Hypomagnesemia is defined as a serum magnesium level below 1.7 mg/dL.
Most patients with borderline hypomagnesemia are asymptomatic.
Hypomagneemia is present 3 to 10% of the general population and its prevalence is increased among individuals with type two diabetes and hospitalized patients, especially those in the ICU.
Hypomagnesia is associated with an elevated risk of death from any cause and death from cardiovascular causes.
May cause hypocalcemia, paresthesias, and seizures.
More than 60% of the body’s magnesium stores reside in bone, and nearly 70% of serum magnesium circulates freely, not bound to plasma proteins.
Can be responsible for neurological, respiratory and cardiovascular symptoms.
Hypomagnesemia is seen in 2% of the general population, 10-20% in hospitalized patients, 50-60% in intensive care unit patients, 60-80% of alcoholics, and 25% of diabetics.
Associated with impaired intake in alcoholics, undernourished, with intestinal malabsorption syndrome, prolonged vomiting and with the use of nasogastric tubes and in ICU setting.
Hypomagnesia may result from inadequate dietary intake, increased gastrointestinal, loss, reduced renal reabsorption, or redistribution of magnesium from the extracellular to the cellular space.
Excessive renal losses seen with loop diuretics, thiazide and saline infusions, and interstitial nephritis.
In patients with heart failure, the critically ill, and patients recently undergoing dialysis is associated with the high mortality rate.
For every 0.49 mg of deciliter serum reduction there is a 30% increase in cardiovascular disease.
Low serum magnesium levels are associated with an increased incidence of hospitalization and increased mortality, especially when associated with concurrent hypokalemia.
Seen with hyperaldosterone states such as primary hyperaldosteronism, cirrhosis, congestive heart failure and fluid depletion.
Can be seen with osomotic diuresis associated with diabetes mellitus.
Seen with nephrotoxic drugs cisplatin, amphotericin, aminoglycoside antibiotics.
Associated with hypokalemia, hypercalcemia and hypercalciuria.
Associated with lesions of the proximal tubules, such as Fanconi’s disease and interstitial nephritis.
Magnesium absorbed in the small intestine, mainly in the ileum, via active and passive transport mechanisms.
Magnesium excreted in the stool and urine.
Regulation of serum levels of magnesium under renal control.
Most renal absorption of magnesium occurs in the proximal tubule and the ascending limb of the loop of Henle.
Magnesium in the presence of hypomagnesememia the kidney may excrete as little as 1 mEq/L.
Magnesium in times of deficiency may be removed from bone.
Low blood magnesium makes spontaneous cardiac muscle depolarization more likely.
Hypomagnesemia is sometimes caused by the proton-pump inhibitor (PPI) inhibitors.
Hypomagnesemia is usually associated with other electrolyte derangements, including hypocalcemia, hypokalemia, and metabolic alkalosis.
Only in severe cases of hypomagnesemia with serum levels of less than 1.2 mg/dL do symptoms, such as neuromuscular irritability, cardiovascular abnormalities and metabolic disorders become evident.
Treatment depends on the degree of deficiency and the clinical status.
Oral replacement is appropriate for a mild process, while IV replacement is indicated for severe clinical disease.
Impaired renal function may increase toxicity of magnesium administration.
Diarrhea is most common adverse effect of oral magnesium.
Intravenous therapy is with 2-4 g of 50% magnesium sulfate diluted in saline or dextrose IV over 30-60 minutes.
In cases of life-threatening arrhythmias intravenous push of the magnesium sulfate is appropriate.
Intravenously administered magnesium may alter cardiac conduction, leading to heart block in digitalized patients decrease respiratory rate, impair deep tendon reflexes.
Renal function should be monitored when magnesium is administered parenterally.
Administering magnesium intravenously may produce significant hypertension or asystole.
If an overdose occurs, calcium gluconate, 10-20 mL of 10% solution IV, can be given as antidote for hypermagnesemia.