What are the guidelines for replacing calcium intravenously (IV) in patients with severe hypocalcemia?

Guidelines for Intravenous Calcium Replacement in Severe Hypocalcemia

For patients with severe hypocalcemia, calcium chloride is the preferred agent for intravenous replacement due to its higher elemental calcium content compared to calcium gluconate. 1

Definition and Monitoring

• Severe hypocalcemia is defined as total or albumin-corrected calcium <7.5 mg/dL (<1.87 mmol/L) or ionized calcium <0.9 mmol/L 1
• Ionized calcium levels should be monitored and maintained within the normal range (1.1-1.3 mmol/L) in all patients with severe hypocalcemia 1
• Monitor ionized calcium during intermittent infusions every 4-6 hours and during continuous infusion every 1-4 hours 2

Preferred Agent Selection

• Calcium chloride is the preferred agent for IV calcium replacement in severe hypocalcemia 1
  • 10 mL of 10% calcium chloride solution contains 270 mg of elemental calcium 1, 3
  • In comparison, 10 mL of 10% calcium gluconate contains only 90 mg of elemental calcium 1
• Calcium chloride is particularly preferable in patients with liver dysfunction, where decreased citrate metabolism results in slower release of ionized calcium 1

Dosing Guidelines

Adult Dosing:

• For severe symptomatic hypocalcemia: 200 mg to 1 g (2-10 mL) of calcium chloride administered intravenously 3
• Administer by slow intravenous injection, not exceeding 1 mL/min, preferably in a central or deep vein 3
• Repeat injections may be required every 1-3 days depending on patient response and ionized calcium levels 3

Pediatric Dosing:

• 2.7 to 5.0 mg/kg of calcium chloride (equivalent to 0.136 to 0.252 mEq elemental calcium per kg) 3
• Repeat dosages may be administered every 4-6 hours as needed based on calcium levels 3

Administration Considerations

• Halt injection if the patient reports discomfort; resume when symptoms disappear 3
• Patient should remain recumbent for a short time following injection 3
• Calcium chloride should be administered via a secure intravenous line to prevent tissue necrosis from extravasation 1, 2
• Calcium chloride is not physically compatible with fluids containing phosphate or bicarbonate; precipitation may result if mixed 2

Special Clinical Scenarios

Massive Transfusion

• Hypocalcemia is common during massive transfusion due to citrate-mediated chelation of calcium 1
• Each unit of packed red blood cells or fresh frozen plasma contains approximately 3g of citrate that chelates calcium 1
• In hemorrhagic shock with massive transfusion, liver function is often impaired due to hypoperfusion, resulting in decreased citrate metabolism and worsening hypocalcemia 1

Chronic Kidney Disease

• In patients with CKD, hypocalcemia is common and may require correction, particularly when severe 1
• Previous guidelines suggested permissible hypocalcemia with calcimimetic use, but given the well-understood risks of severe hypocalcemia, correction is now considered reasonable 1

Monitoring for Complications

• Watch for signs of cardiac dysrhythmias, which are associated with ionized calcium levels below 0.8 mmol/L 1
• Monitor for tissue necrosis and calcinosis cutis, which can occur with or without extravasation 2
• If extravasation occurs, immediately discontinue administration at that site 2

Cautions

• Rapid administration can cause hypotension, bradycardia, and cardiac arrhythmias; administer slowly with careful ECG monitoring 2
• Use caution in patients on cardiac glycosides, as concomitant calcium administration may cause synergistic arrhythmias 2
• Avoid overcorrection which can result in iatrogenic hypercalcemia, renal calculi, and renal failure 1

By following these guidelines, clinicians can effectively and safely manage severe hypocalcemia with intravenous calcium replacement.