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Phase 4 - GR > Clinical chemistry > Flashcards

Clinical chemistry Flashcards

1
Q

Name 4 things causing hyponatraemia

A

• Hypovolaemic (decreased extracellular volume)
–– Renal losses (diuretics, salt-losing nephropathy)
–– Non-renal losses (vomiting, diarrhoea)
–– Adrenal insufficiency (Addison’s disease)

• Euvolaemic
–– Excess fluid replacement (5 per cent dextrose for example)
–– Syndrome of inappropriate ADH secretion
–– Hypothyroidism
–– Psychogenic polydipsia (excess water consumption)

• Hypervolaemic (increased extracellular volume)
–– Congestive cardiac failure
–– Nephrotic syndrome
–– Cirrhosis with ascites

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2
Q

Typical findings in SIADH biochem

A

Hyponatraemia with a low plasma osmolality and inappropriately high
urine osmolality and urine sodium levels is typical of SIADH

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3
Q

Name 3 causes of raised prolactin

A

physiological factors, such as emotional stress,
pregnancy and breast feeding;

drugs especially dopaminergic antagonists such as
chlorpromazine, risperidone, domperidone and metaclopramide;

pituitary tumours;

polycystic ovary syndrome;

and severe thyroid failure

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4
Q

3 causes of raised bNP

2 causes of lowered

A

Heart failure
left ventricular hypertrophy, myocardial
ischemia, tachycardia, right ventricular overload, hypoxaemia (including pulmo
nary
embolism), renal dysfunction, sepsis, chronic obstructive pulmonary disease (COPD), diabetes, age
>70 years, cirrhosis of the liver, obesity

Lowered in…
Treatment with diuretics, ACE (angiotension
converting enzyme) inhibitors, beta-blockers, angiotensin II receptor antagonists
(ARBs) and aldosterone antagonists

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5
Q

3 conditions causing hyperK

A

Acute renal failure, Addison’s disease, metabolic acidosis of any aetiology, tumour
lysis syndrome

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6
Q

3 key biochem in conns (Primary hyperaldosteronsism)

How would 2ndary be different?

A

hypoK
HyperNa -> HTN
+ metabolic Alkalosis
Low renin (due to -ve feedback from aldosterone)

(Due to tumor -> excess aldosterone on K/Na channel + H+ channel )

2nd - High renin

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7
Q

Mx of hyperaldosteronism

A

spironolactone

surgery if tumour eg conns

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8
Q

Name 3 causes of HypoK

A

Conns / 2nd hyperaldosteronism / familial (AD)
Saline infusion
loop diuretics
D+V

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9
Q

Mx of familial hyperaldosteronism

A

dexamethasone

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10
Q

3 causes of hypoCa

A 
Malabsorption 
vit D deficiency / hypoPTH 
chronic renal failure 
Pancreatitis 
Cell breakdown - rhabdomyolysis / Tumour lysis
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11
Q

How does lithium relate to hypothroidism

A

increases intrathyroid iodine

inhibits production of t3/4

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12
Q

name 3 drugs that affect TFTs

A

lithium
SSRI
phenytoin / carbamazepine
amiodarone

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13
Q

Cerebral causes of diabetes insipidus

A

cerebral trauma, infection, tumours

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14
Q

Nephrogenic causes of DI

A

chronic renal failure,

interstitial nephritis, hypercalcaemia, hypokalaemia and drugs, such as lithium

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15
Q

How would you differentiate cranial / nephro DI and psychogenic polydipsia

A

water deprivation test

Check urine osmolality following:
[Deprive of water] - {give synthetic ADH}

Normal (psychogenic) [High] - N/A
Cranial DI [Low] - {High}
Nephrogenic DI [Low] - {Low}

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16
Q

3 causes of hyperCa

A 
Bony mets
HyperPTH / vit d 
High bone turnover 
addisons 
acromegaly 
thiazides
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17
Q

Name 4 causes of a high anion gap

A

‘Dr Maples’

D, DKA
R, renal failure
M, methanol
A, alcoholic ketosis
P, paracetamol poisoning
L, lactic acidosis
E, ethylene glycol
S, salicylate poisoning
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18
Q

Name 4 things on examination to indicate fluid loss

A

pulse (tachy) and blood pressure postural drop, loss of skin elasticity, dry mucus membranes,
increased respiratory rate, thirst, low urine volume and high urine concentration

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19
Q

Is fluid loss from upper GI hyper/iso/hypo tonic

A

isotonic -> losses provoke severe dehydration quickly compared to water loss

[Think of body compartments …. in a 70kg
-Isotonic fluid loss is taken just from the 18 litres of extracellular fluid
-water loss is taken from the 42 litres
of total body water.
Hence the symptoms of shock are present only following a much greater fluid loss if this is hypotonic.]

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20
Q

Urea / creatinine in dehydration

A

Urea is raised more (both raised tho)

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21
Q

2 reasons Why would someone have hypoK in prolonged vomiting

A

Vomit some out

Main is due to Poor kidney perfusion

  • > secretion of renin
  • > aldosterone
  • > loss of K from tubules (and retention of Na)
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22
Q

What clinical conditions are associated with a respiratory alkalosis?

A

Hyperventilation, e.g. anxiety state

• Drugs , e.g. Aspirin (salicylate), theophylline,
catecholamines
• Hypoxia in early pulmonary disease, e.g. asthma, pulmonary embolus
• Increased cerebral respiratory drive, e.g. head injury, stroke, meningitis
• Non-cerebral increase in respiratory drive, e.g. heat exposure, hepatic failure

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23
Q

How do you calculate an anion gap

Nomal range?

A

(sodium concentration + potassium concentration)
− (chloride concentration + bicarbonate concentration)

10–20 mmol/L

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24
Q

Why does blood glucose get raised in sepsis

A

Metabolic response to injury

  • glucose mobilization via glycogenolysis and gluconeogenesis - due to high glucagon / catechloamines
  • Inhibition of insulin
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25
Q

2 reasons you might have low t4 and low TSH and how to differentiate

A

Sepsis / pit failure

Cortisol secretion - high in sepsis, low in pit failure

26
Q

Bar low GFR, nbame 3 other markers of CKD

A

high
creatinine and urea, anaemia, hypocalcaemia, hyperphosphataemia, raised alkaline
phosphatase, raised PTH and raised triglyceride

27
Q

low bicarbonate and CKD… what acid base balance would you suspect and why

A

chronic metabolic acidosis.

The acidosis is due to the accumulation of organic acids together with anions,
such as phosphate and sulphate

28
Q

Why do you get secondary hyperPTH in CKD

A

HyperPO4 - stimulates
HypoCa - Ca usually inbitis
Lack of calcitrol by kidney - calcitrol usually inhibits
- [calcitrol also usually helps intestinal absorbsion of Ca]

29
Q

Why might an ALP be high in a teenager

A

due to bones growing

30
Q

Conditions predisposing to calcium phosphate stones

A

hyperparathyroidism and renal tubular acidosis.

31
Q

Is raised FSH/LH in an older woman diagnostic of the menopause ?

A

No, they are consistent with menopause, they cannot
be considered diagnostic.

Menopause is: absence of menstrual activity for 2 years

32
Q

3 causes of riased t3/4

A

Graves

thyroiditis (viral infection) - will be tender

Hashimoto’s (early stage) - then low

Adenoma - thyroid / pituitary TSH

amiodarone - could be raised / low levels

thyroxine

33
Q

What conditions have a raised TPO?

A

hashimotos 95%
primary myxodema 90%
graves 18%

34
Q

Why might you get variation in TSH levels when on thyroxine

A

missed doses

time of day taking dose

35
Q

name 3 medical conditions or treatments may be associated with elevated troponin T
concentrations

A 
congestive heart failure
cisplatin treatment
end-stage renal failure
 myocarditis, NSTEMI (non-ST elevation myocardial infarction)
polymyositis
pulmonary embolus 
severe infections

they are really markers of any process that damages cardiac muscle whether that be from ischaemia, trauma, infection, ‘strain’ on the heart or toxic effects.
[Eg 30% of marathon runners have raised troponin levels after a race]

36
Q

why are troponin assays good for a marker of MI

A

they rise within 4 hours
high sensitivity

[its good to take them again later Eg at 6hrs and see if they have raised more]

37
Q

SOB and raised bilirubin levels.
Dx?
What type of bilirubin?
Other findings?

A

PE

unconjugated
raised (AST) and  LDH

[to the breakdown of red cells in the blood clot that is causing the embolus]

[ALT/ALP would be normal unless there is right heart failure -> liver damage]

38
Q

3 causes of raised d dimer

A 
DVT/PE 
disseminated intravascular coagulation; 
following surgery 
trauma; 
aortic dissection; 
in inflammatory conditions, including rheumatoid arthritis,
malignancy, liver disease
and in pregnancy
39
Q

Why might you get hyperglycaemia in hypothermia

A

increased release of glucagon and catecholamines (stress response) causing increased glycogenolysis and gluconeogenesis

40
Q

Why do you get elevated lactate following reperfusion in hypothermia

A

vascular shut down associated with hypothermia, increased lactate production [lack of oxygen].

On reperfusion, lactate which has accumulated in muscle is washed out and plasma lactate levels rise

41
Q

2 causes of raised CK in someone found on floor

A

hypothermia
pressure

[both cause muscle damage]

42
Q

Half life of PSA

A

2-3 days

43
Q

How does free PSA reflect cancer risk

A

if free PSA is BELOW 15% (of total PSA)

This reflects increased Ca risk

44
Q

Why does reference range of PSA increase with age

A

The volume of the prostate increases with age and therefore the amount of PSA it produces

45
Q

Give 3 uses of cancer markers

A 
Aid diagnosis 
Determine prognosis 
Guidance for potential reposnse to treatment Eg HER2/Oestrogen
Monitoring response to therapy 
Marker of reccurence
46
Q

3 issues with using cancer markers

A

Lack of specificity [bar PSA]
Often inefficient at detecting early disease
lack of sensitivity

47
Q

Causes of raised metanephrines

A 
Phaeochromocytoma 
acute psychological
stress, 
hypoglycaemia, 
obstructive sleep apnoea, 
vigorous exercise, 
conditions
linked to clinical shock, such as myocardial infarction, severe injury, pulmonary
embolus, 
and use of recreational drugs, such as cocaine.
48
Q

In suspected phaeochromocytoma why would you repeat 24hr urinary metanephrines if values were 3x normal?

When is best to start collection

A

values 1-4x are not diagnositic and could be due to other reasons

Should start collection at onset of Sx

49
Q

Bar metanephrines, what other test would you do in suspected phaeo ? Why?

A

Chromogranin A

Adrenal medullary tissue is derived from chromaffin cells which secrete chromogranin A
[high levels found in tumours]

50
Q

Why do you get increased glucose during an attack of phaeo?

A

increased catechloamines
-> increased mobilisation of glucose
[gluconeogeneis, inhibit insulin]

51
Q

If phaeo and rasied Calcium what are you thinking?

A

hyperparathyroidism and that the phaeochromocytoma is part of MEN2

[thyroid, phaeochromocytoma
and parathyroid adenoma]

52
Q

Relevance of ST segment depression with digoxin therapy

A

This is a marker of therapy - NOT toxicity

53
Q

name 2 metabolic conditions enhance digoxin toxicity

A

hypokalaemia, hypercalcaemia, diuretics (e.g.

furosemide), hypomagnesaemia and hypothyroidism

54
Q

Route of elimiation of dixogin

A

Kidney

-> injury will increase levels

55
Q

After Mx with Digibin (digoxin antidote) why would levels still be high?

A

captures digoxin in the circulation making it unavailable
for uptake by tissues
-still detectable though

56
Q

Bar liver what other tissues have ALP?

How could you differentiate the cause between these?

A

bone, liver and placenta (+Smalll amount in intestines)

separated by electrophoresis

57
Q

In primary biliary cirrhosis and gall stone obstruction

ALP+?

A

GGT

[ALP + GGT = biliary obstruction]

58
Q

Alcoholic cirrhosis LFTs?

A

AST is usually elevated more than the ALT and in addition

the GGT would usually be elevated.

59
Q

What Is a better marker of iron overload
ferritin or %saturation of transferrin

Causes of increased saturations ? Name 2

A

%sat of transferrin
[ferritin could be raised in any liver damage + is an acute phase protein]

A high saturation may be found in
haemochromatosis, haemosiderosis, haemolytic anaemia,
sideroblastic anaemia and iron poisoning

60
Q

Name 2 non haem/iron conditions may be associated with an elevated serum ferritin?

What could you do to see if the rise was due to ferritins properties as an acute phase protein

A

Obesity, NAFLD, thyrotoxicosis

measure CRP when ferritin is requested

61
Q

Which organs may be affected by haemachromatosis and with what effect

A

liver, testicles, skin, thyroid, pancreas, joints, heart and pituitary.

[Love The Skin That Protects Hamish’s Joints]

Liver - cirrhosis and Ca [usually first organ affected]

Testie / Pit - ED

Skin - Bronze

Pancreas - deposit in beta cells leading to glucose intolerance and eventually overt diabetes

Joint - Pain

Heart - heart failure / arrythmia

Thyroid - Hypo

62
Q

AST:ALT in Alcoholic vs NAFLD ?

In obesity / diabetes?

A

AST:ALT ratios > 2 indicate alcoholic disease.

In obesity and diabetes, the AST:ALT ratio is usually less than 1

Phase 4 - GR (22 decks)

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