LAUSR

The article from Cheminet et al. [1], published in this issue of Internal and Emergency Medicine, highlights the need for clinicians to remain cognizant of the potential clinical impact of extreme hypomagnesemia, which is perhaps underrecognized and underappreciated compared to other electrolyte dyscrasias. Magnesium, an inorganic cofactor for hundreds of vital physiological enzymatic reactions, is one of the most abundant cations in the body [2]. Hypomagnesemia most often occurs due to excessive gastrointestinal or renal losses, or impaired uptake, and is relatively frequent in inpatient settings [3]. Due to the ubiquity of the magnesium cation, hypomagnesemia has a broad symptomatic profile with significant neurologic, muscular, and cardiovascular effects. Severe hypomagnesemia classically manifests with tetany, seizures, dysrhythmias, hypotension, and may result in death. Symptoms of severe hypomagnesemia may not be observed until serum levels decrease below 1.2 mg/dL (0.5 mmol/L). As mentioned in the accompanying article, there is a paucity of medical literature describing the characteristics of patients with hypomagnesemia below this range. In clinical practice, magnesium levels are most often checked in conjunction with other electrolytes. The appreciation of its significance seems low; as the article notes, only 10.3% of inpatients at George Pompidou European Hospital between 2000 and 2015 had magnesium level assessment. Furthermore, of the 119 patients identified to have extreme hypomagnesemia, 44 (37%) received no magnesium supplementation, and had no further magnesium laboratory assessment. It would be difficult to imagine a similar proportion of no follow-on care or evaluation in, for example, a population of inpatients found to have extreme hypocalcemia. Clinical correlation of measured magnesium levels is further muddled by the fact that serum magnesium may not accurately reflect intracellular or total body magnesium. For example, serum ionized magnesium levels are lower than serum magnesium concentration in diabetic patients [4] and in patients with Alzheimer’s disease [5]. Other tests such as ionized Mg, tissue Mg, free Mg, and Mg retention tests may more accurately reflect Mg adequacy, but these tests are often not available to clinicians. There is good evidence for the use of supplemental Mg in preeclampsia/eclampsia, various cardiac dysrhythmias, migraine headache, metabolic syndrome, diabetes and diabetic complications, premenstrual syndrome, hyperlipidemia, and asthma [6]. Further studies are needed to ascertain the baseline magnesium profile in these clinical settings, and to better understand the role for magnesium level testing in acute and chronically ill patients.