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

Magnesium Imbalances: Causes and Manifestations
Hypermagnesemia (Mg⁺ >2.5 mEq/L [1.25 mmol/L])	Hypomagnesemia (Mg⁺ <1.5 mEq/L [0.75 mmol/L])
Cause
Renal failure	GI tract fluid losses (e.g., diarrhea, NG suction)
IV administration of magnesium, especially for treatment of eclampsia	Chronic alcoholism
Tumor lysis syndrome	Malabsorption syndromes
Hypothyroidism	Prolonged malnutrition
Metastatic bone disease	Increased Urine output
Adrenal insufficiency	Hyperglycemia
Antacids, laxatives	Proton pump inhibitor therapy

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