CONTENTS

• Diagnosis
• Causes
• Evaluation
• Treatment
• Podcast
• Questions & discussion
• Pitfalls

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diagnosis

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rough correlation between Mg level and symptoms

physical examination

• Hyporeflexia
  • Presence of reflexes argues against severe hypermagnesemia.
  • Hyporeflexia is nonspecific, however (e.g. some patients have sluggish reflexes at baseline).
• Bradycardia, hypotension

EKG findings

• wide QRS and peaked T-waves (can mimic hyperkalemia)
• heart block

range of symptoms that may occur

• Cardiac
  • Hypotension
  • Bradycardia, complete heart block
• Neurologic
  • Muscular weakness (can progress to respiratory failure from diaphragmatic involvement)
  • Delirium, coma
  • Smooth muscle paralysis: urinary retention, intestinal ileus, pupillary dilation

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causes

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Renal Failure plus:

• Persistent hypermagnesemia requires renal failure (or, less commonly, and ongoing source of magnesium).
• However, in addition to renal failure, there is usually another source of magnesium

(1) exogenous magnesium

• Magnesium infusions for pre-eclampsia
• Magnesium-containing antacids
• Magnesium-containing laxatives or enemas

(2) endogenous magnesium from cellular lysis

• Rhabdomyolysis
• Hemolysis
• Tumor lysis syndrome
• Crush injury, severe burns

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evaluation

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investigations

• If the lab is hemolyzed, repeat it (hemolysis may cause pseudo-hypermagnesemia)
• Obtain complete set of electrolytes including Ca/Mg/Phos (to evaluate for additional concurrent electrolyte abnormalities).
• Consider LDH, creatinine kinase, or uric acid (to evaluate for hemolysis, rhabdomyolysis, or tumor lysis).

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treatment

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moderate hypermagnesemia (e.g. Mg <10 mg/dL, no cardiac/respiratory symptoms)

• Volume resuscitation
• Treatment of underlying cause
• Furosemide may be considered to enhanced magnesium excretion, but make sure to replace excreted volume to avoid hypovolemia.

severe hypermagnesemia (cardiac and/or respiratory consequences)

• IV calcium may stabilize myocardium
  • Two grams of calcium gluconate IV over 5-10 minutes (or one gram of calcium chloride).
  • May need to repeat or, in extreme cases, give as a continuous infusion.
• Elimination
  • Not oliguric: forced diuresis with furosemide plus saline (with close monitoring of volume status and other electrolyte levels).
  • Oliguric: emergent dialysis

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podcast

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The segment of this podcast about hypermagnesemia begins at 18:30:

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questions & discussion

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To keep this page small and fast, questions & discussion about this post can be found on another page here.

• Moderate hypermagnesemia (e.g. Mg 5-8 mg/dL) is generally pretty well tolerated. Be careful about attributing severe symptoms to this degree of hypermagnesemia.

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