Hypocalcemia

Hypocalcemia: Excerpt from In A Page: Pediatric Signs and Symptoms

Hypocalcemia is defined as total calcium <7.5 mg/dL. Causes include inadequate inflow of calcium from the GI tract, bone, or kidney, or excessive loss of calcium into urine, stool, and bone. Calcium level is affected by pH: Systemic acidosis decreases total calcium and increases the ionized form (Ca⁺⁺), whereas systemic alkalosis increases total calcium and lowers Ca⁺⁺.

Differential Diagnosis

• Hypoparathyroidism
  –Congenital: Transient neonatal vs heritable forms
  –Acquired: Autoimmune, postsurgical, radioablation, infiltrative
  –DiGeorge Syndrome
  –Polyglandular autoimmune disease type 1 (Blizzard syndrome)
  –Pseudohypoparathyroidism (PHP) or PTH resistance
        –PHP type IA (Albright dereditary osteodystrophy)
        –PHP type IB, type II

• Vitamin D deficiency
  –Nutritional deprivation
        –Most common cause of rickets
        –Seen in breast-fed and black children
  –Malabsorption/steatorrhea/liver disease
  –1-αhydroxylase deficiency
  –Chronic renal disease

• Calcium deficiency
  –Nutritional deprivation
  –Malabsorption
  –Hypercalciuria
• Hypomagnesemia
  –Impairs secretion of, and end-organ responsiveness to, PTH
  –Inherited forms
  –Intestinal losses
  –Renal wasting: RTA, drugs
• Hyperphosphatemia
• Hypoproteinemia
  –Total calcium is a measure of calcium bound to albumin
• Drugs
  –Loop diuretics (furosemide) promote renal calcium excretion
  –Anticonvulsants interfere with GI vitamin D absorption
  –Antacids impair GI calcium absorption
  –Antineoplastic agents
  –Citrated blood products
• Critical illness
  –Rhabdomyolysis
  –Toxic shock syndrome
  –Pancreatitis
• Organic acidemia
• Infant of a diabetic mother

Workup and Diagnosis

• History
  –Age at onset, age developmental milestones reached
  –Dietary intake, recurrent infections, medications
  –Paresthesias, jitteriness, seizures
  –Muscle cramping, tetany, carpal-pedal spasm
  –Cardiac disease, neck surgery
  –Autoimmune disorders, liver disease, renal disease

• Physical exam
  –Vital signs, growth parameters
  –Facial dysmorphism (DiGeorge syndrome, PHP IA)
  –Skeletal deformities (bowed legs, widened wrists/ankles, rachitic rosary, frontal bossing)
  –Cardiac exam (heart murmur with DiGeorge)
  –DTRs for hyperreflexia, carpal-pedal spasm
  –Chvostek sign (twitching of circumoral muscles after tapping on facial nerve in front of the ear)
  –Trousseau sign (carpal-pedal spasm after maintaining arm BP cuff 20 mmHg above systolic BP for 3 minutes)
  –Thrush, vitiligo, alopecia, nail fungal infection (for Blizzard)

• Labs: PTH, total and ionized calcium, vitamin D levels, alkaline phosphatase, LFT, BUN, Cr, magnesium, phosphorus, albumin; urine calcium and Cr
• ECG: Prolonged QT interval
• CXR: Absent thymus in DiGeorge
• Long bone films: Rachitic changes
• CT brain: Evaluate for calcification of basal ganglia

Treatment

• Acute correction of hypocalcemia: IV calcium gluconate (bolus or infusion) until Ca >7 mg/dL
• Hypoparathyroidism
  –Oral calcium supplement (dose as elemental calcium)
  –1,25-(OH)₂-vitamin D analog (calcitriol)
• Vitamin D deficiency (nutritional rickets)
  –25-OH-vitamin D analog (ergocalciferol) 2,000–4,000 IU/day
  –Oral calcium supplement (dose as elemental calcium) to prevent “hungry bone syndrome”
• Hypomagnesemia
  –Treat with magnesium supplementation
• Drugs
  –Discontinue offending agents if possible
• Goals of management
  –Hypoparathyroidism: Maintain calcium at 8–9 mg/dL to avoid nephrocalcinosis
  –Vitamin D deficiency: Maintain normal calcium range

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

More About Hypoparathyroidism

• Back to disease: Hypoparathyroidism: Introduction
• Next Book Extract About Hypoparathyroidism: HYPOCALCEMIA (Differential Diagnosis in Primary Care)
• More Book Extracts: All Online Books for Hypoparathyroidism

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9

 » Next page: HYPOCALCEMIA (Differential Diagnosis in Primary Care)

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