Link To Hypomagnesemia From The Internet Book Of Critical Care

In this post I link to and excerpt from the Internet Book Of Critical Care [Link is to the Table of Contents] chapter: Hypomagnesemia, August 15, 2019 by Dr. Josh Farkas.

I’ve reviewed this chapter previously in the blog but as these are just my study notes, so I’m reviewing the chapter again.

Here are direct links that Dr. Farkas has provided us to various sections of his chapter:


Here are excerpts:


magnesium level

physical examination 
  • Hyperreflexia
EKG manifestations
  • Most common is prolonged QT interval, which may progress to Torsade de Pointes.
  • May prolong all intervals (PR, QRS, QT).
  • May increase risk of various other arrhythmias (especially atrial fibrillation).


  • Cardiac arrest from Torsade de pointes.
  • Atrial fibrillation or atrial flutter
  • Frequent premature atrial complexes or premature ventricular complexes
neuromuscular hyperexcitability
  • seizure
  • delirium, depression, psychosis
  • cerebellar dysfunction (ataxia, downbeat nystagmus, slurred speech, tremor)
  • paresthesias
  • muscle cramps, tremors, fasciculation, hyperreflexia, even tetany

Downbeat nystagmus may be caused by hypomagnesemia, Wernicke’s encephalopathy, or structural brain lesions.  Get a CT scan, but also check electrolytes & consider thiamine.  

other potential consequences
  • Insulin resistance


  • Diuretics (except for potassium-sparing diuretics)
  • Antibiotics
    • Aminoglycosides
    • Amphotericin B
    • Pentamidine
    • Foscarnet
  • Cyclosporine & tacrolimus
  • Platinum-based chemotherapy
  • EGFR receptor blockers (cetuximab, panitumumab, matuzumab)
  • Proton pump inhibitors
other electrolyte abnormalities (electrolytic disarray)
  • Hypercalcemia
  • Hyperphosphatemia
  • Metabolic acidosis
renal disease
  • Chronic tubulointerstitial disease
  • Diuresis after recovery from ATN or renal obstruction
  • Administration of Mg-free IV fluid
  • Osmotic diuresis (e.g. hyperglycemia)
  • Renal tubular acidosis
gastrointestinal disease
  • Malabsorption
    • Proton pump inhibitors
    • Inflammatory bowel disease
  • Diarrhea, vomiting, NG suction
  • Pancreatitis
  • Diarrhea
specific situations
  • Chronic alcoholism, protein calorie malnutrition, anorexia
  • Diabetes, insulin, refeeding syndrome
  • Large volume transfusion of citrated blood products
  • Continuous renal replacement therapy (CRRT)
  • Ethylene glycol intoxication
  • Sepsis

evaluation of cause

  • Check complete panel of electrolytes (including Ca/Mg/Phos).


Click the above link for treatment details.

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