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Paediatrics > Sickle Cell > Flashcards

Sickle Cell Flashcards

1
Q

What do you ask about history of current episode for sickle cell disease?

A

Site(s) of pain
it is their usual sickle pain ?precipitant
What painkillers have they already taken

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2
Q

What do you ask a sickle patient in a history of their sickle?

A

usual place of care

genotype - HbSS or HbSC

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3
Q

How do you assess the clinical severity of a patients sickle history?

A

frequency and severity of sickle crises
previous complications, especially acute chest syndrome
previous ITU admissions
Transfusions - regular, episodic, when and where last transfused, any previous reactions?

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4
Q

What do you look for O/E of a sickle patient?

A 
pulse, bp, O2 sats (on air), temp, RR
listen to the chest - lungs, heart 
palpate for liver and spleen size
pallor
jaundice
skin- ulcers
bony pains/joints - look for swelling
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5
Q

What is the genetics behind sickle cell?

A 
AR
point mutation in beta-globin gene
on Chr 11:
single nucleotide substitution GAG for GTG 
= A --> T 
= glutamic acid --> Valine 
overall = abornal B globin chains 
HbA is normal = HbS (sickle)
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6
Q

what is the pathophysiology of sickle cells causing problems?

A

HbS is unstable
they polymerise when deoxygenation
the RBC deform & sickle*
*cold dehydration and dc O2 tension/hypoxia
- Initially this is reversible, but once this happens a few times it is irreversible
this process damages RBC membrane
they adhere to vessel walls & block small vessel causing ISCHAEMIA & INFARCTION
cells are fragile and HAEMOLYSE (breakdown)

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7
Q

What does haemolysis in sickle cell lead to?

A

release of hb and consumption/release of NO (from vasculopathy and endothelial dysfunction too) leading to functional deficiency of Hb & VASOCONSTRICTION
–> Pulm HTN, priaprism, leg ulcers, cerebrovascular disease (blockage/haem/malformation)

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8
Q

What does infarction from HbSS vaso-occlusion lead to?

A

infarction of downstream tissues where vaso-occlusion has happened resulting in tissue death and inflammation

  • -> acute pain
  • -> acute chest syndrome
  • -> hyposplenism
  • -> osteonecrosis (AVascular)
  • -> Nephropathy
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9
Q

What does HbSS mean?

A

homozygous sickle cell
no normal β-globin
NB: HbA2 and HbF are still produced

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10
Q

What is HbAS (sickle trait carriers) / HbSC (sickle + another point mutation of B-globin genes)?

A

they are sickle carriers
no disability except hypoxia e.g. know for GA or high altitude
protects against malaria
HbSC = milder form of sickle cell disease

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11
Q

What is HbC?

A

another point mutation of the β-globin gene

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12
Q

What happens if HbS carrier and B-thalassemia parent have a child?

A

sickle cell b-thalassaemia

the severity depends on the amount of normal B-chain synthesis

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13
Q

What crises can present at 6 months old?

A

when HbF concentration is greatly decreased; acute anaemia (sudden drop in Hb) due to:
Haemolytic Crises
Aplastic Crises
equestration

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14
Q

what symptoms do these crises present at 6 months old?

A

anaemia and jaundice

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15
Q

What is a haemolytic crises (@6m old)?

A

associated with infection that causes the HbF to be greatly decreased –> acute anaemia

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16
Q

What is the an Aplastic crises (@6m old)?

A

most often parvovirus B19 as this virus suppresses bone marrow erythropoietic activity –> severe anaemia usually self-limiting <2weeks;
transfusion may be needed

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17
Q

What is a sequestration crises @6m old?

A

Enlargement of spleen with abdominal pain &
circulatory collapse due to accumulation of cells within the spleen,
(the spleens narrow vessels and functioning in clearing defective TBC renders it very susceptible to microinfarction)
Rx: is supportive with transfusions if required

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18
Q

What happens in painful vaso-occlusive crises?

A

vaso-occlusion results in ischaemia–> pain;
in bones, abdomen
can occur anywhere in the body though

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19
Q

What happens in a chest crises?

A

most common cause of mortality in HbSS

vaso-occlusion –> collpase in the lungs,
–>commonest cause of mortality (20%)

pulmonary infiltrates involving complete lung segments

  • fat embolism from bone marrow
  • or infection with Chlamydia, Mycoplasma or viruses
20
Q

What happens in a cerebrovascular crisis?

A

AKA stroke
10% patients suffer strokes during childhood
vaso-occlusion in cerebral circulation; cause of significant mortality & morbidity prevention programme

21
Q

Why is infection more likely in HbSS?

A

due to hyposplenism
Risk of overwhelming sepsis more common in childhood
Increased incidence of osteomyelitis due to salmonella etc.
Increased incidence of infection with encapsulated organisms e.g. Strep pneumoniae & HiB

22
Q

What is the pathophysiology of priaprism in sickle cell?

A

Persistent and painful erection:
needs urgent treatment since it may lead to fibrosis of the corpus cavernosum with subsequent erectile dysfunction,
- usually nocturnal with risk of long-term impotence

23
Q

When is splenomegaly common?

A

in children

24
Q

What are the long term impact of HbSS on children?

A
  • Short stature & delayed puberty
  • Cardiac enlargement & heart failure due to chronic anaemia
  • Renal damage
  • Adenotonsilar hypertrophy
  • Gallstones due to excessive bilirubin production (from heme breakdown/sickle)
  • Cognitive problems
  • Psychological problem
25
Q

Why might cognitive problems occur in HbSS?

A

not only due to strokes but also subtle cerebral damage that occurs

26
Q

What may adenotonsilar hypertrophy cause?

A

adenotonsilar hypertrophy –> causing sleep apnoea syndrome leading to nocturnal hypoxaemia which may trigger vaso-occlusive crises

27
Q

What may renal damage cause in HbSS children?

A

–> resulting in an inability to concentrate urine –> causing enuresis & dehydration

28
Q

What are the adult acute crises?

NB: they are similar to paeds ones

A
  • Pain (e.g. bone, often microvascular occlusion of marrow)
  • Strokes/seizures/ cognitive defects
  • Chest Crisis
  • Abdominal Crisis (mesenteric ischaemia)
  • Priapism
  • Leg ulcers
  • Infections
  • Hyposplenic
  • Osteomyelitis
  • Avascular necrosis (articular surface of long bones
29
Q

What are the chronic complications in adults with HbSS?

A
  • Lungs (hypoxia -> fibrosis -> pulmonary HTN)
  • Heart
  • Kidneys
  • Gallstones
  • Retinal disease
  • Iron overload or infections from transfusions
30
Q

Where do vaso-occlusive crises affect infants?

A

usually in hands and feet

growth plates can be affected!

31
Q

Where do vaso-occlusive crises affect children?

A

back, upper and lower extremities

32
Q

What can trigger vaso-occlusive crises?

A

hypoxia
infection
cold exposure

33
Q

What is hand-foot syndrome?

A

most common complication in HbSS
Swelling of the fingers and feet due to vaso-occlusion; Dactylitis
–> pain due to infarction, necrosis

34
Q

What are the signs and syx of chest crises?

A 
pleuritic chest pain, 
SOB, 
hypoxia, 
fever, 
wheeze/cough, 
tachypnoae 
- up to 20% mortality
35
Q

What are the ususal precipitants for a chest crises?

A 
dehydration, 
infection, 
cold/damp,
unaccustomed exercise, 
stress, 
pregnancy, 
operations
36
Q

What should you also rule out (DDx) for people coming in with chest crisis?

A

pneumonia
pneumothorax
PE

37
Q

How do you investigate a chest crisis?

A

haemoglobin electrophoresis
- shows HbS, absent HbA, variable HbF
exchange transfusion maybe needed to reduce level of sickle cells <30%

38
Q

How do you manage a chest crisis?

A 
hospital admission, 
ANALGESIA
A/B - O2, 
C- IV fluids, 
antibiotics for infection;

exchange transfusion may be needed to reduce level of sickle cells to <30%

39
Q

How can you investigate if someone has Hbss?

A
  • can diagnose with new-born screening heel-prick test/ cord blood
    Haemoglobin & reticulocytes
    Blood film
    Sickle solubility test - +ve
    Hb electrophoresis or HPLC (high performance liquid chromatography) - will reveal genotype
    Bilirubin & LDH - variable; depends on degree of haemolysis
    Creatinine - usually below normal limit (lower BP, reduced concentrating ability, increased excretion)
40
Q

What do haemoglobin and reticulocytes show in HbSS?

A

Microcytic, hypochromic RBC

Anaemia:
60-90g/l for HbSS,
90-140g/l for HbSC,

Usually reticulocytosis (slightly lower for HbSC than HbSS)

41
Q

What do you see on blood film in HbSS/HbSC?

A

sickle cells present, target cells prominent in HbSC

42
Q

What does a sickle solubility test show?

A

if have HbS or not

HbS polymerises when you add phosphate buffer + becomes clear - but doesn’t differentiate trait vs HbSS

43
Q

What Rx can you give to PREVENT a crisis?

A

folic acid supplements OD to meet the increased demand caused by increased haemolysis

Prompt treatment of infection

Presence of hyposplenism –> BD phenoxymethylpenicillin prophylaxis

Avoid exacerbating factors e.g. cold, excessive exercise, stress

Immunisations are important

Transcranial doppler screening to assess risk of stroke

44
Q

How do you treat an acute crises?

A

Quick, adequate analgesia e.g. IV opiates
Regular reviews & pain scores
Bloods:
Crossmatch; FBC, reticulocytes,
blood cultures,
- Measure Packed Cell volume/haematocrit, reticulocytes, liver & spleen size daily
- Blood transfusion if Hb or reticulocytes fall sharply
Urine: MSU +/- CXR if fever or chest signs
Hyper-hydrate with IVI & keep warm
O2 if sats <95%
“Blind” antibiotics e.g. cephalosporin if fever, unwell or chest signs
Exchange transfusion (patient blood is removed & donor blood given in stages - for those rapidly worsening; reduce level of sickle cells to <30%)

45
Q

What can be given in case of recurrent painful crises if ~6m?

A

Hydroxyurea

raises HbF level & reduces numbers of crises

46
Q

What is the Rx (surg and med) can be given in cases of recurrent painful crises (except hydroxyurea)?

A

Medical:
Transfusion programme
- Regular transfusions +/- Exjade
(iron overload due to repeated transfusions so give with chelating agent)

Surgical:
Bone marrow transplant

47
Q

What is the prognosis in someone with sickle cell?

A
  • 3% mortality during childhood, mainly due to infection in the first 3 years of life
  • Mean survival is 40-50 years of age

Paediatrics (16 decks)

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