Week Review Flashcards
causes of macrocytosis?
alcohol (mild)
liver disease
hypothyroid
physiological (pregnancy, neonatal, reticulocytosis)
nuclear maturation defect (megaloblastic - B12 or folate deficiency, myelodysplasia - stem cell mutation)
is macrocytosis always associated with anaemia?
no
what is pernicious anaemia associated with?
autoimmune disorders eg hypothyroid
what can influence serum folate?
diet
approach to diagnosing macrocytosis?
by severity
whether anaemia is present
if neutrophils or platelets are low
blood film
MCV >120 indicates what?
B12 or folate deficiency
macrocytosis with anaemia indicates what?
megaloblastic or myelodysplasia
low platelets/neutrophils indicates what in macrocytosis?
myelodysplasia or megaloblastic
possible features on blood film in macrocytosis?
hypersegmented neutrophils and oval macrocytes (megaloblastic)
uniform microcytosis (probably alcohol)
dysplastic neutrophils (myelodysplasia)
polychromasia (reticulocytosis)
agglutinates (artefact with cold agglutinins)
how can iron status be measured?
3 compartments
- functional iron (Hb conc)
- storage iron (serum ferritin, bone marrow biopsy with perls stain)
- transport iron (serum transferrin % saturation with iron)
which compartment of iron is used up first?
storage iron exhausted first before transport iron, only then is RBC production affected
causes of iron deficiency
diet
increased physiological requirement
blood loss
malabsorption (jejunum, need gastric acid)
how is iron deficiency investigated?
history blood loss (FOB testing of little value in iron deficiency) GI tract investigations (upper GI endoscopy, barium enema or colonoscopy)
normal initial reticulocyte response?
reticulocytosis 6-12 hrs after bleed as immature retics released
proliferative response to increased erythropoietin production 1-2 days after acute bleed, peaking at day 8-10
what does reticulocyte response indicate?
normal marrow response
normal iron as only possible if iron supply is adequate
normal marrow response to marked anaemia?
6-8X increase in absolute reticulocyte count
3-4X increase in amount of erythropoiesis
earlier release of reticulocytes into blood
signs of shock?
tachycardia
hypotension (can be postural in young people)
tachypnoea
peripheral vasoconstriction (pallor, delayed capillary refill)
oliguria
causes of shock?
hypovolaemic (acute blood loss)
cardiogenic (pump failure)
neurogenic (lack of sympathetic tone - can happen after sudden neck injury)
vasogenic (anaphylactic or septic)
how is Hb affected in hypovolaemic shock?
unchanged until redistribution of body water
how is shock treated?
synthetic colloids as immediate fluid of choice
how can oxygen delivery be restored in shock?
Hb
supplemental oxygen
optimise cardiopulmonary dynamics (fluids and pharmacological interventions)
what are the 3 elements of cross matching?
ABO and RhD antigen grouping
screen for alloantibodies in patient (identify alloantibodies in the patient to antigens which might be on the donor RBCs and if found, check that donor blood doesn’t have that antigen)
mix donor cells and recipient plasma to double check
confirm historical records for electronic cross match
how available is crossmatched blood?
not in a hurry
ABO group is quickest test
alloantibody takes longer (difficult to get ag -ve blood etc)
what types of blood are available quickly?
O RhD -ve
ABO type specific
fully crossmatched
electronic crossmatched (if historical group and -ve alloantibody screen)
what can incompatible ABO transfusion cause?
immediate transfusion reaction
- DIC and death due to presence of preformed IgM antibodies (anti-A/B)
how does a delayed transfusion reaction occur?
IgG alloantibody to RBC antigen
acquired following previous transfusion or pregnancy
low level 2ndary response 10 days later
complications of transfusion?
infective
overload (fluid overload/TACO, iron overload)
immune complications (febrile non-haemolytic reactions, urticarial reactions, taGVHD, PTP, IgA deficiency, TRALI)
