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2A week 1 - anaemia, RBC metabolism etc. > red cell metabolism > Flashcards

red cell metabolism Flashcards

1
Q

avg RBC diameter and its clinical significance

A

7-8 μm - important to know as if transfusion is given via a cannula with a smaller bore than this (pink) the RBCs will lyse instead of being transfused through

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2
Q

what can occur with high K+ levels

A

complete systolic arrest -> massive MI

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3
Q

6 functions of the RBC

A
  1. oxygen carriage and delivery;
  2. energy release;
  3. deoxygenated promote blood flow;
  4. immune response (free radical release);
  5. intra-cellular buffer;
  6. K+ homeostasis
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4
Q

where does haem synthesis occur

A
  1. mitochrondria (precursor found here);
  2. cytoplasm (many intermediate steps);
  3. mitochrondria (final haem producing step)
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5
Q

why does a build up of the intermediate ring molecules in haem synthesis lead to damage

A

they easily fluoresce (drop down to lower energy state, releasing energy into cell) which causes damage

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6
Q

what is the rate limiting reaction for Haem synthesis (important!!)

A

the formation of ALA;
condensation of succinyl CoA + glycine -> enzyme bound alpha-amino-beta-ketoadipate -> decarboxylation to delta-aminolevulinate (ALA)

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7
Q

what disease can be causes by a build up of ALA

A

ALAD porphyria

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8
Q

porphobilinogen synthesis (from ALA)

A

ALA –(ALA dehydratase)–> phorphobilinogen (a pyrrole)

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9
Q

what does ALA dehydratase contain and why is this important

A

it is a -SH containing enzyme -> easily inhibited by trace heavy metals binding e.g. lead

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10
Q

what does uroporphyrinogen I synthase catalyse

A

prophobilinogen –(Deamination)–> linear tetrapyrrole with alternating acetic acid and pronoic acid groups

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11
Q

what molecule is transported from the cytoplasm to the mitochondria for the final steps of haem synthesis

A

coproporphyrinogen III

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12
Q

what does ferrochelatase catalyse

A

protoporphyrin IX – (Fe2+, absorbic acid, cysteine)–> Haem

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13
Q

what can inhibit ferrochelatase

A

lead

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14
Q

what is porphyria

A

a rare autosomal dominant inherited disorder characterised by a partial deficiency of porphobilinogen deaminase, which leads to the accumulation of porphyrin precursors and porphyrins in the body

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15
Q

4 porphyria types and their symptoms

A
  1. acute attacks: unexplained abdominal pain; nausea; vomiting; constipation; neuropsychiatic conditions
  2. erosive photodermatosis: blisters, skin fragility, hypertrichosis
  3. acute painful photosensitivity: burning seensations after sun exposure
  4. neonatal prophyrias: neonatal issues, haemolytic anaemia, bullae, severe neruological defects
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16
Q

4 porphyria types and what findings are seen in them (urine, plasma etc.)

A

acute attacks: PBG + AL in urine;
erosive photodermatosis: plasma fluorescence emission peak;
acute painful photosensitivity: protoporphyrin IX in erythrocytes;
PGB, ALA + porphyrins in urine

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17
Q

what are the major enzymes involved in porphyria (important!) -3

A

Urine Porphobilinogen (PBG); delta-aminolevulinic acid (ALA) dehydratase (leads to accumulation of ALA); ferrochelatase (leads to protopophyrin IX accumulation)

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18
Q

what investigation should be done if pt presents with acute neurovisceral features (w/wo skin lesions)

A

quantify PBG and ALA in urine

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19
Q

investigations for presentation with sun-induced urticaria or erythema

A

measure erythrocyte protoporphyrin concentration

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20
Q

investigation for presentation of active skin lesions (erosions/bullae)

A

measure plasma/urine porphyrin profile

21
Q

why does unconjugated bilirubin accumulate (compared to conjugated)

A

unconjugated bilirubin is lipid soluble and so cannot be easily dissolved and excreted -> conjugated can be

22
Q

blockages where results in bilirubin retention

A

bile duct

23
Q

what is seen with bilirubin blockage (stools)

A

white stools

24
Q

what are the first 3 substrates in the Hb breakdown reaction

A

haem; 3O2; NADPH

25
Q

biliverdin production reaction

A

haem + 3O2 + NADPH –(haem ogygenase)–> biliverdin + Fe2+ + CO + H2O + NADP+

26
Q

bilirubin production reaction

A

biliverdin –(NADPH + Biliverdin reductase (catalyst providing H+))–> bilirubin

central methene bridge is reduced to methane

27
Q

what is gilbert’s syndrome

A

an inherited (genetic) liver disorder that affects the body’s ability to process bilirubin -> short episodes of jaundice, where the skin and whites of the eyes turn yellow

28
Q

what molecule does bilirubin become conjugated to

A

glucuronic acid x2

29
Q

what is kernicterus

A

high levels of unconjugated bilirubin in a baby’s blood which causes it to be deposited in the brain and cause defects

30
Q

what do bacteria break conjugated bilirubin into in the gut

A

Stercobilinogen

31
Q

2 causes of dark urine

A

obstruction (gall stone disease); pancreatic cancer

32
Q

where is stercobilinogen reuptaken and in what from

A

in the small bowel as urobilinogen

33
Q

causes of haemolytic jaundice (2)

A
  1. alloimmunization (maternal–fetal blood type incompatibility);
  2. congenital disorders of red blood cells, such as hereditary spherocytosis and G6PD (glucose-6-phosphate dehydrogenase)
    deficiency;
34
Q

haemolytic jaundice pathophys

A

increased red blood cell destruction leading to more bilirubin present -> more being conjugated and excreted than normal but the system is overwhelmed and so an abnormally large amount of unconjugated bilirubin is found in the blood

35
Q

what happens if hepatocytes cannot take up bilirubin from the blood

A

accumulation of unconjugated bilirubin

36
Q

what can increase conjugated bilirubin levels in the blood

A
  1. defective secretion of conjugated bilirubin by hepatocytes (=> retuns to the blood);
  2. obstruction in the biliary network;
37
Q

what can painless jaundice be indicative of

A

pancreatic cancer

38
Q

obstructive liver disease test results (urine, faeces, bilirubin, urobilogen)

A

urine - dark;
faeces - pale;
bilirubin - elevated (conjugated);
urobilogen - negative

39
Q

hepatic liver disease test results (urine, faeces, bilirubin, urobilogen)

A

urine - normal
faeces - normal
bilirubin - elevated
urobilogen - elevated/normal

40
Q

haemolytic liver disease test results (urine, faeces, bilirubin, urobilogen)

A

urine - normal
faeces - normal
bilirubin - elevated (unconjugated)
urobiligen elevate

41
Q

what can trigger haemolytic anaemia in those with G6DP deficiency

A

malaria prophylaxis e.g. primaquine

42
Q

what are the 6 blood transfusion reactions

A
  1. Febrile non haemolytic transfusion - most common, Occurs within 4h due to accumulated inflammatory cytokines in donor blood;
  2. haemolytic transfusion reaction (delayed and acute) - due to mismatch of donor antigens (ABO/Rh) and recipient antibodies (acute - minor antigens in delayed);
  3. allergic - anaphylaxis (non-IgE), due to antibodies against proteins on donor plts, leukocytes or in plasma;
  4. Transfusion related acute lung injury (TRALI) - Leading cause of transfusion related death, Resembles ARDS, usually occurs due to leukoagglutinins in plasma targeting recipient leucocyte antigens on neutrophils sequestered in the lungs, resulting in an immune reaction;
  5. Transfusion associated cardiac overload (TACO) - Volume overload from transfusion;
  6. Transfusion associated graft versus host disease - due to donor leukocytes attacking immunosuppressed recipient
43
Q

how is febrile non haemolytic transfusion reaction treated

A

stop transfusion, give APAP (automatic positive airway pressure) and H2 blockers, meperidine

44
Q

how is haemolytic transfusion reaction

A

acute - stopping transfusion, notifying blood bank, testing for haemolysis and DIC, Aggressive IV hydration needed;
delayed - Treatment with notification of blood bank, repeat testing for minor antigens (DAT, type and screen ect)

45
Q

how is allergic transfusion reaction treated

A

adrenaline, H2 blockers and steroids

46
Q

how is TRALI treated

A

ventilatory support and use of platelets from male donors in future

47
Q

how is TACO treated

A

diuretics, give minimum units recquired

48
Q

how can graft vs host reaction be prevented

A

irradiated and leukocyte reduced blood in immunosuppressed recipients

2A week 1 - anaemia, RBC metabolism etc. (5 decks)

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