Electrolyte abnormalities - hypo- and hypercalcaemia
Description
Always correct or measure ionised calcium first
- Corrected Ca = measured Ca + 0.02 x (40 - albumin g/L)
- Ionised calcium is the physiologically active fraction (~50%) - measure it directly when albumin is abnormal, in critical illness, or in acid-base disturbance
- *Alkalosis increases albumin binding -> ionised Ca falls with a normal total Ca* - the mechanism of tetany in hyperventilation
Reference points
| Total Ca (corrected) | |
|---|---|
| Normal | ~2.10-2.60 mmol/L |
| Hypocalcaemia | <2.10 (severe <1.90 or symptomatic) |
| Hypercalcaemia | >2.60; moderate 3.0-3.5; severe >3.5 = emergency |
- The renal angle: calcium disorders both cause and are caused by kidney disease - CKD-MBD, hypercalcaemic nephropathy, nephrolithiasis, nephrogenic DI
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