What is the appropriate dose of calcium (Ca) for treating acute hypotension?

Calcium Dosing for Acute Hypotension

For acute hypotension, administer 0.3 mEq/kg of calcium (0.6 mL/kg of 10% calcium gluconate solution or 0.2 mL/kg of 10% calcium chloride solution) IV over 5-10 minutes, followed by an infusion of 0.3 mEq/kg per hour if needed. 1

Calcium Selection and Administration

Initial Bolus Dosing

• Calcium gluconate (10%): 0.6 mL/kg (contains 9.3 mg elemental calcium per mL)
• Calcium chloride (10%): 0.2 mL/kg (higher elemental calcium content)
• Administer over 5-10 minutes to avoid adverse effects

Continuous Infusion (if needed)

• 0.3 mEq/kg per hour, titrated to hemodynamic response
• For calcium channel blocker toxicity: 20-50 mg/kg per hour may be required 1

Route Considerations

• Preferably administer through a central venous catheter
• If using peripheral IV, ensure it's secure and monitor for extravasation
• Calcium chloride is more irritating to veins than calcium gluconate 2

Specific Clinical Scenarios

Calcium Channel Blocker Overdose

• Calcium administration is reasonable (Class IIa, LOE C-LD) 1
• May require higher doses than standard hypotension management
• Consider high-dose insulin with glucose as adjunctive therapy 1

β-Blocker Overdose

• Calcium may be considered (Class IIb, LOE C-LD) 1
• Less evidence than for calcium channel blocker toxicity
• Often requires additional therapies like glucagon or high-dose insulin 1

Hypocalcemia-Associated Hypotension

• Studies show direct relationship between ionized calcium levels and arterial pressure 3
• Target ionized calcium >1.02 mmol/L to reduce risk of hypotension 4

Monitoring and Precautions

Required Monitoring

• Continuous ECG monitoring during administration
• Blood pressure monitoring every 5 minutes during bolus
• Serum ionized calcium levels every 1-4 hours during continuous infusion 5
• Monitor for hypercalcemia (ionized calcium levels >twice normal) 1

Contraindications and Cautions

• Avoid in patients with hypercalcemia 5
• Use cautiously with cardiac glycosides due to risk of arrhythmias 5
• Calcium is incompatible with fluids containing phosphate or bicarbonate 5
• Rapid administration can cause vasodilation, hypotension, bradycardia, and arrhythmias 2

Common Pitfalls

1. Extravasation risk: Calcium solutions are irritating and can cause tissue necrosis if extravasated
2. Inadequate monitoring: Failure to monitor ionized calcium levels can lead to hypercalcemia
3. Drug incompatibilities: Mixing calcium with bicarbonate or phosphate-containing solutions causes precipitation
4. Rapid administration: Too rapid infusion can paradoxically worsen hypotension or cause arrhythmias
5. Inadequate dosing: Underdosing in calcium channel blocker toxicity may fail to reverse hypotension

Remember that calcium administration is just one component of hypotension management and should be integrated with other appropriate therapies based on the underlying cause of hypotension.