Question 25

List 5 major causes and 3 important clinical manifestations of hypocalcaemia  in the critically ill patient.

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College Answer


Calcium chelation (eg. alkalosis, citrate toxicity, tumour lysis, rhabdomyolysis)

Drug induced (eg. phenytoin, diphosphonates)

Hypoparathyroidism (eg. hypo and hypermagnesemia, sepsis, surgerical removal) Hypovitaminosis D (eg. inadequate intake, malabsorption, liver disease)

Reduced bone turnover (eg. osteoporosis, elderly, cachexia)

Clinical manifestations

Central nervous system (eg. circumoral and peripheral paraesthesia, muscle cramps, tetany, seizures, psychosis)

Cardiovascular (eg. arrhythmias, hypotension, inotrope unresponsiveness, prolonged QT intervals)

Respiratory (eg. apnoea, laryngospasm, bronchospasm)


Causes of hypocalcemia and consequences of hypocalcemia are discussed in detail elsewhere.

Here, I will reproduce the tables for the aetiologies of hypocalcemia and its clinical manifestations.

Causes of Hypocalcemia

Low Parathyroid Hormone

  • Primary hypoparathyroidism (i.e. destruction of the parathyroid glands)
  • Post-operative hypoparathyroidism
  • Hungry bone syndrome
  • HIV infection
  • Haemochromatosis


High or normal Parathyroid hormone

  • Vitamin D deficiency
  • Hypomagnesemia
  • Hyperphosphataemia
  • Renal failure (pseudohypoparathyroidism)
  • Tumour lysis syndrome
  • Acute pancreatitis
  • Alkalosis
  • Depletion in coagulopathy



  • Phenytoin
  • Fluoride toxicity
  • Foscarnet
  • EDTA
  • Citrate
  • Phosphate
  • Bisphosphonates
Clinical Manifestations of Hypocalcemia

Mild hypocalcemia

  • Generalised myalgia
  • Twitching, fasciculations
  • QT prolongation
  • Chvostek’s sign
  • Confusion, delirium, psychosis

Severe hypocalcemia

  • Carpopedal spasm (Trousseau’s sign)
  • Tetany and seizures
  • Papilloedema
  • Cardiac arrhythmias, esp. Torsades
  • Hypotension


UpToDate has a nice summary of this topic for the paying customer.


Cooper, Mark S., and Neil JL Gittoes. "Diagnosis and management of hypocalcaemia." BMJ: British Medical Journal 336.7656 (2008): 1298.


Tohme, J. F., and J. P. Bilezikian. "Hypocalcemic emergencies." Endocrinology and metabolism clinics of North America 22.2 (1993): 363-375.


Diercks, Deborah B., et al. "Electrocardiographic manifestations: electrolyte abnormalities." The Journal of emergency medicine 27.2 (2004): 153-160.