Medical Care
Symptoms and signs of magnesium intoxication respond to intravenous calcium. Calcium chloride (5 mL of a 10% solution) may be administered intravenously over 30 seconds to directly antagonize the cardiac and neuromuscular effects of excess extracellular magnesium. Monitor these patients in an intensive care unit (ICU) setting and give careful attention to ECG parameters.
In order to promote a more sustained decrease in serum magnesium, patients with normal urine output and renal function may be treated with intravenous saline infusions and furosemide diuresis.
Dialysis for hypermagnesemia may be used for patients with the following:
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Renal insufficiency
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Severe asymptomatic hypermagnesemia (>8 mg/dL)
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Serious cardiovascular or neuromuscular symptoms at any serum magnesium level
Cathartics or enemas that do not contain magnesium may be used to enhance GI clearance of excess ingested magnesium.
Resolution of hypermagnesemia should occur before discharge from the hospital.
Consultations
A nephrology consult may be obtained for refractory cases of hypermagnesemia or for patients with hypermagnesemia who require urgent dialysis.
Diet
Advise the patient with hypermagnesemia to discontinue oral laxatives, antacids, or other preparations that contain magnesium.
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(A) Magnesium reabsorption in the thick ascending limb of the loop of Henle. The driving force for the reabsorption against a concentration gradient is a lumen-positive voltage gradient generated by the reabsorption of NaCl. FHHNC = Familial hypomagnesemia with hypercalciuria and nephrocalcinosis. ADH = autosomal dominant hypocalcemia. FHH/NSHPT = Familial hypomagnesemia/neonatal severe hyperparathyroidism. (B) Magnesium reabsorption in the distal convoluted tubule. Active transcellular transport is mediated by an apical entry through a magnesium channel and a basolateral exit, presumably via a Na+/Mg2+ exchange mechanism. HSH = Hypomagnesemia with secondary hypocalcemia. GS = Gitelman syndrome. IDH = Isolated dominant hypomagnesemia. Source: Konrad M, Schlingmann KP, Gudermann T: Insights into the molecular nature of magnesium homeostasis. Am J Physiol Renal Physiol 2004; 286: F599-F605.
