Hypermagnesemia

Excerpt

Magnesium is a glossy gray solid included in the second column (group 2, or alkaline earth metals) of the periodic table. Joseph Black discovered this element in 1755. The origin of the name derives from Magnesia, a district of Eastern Thessaly in Greece. Magnesium improves the mechanical features of aluminum and is thus has uses as an alloying agent for airplane and car construction. It also serves as a mordant for dyes (magnesium sulfate), added to plastics to make them fire retardant (magnesium hydroxide), in electronics (e.g., phones, laptops, tablet computers, cameras, and other electronic components), in heat-resistant cookware (magnesium oxide), and in agriculture as a fertilizer. Furthermore, magnesium is widely used in medicine, for instance, in the treatment of ventricular arrhythmia associated with torsade de pointes, or as an antacid and laxative. Regimens using intravenous or intramuscular magnesium sulfate are recommendations for the prevention and treatment of eclampsia.

Magnesium is an essential element for the life of plants as it is part of chlorophyll. Moreover, it is abundant in animal tissues, where it is fundamental for enzymatic action, transporters, and the synthesis of nucleic acids. It influences other electrolytes such as sodium, calcium, and potassium. Together with calcium, extracellular magnesium is of paramount importance for neuromuscular functions as well as for electrical activity of the myocardium and vascular tone. Magnesium introduced into the diet, in particular through vegetables, is absorbed in the intestinal tract, especially in the small intestine. Factors that improve its absorption include vitamin D, parathormone, growth hormone, thyroid hormones, and the presence of sodium in the diet. Calcium, fats, phosphates, and phytic acid can decrease intestinal absorption. Normally, an adult individual possesses about 25 g of magnesium. It is present mainly in the bones as salts (about 65%) and muscles, and only 1% in extracellular fluids. Serum levels vary from 0.7 to 1.0 mmol/L (or 1.5 to 2.0 mEq/L, or 1.7 to 2.4 mg/dL).

Small changes in values may not be clinically relevant, and critical reference values are below 0.5 mmol/L (or 1.0 mg/L) and above 2.0 mmol/L (or 4.9 mg/dL). Hypomagnesemia is quite frequent, although the symptomatology (cramps, muscle spasms, paresthesia, and arrhythmias) appears only when exceeding the critical value. On the other hand, hypermagnesemia is a rare but serious electrolytic disorder, which can be fatal if not recognized and treated promptly.