What is the acute management of hypermagnesemia, including the use of calcium gluconate, diuretics, and dialysis for severe or renal‑failure cases?

Acute Management of Hypermagnesemia

For severe symptomatic hypermagnesemia, immediately administer intravenous calcium (calcium chloride 10% 5-10 mL or calcium gluconate 10% 15-30 mL IV over 2-5 minutes) as the primary antidote, discontinue all magnesium-containing medications, and initiate urgent hemodialysis for life-threatening presentations. 1, 2

Immediate Recognition and Stabilization

Clinical Presentation by Severity

• Mild hypermagnesemia (2.5-5 mmol/L): ECG changes including prolonged PR interval and widened QRS complex 1
• Severe hypermagnesemia (6-10 mmol/L): Progressive symptoms including muscular weakness, paralysis, ataxia, drowsiness, confusion, depressed consciousness, vasodilation, hypotension, bradycardia, cardiac arrhythmias, hypoventilation progressing to respiratory paralysis, and complete cardiovascular collapse 2, 3
• Cardiac arrest: Can develop from severe hypermagnesemia, particularly in obstetric settings with magnesium sulfate therapy for preeclampsia/eclampsia 1

First-Line Interventions

• Stop all magnesium sources immediately: Discontinue magnesium-containing medications, supplements, laxatives, and antacids 2, 3
• Administer IV calcium as antidote: Calcium chloride (10%) 5-10 mL OR calcium gluconate (10%) 15-30 mL IV over 2-5 minutes 2
  • This is the primary antidote that directly antagonizes magnesium's cardiotoxic and neuromuscular effects 2
  • For cardiac arrest with known or suspected hypermagnesemia, empirical IV calcium administration may be reasonable (Class IIb, Level of Evidence C) 1

Definitive Treatment Based on Severity

Severe Symptomatic Cases (Magnesium >6 mmol/L or Life-Threatening)

• Urgent hemodialysis or CRRT: This is the definitive treatment for life-threatening hypermagnesemia 2, 4
  • Hemodialysis rapidly removes magnesium and should be initiated promptly if basic supportive interventions are ineffective 4
  • Case reports demonstrate successful management of severe hypermagnesemia (levels 9.9-13.5 mg/dL) with hemodialysis, even in patients with normal renal function 4, 5, 6
  • CRRT is an alternative for hemodynamically unstable patients 7

Moderate Cases with Normal Renal Function

• High-volume IV fluid therapy: Administer normal saline to promote renal magnesium excretion 6
• Loop diuretics: Use IV furosemide to enhance renal magnesium elimination 6
• Calcium preparation: Continue calcium administration as needed for cardioprotection 6
• Severe hypermagnesemia (13.5 mg/dL) with normal renal function can improve with symptomatic treatment alone without hemodialysis if the patient is not critically unstable 6

Critical Monitoring Requirements

Cardiovascular Monitoring

• Continuous ECG monitoring: Assess for conduction abnormalities, bradycardia, and arrhythmias 2
• Blood pressure monitoring: Watch for progressive hypotension requiring vasopressor support 2

Respiratory Monitoring

• Prepare for mechanical ventilation: If hypoventilation or respiratory depression develops, as respiratory paralysis can occur at extremely high levels 2
• Monitor respiratory rate and effort: Progressive respiratory compromise is a life-threatening complication 2

Laboratory Monitoring

• Serial serum magnesium levels: Monitor frequently during treatment to assess response 3, 7
• Renal function: Check creatinine and GFR, as patients with GFR <30 mL/min are at highest risk 2

Special Clinical Scenarios

Obstetric Patients on Magnesium Sulfate

• High-risk population: Severe hypermagnesemia most commonly occurs in obstetric settings with IV magnesium for preeclampsia/eclampsia 1
• Monitor for oliguria: Iatrogenic overdose is particularly dangerous if oliguria develops 2
• Empirical calcium may be lifesaving: In pregnant women receiving magnesium sulfate with signs of toxicity 2

Patients with Renal Failure

• Lower threshold for toxicity: Patients with substantially decreased kidney function (GFR <30 mL/min) develop life-threatening toxicity at relatively lower magnesium doses 2
• Hemodialysis indicated: For patients with end-stage renal disease and hypermagnesemia, continue or initiate hemodialysis 5, 7

Patients with Bowel Disorders

• Increased absorption risk: Constipation, intestinal obstruction, or sigmoid volvulus can lead to excessive magnesium absorption from laxatives even with normal renal function 5, 6
• Common culprit: Over-the-counter magnesium hydroxide or magnesium oxide laxatives in elderly patients 5, 7

Common Pitfalls to Avoid

• Failure to recognize early signs: Missing initial symptoms like weakness and depressed reflexes can allow progression to cardiovascular collapse 2
• Delayed dialysis initiation: When calcium and fluids are ineffective, hemodialysis should be initiated promptly rather than continuing ineffective supportive measures 4
• Underestimating risk in normal renal function: Severe hypermagnesemia can occur with normal kidney function in the setting of excessive intake and bowel disorders 6, 7
• Inadequate monitoring in high-risk patients: Elderly patients and those with impaired renal function taking magnesium-containing preparations require regular magnesium level monitoring 7