How to replete calcium in a patient with hypocalcemia?

How to Replete Calcium in Hypocalcemia

For acute symptomatic hypocalcemia, administer intravenous calcium gluconate 1,000-2,000 mg (93-186 mg elemental calcium) diluted in 5% dextrose or normal saline over 10-20 minutes, not exceeding 200 mg/minute infusion rate in adults, with continuous ECG monitoring. 1

Acute Management: Symptomatic Hypocalcemia

Immediate IV Calcium Administration

• Administer calcium gluconate when ionized calcium falls below 0.9 mmol/L or total corrected calcium is ≤7.5 mg/dL, especially if symptomatic (paresthesias, Chvostek's/Trousseau's signs, bronchospasm, laryngospasm, tetany, seizures) 2, 3
• Calcium gluconate is preferred over calcium chloride in most settings: 10 mL of 10% calcium gluconate contains 90 mg elemental calcium versus 270 mg in calcium chloride 2, 1
• However, calcium chloride may be preferable in patients with abnormal liver function due to higher elemental calcium content 2

Administration Protocol

• Dilute calcium gluconate to 10-50 mg/mL concentration in 5% dextrose or normal saline 1
• Infusion rate must NOT exceed 200 mg/minute in adults or 100 mg/minute in pediatric patients 1
• Administer via secure IV line to prevent calcinosis cutis and tissue necrosis from extravasation 1
• Continuous ECG monitoring is mandatory during administration to detect arrhythmias, particularly bradycardia and cardiac arrest 1

Dosing for Acute Symptomatic Hypocalcemia

• Adults: 1,000-2,000 mg calcium gluconate (93-186 mg elemental calcium) IV bolus 1
• Pediatric patients: Individualize within recommended range based on severity 1
• Neonates: Use lowest recommended dose with careful monitoring 1
• For continuous infusion: dilute to 5.8-10 mg/mL and monitor serum calcium every 1-4 hours 1

Chronic Management: Oral Calcium Supplementation

Choice of Oral Preparation

• Calcium carbonate is the preferred oral supplement due to highest elemental calcium content (40%) 2, 4
• Calcium acetate (25% elemental calcium) is an alternative, particularly useful in CKD patients requiring phosphate binding 2
• Avoid calcium citrate in CKD patients 2
• Avoid calcium chloride for oral use due to metabolic acidosis risk 2

Oral Dosing Strategy

• For severe hypocalcemia (calcium <7.5 mg/dL): Start with 1-2 g calcium carbonate three times daily (providing 1,200-2,400 mg elemental calcium daily) 2
• Total elemental calcium intake (dietary plus supplements) must not exceed 2,000 mg/day 4, 5, 2
• Take calcium supplements between meals to maximize absorption, unless using as phosphate binder 2
• Do not give calcium with high-phosphate foods or medications as intestinal precipitation reduces absorption 2

Vitamin D Supplementation

• Add vitamin D supplementation if 25-hydroxyvitamin D is <30 ng/mL 2
• For persistent hypocalcemia with elevated PTH in CKD patients, use active vitamin D sterols (calcitriol, alfacalcidol, or doxercalciferol) 2
• Vitamin D effects may be delayed 15-25 days, so do not rely on it for acute correction 6

Monitoring Requirements

Acute Setting

• Measure serum calcium every 4-6 hours during intermittent IV infusions 1
• Measure serum calcium every 1-4 hours during continuous infusion 1
• Continuous ECG monitoring during IV administration 1
• Monitor for signs of extravasation and calcinosis cutis 1

Chronic Management

• Check serum calcium and phosphorus every 3 months 2
• Reassess vitamin D levels annually 2
• Monitor for hypercalciuria, which can lead to nephrocalcinosis, especially with combined calcium and vitamin D therapy 2

Special Populations and Considerations

Chronic Kidney Disease Patients

• In CKD, individualize treatment rather than correcting all hypocalcemia - mild asymptomatic hypocalcemia may be harmless, especially with calcimimetic therapy 4
• Initiate at lowest dose range and monitor serum calcium every 4 hours 1
• Consider calcium supplementation when PTH begins rising (GFR <60 mL/min/1.73 m²) 4
• Maintain calcium in low-normal range to minimize hypercalciuria and renal dysfunction 3

Neonates and Pediatric Patients

• Early neonatal hypocalcemia (first 24-48 hours) is common and usually asymptomatic due to delayed PTH surge 4
• Calcium infusion prevents or treats early neonatal hypocalcemia 4
• Maximum infusion rate: 100 mg/minute in pediatric patients 1
• CONTRAINDICATED: Concurrent ceftriaxone and IV calcium in neonates ≤28 days due to fatal ceftriaxone-calcium precipitates 1

Renal Impairment

• Start at lowest recommended dose range 1
• Monitor serum calcium every 4 hours 1
• Balance calcium supplementation with phosphate control 2

Critical Drug Interactions and Contraindications

Absolute Contraindications

• Do not administer IV calcium to neonates ≤28 days receiving ceftriaxone - fatal precipitates can form 1
• Hypercalcemia is a contraindication 1

Important Drug Interactions

• Cardiac glycosides: Synergistic arrhythmias may occur - if concurrent therapy necessary, give calcium slowly in small amounts with close ECG monitoring 1
• Calcium channel blockers: Calcium administration may reduce their response 1
• Do not mix with ceftriaxone, bicarbonate, phosphate, or minocycline - precipitation or inactivation occurs 1
• Drugs causing hypercalcemia (vitamin D, vitamin A, thiazides, estrogen, calcipotriene, teriparatide) require plasma calcium monitoring 1

Common Pitfalls to Avoid

• Never administer IV calcium rapidly - this causes hypotension, bradycardia, and cardiac arrhythmias 1
• Never exceed 2,000 mg/day total elemental calcium intake - risk of hypercalcemia and vascular calcification 4, 2
• Do not treat mild asymptomatic hypocalcemia aggressively in CKD patients, especially those on calcimimetics 4
• Always correct for albumin when interpreting total calcium levels: Corrected calcium (mg/dL) = Total calcium + 0.8 [4 - Serum albumin (g/dL)] 5
• Ensure secure IV access - extravasation causes calcinosis cutis, tissue necrosis, and ulceration 1
• Monitor calcium-phosphate product in CKD patients - products >72 increase mortality risk 4