What is the recommended protocol for intravenous (IV) calcium repletion in severe hypocalcemia?

IV Calcium Repletion Protocol for Severe Hypocalcemia

For severe hypocalcemia, administer calcium chloride 20 mg/kg (0.2 mL/kg of 10% solution) IV, infused over 30-60 minutes for non-cardiac arrest situations, with repeat doses based on clinical response and calcium levels. 1

Choice of Calcium Preparation

Calcium Chloride (Preferred for Critical Situations)

• Contains 27 mg (1.36 mEq) of elemental calcium per mL of 10% solution
• Preferred for critically ill patients due to more rapid increase in ionized calcium 1
• Should be administered through a central venous catheter when possible
• Dosage: 20 mg/kg (0.2 mL/kg of 10% solution)

Calcium Gluconate (Alternative)

• Contains 9.3 mg (0.47 mEq) of elemental calcium per mL of 10% solution 2
• May be used if calcium chloride unavailable
• Dosage: 60 mg/kg if substituting for calcium chloride 1
• Better tolerated through peripheral IV lines but less effective at rapidly increasing calcium levels

Administration Protocol

For Severe Symptomatic Hypocalcemia:

1. Initial Bolus:

   • Calcium chloride: 20 mg/kg IV over 5-10 minutes for cardiac arrest; over 30-60 minutes for other indications 1
   • Monitor heart rate continuously; stop if symptomatic bradycardia occurs

2. Follow-up Infusion (if needed):

   • For persistent hypocalcemia: Consider continuous infusion at 0.3 mEq/kg/hour (titrate to response) 1
   • For moderate-severe hypocalcemia (ionized Ca <1.0 mmol/L): 4g calcium gluconate infusion at 1g/hour has shown 95% success in achieving ionized calcium >1.0 mmol/L 3

3. Monitoring:

   • Measure serum calcium during intermittent infusions every 4-6 hours
   • During continuous infusion, monitor every 1-4 hours 2
   • Monitor ECG for cardiac arrhythmias during administration

Special Considerations

Administration Safety:

• Use central venous access for calcium chloride administration
• For peripheral administration, use calcium gluconate to reduce risk of tissue injury
• Stop injection immediately if symptomatic bradycardia occurs 1
• Extravasation can cause severe skin and soft tissue injury

Contraindications/Cautions:

• Do not mix calcium with bicarbonate or phosphate-containing solutions (precipitation risk) 2
• Use with extreme caution in patients on cardiac glycosides - may cause arrhythmias 2
• Avoid rapid administration - can cause hypotension, bradycardia, and cardiac arrhythmias 2

Specific Clinical Scenarios:

• Cardiac arrest with documented hypocalcemia: Give calcium chloride as slow IV push 1
• Trauma patients: For moderate-severe hypocalcemia, 4g calcium gluconate infusion at 1g/hour is effective in 95% of cases 3
• Calcium channel blocker toxicity: Same dosing as above; may require higher or repeated doses 1

Common Pitfalls to Avoid

• Failing to use central venous access for calcium chloride
• Administering calcium too rapidly (risk of cardiac arrhythmias)
• Not monitoring calcium levels frequently enough during repletion
• Mixing calcium with incompatible solutions (bicarbonate, phosphate)
• Underestimating calcium needs in severe hypocalcemia

Remember that calcium chloride provides approximately three times more elemental calcium than an equivalent volume of calcium gluconate, making it the preferred agent for emergency treatment of severe hypocalcemia when rapid correction is needed.