Total serum calcium

• The calcium level obtained on routine BMP/CMP is the total serum calcium.
• When the blood becomes too alkaline (alkalosis), more calcium gets tied up with albumin (a protein in your blood). This reduces the amount of free, or ionized, calcium
• Free or ionized calcium is the active form of calcium and is the one that gets regulated by PTH and vitamin D.
• Total calcium level doesn’t tell you much about free calcium levels.
• Total calcium levels can be falsely elevated or lowered by high or low albumin levels.

Diagnosis

Free/ionized calcium level:

• The gold standard to diagnose hypo/hypercalcemia.
• Expensive and not readily available.
• Normal reference values are assay-dependent and may vary from facility to facility (check your lab’s references).
• Alkalosis increases albumin-bound calcium and therefore reduces free/ionized calcium as in hyperventilation.
• PTH decreases albumin-bound calcium and therefore increases free/ionized calcium.
• Phosphorus binds calcium and therefore hyperphosphatemia decreases the ionized/free calcium as in CKD.

Total serum calcium level:

• This is the value obtained on routine BMP/CMP
• Correct total serum calcium level to albumin level whether albumin is high or low (no need if albumin is normal 4 gm/dl).
• Total serum calcium level changes by 0.8 mg/dl for each 1 gm change in albumin.
• Hypocalcemia = Ca level < 8 mg/dl (Corrected to albumin).
• Hypercalcemia = Ca level < 10 mg/dl (Corrected to albumin).

Confirm the diagnosis

Initial w/u

Check PTH and vitamin D levels.

Check Mg and phosphorus levels.

Check EKG (QTc).

Treatment

Acute hypocalcemia

• Acute drop in calcium level to < 7.5 mg /dl compared to a recent baseline.
• If no baseline is available, we consider it chronic.

Severe signs/symptoms

• Prolonged QTc.
• Chvostec’s/Trousseau’s sign.
• Seizures.
• Spasm:
  • Carpopedal.
  • Laryngeal.
  • Bronchospasm.
• Irritability, anxiety, and depression.

Inpatient/urgent treatment

• A bolus or two of IV calcium will lead to a quick but temporary rise in serum calcium level enough to relieve or alleviate hypocalcemia-related symptoms.
• A slow calcium infusion or repeated boluses (at a slower rate) will lead to a more sustained rise in calcium levels.

   

• Infuse 1-2 gm of Calcium gluconate or 0.5-1 gm of calcium chloride over 10 minutes. A second bolus may be given if symptoms persist
• Symptoms resolved or improved, follow that with slow calcium infusion:
  • Calcium drip at 50 ml/hr.
  • Repeated scheduled boluses (every 6-8 hours) infused over 1-2 hours.
• Calcium drip:
  • Mix 11 gm of calcium gluconate (990 mg elemental calcium) in 1000 of 0.9 NS or D5W and infuse at 50 ml/hr.
  • Or mix 3.67 gm of calcium chloride (999 mg of elemental calcium) in 1000 of 0.9 NS or D5W and infuse at 50 ml/hr.
• Start oral calcium as soon as possible.
• Start vitamine D if defecient.
• Discontinue IV calcium if: Symptoms resolved + oral calcium and vitamin D supplements started.
• Replace any magnesium deficiency as hypomagnesemia makes it difficult to treat hypocalcemia.

Outpatient/nonurgent treatment

• Start oral calcium to provide 1-2 gm of elemental calcium/day including dietary calcium.
• Start vitamin D if defecient.

Disease-specific treatments

• Acute hypoparathyroidism: Oral calcium and vitamin D (calcitriol) should be started together. This is in addition to the urgent treatment.
• CKD: Hyperphosphatemia is the problem here, high phosphorus level decreases free calcium level, Calcium acetate is the mainstay treatment as a phosphorus binder rather than a calcium supplement. Vitamin D (Calcitriol) should added if defecient.
• Vitamin D deficiency:
  • Ergocalciferol (D2) and Cholecalciferol (D3) need to be metabolized to active forms by the kidney and liver.
  • Calcitriol is an active form of vitamin D that bypasses the renal or hepatic metabolism with a quick onset of action, perfect in renal and hepatic impairments patients and when a fast response is required as in acute hypoparathyroidism.

Monitoring

• Watch the resolution of symptoms.
• Check calcium level in 12-24 hours.
• Discharge patient once symptoms resolved, calcium level is >= 8 mg/dl, and oral calcium and vitamin D started and tolerated.