In this section : Electrolyte Disturbances
Hyperkalaemia
Hypomagnesaemia
Hypophosphataemia
Hypernatraemia
Hypokalaemia
Hyponatraemia
Hypocalcaemia
Hypercalcaemia
Hypocalcaemia
Last updated 21st January 2021
Content by Chris Isles
Introduction
- Current reference for adjusted calcium is 2.12 to 2.62 mmol/l
- Acute hypocalcaemia can be life threatening
- Investigations can be organised and treatment started (if necessary) before the results are back
Causes
- Commonest is damage to parathyroid with total thyroidectomy
- Following parathyroidectomy
- Severe Vitamin D deficiency
- Magnesium deficiency – think PPI associated hypocalcaemic hypomagnesaemic hypoparathyroidism
- Others include cytotoxic drug induced hypocalcaemia, pancreatitis, rhabdomyolysis, large volume blood transfusions
Presentation
- Typically develop when adjusted calcium falls below 1.9mmol/l but can be asymptomatic if rate of fall is slow
- Clinical evidence of hypocalcaemia includes:
- perioral and digital paraesthesia
- tetany and carpopedal spasm
- laryngospasm
- Trousseau’s sign – inflation of sphygmomanometer cuff above systolic pressure for 3 minutes induces tetanic spasm of fingers and wrist (ie Trousseau positive)
- Chvostek’s sign – gentle tapping over the facial nerve induces twitching of the facial muscles (ie Chvostek positive)
- Prolonged QT interval on ECG and arryhthmias
- Seizure
Investigation
- U&E
- Phosphate
- PTH
- Serum 25OHD
- Magnesium
Mild Hypocalcaemia – >1.9mmol/L and Asymptomatic
- Give oral calcium supplements eg Calvive (formerly Sandocal) 1000 2 tabs bd or Calcichew Forte 2 tabs bd (one tab of each contains 1g calcium equivalent to 25mmol calcium)
- If post thyroidectomy and serum calcium remains 1.9-2.1mmol/l after 24 hours increase Calvive 1000 to 3 tabs bd
- If remains 1.9-2.1mmol/l after 72 hours despite Calvive add Alfacalcidol 0.25 micrograms od and repeat serum calcium at one week
Severe Hypocalcaemia – <1.9mmol/L and/or Symptomatic
- This is a medical emergency
- Initially, give 10 – 20 ml 10% calcium gluconate in 50-100 ml of 5% Dextrose IV over 10 minutes with ECG monitoring. This can be repeated until the patient is asymptomatic.
- Follow with a calcium gluconate infusion by diluting 100ml of 10% calcium gluconate (ten vials) in 1 litre of saline 0.9% or dextrose 5% and infuse at 50 – 100 ml/hr to achieve normocalcaemia
- Avoid Calcium Chloride which is more potent than Calcium Gluconate and causes tissue necrosis if extravasates.
- If post op hypocalcaemia following parathyroidectomy or thyroidectomy give Alfacalcidol starting at 0.25 – 0.5micrograms od.
Treat The Underlying Cause
- If hypomagnesaemia, give 20mmol Mg as 10ml of 50% Magnesium sulphate. Dilute to 50ml in Glucose 5% for central administration or to 250-500ml in Glucose 5% for peripheral administration. Infuse over minimum of 5 hours, max 24 hours. Note conversion 1gram Mg = 4mmol Mg.
- If Vitamin D deficiency, load with Colecalciferol 50,000 units weeklt for 6 weeks, followed by a maintenance dose of 1,000 units daily (this is the current go-to regimen as per DGRI formulary under Vit D deficiency guidelines)
- Note that we keep various strengths Colecalciferol in stock: 25,000 units, 3,200 units, 1,000 units, 800 units tablets/capsules.