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Low Magnesium in Children has a generally similar approach to adults, however the etiology may be different.
Children can present with low magnesium levels due to many causes including but not limited to renal wasting (which may be drug related), malnutrition, malabsorption, refeeding syndrome, short gut syndrome, or genetic mutations
Hypomagnesemia is often coupled with hypocalcemia or hypokalemia which can be refractory until the magnesium is replaced.
Symptoms may be vague particularly in younger patients, with neuromuscular irritability, though in extreme cases (typically <1.0mg/100ml) seizure activity may occur with severely low levels, and long QTc may cause dysrhythmia
Oral replacement can be used for asymptomatic patients with levels greater than 1.0 mg/100mL
PO replacement:
Goal of 10-20mg/kg/dose (Max 2 g) elemental Magnesium
Magnesium oxide is the most common replacement but does come in pill form and is given up to four times daily
IV replacement with Magnesium Sulfate (given over 2 -4 hours*):
Neonate: 25–50 mg/kg/dose every 8–12 hours
Child: 25–50 mg/kg/dose every 4–6 hours (maximum 2 g/dose)
*In patients with life threatening hypomagnesemia such as those with seizures, a 50mg/kg dose given over 1-5 minutes is warranted.
References
Anderson S, Farrington E. Magnesium Treatment in Pediatric Patients. J Pediatr Health Care. 2021 Sep-Oct;35(5):564-571. doi: 10.1016/j.pedhc.2021.03.003. PMID: 34479684.