Hypermagnesemia occurs primarily in patients with acute or chronic kidney disease. In these individuals, some conditions, including proton pump inhibitors, malnourishment, and alcoholism, can increase the risk of hypermagnesemia. Hypothyroidism and especially cortico-adrenal insufficiency, are other recognized causes.
Hyperparathyroidism and alterations in calcium metabolism involving hypercalcemia and/or hypo-calciuria can lead to hypermagnesemia through an increased calcium-induced magnesium absorption in the tubule. Patients with familial hypocalciuric hypercalcemia (FHH), a rare autosomal dominant condition, can manifest hypermagnesemia.
Lithium-based psychotropic drugs can also lead to hypermagnesemia by reducing excretion. Patients with milk-alkali syndrome due to the ingestion of large amounts of calcium and absorbable alkali are more susceptible to develop hypermagnesemia. Magnesium levels can increase in hemolysis patients. Red blood cells contain three times as much magnesium as compared to plasma. The rupture of these cells pours magnesium into the plasma. However, symptomatic hypermagnesemia occurs only in the case of aggressive hemolysis. Tumor lysis syndrome, rhabdomyolysis, and acidosis (e.g., decompensated diabetes with ketoacidosis) can also induce hypermagnesemia through extracellular shifts.
Summary:
- Mild hypermagnesemia (less than 7 mg/dL) - Asymptomatic or pauci-symptomatic: weakness, nausea, dizziness, and confusion
- Moderate hypermagnesemia (7 to 12 mg/dL) - Decreased reflexes, worsening of the confusional state and sleepiness, bladder paralysis, flushing, headache, and constipation. A slight reduction in blood pressure, bradycardia, and blurred vision caused by diminished accommodation and convergence are usually present.
- Severe hypermagnesemia (greater than 12 mg/dL) - Muscle flaccid paralysis, decreased breathing rate, more evident hypotension and bradycardia, prolongation of the P-R interval, atrioventricular block, and lethargy are common. Coma and cardiorespiratory arrest can occur for higher values (over 15 mg/dL).
