How should hypermagnesemia be managed according to serum magnesium level, symptoms (muscle weakness, hypotension, bradycardia, respiratory depression, ECG changes), and renal function, including calcium administration, diuretics, dialysis, and bowel irrigation?

Treatment of Hypermagnesemia

Immediately discontinue all magnesium-containing medications and supplements, administer intravenous calcium for symptomatic or severe cases, and initiate urgent hemodialysis for life-threatening presentations or when conservative measures fail. 1

Immediate Assessment and Stabilization

Clinical Severity Stratification

Assess symptom severity and serum magnesium level to guide treatment intensity:

• Mild hypermagnesemia (2.5-5 mmol/L): ECG changes including T-wave flattening, ST-segment depression, and prolonged PR/QRS intervals 1
• Moderate hypermagnesemia (5-6 mmol/L): Neuromuscular manifestations including loss of deep tendon reflexes, muscle weakness, drowsiness, and confusion 1, 2
• Severe hypermagnesemia (6-10 mmol/L): Life-threatening complications including complete cardiovascular collapse, respiratory paralysis, bradycardia, hypotension, cardiac arrhythmias, and cardiorespiratory arrest 1

Cardiovascular and Respiratory Monitoring

Obtain immediate ECG and establish continuous cardiac monitoring for all symptomatic patients, as conduction abnormalities progress with increasing magnesium levels. 1

• Monitor for bradycardia, hypotension, and arrhythmias continuously 1
• Prepare for mechanical ventilation if hypoventilation or respiratory depression develops, particularly at extremely high magnesium levels 1, 2
• Assess for altered level of consciousness ranging from drowsiness to coma 1, 2

Treatment Algorithm by Severity

Step 1: Universal First Measures (All Cases)

Stop all magnesium sources immediately:

• Discontinue all magnesium-containing medications, supplements, laxatives (magnesium oxide, magnesium hydroxide, Epsom salts), and antacids 1, 3, 4
• Remove magnesium from parenteral nutrition or dialysis solutions 5
• Recognize that hypermagnesemia can occur even with normal renal function when bowel obstruction or constipation is present, as magnesium absorption increases with prolonged intestinal transit time 4, 6

Step 2: Calcium Administration for Symptomatic Cases

Administer intravenous calcium immediately for severe symptomatic hypermagnesemia, cardiac manifestations, or neuromuscular compromise:

• Calcium chloride 10%: 5-10 mL IV over 2-5 minutes 1
• Calcium gluconate 10%: 15-30 mL IV over 2-5 minutes (alternative if calcium chloride unavailable) 1, 3
• Calcium directly antagonizes the cardiac and neuromuscular effects of magnesium at the cellular level 7, 1
• The American Heart Association provides a Class IIb, Level of Evidence C recommendation for calcium administration during cardiac arrest associated with hypermagnesemia 1
• Repeat calcium doses as necessary based on clinical response, monitoring heart rate closely 7

Common pitfall: Calcium administration is temporizing only—it reverses symptoms but does not lower serum magnesium levels. 1, 3

Step 3: Enhanced Renal Elimination (Patients with Normal Renal Function)

For patients with creatinine clearance >30 mL/min and mild-to-moderate hypermagnesemia:

• Administer high-volume intravenous normal saline (2-4 L initially, then titrate to urine output) 3, 4, 6
• Add loop diuretics (furosemide 40-80 mg IV) to enhance renal magnesium excretion after adequate volume resuscitation 3, 4, 6
• Monitor urine output, aiming for 200-300 mL/hour to maximize magnesium clearance 3, 4

This approach can successfully treat severe hypermagnesemia (magnesium >13 mg/dL) in patients with normal renal function without requiring hemodialysis. 4

Step 4: Urgent Hemodialysis (Life-Threatening Cases or Renal Dysfunction)

Initiate urgent hemodialysis or continuous renal replacement therapy (CRRT) for:

• Life-threatening presentations including cardiorespiratory arrest, severe bradycardia, profound hypotension, or respiratory paralysis 1, 8
• Magnesium levels >6-10 mmol/L with severe symptoms 1, 3
• Renal dysfunction (GFR <30 mL/min) preventing adequate magnesium excretion 1
• Failure of conservative measures (calcium, fluids, diuretics) to halt symptom progression 8, 3, 6

Hemodialysis results in rapid correction of magnesium levels and is the definitive treatment for severe hypermagnesemia. 8, 3

• Magnesium levels correct rapidly after dialysis initiation, often within hours 8, 3
• The American Heart Association emphasizes urgent hemodialysis for life-threatening presentations 1
• Do not delay dialysis in critically ill patients—primary supportive interventions may be ineffective in severe cases 8

Special Clinical Scenarios

Hypermagnesemia with Bowel Obstruction or Constipation

Recognize that severe hypermagnesemia can occur in patients with normal renal function when intestinal obstruction or severe constipation is present:

• Prolonged intestinal transit time dramatically increases magnesium absorption from oral sources 4, 6
• Patients taking magnesium oxide for constipation are at particularly high risk when bowel obstruction develops 4, 6
• Surgical intervention may be necessary to relieve obstruction while simultaneously treating hypermagnesemia 6

Iatrogenic Magnesium Overdose

For accidental intravenous magnesium overdose (as in preeclampsia treatment errors):

• Initiate cardiopulmonary resuscitation immediately if pulseless 8
• Administer calcium gluconate or calcium chloride as first-line antidote 8
• Proceed directly to hemodialysis if basic supportive interventions are ineffective 8

Pregnant Patients with Preeclampsia/Eclampsia

For pregnant women receiving magnesium sulfate therapy:

• Monitor closely for oliguria and toxicity 1
• Empirical calcium administration may be lifesaving in overdose 1
• The American College of Obstetricians and Gynecologists recommends heightened vigilance in this population 1

Monitoring During Treatment

Serial magnesium measurements every 2-4 hours during acute treatment:

• Continue monitoring until magnesium <2.5 mmol/L and symptoms resolve 1, 3
• Assess deep tendon reflexes—return of patellar reflexes indicates improving magnesium toxicity 1, 4
• Monitor for signs of magnesium toxicity reversal: improved level of consciousness, return of muscle strength, normalization of blood pressure and heart rate 1, 4

Concurrent electrolyte monitoring:

• Check calcium, potassium, and renal function during treatment 1
• Hypocalcemia often accompanies hypermagnesemia and may require correction 7, 1

Common Pitfalls to Avoid

• Failing to recognize hypermagnesemia in patients with normal renal function: Bowel obstruction, constipation, or excessive oral magnesium intake can cause severe toxicity even with normal kidney function 4, 6
• Delaying hemodialysis in severe cases: When calcium and fluids fail to improve symptoms, dialysis should be initiated promptly rather than continuing ineffective conservative measures 8, 3
• Overlooking magnesium-containing medications: Antacids (Maalox, milk of magnesia), laxatives (magnesium oxide, Epsom salts), and supplements are common culprits 3, 4, 6
• Assuming calcium alone is sufficient: Calcium reverses symptoms temporarily but does not lower magnesium levels—definitive treatment requires enhanced elimination 1, 3
• Missing the diagnosis entirely: Hypermagnesemia is often clinically unexpected, so maintain high suspicion in patients with unexplained weakness, hypotension, bradycardia, or altered mental status, particularly those taking magnesium-containing products 6