Calcium Gluconate Infusion for Severe Hypocalcemia in Transient Hypoparathyroidism
For severe symptomatic hypocalcemia following thyroid or parathyroid surgery, initiate a continuous intravenous calcium gluconate infusion at 1-2 mg elemental calcium per kg body weight per hour when ionized calcium falls below 0.9 mmol/L (3.6 mg/dL) or corrected total calcium falls below 7.2 mg/dL (1.80 mmol/L). 1
Dosing and Preparation
Elemental calcium content:
- One 10-mL ampule of 10% calcium gluconate contains 90-93 mg of elemental calcium 1, 2, 3
- Calculate infusion rate based on elemental calcium, not total calcium gluconate 4, 2
Practical dosing example for a 70 kg patient:
- Target infusion rate: 70-140 mg elemental calcium per hour 1
- This translates to approximately 4.5-9.0 mL/hour of 10% calcium gluconate 5
- Start at the lower end (1 mg/kg/hr) and titrate upward based on calcium levels 1, 5
Administration Route and Safety
Administer through a secure central venous catheter whenever possible to prevent severe skin and soft tissue injury from extravasation 4, 3. If peripheral access is used, monitor the site continuously for signs of infiltration 3.
Dilute calcium gluconate in 5% dextrose or normal saline before infusion to reduce the risk of hypotension, bradycardia, and cardiac arrhythmias 3.
Monitoring Protocol
Measure ionized calcium levels:
- Every 4-6 hours during the first 48-72 hours post-surgery 1
- Every 1-4 hours during continuous infusion once treatment is initiated 3
- Twice daily once levels stabilize 1
Target ionized calcium range: 1.15-1.36 mmol/L (4.6-5.4 mg/dL) 1, 6
Continuous ECG monitoring is essential during calcium administration, particularly watching for QT interval changes and arrhythmias 4, 3.
Titration Algorithm
Adjust infusion rate based on calcium levels:
- If ionized calcium remains <2.0 mmol/L (8.0 mg/dL): start at 4.5 mL/hour of 10% calcium gluconate 5
- If calcium continues falling: increase to 6.5 mL/hour 5
- If still inadequate: increase to 9.0 mL/hour (maximum rate) 5
- Gradually reduce the infusion when ionized calcium attains and remains stable in the normal range 1
Transition to Oral Therapy
When oral intake is possible, initiate:
- Calcium carbonate 1-2 g three times daily 1
- Calcitriol up to 2 mcg/day 1
- Continue adjusting doses to maintain ionized calcium in the normal range 1
Wean the intravenous infusion gradually as oral supplementation takes effect, typically over 24-48 hours 1.
Critical Precautions and Pitfalls
Do not mix calcium gluconate with phosphate-containing or bicarbonate-containing fluids as precipitation will occur 3. This is a common and dangerous error.
Exercise extreme caution in patients with hyperphosphatemia due to risk of calcium-phosphate precipitation in tissues causing obstructive uropathy 4. Check serum phosphorus levels before initiating therapy.
If extravasation occurs or calcinosis cutis develops, immediately discontinue the infusion at that site as tissue necrosis, ulceration, and secondary infection can result 3.
Avoid concomitant cardiac glycoside use when possible as synergistic arrhythmias may occur; if necessary, give calcium slowly in small amounts with close ECG monitoring 3.
Peak calcium efflux typically occurs 26-27 hours postoperatively, so hypocalcemia may not manifest until 2 days after surgery 5. Do not discontinue monitoring prematurely.
Account for pH changes when interpreting ionized calcium levels: each 0.1 unit increase in pH decreases ionized calcium by approximately 0.05 mmol/L 6.
Duration of Therapy
Continue monitoring for at least 4 days postoperatively even if hypocalcemia has not developed, as onset can be delayed 5. If hypocalcemia persists beyond 6 days, consider stopping the infusion with continued monitoring for 24 hours to assess for rebound 5.
Transient hypocalcemia resolves in approximately 25% of post-parathyroidectomy patients, while 11% develop persistent hypocalcemia requiring long-term oral supplementation 5, 7.