ChemPath: Clinical Chemistry CPC Flashcards
Describe the effect of hypokalaemia on the myocardium.
Increases the myocardial irritability -> arrhythmias (tachy)
Describe the cardiac consequences of plasma potassium being too high or too low.
- Too low - arrhythmias, ventricular fibrillation
- Too high - asystole (ultimate stable rhythm)
What is the difference between a Colles’ fracture and a Smith’s fracture?
- Colles’ - fracture caused by FOOSH. The radial head will be displaced anteriorly (away from the palm).
- Smith’s - fracture caused by falling on a flexed wrist. The radial head will be displaced posteriorly (towards the palm)
What is a Pott’s fracture?
Ankle fracture involving the tibia and fibula
What would you expect to see on the urine dipstick of someone with subacute bacterial endocarditis?
Microscopic haematuria
What is the physiological role of PTHrP?
- Our genome encodes a gene for PTHrP
- This is important in foetal life because it allows us to steal calcium from our mother to help form our skeleton
NOTE: PTHrP is also produced by the lactacting breast
NOTE: PTHrP stimulates cancer cells to invade bone
Name and describe an eye sign of hypercalcaemia.
- Band keratopathy - calcium deposition across the front of the eye
- It is a feature of chronic hypercalcaemia (i.e. it will not be caused by hypercalcaemia of malignancy)
What is a key difference between calcium stones and urate stones?
Calcium stones are radio-opaque
Urate stones are radiolucent
List some complications of pri hyperparathyroidism.
- Renal stones
- Pancreatitis
- Peptic ulcer disease
- Skeletal changes (osteitis fibrosa cystica or ‘pepperpot skull’) if long standing
Which bacterium has a predilection to infect urinary tract stones?
Proteus mirabilis
What are the main investigations used for urinary tract stones?
- CT-KUB
- Stone analysis
- Urine and serum biochemistry
What are some management options for urinary tract stones?
- Lithotripsy (external laser)
- Cystoscopy (pass tube up)
- Lithotomy (open)
How can urinary tract stones be prevented?
- Drink more water
- Treat hypercalciuria (thiazides reduce urine calciuml)
- Treat hypercalcaemia
NOTE: loop diuretics increase urine calcium
At what point would you use emergency management of hypercalcaemia?
When serum calcium > 3 mmol/L or very unwell (e.g. dehydrated, confused, drowsy, seizures)
Outline the emergency management of hypercalcaemia.
- IV access
- Insert catheter
- IV 0.9% saline
1st litre given quickly over 1hr then 1 litre/ 4-6hr
total 3-6 litres - IV furosemide (for calciuresis/to pee out calcium AND to prevent fluid overload/pulm oedema in elderly pts)
- ?IV pamidronate 30-60mg
indicated if hypercalcaemia due to CANCER
but not given in all circumstances
Which drug may be used under desperate circumstances when managing hypercalcaemia?
- Pamidronate (IV)
- Good at treating bone pain as inhibits osteoclasts but takes at least 1 week to start working and gets incorporated into bone for a very long time
In which group of patients would you used dextrose rather than saline?
Liver failure - they have a tendency to retain salt
Outline the treatment of non-emergency hypercalcaemia.
- Keep well hydrated
- Avoid thiazides (they reduce hypercalciuria but they increase plasma calcium concentration)
- Surgery
What is minimally invasive parathyroidectomy?
- A 99technetium sesta MIBI scan and USS performed
- If both tests are concordant: whole neck does not need to be opened
- If not concordant: the surgeon will need to view all four glands and take out the largest one
What feature may you see on an X-ray of the hands in a patient with primary hyperparathyroidism?
Cystic changes in the radial aspect
What is a characteristic histological feature of long-standing undiagnosed hyperparathyroidism?
Brown tumours - they are multinucleated giant cells in the bone. The giant cells are activated osteoclasts.
What is the mainstay of treatment of sarcoidosis?
Steroids
What is the histological hallmark of sarcoidosis?
Non-caseating granulomas
Differentials for hypercalcaemia?
Malignancy - bone mets, HHM, haem
Primary hyperPTH
Sarcoidosis
In primary hyperparathyroidism, what is the PTH level?
High
Can also be NORMAL - if calcium is high, pth should be super low/zero, so PTH being normal is inappropriate
Types of renal stones
Calcium oxalate - most common
Calcium phosphate - common
Uric acid - these are radioLUCENT
Struvite and cystine - can be staghorn
Why does sarcoidosis result in hypercalcaemia
Macrophages express 1-alpha hydroxylase
Hence hypercalcaemia (especially in summer) - more vitamin D -> calcium
How does haematuria differ in renal stones, glomerulonephritis & subacute bacterial endocarditis?
Renal stones = macroscopic haematuria (can also be micro)
Glomerulonephritis = microscopic
Subacute bacteria endocaditis = microscopic
Presentation of renal stones
Loin pain
MACROSCOPIC haematuria
Recurrent infection (proteus mirabilis)
Renal failure
