Purpose and Clinical Use of Calcium Gluconate
Calcium gluconate is indicated for three primary emergencies in adults: symptomatic acute hypocalcemia, severe hyperkalemia with ECG changes, and calcium-channel-blocker toxicity—each with distinct dosing regimens and monitoring requirements. 1, 2, 3
1. Symptomatic Acute Hypocalcemia
Indications for Treatment
- Treat immediately when ionized calcium <0.9 mmol/L with symptoms (tetany, seizures, laryngospasm, bronchospasm, cardiac arrhythmias, or Chvostek's/Trousseau's signs). 2, 3
- Asymptomatic hypocalcemia does not require calcium replacement, even in tumor-lysis syndrome. 2, 3
- Ionized calcium <0.8 mmol/L is particularly concerning for dysrhythmias and warrants urgent correction. 2
Dosing Protocol
- Initial bolus: 15–30 mL of 10% calcium gluconate IV over 2–5 minutes (equivalent to 1.35–2.7 g or 135–270 mg elemental calcium). 2, 3
- Continuous infusion: Dilute 100 mL (10 ampules) of 10% calcium gluconate in 1 L normal saline or 5% dextrose; infuse at 50–100 mL/h (equivalent to 1–2 mg elemental calcium/kg/h). 2, 4
- Target: Maintain ionized calcium 1.15–1.36 mmol/L (normal range). 2
Monitoring Requirements
- Measure ionized calcium every 4–6 hours initially until stable, then twice daily. 2
- Continuous ECG monitoring is mandatory; stop infusion immediately if heart rate drops ≥10 beats/minute or symptomatic bradycardia develops. 2, 5, 3
Critical Cofactor Correction
- Check and correct magnesium first—hypomagnesemia is present in 28% of hypocalcemic ICU patients and prevents calcium normalization. 2
- Administer IV magnesium sulfate before expecting full calcium correction. 2
Transition to Oral Therapy
- Once ionized calcium stabilizes and oral intake is possible, switch to calcium carbonate 1–2 g three times daily plus calcitriol up to 2 μg/day. 2
- Total elemental calcium intake should not exceed 2,000 mg/day. 2
2. Calcium-Channel-Blocker Toxicity
Indications
- Administer calcium as first-line therapy for CCB-poisoned adults with hemodynamic instability (hypotension, bradycardia, or myocardial dysfunction). 1
- Calcium improves contractility and blood pressure based on case series and animal studies. 1
Dosing Protocol
- Bolus: 30–60 mL (3–6 g) of 10% calcium gluconate IV every 10–20 minutes. 1, 5
- Continuous infusion: 0.6–1.2 mL/kg/h (0.06–0.12 g/kg/h) of 10% calcium gluconate. 1, 5
- Rationale: Calcium gluconate is preferred over calcium chloride to minimize peripheral vein irritation. 1, 5
Adjunctive Therapies
- If myocardial dysfunction is documented, add high-dose insulin (1 U/kg bolus, then 1 U/kg/h infusion) with dextrose to maintain euglycemia. 1
- Use norepinephrine for vasoplegic shock or epinephrine for cardiogenic shock with bradycardia. 1
- Atropine 0.5 mg IV every 3–5 minutes for symptomatic bradycardia or conduction disturbances. 1
3. Severe Hyperkalemia with ECG Changes
Indications
- Administer calcium for membrane stabilization when hyperkalemia causes ECG changes (peaked T waves, widened QRS, sine-wave pattern, or dysrhythmias). 3, 6
- Calcium does not lower potassium levels—it must be combined with therapies that shift potassium intracellularly (insulin/glucose, albuterol, bicarbonate) and promote excretion (dialysis, diuretics). 3, 6
Dosing Protocol
- Standard dose: 15–30 mL of 10% calcium gluconate IV over 2–5 minutes. 3, 6
- Cardiac arrest: Use 10 mL of 10% calcium chloride instead (provides 3× more elemental calcium per volume). 6
- Pediatric dose: 100–200 mg/kg calcium gluconate via slow infusion with ECG monitoring. 5, 3
Monitoring
- Continuous ECG monitoring is required. 3, 6
- Calcium's cardioprotective effect lasts 30–60 minutes; repeat dosing may be necessary while definitive potassium-lowering therapies take effect. 6
Critical Administration Considerations
Route and Vascular Access
- Central venous access is strongly preferred to avoid extravasation injury, calcinosis cutis, and skin necrosis. 2, 5, 3
- If only peripheral access is available, calcium gluconate is safer than calcium chloride (which is more caustic), but the line must be secure and closely monitored. 5, 3
Drug Incompatibilities
- Never mix calcium with sodium bicarbonate in the same IV line—precipitation occurs. 2, 5, 3
- Avoid concurrent infusion with vasoactive amines (epinephrine, dopamine, norepinephrine). 2, 5
- Exercise extreme caution in patients on digoxin—if calcium is absolutely required, give slowly in small aliquots with close ECG monitoring to prevent precipitating digoxin toxicity and life-threatening arrhythmias. 2, 3
Special Precautions
- In tumor-lysis syndrome with hyperphosphatemia: Use calcium only for symptomatic patients; excess calcium precipitates calcium-phosphate crystals in tissues, causing obstructive uropathy. Obtain renal consultation before aggressive replacement. 2, 5, 3
- In massive transfusion: Citrate toxicity from blood products causes hypocalcemia; maintain ionized calcium >0.9 mmol/L (optimal 1.1–1.3 mmol/L) with serial measurements every 4–6 hours. 2
- Avoid rapid infusion to prevent hypotension, bradycardia, and cardiac arrhythmias. 5, 3
Calcium Gluconate vs. Calcium Chloride
Elemental Calcium Content
- 10 mL of 10% calcium gluconate = 90 mg elemental calcium (2.2 mmol). 2, 4
- 10 mL of 10% calcium chloride = 270 mg elemental calcium (3× more potent). 2
Clinical Selection
- Calcium gluconate is preferred for peripheral administration and CCB toxicity (less vein irritation). 1, 5, 3
- Calcium chloride is preferred for cardiac arrest, severe hypocalcemia in patients with liver dysfunction (faster release of ionized calcium), and when rapid correction is critical. 2, 6
- Calcium chloride should only be given via central line due to its caustic properties. 5, 3
Common Pitfalls to Avoid
- Do not treat asymptomatic hypocalcemia—even in tumor-lysis syndrome, calcium replacement is unnecessary and potentially harmful. 2, 3
- Do not rely on adjusted calcium (AdjCa) in ICU settings—it has only 78% sensitivity and 63% specificity for predicting low ionized calcium; always measure ionized calcium directly. 7
- Do not ignore magnesium deficiency—hypocalcemia cannot be fully corrected without adequate magnesium. 2
- Do not overcorrect—severe hypercalcemia (ionized calcium >2× upper limit of normal) can cause renal calculi and renal failure. 2
- Standard coagulation tests (PT/PTT) may appear falsely normal in severe hypocalcemia because laboratory samples are recalcified before analysis; do not rely on them to assess coagulopathy. 2