sickle cell + crises Flashcards
inheritance pattern of sickle cell
autosomal recessive
sickle cell anaemia
autosomal recessive condition that results from synthesis of an abnormal haemoglobin chain termed HbS
- more common in Africans - offers protection against malaria
- some who are carriers of HbS (heterozygous) are only symptomatic if severly hypoxic
when do symptoms develop in homozygotes of HbS (sick cell)
4-6months
- when the abnormal HbSS molecules take over from fetal haemoglobin
normal haemoglobin vs sickle cell trait vs sickle cell disease
normal Hb - HbAA
sickle cell trait - HbAS
homozygous sickle cell disease - HbSS
how does HbS cause harm
in the deoxygenated state, the HbS molecules polymerise and cause RBCs to sickle
- sickle cells are fragile + haemolyse
–> they block small blood vessels + cause infarction
definitive diagnosis of sickle cell disease
haemoglobin electrophoresis
long term managment of sickle cell anaemia, how does it work?
hydroxyurea
- increases the HbF levels + is used in the prophylactic mx to prevent painful episodes
pneumococcal polysaccharide vaccine every 5yrs
sickle cell disease course
characterised by periods of good health with intervening crises
types of sickle cell crises
- thrombotic - vaso-occlusive, painful crises
- acute chest syndrome
- anaemia - aplastic, sequestration
- infection
what are sickle cell thrombotic crises (painful or vaso-occlusive) precipitated by? what happens?
precipitated by:
- infection
- dehydration
- deoxygenation (high altitudes)
infarcts occur in various organs
- AVN of hip
- lungs
- spleen, brain
- hand-foor syndrome in kids
diagnosis of sickle cell thrombotic crises (painful or vaso-occlusive)
clinical !
acute chest syndrome
vaso-occlusion within the pulmonary microvasculature –> infarction in the lung parenchyma
commonest cause of death after childhood
acute chest syndrome presentation
dyspnoea
chest pain
pulmonary infiltrates on CXR
low pO2
management of acute chest syndrome
pain relief
oxygen
antibiotics - infection may precipitate
transfusion -> improves oxygenation
sickle cell aplastic crises
caused by infection with parovirus
sudden fall in Hb
bone marrow suppresion can cause REDUCED reticulocyte count
sequestration crises
sickling within organs such as spleen or lungs causes pooling of blood with worsening of the anaemia
assoc with INCREASED reticulocyte count
general management of sickle cell crises
analgesia (opiates)
rehydrate
oxygen
antibiotics if evidence of infection
blood transfusion / exchange transfusion IF meets INDICATIONS
blood transfusion indications in sickle cell crises
- severe/symptomatic anaemia
- pregnancy
- pre-operative
does not rapidly reduce the % of HbS containing cells
exchange transfusion indications in sickle cell crises
- acute vaso-occlusive crisis
- stroke
- acute chest syndrome
- multiorgan failure
- splenic sequestration crisis
DOES rapidly reduce the % of Hb S containing cells
why is exchange transfuion better than a blood transfusion
rapidly reduces % of Hb S containg cells
