Definitions & Classifications
- Term or preterm > 1,500 g: Total calcium < 8 mg/dL (2 mmol/L) OR Ionized calcium < 4.4 mg/dL (1.1 mmol/L)
- Preterm ≤ 1,500 g: Total calcium < 7 mg/dL (1.75 mmol/L) OR Ionized calcium < 4 mg/dL (1 mmol/L)
- Early-onset hypocalcemia: Occurs within first 72 hours of life. Often related to impaired physiologic response to calcium nadir.
- Late-onset hypocalcemia: Occurs > 72 hours of life (usually first week). Often related to nutrition, high phosphate, Vit D deficiency, or hypomagnesemia.
- Normal Fetal Metabolism: Calcium active transport primarily 3rd trimester. At term, fetal total Ca is 10-11 mg/dL, ionized 6 mg/dL.
- Postnatal Nadir: Drops to 7.5-8 mg/dL within 48-72 hours, PTH surges to correct to normal by day 3.
Differential Diagnosis
- EARLY-ONSET Causes: Prematurity, SGA/IUGR, maternal diabetes (gestational/pregestational), transient hypomagnesemia, perinatal asphyxia, sepsis.
- EARLY-ONSET Medications: Loop diuretics (furosemide), aminoglycosides (gentamicin), antiseizure meds (phenytoin/phenobarbital), citrated blood, lipid emulsions.
- LATE-ONSET Causes: Hyperphosphatemia (cow's milk/high-fiber formula), insufficient dietary calcium, maternal/infant Vitamin D deficiency.
- LATE-ONSET Endocrine: Primary hypoparathyroidism, maternal hyperparathyroidism (suppresses fetal PTH), parathyroid hormone resistance (pseudohypoparathyroidism).
Clinical Presentation
- Usually asymptomatic (especially early-onset). Neuromuscular signs: jitteriness, exaggerated startle reflex, tremor, hyperacusis, myoclonic jerks.
- Cardiopulmonary signs: Apnea, tachypnea, cyanosis. Laryngeal signs: Stridor (laryngospasm), wheezing (bronchospasm).
- Severe hypocalcemia: Presents with true seizures or tetany. Requires prompt IV correction.
- ECG Findings: Prolonged QT interval, QRS and ST changes, ventricular arrhythmias.
Management of Severe Symptomatic Hypocalcemia
- Consult pediatric endocrinologist for persisting cases.
- 10% Calcium Gluconate (Preferred): 100 mg/kg IV (10 mg/kg elemental) once over 10-20 mins (max 100 mg/min) with cardiac monitoring. May repeat in 10-20 mins.
- 10% Calcium Chloride (Alternative for poor cardiac function): 37-74 mg/kg IV once.
- Continuous Infusion: 50-80 mg/kg/day elemental calcium (equivalent to 10% calcium gluconate 538-860 mg/kg/day) IV for 48 hours.
- Weaning: If stable after 48 hours, decrease infusion by 50% for next 24 hours, then discontinue.
- DO NOT administer via UAC (umbilical artery catheter) due to arterial spasm risk. Central line preferred to avoid severe extravasation/necrosis.
- Monitor Mg levels: Hypocalcemia will not correct if concurrent hypomagnesemia is present. Treat with MgSO4 25-50 mg/kg IV over 2h.
Management of Less Severe & Specific Causes
- Enteral Administration: 40-80 mg/kg/day elemental calcium orally in 3-4 divided doses.
- High Phosphate Load: Diet high in calcium, low in phosphate. Use human milk or reduced-phosphate formulas. Administer Calcium:Phosphate at 4:1 ratio.
- Hypoparathyroidism: Calcitriol 0.25-1 mcg (0.08-0.1 mcg/kg) PO daily to maintain low-normal serum calcium. Thiazide diuretics may be used to decrease renal calcium loss.
- Vitamin D Deficiency: Supplement with Vitamin D2 (ergocalciferol) or D3 (cholecalciferol) 1,000-2,000 units PO daily.
Diagnostic & Management Algorithm
- Neonatal Hypocalcemia Rescue: [START] Tremors + Ca < 7.0 mg/dL -> [ACTION] Stop feeds -> [PHARMACOLOGY] Calcium Gluconate 10% 100-200 mg/kg IV slowly -> [MONITOR] Telemetry for bradycardia
References for this guideline are being added; see the methodology for our source hierarchy.
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