Hypomagnesemia

Aka: Hypomagnesemia, Low Serum Magnesium, Magnesium Deficiency, Hypomagnesemia Causes

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II. Causes

  1. Decreased Intake
    1. Protein calorie Malnutrition
    2. Starvation
    3. Alcoholism (Prevalence: 30-80% of Alcoholics)
      1. Among the most common causes of Hypomagnesemia in the Emergency Department
    4. Prolonged IV Therapy
      1. Inadequate Parenteral supplementation
  2. Decreased Absorption
    1. Malabsorption (e.g. Celiac Sprue, Crohns Disease, Bariatric Surgery)
    2. Small Intestine absorption
    3. Neonatal gut immaturity
  3. Excessive Gastrointestinal losses
    1. Prolonged gastric suction
    2. Laxatives
    3. Intestinal or biliary fistula
    4. Severe Diarrhea
  4. Excessive Renal Losses
    1. Diuretics
    2. Acute Tubular Necrosis (Diuretic phase)
    3. Acute Renal Failure diuresis
    4. Primary Aldosteronism
    5. Hypercalcemia
    6. Renal Tubular Acidosis (RTA)
    7. Idiopathic renal wasting
    8. Chronic Renal Failure with wasting
  5. Miscellaneous Causes
    1. Idiopathic
    2. Acute Pancreatitis
    3. Porphyria with SIADH
    4. Multiple transfusions with citrated blood
  6. Endocrine
    1. Hyperthyroidism
    2. Hyperparathyroidism
    3. Poorly controlled Diabetes Mellitus and Diabetic Ketoacidosis
    4. Hyperaldosteronism
  7. Medications
    1. Proton Pump Inhibitors
      1. Florentin (2012) World J Nephrol. 2012 Dec 6;1(6):151-4 +PMID: 24175253 [PubMed]
      2. Srinutta (2019) Medicine 98(44):e17788 +PMID: 31689852 [PubMed]
    2. Cisplatin
    3. Cyclosporin
    4. Aminoglycosides (e.g. Gentamycin)
    5. Ticarcillin
    6. Carbenicillin
    7. Amphotericin B
    8. Foscarnet

III. Symptoms (Serum Magnesium <1.2 mg/dl)

  1. Loss of appetite
  2. Nausea or Vomiting
  3. Fatigue
  4. Weakness
  5. Vertigo
  6. Dysphagia
  7. Paresthesias

IV. Signs

  1. Seizures
  2. Muscle cramps to Tetany
  3. Chvostek's Signs
  4. Vertical Nystagmus
  5. Arrhythmias

V. Labs

  1. See Serum Magnesium
  2. Serum Magnesium reflects only 1% of total Magnesium
    1. Muscles and bone contain 99% of Magnesium stores
  3. Serum Potassium is a marker of total Magnesium
    1. When Serum Potassium is low, magenesium is often also depleted

VI. Diagnostics

  1. Electrocardiogram (EKG)
    1. Frequent Premature Contractions (PVCs)
    2. Non-sustained Ventricular Tachycardia
    3. Prolonged QTc (with risk of Torsades de Pointes)

VII. Differential Diagnosis

  1. Hypocalcemia
    1. Hypocalcemia and Hypomagnesemia share similar initial, early symptoms
    2. Both may demonstrate Chvostek Sign, Trousseau Sign
  2. Seizure Disorder
    1. Hypomagnesemia may be associated with Tetany in more severe cases
    2. However, patient will be alert with Tetany, while unresponsive in Generalized Tonic Clonic Seizures
    3. Seizures may also occur with Hypomagnesemia

VIII. Management

  1. See Magnesium Replacement
  2. See Potassium Replacement (Potassium is frequently depleted when Magnesium is depleted)
  3. Asymptomatic and mildly symptomatic patients (e.g. Muscle Weakness) may undergo oral Magnesium Replacement
  4. Severe symptoms should be managed with intravenous Magnesium Replacement
    1. Start with Intravenous Magnesium 2 g IV over 30 to 60 minutes
    2. Next initiate an infusion at 1 gram/hour
    3. Use decreased Magnesium doses in Renal Insufficiency

IX. References

  1. Willis and Swaminathan in Swadron (2023) EM:Rap 23(6): 4-5

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