What is the evaluation and treatment for hypocalcemia (low calcium levels)?

Evaluation and Treatment of Hypocalcemia

Immediate Assessment and Acute Management

For symptomatic hypocalcemia (tetany, seizures, cardiac arrhythmias, prolonged QT), administer intravenous calcium chloride 10% solution, 10 mL (270 mg elemental calcium) over 2-5 minutes with continuous ECG monitoring. 1, 2

Symptomatic vs Asymptomatic Hypocalcemia

• Symptomatic hypocalcemia presents with neuromuscular irritability, tetany, seizures, cardiac arrhythmias, prolonged QT interval, or Chvostek's/Trousseau's signs and requires immediate IV calcium 1, 2, 3
• Asymptomatic hypocalcemia (ionized calcium >0.9 mmol/L or corrected total calcium >7.5 mg/dL) does not require emergent treatment in most contexts 1, 2

Choice of Calcium Preparation

Calcium chloride is superior to calcium gluconate for acute correction because 10 mL of 10% calcium chloride contains 270 mg elemental calcium versus only 90 mg in the same volume of calcium gluconate 1, 2. Calcium chloride is also preferable when liver function is impaired, as it does not require hepatic metabolism for calcium release 1.

Administration Protocol for Acute Symptomatic Hypocalcemia

• Dilute calcium chloride or gluconate in 5% dextrose or normal saline to concentration of 10-50 mg/mL 4
• Infusion rate: Do NOT exceed 200 mg/minute in adults or 100 mg/minute in pediatric patients 4
• Monitor continuously with ECG during administration for cardiac arrhythmias 1, 2, 4
• Avoid administration through the same line as sodium bicarbonate due to precipitation risk 2
• Use a secure IV line to prevent extravasation, which causes calcinosis cutis and tissue necrosis 4

Specific Dosing by Clinical Context

Tumor Lysis Syndrome: Administer calcium gluconate 50-100 mg/kg IV slowly only if symptomatic (tetany, seizures), as asymptomatic hypocalcemia does not require treatment 1. Exercise caution when phosphate levels are elevated due to calcium-phosphate precipitation risk 1, 2.

Trauma/Massive Transfusion: Correct ionized calcium below 0.9 mmol/L promptly, as hypocalcemia results from citrate in blood products binding calcium 1, 2. Citrate metabolism is impaired by hypoperfusion, hypothermia, and hepatic insufficiency 2.

Pediatric Septic Shock: Replace calcium to normalize ionized calcium concentration, but avoid overtreatment as calcium toxicity may occur 1.

Evaluation of Underlying Etiology

Essential Laboratory Assessment

Measure the following to determine the cause:

• Ionized calcium (pH-corrected) - most accurate measure 1, 2
• Parathyroid hormone (PTH) - distinguishes hypoparathyroidism from other causes 1, 2
• Magnesium - hypomagnesemia impairs PTH secretion and causes end-organ PTH resistance 1, 2
• Phosphate - elevated in hypoparathyroidism and renal failure 1
• Creatinine - assess renal function 1, 2
• 25-hydroxyvitamin D - identifies vitamin D deficiency 3
• Albumin - to calculate corrected total calcium if ionized calcium unavailable 2

Common Etiologies to Consider

• Hypoparathyroidism (75% post-surgical, 25% primary) - most common cause of chronic hypocalcemia 1, 3
• Vitamin D deficiency - impairs intestinal calcium absorption 3
• Hypomagnesemia - must be corrected before calcium normalizes 1, 2
• Chronic kidney disease - impaired vitamin D activation 2
• Massive transfusion - citrate chelation of calcium 1, 2
• Tumor lysis syndrome - hyperphosphatemia-induced calcium precipitation 1

Critical Pitfall: Hypomagnesemia

Always check and correct magnesium levels concurrently, as hypomagnesemia causes hypocalcemia through two mechanisms: impaired PTH secretion and end-organ PTH resistance 2. Calcium supplementation alone will fail if magnesium is not repleted 2. Administer magnesium sulfate 1-2 g IV bolus for symptomatic patients before calcium replacement 2.

Chronic Management and Maintenance Therapy

Standard Long-Term Treatment

• Daily vitamin D supplementation for all patients with chronic hypocalcemia 1, 2, 3
• Oral calcium supplementation (calcium carbonate preferred) when dietary intake insufficient 2, 3
• Total elemental calcium intake should not exceed 2,000 mg/day to avoid hypercalciuria and renal complications 2

Advanced Therapy for Refractory Cases

Reserve hormonally active vitamin D metabolites (calcitriol) for severe or refractory hypocalcemia, typically requiring endocrinologist consultation 1, 2. The goal is to maintain serum calcium in the low-normal range (8.4-9.5 mg/dL) to minimize hypercalciuria and prevent renal dysfunction 2, 3.

Monitoring Requirements

• Regular monitoring of pH-corrected ionized calcium, magnesium, PTH, and creatinine 1, 2
• Measure serum calcium every 4-6 hours during intermittent IV infusions 4
• Measure serum calcium every 1-4 hours during continuous IV infusions 4
• Targeted monitoring during vulnerable periods: perioperatively, perinatally, during pregnancy, and acute illness 1, 2

Special Populations and Contexts

22q11.2 Deletion Syndrome

Eighty percent of these patients have lifetime hypocalcemia risk due to hypoparathyroidism, which may recur at any age despite childhood resolution 1, 2. Biological stressors (surgery, childbirth, infection, fracture) precipitate hypocalcemia 1, 2. Recommend daily calcium and vitamin D supplementation universally, avoid alcohol and carbonated beverages (especially colas), and provide heightened surveillance during stress periods 1, 2.

Post-Parathyroidectomy ("Hungry Bone Syndrome")

• Measure ionized calcium every 4-6 hours for first 48-72 hours, then twice daily until stable 2
• Initiate calcium gluconate infusion at 1-2 mg elemental calcium/kg/hour if ionized calcium falls below 0.9 mmol/L 2
• Provide oral calcium carbonate 1-2 g three times daily plus calcitriol up to 2 mcg/day when oral intake possible 2

Chronic Kidney Disease/Dialysis Patients

Maintain corrected total calcium in normal range, preferably toward lower end (8.4-9.5 mg/dL) 2. Limit elemental calcium from phosphate binders to ≤1,500 mg/day 2. Do not use calcium-based phosphate binders when corrected calcium >10.2 mg/dL, PTH <150 pg/mL on two consecutive measurements, or severe vascular calcifications present 2.

Critical Safety Warnings

Overcorrection Risks

Avoid overcorrection, which causes iatrogenic hypercalcemia, renal calculi, and renal failure 1, 2. This occurs inadvertently with dehydration or treatment compliance changes 1.

Drug Interactions

Never mix calcium with ceftriaxone - forms precipitates 4. Concomitant use is contraindicated in neonates ≤28 days old 4.

Renal Impairment

For patients with renal impairment, initiate at the lowest recommended dose and monitor serum calcium every 4 hours 4.