What is the most likely cause of hypermagnesemia?

Hypermagnesemia: Causes and Risk Factors

Oliguric renal failure (option c) is the most common cause of hypermagnesemia, as the kidneys are the primary organ for magnesium excretion. 1

Pathophysiology of Hypermagnesemia

Hypermagnesemia typically develops through two main mechanisms:

1. Decreased renal excretion

   • Renal insufficiency is the primary cause of hypermagnesemia 1
   • The kidneys normally excrete excess magnesium
   • When glomerular filtration rate decreases, magnesium excretion is impaired

2. Excessive magnesium intake (usually in combination with impaired renal function)

   • Magnesium-containing medications (antacids, laxatives)
   • Magnesium sulfate therapy (e.g., for preeclampsia/eclampsia)

Analysis of Answer Options

Let's analyze each option:

• (a) Extensive burns: Not directly associated with hypermagnesemia

• (b) Acute pancreatitis: Not a direct cause of hypermagnesemia

• (c) Oliguric renal failure: Correct answer. Renal insufficiency is the primary cause of hypermagnesemia as the kidneys are the main route of magnesium excretion 1

• (d) Resection of the terminal ileum: Not associated with hypermagnesemia

• (e) Diuretic therapy: Most diuretics actually cause hypomagnesemia, not hypermagnesemia

Supporting Evidence

Multiple case reports document hypermagnesemia in patients with renal failure:

• Fatal hypermagnesemia has been reported in patients with end-stage renal disease taking magnesium hydroxide for constipation 2

• Cardiopulmonary arrest due to hypermagnesemia occurred in a patient with nephritic syndrome and renal dysfunction taking magnesium-containing laxatives 3

• Severe symptomatic hypermagnesemia developed in a patient with renal failure taking over-the-counter laxatives 4

Clinical Manifestations of Hypermagnesemia

Hypermagnesemia severity can be classified as:

• Mild: 2.2-2.5 mEq/L (often asymptomatic)
• Moderate: 2.5-5.0 mEq/L (hyporeflexia, nausea, vomiting, facial flushing, lethargy)
• Severe: >5.0 mEq/L (loss of deep tendon reflexes, hypotension, respiratory depression, heart blocks, coma) 1

Clinical Pearls and Pitfalls

• Pitfall: Failing to recognize that patients with normal renal function can also develop hypermagnesemia with excessive magnesium intake 2

• Pitfall: Overlooking magnesium-containing medications as a source of hypermagnesemia in patients with renal impairment

• Pearl: Guidelines specifically warn that "magnesium and sulfate salts can lead to hypermagnesaemia and should be used cautiously in renal impairment" 5

• Pearl: Regular monitoring of magnesium levels is crucial in high-risk patients, particularly those with renal insufficiency taking magnesium-containing medications 1

Management Considerations

For patients with hypermagnesemia:

1. Discontinue all magnesium-containing medications
2. Administer intravenous calcium as a physiological antagonist in severe cases
3. Consider hemodialysis for severe cases with inadequate response to conservative measures 1