Sickle Cell Flashcards
(33 cards)
define “electrophoresis”
method of analysing molecules on the basis of charge and weight by measuring their migration in an electric field
What changes HbA to HbS
- point mutation in beta-globin gene causes change in amino acid 6 from glutamate (-ve charge hydrophilic) to valine (hydrophobic uncharged) resulting in HbS.
- hydrophobic interactions = clump together + affect b-globin chain
does HbA or HbS move closer to the anode?
-HbA is more –vely charged
(as glutamate = hydrophilic and -ve) so migrates further towards anode
what shows up on the electrophoresis if the person is a carrier?
some of HbA and some of HbS = carrier as they are heterozygous HbAS
results of a full blood count for a sickle cell sufferer?
- low [Hb] (sign of anaemia)
- bigger MCV as more reticulocytes (immature red blood cells which are larger than fully mature rbc) as anaemia so bone marrow making more red blood cells
- high reticulocyte count - due to the premature death of RBCs so bone marrow keeps producing more RBCs
why can the MCV sometimes be low?
if you have lost blood / anaemia the iron from the Hb can not be recycled so less rbc can be made
what shows anaemia on a blood film?
- paler rbc = low conc. of Hb (hypochromasia)
- less cells per unit volume
(3. microcytic cells)
sickle cell characteristics in a blood film
- sickle cells (poikilocytosis)
- nucleated RBCs (immature)
- hypochromic rbcs (paler = low Hb levels)
- microcytic cells (macrocytic cells arise when there are problems with problems with dna synthesis) - smaller cells indicate slight anaemia
- Boat cells (poikilocytosis)
- Howell Jolly bodies (left over nuclear remnants that are usually removed when blood cells are in the spleen) - in sickle cell vessels to spleen can be blocked = less efficient
sickle cell carrier on a blood film
you can not see if someone has a sickle cell trait by just looking at their blood film but there may be some early signs of sickling
women vs men blood film
women can be menstruating = more likely to have anaemia
what happens during a vaso-occlusive crisis (pain crisis)?
sickle cell shape = harder to pass through vessels = vasco-occulusive crisis as a vessel gets blocked = necrosis in healthy tissue
impact of sickle cell disease in different areas of the body
- bone marrow ischaemia (in extreme cases avascular necrosis is the death of bone tissue due to a lack of blood supply)
- visual loss (vessels in the eye blocked or e.g. retinal artery or retina can even fall off)
- stroke (blocking arteries to the brain = lack of oxygen to the brain)
types of stoke
- ischeamic stroke (most common)
- hemorrhagic stroke (burst of vessels)
why is a stroke most common in children with sickle cell
blood vessels are smaller and don’t say their problems, doesn’t know when about to have a crisis as not quite used to it
what can trigger a sickle cell crisis
- cold weather = vasoconstriction = more likely to block off
- infection = dehydration, lower o2 levels if it is in the lungs = more sickled cells
- exercise = HR incr. (more o2 needed)
- dehydration, due to low blood volume
- stress
- high altitudes, due to low oxygen
- alcohol
- smoking
- pregnancy
- other medical conditions, such as diabetes
- hypoxia
how people cope with their disease in their daily lives (self)
- hot water bottle - vasodilation
- folic acid = support RBC production
- hydration (high blood volume = wider lumen)
- pain killers
main- pain killer, oxygen, fluids
doctor intervention to help with sickle cell
- stronger pain killers i.e. morphine (opioids)
- antibiotics recommended if there is a chance of infection
- oxygen is part of the treatment (only sickle cell shape when deoxygenated blood)
- blood thinners (anticoagulants) -as these patients have an increase rate of DVT and clotting as HbSS more likely to clot)
- mental support
- extra fluids (ie IV) to hydrate
concept of ICE
Ideas, concerns and expectations - understanding what the patient may be feeling → patient centred care
burden of sickle cell on different parts of body
- CNS (visual loss, pain, stroke, seizures)
- bones (crisis, avascular necrosis)
- cardiac (pain, hypertension)
- spleen (anaemia, Hellman jolly)
- gastro + urology
- depression + anxiety
ICE
- Ideas are unemotional thoughts about the nature - health-seeking response; e.g. she has a clear idea + understands what is needed - a person with a severe sore throat may develop the idea that she needs antibiotics.
- Concerns are the emotional triggers and fears that we all ex- perience to varying degrees. e.g. how it interferes with her life
- Expectations of the doctor’s likely reaction.
e. g. expects morphine, folic acid..
what amino-acid changes when HbA → HbS
glutamate → valine (replace extra COO- with CH3 therefore no longer -vely charged + hydrophilic)
what type of disease is sickle cell anaemia in terms of inheritance?
-Autosomal recessive (if both parents are carriers child has a 25% chance of getting it)
- Homozygous - sickle cell anaemia
- Heterozygous - sickle cell trait (only one mutated allele- most commonly asymptomatic – normal blood count + film)
What happens to RBCs during sickle cell anaemia?
- Distorted RBCs, sickled (poikilocytosis)
- Rigid RBCs
- Dehydrated RBCs
- The red blood cells stick together due to the valine instead of glutamic acid due to the hydrophobic interaction which causes polymerisation- which causes blockage of vessels
- Short survival of RBCs- do not survive the normal 120 days
- RBCs have a lower affinity for oxygen- they are hypoxic. But they do release oxygen more easily to tissues.
what is the epidemiology of sickle cell?
- Sickle cell trait protects from malaria
- Sickle cell trait is more prevalent in sub-saharan Africa, middle east, Mediterranean and India
- The life expectancy is 42-48 (even lower in LIC) - and patients in their 40s usually have organ damage
