Hypocalcaemia

Question 1

An 82 year old male complains of cramps and tingling in his fingers. He received a subcutaneous injection of denosumab by his GP for osteoporosis 7 days prior. He has stable chronic kidney disease with an eGFR of 58 ml/min and his current biochemical tests show a low plasma corrected calcium of 1.58 mmol/L (NR 2.1-2.6 mmol/L). How would you investigate and manage him?

Answer 1

Impression:
Likely is a presentation of serum hypocalcaemia secondary to denosumab injection. CKD would likely be a contributing factor. Nadir of post-denosumab hypocalcaemia occurs at 10-20 days post-injection.

Would want to consider other causes of hypocalcaemia:

• High PTH (primary hypocalcaemia): CKD, Vit D deficiency, calcium loss (acute panc, tumour lysis), hyperphosphataemia (precipitates the Ca)
• Low PTH: hungry bone syndrome, post-surgical thyroidectomy

Goals:

• identify underlying aetiology of hypocalcaemia
• replace calcium losses safely to prevent adverse effects

Question 2

Hypocalcaemia - History

Answer 2

History:

• sx: parasthaesia, muscular excitability, tetany, seizures
• signs of chronicity: nail dystrophy, hair changes, papilloedema, skin changes
• PMHx pancreatitis, malignancy, renal disease
• PSHx: thyroidectomy
• Medications: denosumab
• SNAP

Question 3

Hypocalcaemia - Examination

Answer 3

Examination:

• General observation + vital signs
• Trousseau’s sign (carpopedal spasm on inflation of blood pressure cuff), Chvosteks sign (tapping on parotid region causes twitching of facial muscles)
• Neurological examination
• Cardiovascular screen (Arrhythmias)
• Cognitive assessment

Question 4

Hypocalcaemia - Investigations

Answer 4

Investigations:
Key diagnostic: serum corrected calcium, then investigate for underlying cause.

• Bedside: vitals, VBG, BSL, ECG
• Bloods: Serum calcium, EUC, CMP (serum phosphate), PTH level, check eMR for trend if available, serum albumin,
• Imaging: nil initially

Question 5

Hypocalcaemia - Management

Answer 5

Management:
Definitive
- Endocrinology consult to advise on Ca replacement schedule
- Hypocalcaemia:
- Oral replacement: calcium carbonate
- IV replacement: Calcium Gluconate for IV replacement (calcium chloride is irritative) - administer here given symptomatic, give 10mL of 10% (is 1g), administer over 10-20mins [SLOWLY], whilst on telemetry).
- careful monitoring as rapid correction can lead to cardiac arrhythmias (telemetry)
- diuresis for ?hyperphosphataemia
- Vit D replacement as required: administer PO calcitriol (Activated vit D)

Supportive

• other electrolyte replacement
• treatment of underlying condition (CKD, acute kidney failure, Tumour lysis, etc)
• HDU/ICU review/referral