10. Clinical chemistry CPC Flashcards
Case 1. Born 1939. 1991 (age 52). Depression. Councillor. Refused antidepressants. What alternative is available?
Alternatives include CBT. The patient started on St John’s wort.
What is St John’s wort similar to?
Paroxetine
How effective is St John’s wort?
moderately effective
What electrolyte imbalance is associated with depression?
Hypercalcaemia. Calcium, in general, affects the brain and nervous system
What happens in hypokalaemia?
Your myocardium becomes more an more irritable this leads to arrhythmias. As potassium rises, the myocardium becomes more and more stable, however, the ultimate stable rhythm is asystole. In other words, potassium causes asystole when it is very high, and VF when it is very low.
What does a Smith’s fracture look like? And when does it happen?
The radius has fractured forwards (i.e. towards the palm side). If you fall on a flexed wrist, it will cause a Smith fracture
What does a Colles fracture look like? And when does it happen?
• Falling on an outstretched hand causes a Colles fracture (the radius will then fracture backwards, away from the palm side)
What is a Pott’s fracture?
an ankle fracture that involves the tibia and fibula
How to treat Smith’s fracture?
Treated with manipulation under anaesthesia and plaster
Patient with hypercalcaemia and Smith’s fracture had depression which got worse. In 1992, the patient was admitted with severe abdominal pain. A urine dipstick is performed and is +++ blood. Why is this not glomerulonephritis or subacute bacterial endocarditis? What is it likely to be?
Glomerulonephritis is painless. Subacute bacterial endocarditis causes microscopic haematuria. This is likely to be renal stones.
What investigation for renal stones?
Plain abdominal x-rays will show calcified stones
Abdominal ultrasound is good for visualising nephrocalcinosis but…
takes longer to achieve.
Calcified gallstones and renal stones may look quite similar on …
a plain abdominal X-ray
Renal stones diagnosed. What should be done next?
Measure plasma calcium. Also do plasma PTH.
Is plasma calcium routinely measured when you send U&Es?
No
What is normal plasma calcium?
2.2 - 2.6 mmol/L
Differential diagnosis for hypercalcaemia:
Cancer, primary hyperparathyroidism (a lot of the time, patients tend to be quite well), sarcoidosis
How do you differentiate between the differential diagnoses for hypercalcaemia?
Plasma PTH
The patient with hypercalcaemia has a PTH of 3.0 (1.1 - 6.8 pM). What is the likely diagnosis?
If calcium is high then PTH should be suppressed. So, this patient has primary hyperparathyroidism. In hypercalcaemia of malignancy, PTH would be 0.