Acute metabolic derangements - hypo- and hypercalcaemia
Description
- Normal corrected Ca ~2.10-2.60 mmol/L
- Ionised (free) Ca ~50% is the physiologically active fraction
- 40% albumin-bound, 10% complexed to citrate/phosphate/bicarbonate
Correction and its failure
- Corrected Ca = measured Ca + 0.02 x (40 - albumin g/L)
- The formula fails in: critical illness, myeloma paraproteins, acid-base disturbance, massive transfusion (citrate), pancreatitis
- -> measure ionised calcium on a blood gas when it matters
Severity - hypercalcaemia
| Corrected Ca | |
|---|---|
| 2.6-3.0 | Mild - often asymptomatic |
| 3.0-3.5 | Moderate |
| >3.5 | Severe - emergency regardless of symptoms |
- Rate of rise matters more than the number - a rapid rise to 3.0 is worse than a chronic 3.2
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