Hypermagnesemia is defined as a serum magnesium concentration greater than 1.25 mmol/L.
Etiology
Renal failure is the most common cause of hypermagnesemia, particularly in cases of acute or chronic renal failure accompanied by oliguria or anuria.
Severe dehydration with oliguria can result in reduced urinary excretion of magnesium.
Impaired magnesium excretion by the kidneys occurs in conditions such as adrenal insufficiency or hypothyroidism.
Excessively rapid or large intravenous magnesium supplementation.
Conditions involving increased catabolism, such as diabetic ketoacidosis, in which intracellular magnesium shifts to the extracellular space.
Clinical Manifestations
Hypermagnesemia can suppress the function of visceral smooth muscles, leading to symptoms such as belching, vomiting, constipation, and urinary retention. It impairs neuromuscular excitatory transmission, causing manifestations such as weakness, fatigue, and diminished deep tendon reflexes. Severe cases may result in flaccid paralysis, lethargy, or coma.
The effects of hypermagnesemia on the cardiovascular system include inhibition of atrioventricular and intraventricular conduction, reduced myocardial excitability, and, in severe cases, conduction block, bradycardia, hypotension, or even cardiac arrest. Electrocardiographic findings may show conduction delays.
Treatment
Mild hypermagnesemia in patients with normal kidney function does not require specific treatment, as the kidneys are capable of rapidly eliminating excess magnesium. For patients with significant cardiovascular symptoms, intravenous calcium may be administered immediately, typically 10–20 ml of 10% calcium gluconate or calcium chloride solution by slow injection, to counteract the inhibitory effects of magnesium on the heart and muscles.
Diuretics can be used alongside adequate fluid replacement to promote magnesium excretion. If these measures prove ineffective, dialysis may be considered. Hemodialysis is an effective treatment option for hypermagnesemia associated with renal failure.