Hypocalcaemia DDx
Causes of HYPOcalcaemia
Commonest causes: HYPOalbuminaemia and HYPERventilation
- Factitious (commonest)
- Low albumin
- Metabolic (transcellular as for potassium)
- Primary respiratory alkalosis (HYPERventilation)
- Chronic alkalosis
- Endocrine (Decreased Ca uptake, increased excretion)
- Reduced PTH (associated raised PO4 as cannot excrete)
- Hypoparathyroidism (raised PO4)
- Pseudohypoparathyroidism (raised PO4)
- Thyroid or parathyroid surgery
- Increased calcitonin (decreased Ca and PO4)
- Medullary thyroid carcinoma
- Decreased Vitamin D (decreased GIT calcium absorption (small))
- Reduced PTH (associated raised PO4 as cannot excrete)
- Increased PHOSPHATE(precipitates calcium in serum)
- Tumour lysis syndrome (↑K+ ,↑PO4, ↓Ca++)
- Rhabdomyolysis
- Chronic renal failure
- Excessive CITRATE in circulation (precipitates calcium)
- Whole blood transfusion
- Plasmapheresis
- Increased bone formation and turnover (Osteoblastic activity)
- Malignancy (Breast, lung, thyroid, kidney, prostate)
- Osteomalacia (Increased alkaline phosphatase)
- Other
- Sepsis and Toxic shock syndrome
- Pancreatitis (PO4 normal)
- Overhydration
- Drugs
- B blocker OD, phenytoin, gentamicin, heparin
- Cimetidine, Ca channel blocker
Clinical
Calcium is excitable membrane stabiliser. Neuromuscular excitability and irritability is predominant
- Neurological
- Hyperreflexia and seizures
- Paraesthesia of extremities and face (Digital and peri-oral)
- Confusion, hallucinations, dementia
- Muscular
- Laryngospasm, stridor, tetany
- Muscle spasm, cramps and tetany
- Chvostek sign (Facial nerve tap….twitch corner of mouth)
- Trousseau sign (BP cuff on arm for 3mins induces carpopedal spasm)
- Cardiac
- Decreased myocardial contractility and heart failure
Complication
- Arrhythmia
- ECG changes
- QTc prolongation (With low K+, Mg2+, Ca2+)
- T wave inversion
- Complete heart block
- Torsades des Pointes
Correction
- Assess and treat underlying cause
- Correct acidosis and hypomagnesaemia
- Replace Calcium
Asymptomatic
- Oral Calcium supplements and Vitamin D rich milk
Symptomatic
- Parenteral Calcium
- Calcium chloride (10ml 10% 13.6mEq)
- Calcium gluconate (10ml 10% 4.6mEq)
References and Links
- CCC – Calcium metabolism
- CCC – Calcium basics
- CCC – Hypercalcaemia Overview
- CCC – Hypocalcaemia
- CCC – Calcium replacement (advantages/disadvantages)
- CCC – Calcium as an inopressor
Fellowship Notes
Physician in training. German translator and lover of medical history.
BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital. Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | On Call: Principles and Protocol 4e| Eponyms | Books |