Hypomagnesemia: Clinical Features, Evaluation & Treatment

Hypomagnesemia occurs when the serum magnesium concentration falls below 1.0 mEq/L.

CLINICAL FEATURES

1. Symptoms: Malaise, diffuse weakness, anorexia, nausea, vomiting, and seizures

2. Physical examination findings: Mimic findings of hypocalcemia, with nervous system complaints dominating the clinical picture. Chvostek sign, Trousseau sign, tremors, twitching, clonus, increased deep tendon reflexes, carpopedal spasm, frank tetany, delirium, movement disorders, and dysarthria

EVALUATION

1. Laboratory studies include serum magnesium, calcium, BUN, creatinine, and glucose levels and a serum electrolyte panel.

2. Electrocardiography: ECG findings include atrial and ventricular tachyarrhythmias, torsades de pointes, and a prolonged QT interval. 

Arrhythmias caused by hypomagnesemia may not respond to the usual antiarrhythmic therapy, but they may respond well to intravenous magnesium. Magnesium (2 g) should be administered rapidly over 2 minutes via an intravenous line to patients with pulseless ventricular tachycardia suspected of being hypomagnesemia (e.g., a patient with myocardial infarction who is taking diuretics).

3. Ancillary tests (e.g., radiographs) may be required to diagnose the underlying cause.

THERAPY

1. Mild hypomagnesemia: Oral supplementation. Magnesium hydroxide (200 to 600 mg, four times daily) is usually used.

2. Severe hypomagnesemia: Marked neurologic manifestations or malignant ventricular arrhythmias is treated with 2 to 4 g of magnesium sulfate administered in 100 to 200 mL of 5% dextrose in water over 20 minutes. Additional treatment should be directed toward correcting the underlying cause of hypomagnesemia.

DISPOSITION: Indications for admission include a serum magnesium level below 1 mEq/L, severe central neurologic manifestations, cardiac arrhythmias, and severe underlying disorders.