Makindo Medical Notes

Related Subjects: |Calcium Physiology |Calcitonin |Hypocalcaemia |Hypercalcaemia |Hypomagnesaemia |Hypermagnesaemia |Primary Hyperparathyroidism |Familial hypocalciuric hypercalcaemia (FHH) |Sarcoidosis

⚠️ Always check magnesium in hypocalcaemia — low Mg²⁺ causes end-organ resistance to PTH and blocks the hypocalcaemic feedback loop.

🔢 Calcium Levels (mg/dL → mmol/L multiply ×0.25)

🧬 Aetiology & Pathophysiology

• ⬆️ Neuronal excitability → tetany, seizures, arrhythmias.
• Due to membrane instability: cells depolarise more easily at low Ca²⁺.

📊 Causes of Hypocalcaemia

⚡ Clinical Features

• Acute: Tetany, paraesthesia, carpopedal spasm, stridor, seizures, prolonged QT.
• Chronic: Poor dentition, brittle nails, basal ganglia calcification, cataracts, depression/psychosis.

🧪 Investigations

• U&E, corrected Ca, Mg, phosphate, Vit D metabolites.
• iPTH = key diagnostic test.
• ECG: long QT ± arrhythmias.

📈 Interpretation Patterns

• Low Ca + high PTH → CKD, Vit D deficiency, pseudohypoparathyroidism, hypomagnesaemia, sepsis.
• Low Ca + low PTH → Hypoparathyroidism (post-op, autoimmune, congenital), severe Mg deficiency.

💊 Management

• Mild (Ca 1.9–2.13 mmol/L): Oral Ca + Vit D (e.g., Sandocal, Adcal). Monitor weekly → 3–6 monthly.
• Severe (<1.9 or tetany/seizures):
  • ABC, airway secure if stridor/seizures.
  • 10 mL 10% calcium gluconate IV in 100 mL saline/dextrose over 10–20 min (ECG monitor).
  • If refractory → infusion: 100 mL 10% Ca gluconate in 1L saline at 50 mL/hr. Recheck Ca 4–6 hourly.
  • Switch to oral once stable.
• ⚠️ Administer via large vein (avoid extravasation). Too rapid → flushing, hypotension, arrhythmias.
• Digoxin users → avoid IV calcium unless life-threatening (risk of arrhythmia).
• Consider CaCl₂ if central line in ICU (more irritant than gluconate).

📚 References

• Gloucestershire NHS Hypocalcaemia Guideline
• Leicester NHS Guidance