Pediatric Hypermagnesemia Clinical Presentation

Updated: Aug 23, 2023
  • Author: Alicia Diaz-Thomas, MD, MPH; Chief Editor: Sasigarn A Bowden, MD, FAAP  more...
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Symptoms of hypermagnesemia are nonspecific at lower levels (2-4 mg/dL) 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 mg/dL).


Physical Examination

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

Hypermagnesemia has a negative effect on heart rate. [12]  Beginning with magnesium serum levels of 4.5 mg/dL, 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 mg/dL can lead to complete heart block and asystole.

At varying levels (5-8 mg/dL), 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.