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    Electrolyte abnormalities

    Key points

    1. Hypermagnesaemia is frequently an asymptomatic laboratory diagnosis finding
    2. Cease any magnesium-containing medications or intravenous solutions. Ask about non-prescribed supplements that may contain magnesium
    3. Specialist advice should be sought for symptomatic children with hypermagnesaemia


    • Serum magnesium levels can be a poor reflection of total body stores, as less than 1% of total body magnesium is in the extracellular fluid
    • Asymptomatic laboratory diagnosis is sometimes observed following intravenous magnesium administration
    • Symptomatic hypermagnesaemia usually not until >2 mmol/L
    • Causes of hypermagnesaemia include:
      • Iatrogenic – excessive magnesium administration from intravenous infusion or parental nutrition (especially in presence of underlying renal impairment)
      • Tumour lysis syndrome
      • Renal impairment (particularly moderate-severe renal impairment along with magnesium administration)
      • In some children with post-surgical cardiac conditions, the clinical target may be upper end of normal range to avoid arrhythmia


    History and Examination

    Identify underlying cause and correct where possible

    • Frequently an asymptomatic laboratory diagnosis
    • Check timing of blood sampling in relation to recent magnesium infusions and whether sample was taken from the same intravenous access as where the was infusion administered
    • Ask about non-prescribed supplements that may contain magnesium

    Assess for signs/symptoms of hypermagnesaemia

    • Neurological: loss of deep tendon reflexes
    • Cardiac: hypotension, ECG changes
    • Respiratory: apnoea
    • CNS: decreased consciousness level, somnolence, paralysis



    • Cease any magnesium-containing medications or intravenous solutions
    • For symptomatic children, discuss with PICU
      • Consider role for calcium chloride or calcium gluconate, furosemide or haemodialysis (if anuric)
    • Monitor closely with clinical and biochemical (serum magnesium level) parameters

    Consider consultation with local paediatric team when

    The child is symptomatic or there is a significant abnormality

    Consider transfer when

    The child is symptomatic or requires close monitoring not available in your centre

    For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

    Last Updated November 2021

  • Reference List

    1. Canada TW, et al.  ASPEN Fluids, Electrolytes, and Acid-Base Disorders Handbook. 2015. American Society for Parenteral and Enteral Nutrition. U.S.A.
    2. Rees, L, et al. Paediatric Nephrology (Oxford Specialist Handbooks in Paediatrics), 3rd Edition 2019