Session 5 Chemical Pathology part 2 Flashcards
where is alkaline phosphatase produced?
bone, liver, intestine, placenta- 3rd trimester
when might serum amylase be raised?
pancreatitis
acute MI
ovarian cyst
renal calculi
non-biochemical tests for possible gallbladder pathology?
ultrasound- most accurate
plain abdom X-ray may detect radio-opaque stones
ERCP- look at common bile duct
why must troponin be measured after collection in testube 4hrs after taking sample?
unstable, so drops
why is glucose intolerance seen following MI?
STRESS: cortisol increase
GH increase
catecholamines increase- glycogen release
criteria for prior MI?
development of new pathological Q waves with or without symptoms
imaging evidence of a region of loss of viable myocardium that is thinned and fails to contract, in absence of a non-ischaemia cause
pathological findings of a healed or healing MI
why are myoglobin, total CK and CK-MB more useful as markers for re-infarctions?
shorter 1/2 lives than TnI, which would resultantly still be high if a patient re-infarcted whereas other markers don’t remain elevated
why can troponin not be used alone to diagnose MI?
raised level doesn’t mean MI, but would expect to be raised if MI
examples of conditions with elevated troponins, without overt IHD?
trauma hypertension congestive HF hypotension renal failure sepsis PE
why might arrhytmias occur with sepsis?
acidosis occurs as lactic acid increased via anaerobic met. in tissues receiving poor perfusion
what does a high specificity of BNP mean for diagnosing heart failure?
If BNP is not raised, HF can be ruled out as the diagnosis and BNP is raised in all cases of HF, and so BNP is good for being able to rule out HF
however, BNP may be raised due to other causes
routine lab investigation of HF?
FBC- anaemia worsens prognosis creatinine- HF assoc with RF, GFR falls electrolytes: hyponatraemia as fluid retention, hyperkalaemia, hypokalaemia, hypomagnesaemia albumin- hypo causes oedema LFTs- liver failure may cause oedema ferritin- haemochromatosis can cause HF thyroid function tests- hyper may be assoc with HF as high O2 demand as high met rate, so increased CO hypo may worsen course of HF
classical features of renal failure?
hypocalcaemia high urea high creatinine high anion gap hyperkalaemia met acidosis hyperphosphataemia
common signs and symptoms of HF?
dyspnoea fatigue peripheral oedema orthopnoea weight gain rales- abnormal lung sounds
if patient’s HbA1C is >6.5% without symtoms, why would you want to repeat investigation within 2 wks time to confirm diabetes?
results may have got mixed up
why would you not measure the thyroid hormones in a patient who is really ill?
as they would be raised anyway as reverse (inactive) T3 is raised in sepsis (inflammation)
why increased risk of MI with hypothyroidism?
elevated lipids
why must dose of T4 given to an elderly patient with hypothyroidism be very well monitored?
too much can result in death if CHD as will increase met rate, and so increase HR
describe synacthen test
dynamic function test Give 200mg IV After 30 minutes measure cortisol Should be >550 normal result normally excludes addisons disease
describe the water deprivation test for polyuria
Water deprivation test has 3 stages: 1 – deprive patient of water o Initially osmolarity of urine will go up 2 – ADH (desmopressin) and fluid given Monitor Compare plasma and urine osmolarity In a normal patient Plasma osmolarity will fall and urine osmolarity will increase o Water is being retained Diabetes insipidus o Nephrogenic (Kidneys don’t respond to ADH) No change in urine osmolarity o Psychogenic (pituitary not secreting) Increase in urine osmolarity
what tests should be done on a baby with hypoglycaemia?
Measure cortisol, growth hormone and insulin to identify the cause
Stress test- can look for GH deficiency
o Infusion of insulin
o GH and cortisol should increase
o Glucose must have dipped below 2.2 for results to be effective
what can an echocardiogram be used to do post MI?
assess ventricular and valvular function
why is an abnormal ECG not particularly useful in heart failure?
low specificity for LVSD, so likely to be an abnormal ECG in people who don’t have LVSD
how is heart failure diagnosed?
clinical criteria- dyspnoea, fatigue, weight gain
echocardiography- but expensive and waiting list
laboratory investigation- routine and natriuretic peptides
why is K+ raised in renal failure?
not excreted and acidosis as H+ not being secreted in DCT
why do FBC if classical features of renal failure shown by blood tests?
look for anaemia- normocytic in renal failure, due to haemolysis as red cells have reduced 1/2 life, inhibition of formation of red cells in BM and reduction in erythropoietin production
causes of increased plasma creatinine?
pre-renal failure: reduced renal perfusion: shock/haemorrhage, dehydration, congestive HF
intrinsic- glomerular disease, tubulo-interstitial disease, vascular disease
post-renal- obstructive lesions of UT- tumours, stone, BPH
what are bence jones proteins measured for in urine?
to diagnose and monitor multiple myeloma
2 imaging techniques used in renal failure?
IV pyelogram- can show ulceration of renal papillae, and renal stones
ultrasound- show small kidneys if chronic, and renal calculi and/or ureteric dilatation if present
why might ECG be used in thyrotoxicosis diagnosis?
show atrial fibrillation
how can graves disease be distinguished from other causes of thyrotoxicosis?
thyroid isotope scan
distinguishing AI disease from other causes of thyroiditis?
thyroid peroxidase antibodies
why might TSH still remain low when carbimazole given for hyperthyroidism?
pituitary atrophy as wasn’t stimulated to release TSH as T3 and T4 were high- -ve feedback
why give beta blocker in tment of hyperthyroidism?
tment of palpitations/tachcardia
2 conditions that present with similar symptoms to hyperthyroidism?
pheochromocytoma
carcinoid syndrome
carbimazole is stopped after 2 yrs. 85% will relapse, what does this mean and what tment should they then get?
not a transient hyperthyroidism
can continue carbimazole, or give radio-iodine, or perform subtotal thyroidectomy
