Hypocalcaemia

Last revised December 2nd 2006

More common causes

  • Hypoparathyroidism, usually post parathyroidectomy
  • Hypomagnesaemia
  • Hyperphosphataemia usually with chronic renal failure
  • Tumour lysis syndrome (high phosphate)
  • Pancreatitis
  • Vit D deficiency
  • Drugs – Bisphosphonate / Cinacalcet


Approach

  • Always correct total calcium for hypoalbuminaemia
    (Add 0.02 mmol/L for each gram albumin below 40g/L)
  • If possible, measure ionised calcium – better than measuring total Ca2+
  • Measure PTH; 1,25 Vit D; 25OH Vit D if diagnosis not already known


Check for

  • ECG - prolonged Q-T interval
  • Chvostek's and Trousseau's signs (reflect reduced ionised calcium) – rarely present


Treatment

1. If total (corrected) Ca2+ < 1.90 mmol/L or ionised calcium < 1.0 mmol/L (normal is 1-1.3mmo/L): treat intravenously.

  • 1g (10 mls) of 10% calcium gluconate slowly over 10 mins.

2. Reassess plasma calcium and albumin, or ionised calcium, in 4 hours.

3. If persistent hypocalcaemia repeat 1g bolus as above and commence intravenous infusion:

  • 1.5mg/kg/hr calcium gluconate in 500mls Saline over 12 hrs.
  • Remeasure calcium each 4 hours during infusion.

Eg: A 70kg man with repeat total calcium of 1.70mmol/L needs 1.5mg x 70 /hr. = approx. 100mg/hr
            = 1200mg (1.2g) / 12 hrs

  • This is a guide only so remeasure calcium each 4 hours during infusion and give bolus 1g over 10-20 minutes if total calcium remains <1.90mmol/L or ionised calcium <1.0mmol/L.

4. Treat associated significant hypomagnesaemia (≤ 0.70mmol/L) with IVI Mg Sulphate 2g in 50-100 ml Normal Saline over 20 mins. If still low after 4 hours repeat bolus 2g as above then intravenous infusion of 1g in 100ml Normal Saline per hr.

  • Commence Mg Aspartate 500mg bd.

5. Treat hyperphosphataemia with oral Calcium Carbonate beginning 600mg with each meal.

6. If Vit D deficient – Calcitriol 0.25µg daily.

For patients having parathyroidectomy for secondary hyperparathyroidism see protocol

  • ‘Management of patients undergoing parathyroidectomy’
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