Sickle Cell Flashcards
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
