Magnesium

Hypermagnesemia

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Hypermagnesemia, High Serum Magnesium

  • See Also
  1. Serum Magnesium
  2. Hypomagnesemia
  3. Magnesium Sulfate
  • Definitions
  1. Hypermagnesemia
    1. Serum Magnesium over 2.5 meq/L
    2. Typically asymptomatic until Serum Magnesium >4-5 mg/dl
  • Symptoms
  1. Muscle Weakness
  2. Headache
  3. Excessive thirst
  • Signs
  1. Hyporeflexia
  2. Clonus
  3. Severe findings (Serum Magnesium >10 mEq/dl)
    1. Bradyarrhythmia
    2. Hypotension
    3. Respiratory depression
    4. Pulmonary Edema
  • Causes
  1. Renal Failure
    1. Acute Renal Failure
    2. Chronic Renal Failure (End Stage Renal Disease or ESRD)
  2. Medication overuse
    1. Antacids
    2. Laxative abuse
    3. Milk of Magnesia
    4. Maalox
  3. Adrenal Insufficiency (Addison's Disease)
  4. Hypothyroidism (Myxedema)
  5. Massive Magnesium dosing or intake
    1. Preeclampsia or Eclampsia management
  6. Tissue breakdown
  • Labs
  1. See Serum Magnesium
  2. Serum Magnesium level is reliable in Hypermagnesemia (contrast with Hypomagnesemia)
  3. Serum Magnesium Interpretation
    1. Normal in pregnancy: 1.3 to 2.6 mg/dl
    2. Therapeutic in Preeclampsia: 5.5-7.5 mg/dl
    3. Loss of Patellar Reflex: 10-12 mg/dl
    4. Respiratory depression: 15-17 mg/dl
    5. Paralysis: 15-17 mg/dl
    6. Cardiac Arrest: 30-35 mg/dl
  • Management
  1. Stop all Magnesium Sources
  2. Supportive Care with ABC Management
  3. Hemodialysis
    1. Indicated in End Stage Renal Disease and severe, refractory signs
  4. Cardiotoxicity Management: Calcium
    1. Calcium Chloride (1.4 mEq/ml)
      1. Dose: 5 ml over 10 minutes
      2. May repeat second dose in 5 minutes if EKG not improved
      3. Preferred historically for shock or cardiac instability (especially if central access)
        1. However Calcium Gluconate likely has same efficacy with better peripheral IV safety
        2. See Intravenous Calcium for differences between Calcium preparations
    2. Calcium Gluconate 10% (0.4 mEq/ml)
      1. Preferred agent if only peripheral IV available (Decreased venous sclerosis with infusion)
      2. Initial dose: 10 ml over 2-5 minutes (10 minutes is lower risk if time allows)
      3. Second dose after 5 minutes if EKG not improved
      4. Advantages over Calcium Chloride
  • References
  1. Willis and Swaminathan in Swadron (2023) EM:Rap 23(6): 4-5