rough correlation between Mg level and symptoms
- Presence of reflexes argues against severe hypermagnesemia.
- Hyporeflexia is nonspecific, however (e.g. some patients have sluggish reflexes at baseline).
- Bradycardia, hypotension
- wide QRS and peaked T-waves (can mimic hyperkalemia)
- heart block
range of symptoms that may occur
- Bradycardia, complete heart block
- Muscular weakness (can progress to respiratory failure from diaphragmatic involvement)
- Delirium, coma
- Smooth muscle paralysis: urinary retention, intestinal ileus, pupillary dilation
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
- Tumor lysis syndrome
- Crush injury, severe burns
- 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).
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.
- Not oliguric: forced diuresis with furosemide plus saline (with close monitoring of volume status and other electrolyte levels).
- Oliguric: emergent dialysis
The segment of this podcast about hypermagnesemia begins at 18:30:
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questions & discussion
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- 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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- Hypermagnesemia (WikEM)