List 5 major causes and 3 important clinical manifestations of hypocalcaemia in the critically ill patient.
Aetiology
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.
Low Parathyroid Hormone
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High or normal Parathyroid hormone
Drugs
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Mild hypocalcemia
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Severe hypocalcemia
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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.