Hypocalcemia

Hypocalcemia

David Ray Velez, MD

Definition: Serum Total Calcium (Ca) < 8.5-8.8 mg/dL or Ionized Calcium < 4.5 mg/dL

Causes

  • Vitamin D Deficiency – The Most Common Cause
  • Chronic Kidney Disease (CKD) Induced Vitamin D Deficiency
  • Blood Transfusion (Chelation)
  • Hypocalcemia – From Inhibited PTH Release (Hypoparathyroidism) and End-Organ PTH-Resistance
  • Autoimmune Parathyroid Destruction
  • Parathyroidectomy
  • Parathyroid Injury During Thyroidectomy
  • Medications:
    • Lactate
    • Foscarnet
    • Bisphosphonates
    • Denosumab
    • Cinacalcet
    • Chemotherapy
  • Acute Pancreatitis
  • Surgery
  • Sepsis or Severe Illness

Pseudohypocalcemia

  • Definition: Falsely Low Calcium from Low Protein Levels (Particularly Albumin)
    • Total Calcium is Low from Decreased Protein-Bound Calcium
    • Ionized Calcium Remains Stable
  • Corrected Calcium = Calcium + [0.8 x (4 – Albumin)]

Presentation

  • Perioral Tingling/Numbness – First Sign
  • Tetany
    • Chvostek Sign: Cheek Tap Causes Spasm
    • Trousseau Sign: BP Cuff Inflation Causes Carpopedal Spasm
  • Seizures
  • Anxiety and Depression

EKG Changes

  • Prolonged QT Interval
  • Arrhythmias are Uncommon

Laboratory Measurement

  • Total Calcium
    • Measures Total Calcium in the Blood, Including Both Calcium Bound to Protein and “Free Calcium” Not Bound to Protein
    • Normal Range: 5-10.5 mg/dL
    • Often Inaccurate in Acute Care Practice Due to Protein Deficiency with Pseudohypocalcemia in Acute Illness
  • Ionized Calcium (iCal)
    • Measures “Free Calcium” that is Not Bound to Protein
    • Normal Range: 4.5-5.5 mg/dL (1.16-1.31 mmol/L)
    • Considered the More Accurate Measurement in Clinical Practice in Determining Need for Replacement

Treatment

  • Primary Treatment: Calcium Replacement
  • Calcium Gluconate
    • Correction: Every 1 g IV will Increase Ionized Ca 0.15 mg/dL
    • Preferred for Mild Asymptomatic Deficiencies
  • Calcium Chloride (CaCl2)
    • Correction: Every 1 g IV will Increase Ionized Ca 0.45 mg/dL
    • Provides Three Times the Amount of Elemental Calcium per Gram as Calcium Gluconate
    • Preferred for Severe or Symptomatic Deficiencies
    • Corrosive to Veins and Requires a Central Line
  • Goal is to Achieve the Middle of the Normal Range, Not the Lower Limit of Normal, to Allow for Ongoing Losses
  • Correct Any Underlying Hypomagnesemia as Well