Magnesium Imbalances: Causes and Manifestations

Magnesium

• Roles of Magnesium
  • Coenzyme in metabolism of carbohydrates
  • Required for DNA and protein synthesis
  • Blood glucose control
  • BP regulation
  • Necessary for ATP production
  • Acts directly on myoneural junction
  • Important for normal cardiac function
  • 50% to 60% contained in bone
  • Absorbed in GI tract
  • Excreted by kidneys
• Hypermagnesemia
  • High serum Mg caused by
    • Increased intake or ingestion of products containing magnesium when renal insufficiency or failure is present
    • Excess IV magnesium administration
  • Manifestations
    • Lethargy
    • Nausea and vomiting
    • Impaired reflexes
    • Muscle paralysis
    • Respiratory and cardiac arrest
    • Urinary retention
    • Flushed, warm skin, especially facial
    • Decreased Pulse, Decreased BP
  • Management
    • Prevention first—restrict magnesium intake in high-risk patients
    • IV CaCl or calcium gluconate if symptomatic
    • Fluids and IV furosemide to promote urinary excretion
    • Dialysis
• Hypomagnesemia
  • Low serum Mg caused by
    • Prolonged fasting or starvation
    • Chronic alcoholism
    • Fluid loss from gastrointestinal tract
    • Prolonged parenteral nutrition without supplementation
    • Diuretics
    • Hyperglycemic osmotic diuresis
  • Manifestations
    • Hyperactive deep tendon reflexes
    • Muscle cramps
    • Tremors
    • Seizures and confusion
    • Cardiac dysrhythmias
    • Corresponding hypocalcemia and hypokalemia
    • Chvostek’s and Trousseau’s signs
    • Increased Pulse, Increased BP, dysrhythmias
  • Management
    • Treat underlying cause
    • Oral supplements
    • Increase dietary intake
    • Parenteral IV or IM magnesium when severe