ChemPath: Clinical Chemistry CPC Flashcards
Describe the effect of hypokalaemia on the myocardium.
Increases the myocardial irritability - resulting in arrhythmias
Describe the cardiac consequences of plasma potassium being too high or too low.
- Too low - 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 falling on an outstretched hand. Anterior displacement of the head of the radius (towards the back of hand
- Smith’s - fracture caused by falling on a flexed wrist. The radial head will be displaced forwards (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
Complete the urine dip results for each condition:
- Renal stones
- Glomerulonephritis
- DKA
- Acute rheumatic fever
- Subacute bacterial endocarditis
- Renal stones –> painful macroscopic haematuria
- Glomerulonephritis –> painless microscopic haematuria
- DKA —> acidosis, ketonuria
- Acute rheumatic fever –> proteinuria
- Subacute bacterial endocarditis –> microemboli, microscopic haematuria
If someone presents with renal stones what other investigation should you do?
You should find out why the patient got the stones in the first place - first line check blood calcium and PTH levels.
What is the physiological role of PTHrP?
- PTHrp also acts on PTH receptor but has different actions.
- This is important in foetal life because it allows us for transplacental calcium transportation (calcium from mum to move to foetus for development)
- Can be released in cancers and result in similiar hyperparathyroidism and hypercalcaemia symptoms.
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)
List some risk factors for hypercalcaemia.
Family history
Dehydration
Hyperparathyroidism
List some complications of hypercalcaemia.
- Renal stones
- Pancreatitis
- Peptic ulcer disease
- Skeletal changes (osteitis fibrosa cystica)
What is a key difference between calcium stones and urate stones?
Calcium stones are radio-opaque
Urate stones are radiolucent
Risk factors for renal calcium stones
FHx
Hypercalcuria
Dehydration
Hypercalcaemia
Recurrent UTI
Presentation of renal calcium stones
Painful haematuria
Renal failure
Recurrent infections
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?
- Expectant management with adequate analgesia (PR diclofenac)
- Lithotripsy (US waves to break stone - painful)
- Cystoscopy
- Lithotomy
How can urinary tract stones be prevented?
- Drink more water
- Treat hypercalciuria (thiazides)
- 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
- 3-6 L 0.9% saline over 24 hours
- The first litre should be given quickly (over 1 hour) to correct dehydration
- Elderly patients should also be given furosemide (to prevent pulmonary oedema)
In which group of patients would you used dextrose rather than saline?
Liver failure - they have a tendency to retain salt
Which other drug may be used under desperate circumstances when managing hypercalcaemia?
- Pamidronate (IV)
- Good at treating bone pain but takes at least 1 week to start working and gets incorporated into bone for a very long time
- Helpful for bone mets but not given in all circumstances.
Outline non-urgent hypercalcaemia treatment
- Adequate hydration
- Avoid thiazides
- TUC (parathyroidectomy or treat malignancy)
What is minimally invasive parathyroidectomy?
- A technetium 99m sestamibi scan shows a hyperactive parathyroid
- An USS is also performed and if the results of the sesta MIBI and USS are concordant, the whole neck does not need to be opened
- If they are 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?
Subperiosteal resorption
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.
Histology of bone shows multinucleate giant cells
Most helpful investigation in sarcoidosis
CXR - Bilateral hilar lymphadenopathy
What is the histological hallmark of sarcoidosis?
Non-caseating granulomas
Mechanism of hypercalcaemia in sarcoidosis
Macrophages in lungs express 1-alpha hydroxylase which activate vitamin D resulting in excessive calcium absorption.
PTH is suppressed to undetected levels.
What is the mainstay of treatment of sarcoidosis?
IV Methylprednisolone (Steroids)
MEN 1 and 2 can present with
hypercalcaemia
