What is the calculation and maximum dose for a calcium gluconate continuous infusion in a patient with severe hypocalcemia, hypomagnesemia, and QT interval prolongation?

Calcium Gluconate Continuous Infusion: Calculation and Maximum Dose

For continuous infusion of calcium gluconate in severe hypocalcemia with QT prolongation, dilute 10 grams (100 mL of 10% solution) in 1 liter of normal saline or 5% dextrose and infuse at 50-100 mL/hour, with a maximum total dose of 15 grams over 24 hours in adults. 1

Dosing Calculations by Patient Population

Adults

• Loading dose: 1-2 grams (10-20 mL of 10% calcium gluconate) IV over 10 minutes with continuous ECG monitoring 2, 1
• Continuous infusion: Dilute 10 grams (10 vials of 10% calcium gluconate) in 1 liter of normal saline or 5% dextrose 3
• Infusion rate: 50-100 mL/hour, delivering approximately 0.5-1 gram/hour 1, 3
• Maximum 24-hour dose: 15 grams per the FDA label 1

Pediatric Patients

• Loading dose: 50-100 mg/kg IV over 30-60 minutes with continuous ECG monitoring 2, 1
• Continuous infusion: 200-500 mg/kg/day (maximum 2,000 mg/kg/day) 1
• Infusion rate: DO NOT exceed 100 mg/minute in pediatric patients 1

Critical Administration Parameters

Infusion Rate Limits

• Adults: Maximum rate of 200 mg/minute for bolus administration 1
• Pediatric patients: Maximum rate of 100 mg/minute for bolus administration 1
• Continuous infusion concentration: Dilute to 5.8-10 mg/mL prior to administration 1

Monitoring Requirements

• Serum calcium: Every 4-6 hours during intermittent infusions; every 1-4 hours during continuous infusion 1
• ECG monitoring: Continuous during all calcium administration, particularly critical in patients with QT prolongation 2, 1
• Heart rate: Stop infusion immediately if heart rate decreases by 10 beats per minute or symptomatic bradycardia occurs 4, 2

Special Considerations for Your Clinical Scenario

QT Prolongation Context

• Magnesium first: In patients with hypomagnesemia and QT prolongation, correct magnesium deficiency before or concurrent with calcium replacement, as hypocalcemia cannot be fully corrected without adequate magnesium 5, 6
• Arrhythmia risk: Even "slow push" administration carries arrhythmia risk in patients with QT prolongation; maintain strict rate control 2

Vascular Access

• Central line strongly preferred: Extravasation through peripheral IV can cause severe skin and soft tissue injury (calcinosis cutis and tissue necrosis) 2, 5, 1
• If peripheral access only: Ensure line is secure and closely monitored; calcium gluconate is preferred over calcium chloride for peripheral administration due to less tissue irritation 2, 5

Evidence-Based Dosing Regimen from Research

A well-designed study in critically ill trauma patients demonstrated that 4 grams of calcium gluconate infused at 1 gram/hour successfully corrected moderate to severe hypocalcemia (ionized calcium <1 mmol/L) in 95% of patients, increasing ionized calcium from 0.90 to 1.16 mmol/L 7. This regimen can be repeated based on calcium levels and clinical response.

Critical Drug Incompatibilities

• Never mix with: Ceftriaxone (contraindicated in neonates ≤28 days), bicarbonate-containing fluids, phosphate-containing fluids, or vasoactive amines 1
• Precipitation risk: Mixing with bicarbonate or phosphate causes immediate precipitation 2, 1

Common Pitfalls to Avoid

• Rapid infusion: Causes hypotension, bradycardia, and potentially fatal arrhythmias, especially in patients with baseline QT prolongation 2, 1
• Ignoring magnesium: Attempting to correct calcium without addressing concurrent hypomagnesemia will fail 5, 6
• Inadequate monitoring: Failure to maintain continuous ECG monitoring during infusion in a patient with QT prolongation is dangerous 2, 1
• Exceeding maximum dose: The FDA-approved maximum is 15 grams/24 hours in adults; exceeding this increases toxicity risk without additional benefit 1