Seminars in nephrology
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Magnesium is an important constituent of the intracellular space that affects a number of intracellular and whole body functions. Magnesium balance depends on intake and renal excretion, which is regulated mainly in the thick ascending limb of the loop of Henle. The complex hormonal modulation that responds to changes in plasma concentration of other ions such as calcium and potassium is lacking for magnesium. ⋯ The major direct toxicity of hypomagnesemia is cardiovascular. When urgent correction of hypomagnesemia is required, as with myocardial ischemia, post cardiopulmonary bypass, and torsades de pointes, intravenous or intramuscular magnesium sulfate should be used. Oral magnesium preparations are available for chronic use.
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Although an anion gap at less than 20 mEq/L rarely has a defined etiology, significant elevations in the anion gap almost always signify presence of an acidosis that can be easily identified. Anion gap acidoses can be divided into those caused by lactate accumulation, ketoacid production, toxin/drugs, and uremia. Lactic acidoses caused by decreased oxygen delivery or defective oxygen utilization are associated with high mortality. ⋯ Salicylate toxicity usually is associated with a mild metabolic acidosis and a respiratory alkalosis. Uremia is associated with a mild acidosis secondary to decreased ammonia secretion and an anion gap caused by the retention of unmeasured anions. A decrease in anion gap is caused by numerous mechanisms and thus has little clinical utility.