Expected Increase in Serum Calcium After IV Calcium Gluconate 2g
Intravenous administration of 2g calcium gluconate will increase serum ionized calcium by approximately 0.1-0.15 mmol/L in most patients. This effect is temporary and will typically plateau within 10 hours after completion of the infusion.
Pharmacology of IV Calcium Gluconate
Calcium gluconate contains approximately 90 mg of elemental calcium per 10 mL ampule of 10% solution 1. Therefore:
- 2g calcium gluconate = 180 mg elemental calcium
- The typical infusion rate is 1g/hour 2
Expected Calcium Increase by Patient Population
For Patients with Mild Hypocalcemia (iCa 1.0-1.12 mmol/L):
- 2g calcium gluconate typically increases ionized calcium by approximately 0.1 mmol/L
- This dose normalizes calcium levels in approximately 79% of patients with mild hypocalcemia 3
- About half of the administered elemental calcium is retained in the exchangeable calcium space 2
For Patients with Moderate to Severe Hypocalcemia (iCa <1.0 mmol/L):
- 2g calcium gluconate may be insufficient
- Only 38% of patients with moderate to severe hypocalcemia achieve normal levels with 2-4g doses 3
- Higher doses (4g) result in significantly more elemental calcium retention (201 ± 50 mg vs 81 ± 38 mg) 2
Time Course of Effect
- Peak effect occurs during or shortly after infusion
- Serum ionized calcium concentrations plateau without further decline by approximately 10 hours after completion of the infusion 2
- For monitoring purposes, ionized calcium should be measured at least 10 hours after infusion to assess the efficacy of therapy 2
Clinical Considerations
- Individual response to calcium therapy is highly variable 3
- Calcium chloride provides more rapid increase in ionized calcium than calcium gluconate and is preferred for critically ill patients, but should only be given via central line due to vein irritation 1, 4
- For conversion purposes: 10 mL of 10% calcium gluconate (2.2 mmol calcium) is equivalent to 4.4 mL of 7.35% calcium chloride 4
Important Precautions
- Calcium should be infused slowly (1g/hour) to avoid adverse effects 2, 5
- ECG monitoring is recommended during administration, especially in critically ill patients 1
- Do not mix calcium with sodium bicarbonate or phosphate-containing solutions 1
- Stop infusion if symptomatic bradycardia occurs 1
For optimal management of hypocalcemia, the dose and frequency of calcium supplementation should be guided by serial monitoring of serum calcium levels, with the goal of maintaining ionized calcium within the normal range.