Hypercalcaemia of malignancy and hypocalcaemia Flashcards
Does hypocalcaemia cause bradycardia?
Hypocalcaemia is associated with a prolonged QT interval rather than bradycardia.
What is the most likely diagnosis and why?
- Constipation related to medication
- Hypercalcaemia
- Pancreatitis
- Large bowel obstruction
- Perforated abdominal viscus
- Urinary tract infection
- Chest infection
- Cerebral metastases
What must you exclude?
Hypercalcaemia - intermittent confusion, non-specific pain, constipation suggests hypercalcaemic crisis in a patient with known bone mestastases.
Must exclude pancreatitis, sepsis, and perforation so do MSU, CXR, AXR, serum calcium, LFT’s, amylase.
Low phosphate and low magnesium may occur with hypercalcaemia, as well as ECG abnormalities. Hypercalcaemia, is due to increased osteoclast activity. Renal failure and dehydration may also arise secondary to hypercalcaemia.
What does this show?
- Normal bowel gas pattern
- Sclerotic bony metastases are evident
What is the aetiology of hypocalcaemia?
Failure of any mechanism by which serum calcium is maintained. Usually due to failure of the parathyroid gland
Response to low calcium:
- Osteoclast activation
- Increased gut absorption
- Kidney retains calcium - 1 -alpha hydroxylase is activated in the kidney
What are the risk factors for hypocalcaemia?
Severe vitamin D deficiency
- Renal failure
- Anticonvulsant use
- Lack of sunlight
- Chappatis (phytic acid)
Parathyroid surgery - ‘hungry bone syndrome’
Mg2+ deficiency e.g. PPI associated
Cytotoxic drugs
Pancreatitis, rhabdomyolysis and large volume blood transfusions
How does a low albumin state affect calcium levels?
Bound Ca will be low but free calcium will be normal
About 40% of Ca is bound to albumin so measuring it is essential to diagnosis
45% circulates as biologically active Ca in ionised state
15% is bound to sulfates, phosphates, lactate and citrate
Which type of hyperparathyroidism causes low calcium?
Secondary hyperparathyroidism
What happens to calcium if you have high dietary phosphate intake?
Low calcium because phosphate binds calcium in the kidneys and they are both lost
What is shown on this ECG?
An adjusted QT interval (QTc) of 503 ms while in sinus rhythm = hypocalcaemia
Normal QTc = 350 to 450 ms for adult men and from 360 to 460 ms for adult women
What is the clinical effect of hypocalcaemia (on examination)?
- Neuromuscular excitability
- Trousseau’s sign - when you take BP then you have more albumin. This binds the already low Ca and causes carpal spasm (flexion of the fingers).
- Chvostek’s sign
- Convulsions
NB: these signs will only be seen if Ca falls rapidly; not if chronically low Ca
What investigations should be done in hypocalcaemia?
- Serum total Ca adjusted for albumin
- Albumin
- PTH
- 25-hydroxyvitamin D
- Renal function
- Magnesium
- Amylase/lipase
- Cr, CK
- FBC - T cell counts for ?Di George syndrome
- ECG
Imaging:
- XR for fractures in osteomalacia
- Isotope bone scans - metastases
At what level does hypocalcaemia usually become symptomatic?
<1.9mmol/L but this also depends on the rate of the fall
What is the management of acute severe (<1.9mmol/L) hypocalcaemia?
Aim is to improve symptoms and not to return Ca back to normal. Ca replacement:
- IV calcium gluconate infusion - 10–20 mL 10% calcium gluconate in 50–100 mL of 5% dextrose i.v. over 10 min with ECG monitoring; repeat until patient is asymptomatic
Treat underlying cause e.g. long term Ca treatment of 0.25-0.5mcg/day; in post-operative hypocalcaemia and other cases of hypoparathyroidism, this consists of alfacalcidol or calcitriol therapy.
What is the management of mild hypocalcaemia (>1.9mmol/L and asymptomatic)?
Oral calcium supplements e.g. Calcichew 2 tablets BD
- If Vitamin D is the cause supplement this e.g. 300,000 Units over 6-10weeks
Stop precipitants and treat underlying condition
What bone pathology is caused by long-standing hyperparathyroidism?
Osteitis fibrosa
