- Hypernatremia
- Hyponatremia
- Overview of Disorders of Potassium Concentration
- Hyperkalemia
- Hypokalemia
- Overview of Disorders of Calcium Concentration
- Hypercalcemia
- Hypocalcemia
- Overview of Disorders of Magnesium Concentration
- Hypermagnesemia
- Hypomagnesemia
- Overview of Disorders of Phosphate Concentration
- Hyperphosphatemia
- Hypophosphatemia
- Syndrome of Inappropriate ADH Secretion (SIADH)
Hypermagnesemia is a serum magnesium concentration > 2.6 mg/dL (> 1.05 mmol/L). The major cause is kidney failure. Symptoms include hypotension, respiratory depression, and cardiac arrest. Diagnosis is by measurement of serum magnesium concentration. Treatment includes IV administration of calcium gluconate and possibly furosemide; hemodialysis can be helpful in severe cases.
(See also Overview of Disorders of Magnesium Concentration.)
Symptomatic hypermagnesemia is fairly uncommon. It occurs most commonly in patients with kidney failure after ingestion of magnesium-containing medications, such as antacids or purgatives. Hypermagnesemia may also occur in patients with diabetic ketoacidosis, hypothyroidism, and hyperparathyroidism.
Even asymptomatic hypermagnesemia is rare in patients with normal kidney function.
Symptoms and signs include hyporeflexia, hypotension, respiratory depression, and cardiac arrest.
Diagnosis of Hypermagnesemia
Serum magnesium concentrations > 2.6 mg/dL (> 1.05 mmol/L)
At serum magnesium concentrations of 6 to 12 mg/dL (2.5 to 5 mmol/L), the ECG shows prolongation of the PR interval, widening of the QRS complex, and increased T-wave amplitude.
Deep tendon reflexes disappear as the serum magnesium concentration approaches 12 mg/dL (5.0 mmol/L); hypotension, respiratory depression, and narcosis develop with increasing hypermagnesemia. Cardiac arrest may occur when blood magnesium concentration is > 15 mg/dL (6.0 to 7.5 mmol/L).
Treatment of Hypermagnesemia
Calcium gluconateCalcium gluconate
Diuresis or dialysis
Treatment of severe magnesium toxicity (eg, 12 mg/dL [5.0 mmol/L]) consists of circulatory and respiratory support and administration of 10% calcium gluconate 10 to 20 mL IV. Treatment of severe magnesium toxicity (eg, 12 mg/dL [5.0 mmol/L]) consists of circulatory and respiratory support and administration of 10% calcium gluconate 10 to 20 mL IV.Calcium gluconate may temporarily reverse many of the magnesium-induced changes, including respiratory depression.
Administration of IV furosemide can increase magnesium excretion when kidney function is adequate; volume status should be maintained.Administration of IV furosemide can increase magnesium excretion when kidney function is adequate; volume status should be maintained.
Hemodialysis may be valuable in severe hypermagnesemia, because a relatively large fraction (approximately 70%) of magnesium in the blood is not protein-bound and thus is removable with hemodialysis. When hemodynamic compromise occurs and hemodialysis is impractical, peritoneal dialysis is an option.
