What is the treatment for severe hypocalcemia (low ionized calcium level)?

Treatment for Severe Hypocalcemia (Ionized Calcium 0.9 mEq/L)

For severe hypocalcemia with ionized calcium of 0.9 mEq/L, immediate treatment with intravenous calcium is required, preferably using calcium chloride which provides more bioavailable calcium than calcium gluconate. 1, 2

Immediate Management

• Administer calcium chloride intravenously - 10% calcium chloride solution (10 mL contains 270 mg of elemental calcium) 2, 1
• Initial dosing should be 1-2 mg of elemental calcium per kilogram body weight per hour as an infusion, adjusted to maintain ionized calcium in the normal range (1.15-1.36 mmol/L) 3
• If calcium chloride is unavailable, calcium gluconate can be used, but note that 10 mL of 10% calcium gluconate contains only 90 mg of elemental calcium (less effective than calcium chloride, especially in patients with liver dysfunction) 2, 4
• Monitor ionized calcium levels every 4-6 hours initially until stable, then twice daily 3
• Adjust calcium infusion rate based on serial ionized calcium measurements 3, 2

Transition to Oral Therapy

• When ionized calcium levels stabilize and oral intake is possible, transition to oral calcium supplementation 3
• Administer calcium carbonate 1-2 g three times daily 3
• Consider adding calcitriol up to 2 μg/day to enhance intestinal calcium absorption 3
• Adjust oral therapy as needed to maintain ionized calcium in the normal range 3, 2

Special Considerations

• If hypocalcemia is occurring in the context of massive transfusion, it may be due to citrate toxicity from blood products 3, 2
• Hypocalcemia may be exacerbated by hypoperfusion, hypothermia, or hepatic insufficiency, which impair citrate metabolism 3
• Colloid infusions (but not crystalloids) can contribute to hypocalcemia 3, 2
• If the patient was previously on phosphate binders, these may need to be reduced or discontinued based on serum phosphorus levels 3
• Acidosis can increase ionized calcium levels, so correction of acidosis may worsen hypocalcemia 3, 2

Monitoring and Follow-up

• Continue monitoring ionized calcium levels until consistently stable 3, 2
• Assess for clinical signs of hypocalcemia resolution (reduction in neuromuscular irritability, tetany, seizures) 5
• Low ionized calcium is associated with increased mortality, coagulopathy, and cardiovascular dysfunction, so prompt correction is essential 3, 2
• Target maintaining ionized calcium >0.9 mmol/L to support cardiovascular function and coagulation 3, 2

Potential Complications of Untreated Severe Hypocalcemia

• Neuromuscular irritability, tetany, and seizures 5
• Cardiovascular compromise including hypotension and decreased cardiac contractility 6, 7
• Coagulopathy and increased bleeding risk 3, 2
• Increased mortality in critically ill patients 3, 2