What is the recommended dose of intravenous (IV) calcium gluconate for a patient with hypocalcemia (ionized calcium level of 2.9)?

IV Calcium Gluconate Dosing for Severe Hypocalcemia (Ionized Calcium 2.9 mg/dL)

For a patient with severe hypocalcemia with ionized calcium of 2.9 mg/dL, administer IV calcium gluconate at a rate of 1-2 mg of elemental calcium per kilogram body weight per hour as a continuous infusion to maintain ionized calcium in the normal range (1.15-1.36 mmol/L or 4.6-5.4 mg/dL). 1

Understanding the Severity

An ionized calcium level of 2.9 mg/dL indicates severe hypocalcemia that requires immediate intervention. Normal ionized calcium range is 4.6-5.4 mg/dL (1.15-1.36 mmol/L), and levels below 3.6 mg/dL are considered critically low and can lead to:

• Cardiac arrhythmias
• Hypotension
• Tetany
• Seizures
• Altered mental status

Administration Protocol

Preparation:

1. Use 10% calcium gluconate solution (100 mg/mL)
2. Note that each 10 mL ampule of 10% calcium gluconate contains 90 mg of elemental calcium 1
3. Dilute in 5% dextrose or normal saline to a concentration of 5.8-10 mg/mL prior to administration 2

Dosing Algorithm:

1. Initial bolus (if symptomatic):

   • Dilute calcium gluconate to a concentration of 10-50 mg/mL
   • Administer slowly at a rate NOT exceeding 200 mg/minute in adults or 100 mg/minute in pediatric patients 2

2. Continuous infusion:

   • Calculate dose based on 1-2 mg elemental calcium per kg body weight per hour 1
   • Example: For a 70 kg adult, administer 70-140 mg elemental calcium per hour (approximately 750-1500 mg calcium gluconate per hour)

3. Monitoring:

   • Measure ionized calcium every 1-4 hours during continuous infusion 2
   • Monitor ECG continuously during administration 2
   • Adjust infusion rate to maintain ionized calcium within normal range (1.15-1.36 mmol/L or 4.6-5.4 mg/dL) 1

Important Considerations

Administration Safety:

• Administer via secure intravenous line to avoid calcinosis cutis and tissue necrosis 2
• The solution should appear clear and colorless to slightly yellow; do not administer if there is particulate matter or discoloration 2

Drug Incompatibilities:

• Do not mix with ceftriaxone (can form precipitates) 2
• Do not mix with fluids containing bicarbonate or phosphate 2
• Do not mix with minocycline injection 2

Dose Adjustment:

• For patients with renal impairment, start at the lowest recommended dose and monitor serum calcium levels every 4 hours 2
• Gradually reduce the calcium infusion when ionized calcium attains and remains stable in the normal range 1

Transition to Oral Therapy

When the patient stabilizes and oral intake is possible:

• Transition to oral calcium carbonate 1-2 g three times daily
• Consider calcitriol up to 2 μg/day
• Adjust therapy as necessary to maintain ionized calcium in the normal range 1

Clinical Pitfalls to Avoid

1. Do not rely on total calcium measurements - Ionized calcium is the biologically active form and should be directly measured, especially in critically ill patients who often have hypoalbuminemia 3, 4

2. Do not administer calcium too rapidly - Rapid administration can cause vasodilation, hypotension, bradycardia, arrhythmias, and cardiac arrest 2

3. Do not undertreat severe hypocalcemia - Studies have shown that critically ill patients may require higher doses than generally recommended to restore normal ionized calcium levels 5

4. Do not forget to identify and treat the underlying cause - After stabilizing acute hypocalcemia, investigate and address the underlying etiology 3