Hypocalcemia

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Background

Serum Levels

  • Low <8.5 (<2.0 ionized)
  • Low! <6.5 (<1.5 ionized)
  • Correct for hypoalbumimia
    • Corrected Ca = (0.8 *(Normal Alb - Patient's Alb)) + Serum Ca

Fraction[1]

  • 15% bound to anions (phosphate, lactate, citrate)
  • 40% bound to albumin
  • 45% free (regulated by PTH, Vit-D)

Causes

Clinical Features

Differential Diagnosis

Jaw Spasms

Evaluation

ECG

Hypocalcemia with QTc prolongation
  • QT Prolongation via increasing the ST length
    • Only hypothermia and hypocalcemia prolong QT this way

Trousseau's Sign (Mod to high SN and SP)

Spasm associated with symptomatic hypocalcemia
  • Inflate BP cuff for 2-3 mins
  • Positive = Muscle contractions of the hand and wrist

Chvostek's Sign (Low SN and SP)

  • Tapping on the face just anterior to the ear and just below the zygomatic bone
  • Positive = Ipsilateral facial twitching

Management

Avoid empiric treatment in patients taking digoxin due to risk for Stone Heart

  • Asymptomatic
    • Calcium gluconate 1 gm PO Q6hrs
    • Vitamin D (calcitriol) 0.2 mcg BID
  • Symptomatic
    • Calcium gluconate/chloride 10mL of 10% soln IV over 10min
  • Correct hypomag at same time (otherwise PTH is inhibited)

Disposition

  • Admit all symptomatic patients

See Also

References

  1. Yu, AS. Relation between total and ionized serum calcium concentrations. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on October 6th, 2016.)

Video