In this section : Electrolyte Disturbances
Hyperkalaemia
Hypomagnesaemia
Hypophosphataemia
Hypernatraemia
Hypokalaemia
Hyponatraemia
Hypocalcaemia
Hypercalcaemia
Hypercalcaemia
Last updated 3rd December 2020
Last updated on 14th March 2016 by Fiona Green & Ranjit Thomas. Update due 14th March 2017.
Introduction
- About 99% calcium is found in bone
- Serum calcium is adjusted for serum albumin to give an indirect measure of ionised calcium – reference range in Dumfries is 2.12-2.62mmol/l
- Calcium is regulated by PTH, Calcitonin and Vit D. PTH releases calcium from bone, Calcitonin does the opposite and 1,25OHD increases absorption of calcium from gut
- Numerous mechanisms exist for hypercalcaemia – see below
Causes
- 90% causes are due to:
- Malignancy esp Breast (parathyroid related protein), Lung (ectopic PTH) and Myeloma (release of osteoclastic activating factors)
- Primary hyperparathyroidism
- All other causes are much less common. They include:
- Drugs eg Vitamin D (increased absorption calcium from gut), Lithium (increased secretion PTH) and Thiazides (reduced tubular excretion calcium)
- Sarcoidosis (hydroxylation of vit D in granulomas)
- Thyrotoxicosis (increased osteoclastic activity)
- Milk alkali syndrome
- Tertiary hyperparathyroidism
Presentation
- Classically ‘bones, stones, abdominal groans, psychic moans, thrones and hypertones’ indicating osteoporosis, renal colic, peptic ulcer, depression, polyuria/constipation and hypertension
- In reality 50% patients are asymptomatic and many have non specific symptoms eg lethargy and malaise
- Acute severe hypercalcaemia may present with shock, coma and renal failure
Investigations
- The most useful investigation is PTH in 2.5ml EDTA tube, sent to lab asap even if out of hours
- If PTH detectable or ↑ then primary hyperparathyroidism is likely diagnosis
- If PTH is ↓ or undetectable and no other cause apparent then malignancy with or without bony metastases is likely
- Unless source of tumour obvious then screen for malignancy with CXR, Myeloma screen and CT chest abdo pelvis as appropriate
Serum Calcium <3mmol/l
- Usually asymptomatic and does not require urgent correction
- Advise to avoid factors that can aggravate hypercalcemia, including thiazide diuretic and lithium therapy, volume depletion, prolonged bed rest or inactivity, and a high calcium diet (>1000 mg/day)
Serum Calcium 3-3.5mmol/l
- May be well tolerated if has risen slowly but may be symptomatic and prompt treatment usually indicated
- Rehydrate then give IV biphosphonate
Serum Calcium >3.5mmol/l or Symptomatic
- Requires urgent treatment because risk of shock, coma, renal failure
- Rehydrate then give IV biphosphonate
- May need to consider dialysis if severe renal failure
Rehydration
- Rehydrate with IV N saline 3-4 litres in first 24 hours & 2-3 litres daily thereafter aiming for urine output urine output >2 litres/day
- IV fluid lowers serum Ca, but will not restore normocalcaemia
- Give Frusemide if required to avoid volume overload and heart failure and promote urinary calcium excretion
- Be more cautious in elderly with renal impairment and with LV dysfunction.
After Rehydration – IV Biphosphonates
- IV Biphosphonates are most beneficial for hypercalcaemia of malignancy but can still be used in other causes of hypercalcaemia.
- Do not use until patients are rehydrated
- If GFR >30ml/min and still hypercalcaemic after adequate hydration, give IV Zoledronate 4mg over 15 minutes in 100ml 0.9% sodium chloride
- If GFR <30ml/min after hydration give Pamidronate according to the corrected calcium as follows
- Calcium <3.0: 30mg
- Calcium 3-3.5: 60mg
- Calcium >3.5: 90mg
- Add pamidronate disodium to sodium chloride 0.9% infusion as below and give over:
- 30mg in 100ml – 250ml over 90min
- 60mg in 250ml over 3 hours
- 90mg in 250ml – 500ml over 4 hours
- Full effect of IV biphosphonate may take 3-7 days with duration of action 1-2 weeks.
- If Calcium remains high after 72 hours, a further dose of zolendronic acid may be given
- Patients with refractory hypercalcaemia may require corticosteroids and Calcitonin
- Myeloma patients with hypercalcaemia routinely receive dexamethasone 40mg for 4 days along with omeprazole & allopurinol (corrected for renal function).
Maintenance Therapy
- Discuss treatment options with relevant consultant
- Patients contemplating long term maintenance with bisphosphonates should receive appropriate counselling re osteonecrosis of the jaw and ideally a dental check before treatment
- IV Zolendronate is preferred maintenance for myeloma and SC Denosumab for breast cancer
- Oral Clodronate sometimes still used for myeloma if cannot tolerate IV Zolendronate otr if patient choice because reduced risk osteonecrosis.