See also

Electrolyte abnormalities
Hypomagnesaemia

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

Background

• 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

Assessment

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

Management

Treatment

• 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