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ESSENTIALS OF DIAGNOSIS

  • Often associated with advanced CKD and chronic intake of magnesium-containing drugs.

GENERAL CONSIDERATIONS

Hypermagnesemia is almost always the result of advanced CKD and impaired magnesium excretion. Antacids and laxatives are underrecognized sources of magnesium. Pregnant patients may have severe hypermagnesemia from intravenous magnesium for preeclampsia and eclampsia. Magnesium replacement should be done cautiously in patients with CKD; dose reductions up to 75% may be necessary to avoid hypermagnesemia.

CLINICAL FINDINGS

A. Symptoms and Signs

Muscle weakness, decreased deep tendon reflexes, mental obtundation, and confusion are characteristic manifestations. Weakness, flaccid paralysis, ileus, urinary retention, and hypotension are noted. Serious findings include respiratory muscle paralysis and cardiac arrest.

B. Laboratory Findings

Serum Mg2+ is elevated. In the common setting of CKD, BUN, creatinine, potassium, phosphate, and uric acid may all be elevated. Serum Ca2+ is often low. The ECG may show increased PR interval, broadened QRS complexes, and peaked T waves, probably related to associated hyperkalemia.

TREATMENT

Exogenous sources of magnesium should be discontinued. Calcium antagonizes Mg2+ and may be given intravenously as calcium chloride, 500 mg or more at a rate of 100 mg (4.1 mmol) per minute. Hemodialysis or peritoneal dialysis may be necessary to remove magnesium, particularly with severe kidney disease.

Long-term use of magnesium hydroxide and magnesium sulfate should be avoided in patients with advanced stages of CKD.

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Broman  M  et al. Analysis of hypo- and hypermagnesemia in an intensive care unit cohort. Acta Anaesthesiol Scand. 2018 May;62(5):648–57.
[PubMed: 29341068]
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Chang  WT  et al. Calcium, magnesium, and phosphate abnormalities in the emergency department. Emerg Med Clin North Am. 2014 May;32(2):349–66.
[PubMed: 24766937]
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Haider  DG  et al. Hypermagnesemia is a strong independent risk factor for mortality in critically ill patients: results from a cross-sectional study. Eur J Intern Med. 2015 Sep;26(7):504–7.
[PubMed: 26049918]

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