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CNSLF Path - Ca Metabolism & Disorders of Ca Balance (iii)…
CNSLF Path - Ca Metabolism & Disorders of Ca Balance (iii) Hypocalcaemia
Intro
increased excitability
reliable signs + symptoms
signs
agitations
hyperrefelxia
convulsions
HTN
prolonged QT (increased risk of arrhythmias)
Trousseau's sign (clonic spasm of hand/foot when BP cuff inflated to 20mmHg above sys BP)
Chovstek's sign (muscle spasm when facial N flicked)
symptoms
tetany
personal paraesthesias
spasms
cramps
Causes
hypoparathyroidism
thyroidectomy/neck surgery - most commonly done for tertiary hyperparathyroidism
AI
infiltration
hypomagnesaemia - functional hypoparathyroidism (resolves when Mg restored)
congenital
PTH resistance
Vit D deficiency
calcidiol deficiency from diet or sunlight
calcitriol deficiency from CKD
malabsorption
inactivation by CYP450 (phenytoin, CBZ)
inadequate dietary Ca intake
increased bone uptake
hungry bone syndrome (post-op)
osteoblastic bone mets
pancreatitis
multiple transfusions
resp alkalosis (due to hyperventilation)
bisphosphonates
Dx
1) Cacorr (corrected for hypoalbuminaemia, in mml/L)
2) measure PTH, creatinine, phosphate, magnesium, calcidiol, calcitriol
3) interpret...
primary hypoparathyroidism: PTH low, phosphate high
hypomagnesaemia: Mg low, PTH normal/low
vit D deficiency : calcidiol low, calcitrol variable
CKD: creatinine elevated, calcitriol low
Tx
oral Ca
Ca carbonate 1.5-2g elemental Ca daily in divided doses
IV Ca
if severe (tetany, seizures, prolonged QT, post-parathyroidectomy)
10ml 10% Ca gluconate over 10 mins, repeat as needed, infusion often required for sustained effect
Vit D required when hypocalcaemia from hypoparathyroidism or CKD
calcitriol more expensive that D2 or D3, shorted duration of action + preferred in CKD + hypoparathyroidism
Mg - must repleted to correct low Ca, IV 2-4 g slow infusion