Magnesium is one of the body's major electrolytes. As the second most common intracellular cation, it plays a vital role in many cellular metabolic pathways.[1] Magnesium is required for deoxyribonucleic acid (DNA) and protein synthesis. It is a necessary cofactor for most enzymes in phosphorylation reactions. It is also important for parathyroid hormone synthesis.
The total body content of this central cation is 2000 mEq, or 24 g. The magnesium is distributed in bone (67%), intracellularly (31%), and extracellularly (a mere 1%).[2] The intracellular concentration is 40 mEq/L, while the normal serum concentration is 1.5-2.0 mEq/L. Of this serum component, 25-30% is protein bound, 10-15% is complexed, and the remaining 50-60% is ionized.
Magnesium is absorbed in the ileum and excreted in stool and urine. The minimum daily requirement of magnesium is 300-350 mg, or 15 mmol; this amount is easily obtainable with a normal daily intake of fruits, seeds, and vegetables because magnesium is a component of chlorophyll and is present in high concentrations in all green plants.
The kidney is the main regulator of magnesium concentrations. Absorption occurs primarily in the proximal tubule and thick ascending limb of the loop of Henle.
Hypermagnesemia is a rare electrolyte abnormality because the kidney is very effective in excreting excess magnesium.[3]
Magnesium excess affects the CNS, neuromuscular, and cardiac organ systems. It most commonly is observed in renal insufficiency and in patients receiving intravenous (IV) magnesium for treatment of a medical condition.[4]
United States
Hypermagnesemia occurs only rarely in the United States.
A study by Haider et al that screened 5,339 patients with plasma magnesium concentrations reported that 36.9% of the 151 patients with hypermagnesemia died and that hypermagnesemia was a strong independent risk factor for mortality.[5]
Common causes of hypermagnesemia include renal failure and iatrogenic manipulations.[6] However, other diseases may result in increased magnesium; the degree of elevation determines the symptoms. Acute elevations of magnesium usually are more symptomatic than slow rises.
Magnesium levels of 2-4 mEq/L are associated with the following:
High magnesium levels are associated with depressed levels of consciousness, respiratory depression, and cardiac arrest.
Physical findings are related to the serum magnesium levels.
Serum magnesium levels of 3.5-5 mEq/L are associated with the following:
Serum magnesium levels of 5-6 mEq/L are related to the following:
Serum magnesium levels of 8-10 mEq/L are associated with the following:
Levels of serum magnesium greater than 10 mEq/L are related to the following:
Elevated levels of magnesium also are associated with the following:
Most cases of hypermagnesemia are due to iatrogenic interventions and administration,[1] especially errors in calculating appropriate infusions. Additional causes include the following:
Electrolytes, including potassium, magnesium, and calcium levels[7, 8]
BUN and creatinine levels
Check serum creatine phosphokinase (CPK) level or urine myoglobin level in patients in whom rhabdomyolysis is suspected.
Arterial blood gases (ABG) may reveal a respiratory acidosis.
Thyroid function tests
An ECG and cardiac monitor may show prolongation of the PR interval or intraventricular conduction delay, which are nonspecific findings.
The ECG findings may reflect other electrolyte abnormalities such as hyperkalemia.
Although the effectiveness of dialysis in removing divalent cations is debated, some studies have demonstrated removal of a large amount of magnesium using this modality. Dialysis is best used when levels exceed 8 mEq/L, when life-threatening symptoms are present, or in patients with poor renal function.
Obtain a renal consultation for dialysis if the patient is severely hypermagnesemic.
Arrange ICU monitoring if the symptoms are severe.
Treatment depends upon the level of magnesium and the presence of symptoms. In patients with mildly increased levels, simply stop the source of magnesium. In patients with higher concentrations or severe symptoms, other treatments are necessary. Calcium should be reserved for patients with life-threatening symptoms, such as arrhythmia or severe respiratory depression.
Clinical Context: Both fluids are essentially isotonic, and, while some of their metabolic effects differ, the differences are clinically irrelevant for the purpose of promoting diuresis.
Intravenous fluids work by dilution of the extracellular magnesium. Fluids are used with diuretics to promote increased excretion of magnesium by the kidney.
Clinical Context: Acts at loop of Henle to promote loss of magnesium in urine.
Clinical Context: Directly antagonizes neuromuscular and cardiovascular effects of magnesium. The 10% IV solution provides 100 mg/mL of calcium gluconate that equals 9 mg/mL (0.46 mEq/mL) of elemental calcium. One 10 mL ampule contains 93 mg of elemental calcium.
Calcium directly antagonizes the effects of magnesium. Reserved for patients with severe or symptomatic hypermagnesemia.
Consider transfer if a patient with renal failure has a severe elevation of magnesium and no dialysis is available.
Complications of magnesium administration seen in the ED often are a function of the rate and/or concentration of delivery rather than the total amount administered.
Provide information regarding avoidance of medications that cause hypermagnesemia.