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You are here: Home / IBCC / Hypermagnesemia


Hypermagnesemia

August 15, 2019 by Josh Farkas

CONTENTS

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

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

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

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).

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

podcast

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

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The Podcast Episode

http://traffic.libsyn.com/ibccpodcast/IBCC_Episode_50_Hyper_and_HypoMagnesium.mp3

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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.

Guide to emoji hyperlinks 🔗

  • 🧮 = Link to online calculator.
  • 💊 = Link to Medscape monograph about a drug.
  • 💉 = Link to IBCC section about a drug.
  • 📖 = Link to IBCC section covering that topic.
  • 🌊 = Link to FOAMed site with related information.
  • 🎥 = Link to supplemental media.

References

  • 30220246 Van Laecke S. Hypomagnesemia and hypermagnesemia. Acta Clin Belg. 2019 Feb;74(1):41-47. doi: 10.1080/17843286.2018.1516173 [PubMed]

The Internet Book of Critical Care is an online textbook written by Josh Farkas (@PulmCrit), an associate professor of Pulmonary and Critical Care Medicine at the University of Vermont.


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