Sickle Cell Flashcards
(47 cards)
What do you ask about history of current episode for sickle cell disease?
Site(s) of pain
it is their usual sickle pain ?precipitant
What painkillers have they already taken
What do you ask a sickle patient in a history of their sickle?
usual place of care
genotype - HbSS or HbSC
How do you assess the clinical severity of a patients sickle history?
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?
What do you look for O/E of a sickle patient?
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
What is the genetics behind sickle cell?
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)
what is the pathophysiology of sickle cells causing problems?
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)
What does haemolysis in sickle cell lead to?
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)
What does infarction from HbSS vaso-occlusion lead to?
infarction of downstream tissues where vaso-occlusion has happened resulting in tissue death and inflammation
- -> acute pain
- -> acute chest syndrome
- -> hyposplenism
- -> osteonecrosis (AVascular)
- -> Nephropathy
What does HbSS mean?
homozygous sickle cell
no normal β-globin
NB: HbA2 and HbF are still produced
What is HbAS (sickle trait carriers) / HbSC (sickle + another point mutation of B-globin genes)?
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
What is HbC?
another point mutation of the β-globin gene
What happens if HbS carrier and B-thalassemia parent have a child?
sickle cell b-thalassaemia
the severity depends on the amount of normal B-chain synthesis
What crises can present at 6 months old?
when HbF concentration is greatly decreased; acute anaemia (sudden drop in Hb) due to:
Haemolytic Crises
Aplastic Crises
equestration
what symptoms do these crises present at 6 months old?
anaemia and jaundice
What is a haemolytic crises (@6m old)?
associated with infection that causes the HbF to be greatly decreased –> acute anaemia
What is the an Aplastic crises (@6m old)?
most often parvovirus B19 as this virus suppresses bone marrow erythropoietic activity –> severe anaemia usually self-limiting <2weeks;
transfusion may be needed
What is a sequestration crises @6m old?
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
What happens in painful vaso-occlusive crises?
vaso-occlusion results in ischaemia–> pain;
in bones, abdomen
can occur anywhere in the body though
What happens in a chest crises?
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
What happens in a cerebrovascular crisis?
AKA stroke
10% patients suffer strokes during childhood
vaso-occlusion in cerebral circulation; cause of significant mortality & morbidity prevention programme
Why is infection more likely in HbSS?
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
What is the pathophysiology of priaprism in sickle cell?
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
When is splenomegaly common?
in children
What are the long term impact of HbSS on children?
- 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
