You are in: eMedicine Specialties > Emergency Medicine > ENDOCRINE AND METABOLIC HypermagnesemiaArticle Last Updated: Oct 11, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Nona P Novello, MD, Associate Chair, Department of Emergency Medicine, Franklin Square Hospital Nona P Novello is a member of the following medical societies: American College of Emergency Physicians and Phi Beta Kappa Coauthor(s): Howard A Blumstein, MD, FAAEM, Assistant Professor, Surgery; Medical Director, Department of Emergency Medicine, Wake Forest University School of Medicine Editors: Joseph J Sachter, MD, FACEP, Consulting Staff, Department of Emergency Medicine, Muhlenberg Regional Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Jeffrey L Arnold, MD, FACEP, Chairman, Department of Emergency Medicine, Santa Clara Valley Medical Center; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital Author and Editor Disclosure Synonyms and related keywords: magnesium, high magnesium level, electrolytes, magnesium absorption, electrolyte abnormality, excess magnesium, renal insufficiency, intravenous magnesium, iatrogenic manipulation, adrenal insufficiency, secondary hypermagnesemia, hyperkalemia, hypercalcemia, magnesium toxicity, acute renal failure, maternal eclampsia, tumor lysis syndrome, rhabdomyolysis, milk-alkali syndrome, hypothyroidism, hypoparathyroidism, lithium intoxication, diabetic ketoacidosis, DKA INTRODUCTIONSection 2 of 10
  BackgroundMagnesium 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. 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%). 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. PathophysiologyMagnesium 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. FrequencyUnited StatesHypermagnesemia occurs only rarely in the United States. CLINICALSection 3 of 10
HistoryCommon causes of hypermagnesemia include renal failure and iatrogenic manipulations. 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.
PhysicalPhysical findings are related to the serum magnesium levels.
CausesMost cases of hypermagnesemia are due to iatrogenic interventions and administration, especially errors in calculating appropriate infusions. Additional causes include the following:
DIFFERENTIALSSection 4 of 10
Adrenal Insufficiency and Adrenal Crisis Hypercalcemia Hyperkalemia Hypoparathyroidism Hypothyroidism and Myxedema Coma Renal Failure, Acute Renal Failure, Chronic and Dialysis Complications Rhabdomyolysis Toxicity, Lithium
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| Drug Name | Normal saline or lactated Ringer solution |
|---|---|
| Description | Both fluids are essentially isotonic, and, while some of their metabolic effects differ, the differences are clinically irrelevant for the purpose of promoting diuresis. |
| Adult Dose | 1 L IV |
| Pediatric Dose | 20 mL/kg IV initially |
| Contraindications | Poor renal function; inadequate urine output; pulmonary edema |
| Interactions | None reported |
| Pregnancy | A - Fetal risk not revealed in controlled studies in humans |
| Precautions | Administration of IV fluids requires close monitoring of cardiovascular and pulmonary function; fluids should be stopped when desired hemodynamic response is seen or pulmonary edema develops |
These agents increase excretion of magnesium by the kidney.
| Drug Name | Furosemide (Lasix) |
|---|---|
| Description | Acts at loop of Henle to promote loss of magnesium in urine. |
| Adult Dose | 20-80 mg/dose IV; single dose not to exceed 6 mg/kg |
| Pediatric Dose | 1 mg/kg/dose IV q6-12h prn |
| Contraindications | Documented hypersensitivity; hepatic coma; anuria; severe electrolyte depletion |
| Interactions | Metformin decreases concentrations; interferes with hypoglycemic effect of antidiabetic agents and antagonizes muscle-relaxing effect of tubocurarine; aminoglycosides increase auditory toxicity—hearing loss of varying degrees may occur; may enhance anticoagulant activity of warfarin; may increase plasma lithium levels and toxicity |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Perform frequent serum electrolyte, CO2, glucose, creatinine, uric acid, calcium, and BUN determinations during first few months of therapy and periodically thereafter |
Calcium directly antagonizes the effects of magnesium. Reserved for patients with severe or symptomatic hypermagnesemia.
| Drug Name | Calcium gluconate (Kalcinate) |
|---|---|
| Description | 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. |
| Adult Dose | 100-200 mg 10% solution IV continuous infusion (2-4 mg/kg/h) |
| Pediatric Dose | 2 mg/kg of elemental calcium IV (about 20 mg/kg of calcium gluconate 10%) |
| Contraindications | Renal calculi; hypercalcemia; hypophosphatemia; renal or cardiac disease; digitalis toxicity |
| Interactions | May decrease effects of tetracyclines, atenolol, salicylates, iron salts, and fluoroquinolones; antagonizes effects of verapamil; large intakes of dietary fiber may decrease calcium absorption and levels |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Caution in digitalized patients, respiratory failure, acidosis, or severe hyperphosphatemia |
Article Last Updated: Oct 11, 2007
