Pediatric Hypermagnesemia Clinical Presentation

Updated: Aug 16, 2018
  • Author: Alicia Diaz-Thomas, MD, MPH; Chief Editor: Sasigarn A Bowden, MD  more...
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Symptoms of hypermagnesemia are nonspecific at lower levels (2-4 mEq/L) and may include the following:

  • Nausea

  • Vomiting

  • Flushing

  • Lethargy

  • Weakness

  • Dizziness

Higher levels may lead to a depressed sensorium, and cardiopulmonary arrest may occur at extreme levels (>10-15 mEq/L).



Hypermagnesemia results in loss of deep-tendon reflexes at levels of 4-6 mEq/L. At magnesium levels of more than 5 mEq/L, CNS depression, which may range from drowsiness to coma, begins. Although concentrations of magnesium of more than 10 mEq/L lead to respiratory depression in adults, this may occur at much lower levels in the newborn.

Hypermagnesemia has a negative effect on heart rate. [8] Beginning with magnesium serum levels of 4.5 mEq/L, depression of sinoatrial node activity and atrial fibrillation may occur. Higher magnesium levels increase the P-R interval, widen the QRS complex, and can cause intraventricular conduction delays. Serum magnesium concentrations greater than 15 mEq/L can lead to complete heart block and asystole.

At varying levels (5-8 mEq/L), hypermagnesemia may produce vasodepression of vascular smooth muscle leading to systemic hypotension.

Although the absolute serum levels are important, the rate of rise is even more significant. For instance, a fast rise in serum level can produce cardiovascular symptoms more readily than can a slower rise in serum levels.



Major predisposing factors for the development of hypermagnesemia include the following:

  • Renal failure (acute or chronic)

  • Iatrogenic over administration of magnesium (eg, antacids, cathartics)

  • Neonates born to mothers treated with magnesium sulfate for eclampsia