Treatment of Ionized Calcium Level of 1.0 mmol/L
For an ionized calcium level of 1.0 mmol/L, initiate a calcium gluconate infusion at 1-2 mg elemental calcium per kilogram body weight per hour, which translates to approximately 10-20 mL/hour of 10% calcium gluconate solution for a 70 kg adult (since each 10 mL ampule contains 90 mg elemental calcium). 1
Dosing Algorithm
Initial Assessment
- An ionized calcium of 1.0 mmol/L is below the normal range (1.1-1.3 mmol/L) and requires treatment, particularly if symptomatic or in the context of massive transfusion or post-parathyroidectomy 1
- This level is above the critical threshold of 0.9 mmol/L where cardiovascular and coagulation effects become severely compromised 1
Specific Dosing Recommendations
For Intravenous Infusion:
- Start calcium gluconate at 1-2 mg elemental calcium/kg/hour 1
- For a 70 kg patient, this equals 70-140 mg elemental calcium per hour 1
- Since 10% calcium gluconate contains 90 mg elemental calcium per 10 mL ampule, this translates to approximately 8-16 mL/hour of 10% calcium gluconate solution 1
- Adjust the infusion rate to maintain ionized calcium in the normal range (1.15-1.36 mmol/L) 1
Alternative Bolus Approach (if more rapid correction needed):
- The FDA label indicates individualized dosing based on severity, with monitoring every 4-6 hours during intermittent infusions 2
- Each mL of calcium gluconate injection contains 9.3 mg (0.4665 mEq) of elemental calcium 2
Monitoring Requirements
- Measure ionized calcium every 4-6 hours during infusion 1
- For continuous infusions, monitor every 1-4 hours 2
- Monitor ECG continuously during administration to detect arrhythmias 2
Important Clinical Considerations
Route of Administration:
- Administer through a secure intravenous line, preferably central access in children 3, 2
- Dilute with 5% dextrose or normal saline before administration 2
- Infuse slowly to avoid hypotension, bradycardia, and cardiac arrhythmias 2
Calcium Chloride vs Calcium Gluconate:
- While the guidelines recommend calcium gluconate for this indication 1, calcium chloride provides three times more elemental calcium (270 mg vs 90 mg per 10 mL of 10% solution) and may be preferred in critical situations or with abnormal liver function 1, 3
- The European trauma guidelines specifically recommend calcium chloride for massive transfusion scenarios 1
Context-Specific Adjustments
Post-Parathyroidectomy Setting:
- This dosing regimen (1-2 mg/kg/hour) is specifically recommended when ionized calcium falls below 0.9 mmol/L post-parathyroidectomy 1
- Gradually reduce infusion when calcium reaches normal range and remains stable 1
- Transition to oral calcium carbonate 1-2 g three times daily plus calcitriol up to 2 mcg/day when oral intake possible 1
Massive Transfusion Setting:
- Maintain ionized calcium above 0.9 mmol/L to preserve coagulation function and cardiovascular stability 1
- Citrate from blood products chelates calcium, requiring more aggressive replacement 1
- The 2023 European trauma guidelines emphasize maintaining calcium within normal range during massive transfusion 1
Critical Pitfalls to Avoid
- Do not administer with cardiac glycosides without close ECG monitoring, as synergistic arrhythmias may occur 2
- Avoid mixing with phosphate or bicarbonate-containing fluids, as precipitation will occur 2
- Do not infuse rapidly without dilution and ECG monitoring, as this causes hypotension, bradycardia, and arrhythmias 2
- Monitor for extravasation, as tissue necrosis and calcinosis cutis can occur even without obvious extravasation 2
- Account for pH effects: each 0.1 unit increase in pH decreases ionized calcium by approximately 0.05 mmol/L 1