Diagnosis

Hypermagnesemia

Etiology

Cause [28d]

• Decreased renal excretion:

  • Renal failure is the most common cause

  • Addisons disease

  • Hypothyroidism

  • Hyperparathyroidism (calcium-induced magnesium absorption in the tubule)

  • Familial hypocalciuric hypercalcemia

  • Drugs: lithium, antacids, ACE-inhibitors, NSAIDs

• Increased intake:

  • Drugs: cathartics, laxatives, rectal enema, theophylline, anticholinergics

  • Bowel conditions (enhanced absorption)

  • Milk-alkali syndrome

  • Magnesium therapy (eclampsia): both mother and the newborn

• Compartment shift or leak: Magnesium is mainly in the intracellular compartment

  • Acidosis (diabetic ketoacidosis)

  • Cellular destruction:

    • Shock

    • Burns

    • Leukemia

    • Hemolysis

    • Tumor lysis syndrome

    • Rhabdomyolysis

Pathophysiology [p6s]

1. Magnesium is a physiologic calcium blocker, cofactor in hundreds of enzymatic reactions, critical to diverse molecular and catalytic processes, including energy transfer and maintenance of the genome [p6s][28d]

2. Hypomagnesemia: associated with atherosclerosis and coronary artery disease [n8e]

3. Hypermagnesemia inhibit the secretion of PTH --> hypocalcemia [sem]

4. Distribution of magnesium: [pnf]

   • Bone: 60%

   • Extracellular: 1% (does not reflect total body stores.)

   • Intracellular: 39% (the second most common intracellular cation)

     • Muscle: 25-30%

     • Soft tissue: 10-15%

5. Magnesium balance is determined by:

   • Dietary ingestion

   • Intestinal absorption

   • Bone and soft tissue deposition and efflux

   • Renal excretion and absorption

   • No hormone regulating (unlike calcium (PTH))

Complications [28d]

• Cardiovascular: hypotension and arrhythmia

• Neurological: confusion and lethargy

• Cardiorespiratory arrest

• Coma

Epidemiology

Incidence per 100.000 [b91][p6s][n8e][nwi][nts][oow]

Prevalence per 100.000 [b91][p6s][n8e][nwi][nts][oow]

Approach

• Blood test: Magnesium level, blood urea nitrogen, creatinine, glucose, potassium, phosphate, calcium levels [28d]

• Urine specific gravity

• Arterial blood gas

• ECG

Treatment

1. Preserved renal function and mild asymptomatic hypermagnesemia (<7 mg/dL): [28d]

   • No treatment other than removal of exogenous magnesium

2. Severe cases (>12 mg/dL): monitor ECG, blood pressure, and neuromuscular function

   • Saline IV (150 ml/hour)

   • Loop diuretics IV (Furosemide 1 mg/kg)

   • Calcium gluconate or chloride IV: 1 g in 5 min (repeatable over 5 minutes), counteracts neurologic/muscular manifestations

3. If renal failure: Hemodialysis

Differential diagnoses

Acute renal failure, Adrenal insufficiency, Diabetic ketoacidosis, Drug side effects, Familial hypocalciuric hypercalcemia, Hemolysis, Hypercalcemia, Hyperkalemia, Hyperparathyroidism, Hypoparathyroidism, Hypothyroidism, Leukemia, Milk-alkali syndrome, Renal failure, Rhabdomyolysis