Hypermagnesemia: Causes, Clinical Features & Treatment

Serum magnesium level greater than 2.5 mEq/L

CAUSES: Because the kidney is efficient in excreting excess magnesium, hypermagnesemia is uncommon except in the presence of renal failure or an iatrogenic cause. Other causes of hypermagnesemia include rhabdomyolysis, tumor lysis, burns, tissue trauma, diabetic ketoacidosis, hypothyroidism, cathartic abuse, antacids, preeclampsia or eclampsia treatment, and adrenal insufficiency.

CLINICAL FEATURES

1. Symptoms: Nausea, vomiting, lethargy, mental confusion, and coma

2. Physical examination findings: When the magnesium level exceeds 4 mEq/L. Depression of the deep tendon reflexes, marked muscle weakness, bulbar paralysis, and respiratory insufficiency.

EVALUATION

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

2. Electrocardiography: Dysrhythmias and cardiac arrest can occur at serum magnesium levels exceeding 8mEq/L, but the ECG manifestations of hypermagnesemia are variable and nonspecific.

THERAPY

1. Exogenous sources of magnesium should be removed.

2. Pharmacologic therapy

a) Calcium gluconate or calcium chloride: Because calcium transiently reverses the effects of hypermagnesemia by acting as a direct antagonist, 10 mL of 10% calcium gluconate or calcium chloride solution can be given intravenously in symptomatic patients.

b) Furosemide: In patients with normal renal function, brisk diuresis with intravenous normal saline and furosemide will enhance urinary magnesium excretion.

3. Dialysis: In patients with very high magnesium levels or patients with renal failure, emergency peritoneal dialysis or hemodialysis may be required.

DISPOSITION: Patients with magnesium levels above 8 mEq/L require admission to a monitored bed and should be considered for early dialysis.