Treatment of Hypomagnesaemia in Paediatric

• Severe hypomagnesemia (serum magnesium concentration of <1.0 mg/dL) can result in ECG changes, arrhythmias (including torsades de pointes), seizures, coma, and even death
• Hypomagnesemia may cause concomitant refractory hypokalemia and hypocalcemia.
• Although the exact mechanisms of these observations are unknown, hypokalemia is likely a result of impaired activity of the sodium–potassium pump,113 and hypocalcemia is likely due to impaired parathyroid release or activity
• Causes of hypomagnesemia include excessive GI losses, renal losses, surgery, trauma, infection or sepsis, burns, transfusion of blood preserved with citrate, starvation, malnutrition, alcoholism, and certain medications (e.g., thiazide and loop diuretics, aminoglycosides, amphotericin B, cisplatin, cyclosporine).
• Use of cardiac glycosides (e.g., digoxin) has also been associated with hypomagnesemia, possibly by enhancing magnesium excretion, and hypomagnesemia may potentiate digoxin toxicity (e.g., dysrhythmias)

Treatment

• No specific latest guidelines for paediatric management  
• Treatment of hypomagnesemia is largely empirical because only about 1% of magnesium stores are found in the extracellular space, and serum magnesium levels may not correlate with intracellular concentrations or total body magnesium levels.

Oral Magnesium

• Availability: Syrup Magnesium Sulphate 2mmol/ml
• problems with administration, slow onset of action, and GI intolerance may limit their utility

IV Magnesium Sulphate

• Availability: IV Magnesium Sulphate 2mmol/ml (10mmol/5ml)
• plasma magnesium concentration inhibits magnesium reabsorption in the loop of Henle, the major site of active magnesium transport.
• Thus, when an intravenous magnesium infusion is given, an abrupt but temporary elevation in the plasma magnesium concentration will partially inhibit the stimulus to magnesium reabsorption in the loop of Henle.
• up to 50 percent of the infused magnesium will be excreted in the urine.
• In addition, magnesium uptake by the cells is slow and therefore adequate repletion requires sustained correction of the hypomagnesemia

Dosing

• Needs to be diluted to at least 20%
• IM injection is painful
• Administer over at least 20 min (or not faster than 150mg/min)

Frank Shann

• 0.2ml/kg (0.4mmol/kg) IM or slow IV, followed by 0.16ml/m2/hr

BNF for Children 2014

• Neonate : 0.4mmol/kg BD-QID
• 1 month-12 years: 0.2mmol/kg BD
• 1-18 years: 4mmol BD

Lexiomp

• 0.1-0.2mmol/kg/dose  over 10-20 minutes
  

References:

1. www.uptodate.com
2. BNF for Children 2012
3. NHS Grampian Staff Policy For The Management Of Hypomagnesaemia In Adults
4. Treatment of electrolyte disorders in adult patients in the intensive care unit