HYPOCALCEMIA
MBBS 2011 BATCH
06/08/14
CALCIUM
• Total body calcium content- 1-2 kg
• 99% of it is within the bone in the form of hydroxyapatite
• It is present both in ICF & ECF
• In blood total calcium concentration- 8.5-10.5 mg/dl
• It is present in two forms in blood- (both ≈ 50% each)
1. bound form- bound ionically to proteins and other anions
2. unbound form- free ionic form
• Normally ionic unbound form in the ECF is maintained within
an exquisitely narrow range through a series of feedback
mechanisms that involve PTH and active vitamin D
metabolite.
• Calcium is impotant for many physiological processes such as
neuromuscular signaling, cardiac contractility, blood
coagulation and hormone secretion.
• Recommended dietary intake- 1000-1200 mg/day
Calcium homeostasis
HYPOCALCEMIA
• Serum calcium < 8.4 mg/dl with a normal serum albumin.
Or
an ionized calcium < 4.2 mg/dl.
• It must be differentiated from pseudohypocalcemia, in which
total calcium is reduced due to hypoalbuminemia, but ionized
(physiologically active) fraction remains within normal range.
• An algorithm to correct for protein changes adjusts the total
serum calcium (in mg/dL) upward by 0.8 times the deficit in
serum albumin (g/dL) or by 0.5 times the deficit in serum
immunoglobulin (in g/dL).
CAUSES
1. Hypocalcemia associated with hypoparathyroidism
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parathyroid agenesis
parathyroid destruction
reduced parathyroid function
2. Associated with high parathyroid hormone levels
(secondary hyperparathyroidism)
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Vit D deficiency or impaired action
Parathyroid hormone resistance syndromes
Drugs
Clinical manifestations
• May be asymptomatic (when mild and chronic)
• Moderate to severe hypocalcemia is associated with paresthesias,
usually of the fingers, toes, and circumoral regions, and is caused
by increased neuromuscular irritability.
• Chvostek's sign- twitching of the circumoral muscles in response
to gentle tapping of the facial nerve just anterior to the ear. (may
be present in 10% of normal individuals)
• Trousseau's sign- Carpal spasm induced by inflation of a blood
pressure cuff to 20 mmHg above the patient's systolic blood
pressure for 3 min.
• Severe hypocalcemia can induce seizures, carpopedal spasm,
bronchospasm, and prolongation of the QT interval.
Investigations
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Total and ionic calcium
Serum albumin
Serum PTH
Serum Phosphorus
Vitamin D
Serum Mg
Serum alkaline phosphatase
Approach to Hypocalcemia
ECG manifestations
• P wave, QRS complex unaffected.
• Prolong QT interval (because of elongation of S-T
segment)
• The prolongation of QT interval is inversely proportional
to the serum calcium level.
• T wave is usually normal in duration, configuration and
amplitude.
• Hypocalcemia is the only condition which can prolong
the ST segment without affecting the T wave.
TREATMENT
• Depends on the severity of the hypocalcemia, the rapidity
with which it develops, and the accompanying complications.
• Acute, symptomatic hypocalcemia is initially managed with i/v
calcium gluconate (10% w/v) 1 ampul diluted in 50 mL of 5% D
or NS given over 5 min.
• Continuing hypocalcemia often requires a constant
intravenous infusion ( i.e. 10 ampuls of calcium gluconate in 1
L of 5% D or normal saline over 24 h).
• Accompanying hypomagnesemia, if present, should be
treated with appropriate magnesium supplementation
• Chronic hypocalcemia due to hypoparathyroidism- treated
with calcium supplements (1000–1500 mg/d in divided doses)
and either vitamin D2 or D3 or calcitriol.
• Vitamin D deficiency is treated using vitamin D
supplementation, with the dose depending on the severity of
the deficit and the underlying cause.
• The treatment goal is to bring serum calcium into the low
normal range and to avoid hypercalciuria, which may lead to
nephrolithiasis.
• When hypocalcemia is associated with severe
hyperphosphatemia, reduction of phosphorus should precede
aggressive calcium supplementation.