Expected Increase in Ionized Calcium After 2 Grams Calcium Chloride
Administering 2 grams (20 mL of 10% solution) of calcium chloride intravenously will increase ionized calcium by approximately 30-35% from baseline levels, typically raising ionized calcium concentration by 0.2-0.4 mmol/L in critically ill patients. 1
Pharmacokinetics and Expected Response
Calcium chloride provides 270 mg of elemental calcium per 10 mL of 10% solution, meaning 2 grams (20 mL) delivers 540 mg of elemental calcium (27 mEq). 2, 3
The increase in ionized calcium occurs rapidly:
- Peak effect is achieved within 5 minutes of completing the infusion 1
- The increase is similar whether using calcium chloride or calcium gluconate when equivalent elemental calcium doses are given 1, 4
- Both preparations produce comparable increases of 32-33% from baseline in critically ill patients 1
Duration of Effect
The elevation in ionized calcium is transient:
- Ionized calcium levels begin to gradually decrease over 10-30 minutes following the peak 1, 4
- Repeated injections may be required due to rapid excretion of calcium 2
- During massive transfusion, ionized calcium should be monitored every 4-6 hours as levels can drop quickly 3, 5
Clinical Context and Monitoring
Target ionized calcium levels should be maintained above 0.9 mmol/L during critical illness, with normal range being 1.1-1.3 mmol/L (4.6-5.4 mg/dL). 3, 5
For specific clinical scenarios, dosing recommendations vary:
- In calcium channel blocker toxicity: 2 grams (20 mg/kg) is the standard initial adult dose 3
- During massive transfusion: maintain ionized calcium at 1.5-2 times upper limits of normal, not exceeding this threshold 3
- Post-parathyroidectomy: infusion rates of 1-2 mg elemental calcium/kg/hour may be needed to maintain normal levels 3
Important Caveats
The actual increase in ionized calcium will vary based on several factors:
- Citrate load from blood products chelates calcium and reduces the net increase during massive transfusion 3
- Liver dysfunction impairs citrate metabolism, potentially requiring higher or more frequent calcium doses 3, 4
- Acidosis increases ionized calcium (0.1 pH unit decrease raises ionized calcium by ~0.05 mmol/L), while alkalosis decreases it 3
- Albumin levels affect total calcium but not ionized calcium measurements directly 3
Administer calcium chloride slowly (not exceeding 1 mL/min) through a central or deep vein, as rapid administration or peripheral extravasation causes tissue necrosis. 2
Monitor ECG continuously during administration, as hypercalcemia can precipitate cardiac dysrhythmias including atrioventricular dissociation, particularly in patients on digitalis or with underlying cardiac disease. 5, 6
Do not routinely administer calcium to asymptomatic hypocalcemic patients, as evidence shows no mortality benefit and potential harm from excessive calcium administration. 5, 7