Treatment of Severe Hypocalcemia
For severe hypocalcemia, intravenous calcium replacement with calcium chloride or calcium gluconate is the first-line treatment, with calcium chloride preferred in critical situations due to higher elemental calcium content and faster ionization. 1
Definition and Diagnosis
- 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
- Symptoms may include neuromuscular irritability, tetany, seizures, and cardiac dysrhythmias, particularly when ionized calcium falls below 0.8 mmol/L 1, 2
Immediate Management of Severe Hypocalcemia
First-Line Treatment
- Administer intravenous calcium promptly for symptomatic hypocalcemia 3, 2
- Calcium chloride is preferred in critical situations, containing 270 mg of elemental calcium per 10 mL of 10% solution 1
- Calcium gluconate is an alternative (FDA-approved for acute symptomatic hypocalcemia), containing less elemental calcium than calcium chloride 3
Dosing Guidelines
- For mild hypocalcemia (ionized calcium 1.0-1.12 mmol/L): 1-2 g IV calcium gluconate (effective in 79% of cases) 4
- For moderate to severe hypocalcemia (ionized calcium <1.0 mmol/L): 4 g IV calcium gluconate infusion at 1 g/hour (effective in 95% of cases) 5
- For symptomatic hypocalcemia with tetany or seizures: 50-100 mg/kg calcium gluconate as a single dose, cautiously repeated if necessary 6
Administration Considerations
- Infuse calcium gluconate at a rate of 1 g/hour in a small volume admixture 5
- Monitor ionized calcium levels following administration 1, 4
- Target ionized calcium levels within the normal range (1.1-1.3 mmol/L) 1
Special Clinical Scenarios
Massive Transfusion
- Hypocalcemia commonly occurs during massive transfusion due to citrate-mediated calcium chelation 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, impaired liver function due to hypoperfusion worsens hypocalcemia by decreasing citrate metabolism 1
Chronic Kidney Disease
- Hypocalcemia is common in CKD patients and requires correction when severe 1
- Initiate calcium replacement at the lowest recommended dose in patients with renal impairment 3
- Monitor serum calcium levels every 4 hours in these patients 3
Drug Interactions
- Avoid administration of calcium in patients receiving cardiac glycosides; if necessary, administer slowly in small amounts with close ECG monitoring 3
- Be aware that calcium may reduce the response to calcium channel blockers 3
- Use caution with concomitant administration of cimetidine and nifedipine, which can precipitate severe hypocalcemic tetany 7
Monitoring and Follow-up
- Monitor ionized calcium levels regularly during treatment 1, 4
- Watch for signs of overcorrection and iatrogenic hypercalcemia 1
- Two patients in a study developed mild hypercalcemia (ionized calcium of 1.34 mmol/L and 1.38 mmol/L) after 4g calcium gluconate infusion 5
Addressing Underlying Causes
- Identify and treat the underlying cause of hypocalcemia (hypoparathyroidism, vitamin D deficiency, etc.) 2, 8
- Correct other factors that may interfere with coagulation in trauma patients, including hypothermia, severe acidosis, low hematocrit, and hypocalcemia 6
- In tumor lysis syndrome, treat laboratory abnormalities including hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia 6