See also
Electrolyte abnormalities
Hypermagnesaemia
Key points
- Oral/enteral is the preferred route of magnesium administration
- Consider oral magnesium replacement in asymptomatic children with mild hypomagnesaemia and no gastrointestinal intolerance present eg diarrhoea, nausea, vomiting
- Intravenous magnesium replacement is the preferred route in the setting of symptomatic hypomagnesaemia, significant gastrointestinal intolerance
- Seek specialist advice for symptomatic children with hypomagnesaemia
Background
- Serum magnesium levels may not reflect total body stores
- Less than 1% of total body magnesium stores are in extracellular fluid
- Earlier changes may be identified in urine levels in the context of normal renal function, using 24-hour urinary magnesium excretion
- The clinical context of the child is required to interpret the significance of a low magnesium level eg post-surgical cardiac conditions, where clinical target may be the upper end of normal range to avoid arrhythmia
Causes of hypomagnesaemia
|
Gastrointestinal
|
Increased renal excretion
|
Other
|
|
Reduced intake
Reduced absorption
- Malabsorption
- Short bowel syndrome
Increased losses
- Diarrhoea
- Laxative abuse
- Excessive gastric suctioning or vomiting
|
Drug-induced
- Loop diuretics, thiazides
- Cisplatin
- Tacrolimus, ciclosporin
- Proton pump inhibitors [chronic use]
- Aminoglycosides
Other
- Renal tubular acidosis
- Diuretic phase of acute tubular necrosis
- Hypercalcemic states
- Hyperaldosteronism
|
Intracellular redistribution
- diabetic ketoacidosis
- hyperthyroidism
Miscellaneous
- burns
- cardiopulmonary bypass
|
Assessment
Identify underlying cause and correct where possible
Assess for signs/symptoms of hypomagnesaemia
- Neuromuscular: muscle tremors, fasciculations, hyperreflexia, paraesthesia, muscle weakness, myalgia
- Cardiac: arrhythmias and ECG changes (PR/QT prolongation)
- Metabolic: hypokalaemia, hypocalcaemia
- Central nervous system: nystagmus, seizures, depression, agitation, confusion, irritability
Management
Investigations
Serum magnesium levels should be monitored with frequency depending on the degree of abnormality and whether the child is symptomatic
Treatment
Consider oral magnesium replacement in asymptomatic children with mild hypomagnesaemia, unless significant gastrointestinal intolerance (eg diarrhoea) which oral magnesium will exacerbate:
- 2.5 - 5 mg/kg (0.1 - 0.2 mmol/kg) 3 times daily orally
- Increase to 10 - 20 mg/kg (0.4 - 0.8 mmol/kg) up to 4 times daily orally if required
- Tolerance is better with smaller more frequent dosing
Medication Form for oral/enteral magnesium
| Preparation |
Magnesium*
content
|
|
Magnesium complex solution
|
2.1 mmol per mL
(50 mg/mL)
|
|
Magnesium aspartate tablet (MagMin@; Mag-Sup@)
|
1.55 mmol per tablet
(37.4 mg per tablet)
|
|
Cenovis@ Magnesium tablets
(also contains 6 mg manganese and 49.36 mg pyridoxine per tablet)
|
13.5 mmol per tablet
(325 mg per tablet)
|
Children with severe symptoms (eg tetany, arrythmia, seizures) should be treated with intravenous magnesium
- Seek specialist advice for IV magnesium replacement
- IV magnesium 0.1 - 0.2 mmol/kg up to 0.4 mmol/kg (max dose 8 mmol)
- Administer over 2-4 hours, (reduces risk of adverse effects, also improves cellular uptake of administered dose)
- In children with severe symptoms, can be given over shorter period of time
- Please refer to local guidelines for more detailed administration information
Medication Form for intravenous magnesium
Preparation
(Concentrated magnesium ampoules) |
Magnesium*
content
|
Notes
|
|
DBL Magnesium Sulfate concentrated injection 49.3%
|
2 mmol/mL
(493 mg/mL)
|
Dilute before use
|
|
Magnesium Sulfate Heptahydrate concentrated injection 50%
|
2 mmol/mL
(500 mg/mL)
|
Consider consultation with local paediatric team when
The child is symptomatic, or there is a severe abnormality
Consider consultation with the clinical nutrition, gastroenterology team or local dietitian when
- Hypomagnesaemia in a child on parenteral nutrition
- Hypomagnesaemia in a child with refeeding syndrome
Consider consultation with renal team when
- Unexplained hypomagnesaemia
- Hypomagnesaemia with associated moderate-severe renal impairment (risk of hypermagnesemia with replacement)
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
Consider discharge when
- The child is clinically stable with an appropriate management plan in place
- Any acute or chronic abnormality has resolved
Last Updated November 2021