Calcium - Hypocalcaemia

The classification of causes of hypocalcaemia:

• hypoparathyroidism surgical (post-op) is the commonest cause, can also be auto-immune

• hypomagnesaemia

• vitamin D deficiency/resistance

• renal failure, and renal losses (loopm diuretics)

• drug related-cytotoxics, PPIs

• metastatic disease e.g. osteoblastic secondaries (breast, prostate)

• pancreatitis

• rhabdomyolysis

• large voume blood transfusions

Symptoms and Signs

• Neurological: Seizures, lethargy, paraesthesia, tetany, respiratory arrest

• Cardiovascular: Heart block, heart failure, ECG prolonged QT and rarely Torsades

• Dermatological: Dry skin, brittle hair

• Other: Cataracts, abdominal pain, diarrhea

• Chvostek and Trousseau signs (see below)

Chvostek sign:

• Tapping over the facial nerve anterior to the tragus causes contraction of the facial muscles

Trousseau sign:

• Inflation of a BP cuff causes carpopedal spasm

Management

Mild – moderate (asymptomatic >1.9 mmol/L corrected):

• Oral Calcium supplements

• Find and treat the cause (in hospital setting is often post surgical)

• Correct hypomagnesaemia

Severe (Symptomatic or ≤ 1.9 mmol/L corrected)

• 10mLs 10% Calcium Gluconate in 5% Dextrose over 10mins, can be repeated.

• Infusion is 100mLs of 10% calcium gluconate (ten vials) in one litre of Normal Saline or Dextrose 5% infused starting at 50-100mLs/hour, titrate to normocalcaemia.

• Sampling for levels should be done at 2-6 hourly depending on degree and symptoms.

• Calcium chloride can be used via a central line and will be run at reduced rates as it contains more 3 times more elemantal calcium, avoid use peripherally.

• There appears to be no difference in rate of bio-availability. See ALiEM - Mythbuster Calcium Gluconate Raises Serum Calcium as Quickly as Calcium Chloride.

• Find and treat the cause.

• Correct hypomagnesaemia.