Pediatric Hypermagnesemia Workup

Updated: Aug 16, 2018
  • Author: Alicia Diaz-Thomas, MD, MPH; Chief Editor: Sasigarn A Bowden, MD  more...
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Workup

Laboratory Studies

Laboratory analysis by atomic absorbance spectrophotometry (AAS) is the most specific technique available for measuring total serum magnesium in patients with suspected hypermagnesemia.

Although ion-selective electrodes for measuring free magnesium have been developed, their use has not been tested rigorously, and they are not readily available on a wide-scale basis.

Hypermagnesemia usually is not found as an isolated electrolyte abnormality; hyperkalemia and hypercalcemia often are present concurrently. Hypermagnesemia may secondarily cause hypocalcemia by suppressing parathyroid hormone (PTH) and by directly suppressing non–PTH-mediated renal tubular calcium reabsorption.

Obtain BUN and creatinine levels to determine the presence of renal insufficiency, as serum magnesium levels rise when the creatinine clearance is less than 30 mL/min.

Check creatine phosphokinase (CPK) or urine myoglobin in patients with suspected rhabdomyolysis.

Because hypothyroidism and adrenal insufficiency are rare causes of hypermagnesemia, perform thyroid function tests and at least an early morning serum cortisol test in recurrent or refractory cases of hypermagnesemia.

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Other Tests

An ECG and cardiac monitor may demonstrate prolongation of the P-R interval, intraventricular conduction delay, or other nonspecific findings. [9]

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