Consider intravenous replacement if:

    • child is unable to tolerate oral medication,
    • serum potassium <2.5 mmol/L, or
    • ECG changes present

    Oral/enteral dosing

    Dosage:

    Acute replacement dose

    1 - 2 mmol/kg/dose orally (maximum 20mmol per dose)

    Dose may be repeated, after checking serum potassium level, to a maximum of 5mmol/kg/DAY (maximum daily dose 50mmol)

     

    Maintenance dose

    (if required)

    2 - 5 mmol/kg/DAY orally in divided doses (maximum 20mmol per dose)  


    Medication Forms: 

      Potassium content Notes
    Potassium Chloride Oral Mixture (where available)   1.33mmol/mL  
    • Rapid absorption
    • Expected serum potassium rise after approximately 2 hours

    Effervescent tablet

    e.g. Chlorvescent®

     
    14mmol per tablet    
    • Rapid absorption
    • Ensure tablets are completely dissolved before administration
    • Expected serum potassium rise after approximately 2 hours
     

    Controlled release enteric coated

    e.g. Slow K®

    8mmol per tablet    
    • Slow release, delayed absorption
    • Use for mild or chronic hypokalaemia
    • Tablets must be swallowed whole
    • Expected serum potassium rise after approximately 4 hours
     

     

    Repeat serum potassium level: For acute oral potassium replacement, consider repeat serum potassium level at a time interval guided by the clinical context and the expected serum potassium rise. 

    Intravenous dosing

    Dosage

    • Rapid intravenous administration or overdose may cause cardiac arrest. Administer via an infusion pump using Dose Error Reduction Software (DERS) where available.  
    • Include all sources of potassium when calculating replacement doses and infusion rates (e.g. additives to maintenance fluids, Parenteral Nutrition, oral/enteral supplements).

    Ward Area

    (specific to RCH)

    Acute replacement dose Maintenance dose (if required) ECG monitoring required Repeat serum potassium level   Notes on serum potassium level monitoring
    General ward

    0.2mmol/kg/hour for 3 hours (maximum 10mmol/hour)

     

    Note: Dose likely to require intravenous fluid rate greater than maintenance fluid rate

     

    1 - 4 mmol/kg/day (maximum 10mmol/hour)

     

    Doses greater than 4mmol/kg/day should be discussed with a Senior Clinician or local retrieval service

    Only required if serum potassium <3mmol/L or risk of cardiac arrhythmia   1 hour after replacement completion

    Check serum potassium level before administering further potassium

     

    Continue to monitor serum potassium levels at a frequency guided by the response and clinical situation

    Critical Care Areas  

    0.4mmol/kg/hour for 1 - 2 hours (maximum 20mmol/hour)

     

    Note: Dose likely to require concentrated potassium infusion (see below) and central line

     
    Yes

    1 hour after replacement commencement

    AND

    1 hour after replacement completion

     

    Diabetic Ketoacidosis: For children with Diabetic Ketoacidosis, please refer to the Diabetic Ketoacidosis (DKA) Guideline  

    Administration

    Intravenous Access Potassium concentration Dosage form Notes
    Peripheral line Maximum 60 mmol/L

    Use premixed fluid bags where possible (various concentrations available)  

     

    When adding potassium chloride to an IV fluid bag, mix well by inverting the bag at least 10 times

    Clearly label all bags, syringes, pumps and lines that contain potassium to avoid inadvertent flushing

     
    Monitor intravenous access site for signs of extravasation or thrombophlebitis       
    Central line Concentrations > 60 mmol/L must be given via a central line only

    There are a number of concentrated potassium formulations available

     

    Only administer in areas where there is a clear protocol for administration and monitoring

     

    Contact local retrieval service for further advice

     

    Use should be approved by a Senior Clinician

     

    ECG monitoring required

     

     

    Monitoring

    Ensure regular monitoring of:

    • vital signs
    • clinical and fluid status including urine output
    • any signs of hyperkalaemia (see Hyperkalaemia)
    • IV access site

    Consider consultation with local Paediatric service when:

    • the child requires admission
    • the child requires potassium replacement  

    Consider consultation with local retrieval service when:

    • serum potassium < 2.0
    • symptomatic hypokalaemia
    • ECG changes
    • renal impairment (including oliguria or high/rising creatinine)
    • risk cardiovascular arrhythmia
    • fluid overload
    • neonates
    • complex children with renal, oncological, haematological, cardiac, endocrinological, and metabolic conditions 

    For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.

    Last Updated April, 2019