Anemia Flashcards
What is anemia?
decrease in the number of RBCs or less than normal quantity of hemoglobin in the blood
-results in decreased O2 carrying capacity in blood
-an objective sign of disease
-several etiologies
Where are RBCs formed?
in the bone marrow (termed erythropoiesis)
adults: spine, ribs, sternum, clavicle, pelvic crest, ends of long bones
children: most bone marrow space
Describe the composition of hemoglobin.
protein component (2 alpha/2 beta chains)
-fetus: 2 alpha/2 gamma (higher O2 affinity)
heme (porphyrin ring + iron)
How long does RBC maturation take?
~1 week
Describe erythropoiesis.
erythropoetin:
-stimulates stem cells to differentiate
-increased release of reticulocytes from bone marrow
-induces Hb formation
works on a feedback loop
-decreased tissue O2 signals kidneys to increase production of EPO
normally this system is in balance
-EPO matching new erythrocyte production to the rate loss of RBCs
What is anemia associated with?
nutritional deficiencies
acute or chronic disease
drug induced
How is the pathophysiology of anemia classified?
by pathophysiology or morphology
What are the classifications of anemia by pathophysiology?
- blood loss (trauma, ulcer, hemorhoids, etc)
- inadequate RBC production
-nutritional deficiency: B12, folic acid, iron
-erythroblast deficiency: bone marrow failure or infiltration
-endocrine disorders
-chronic disease (renal, liver, infection) - excessive RBC destruction (autoimmune, drug, infection)
What are the classifications of anemia by morphology?
size:
1. microcytic
2. normocytic
3. macrocytic (megaloblastic, non-megaloblastic)
colour:
1. hypochromic
2. normochromic
3. hyperchromic
How is size of RBC reflected?
by the mean corpuscular volume
-microcytic: <80fL
-normocytic: 80-100fL
-macrocytic: >100fL
How is colour of RBC reflected?
by the mean corpuscular concentration (MCHC)
-hypochromic: pale
-normochromic: normally coloured
-hyperchromic: darker
Describe microcytic RBCs.
primarily a result of Hb synthesis or Hb insufficiency
can be due to issues with the heme portion of the globin portion
Describe normocytic RBCs.
anemia with normocytic cells means the RBC are normal-sized but there is a low a low # of them
decreased production or increased destruction or loss
Describe macrocytic RBCs.
megaloblastic
-impaired DNA synthesis
-ex: B12, folate deficiency
non-megaloblastic
-not caused by impaired DNA synthesis
-ex: liver disease
What is the general presentation of anemia?
onset: may be acute or develop slowly
signs & symptoms vary with degree of RBC reduction & how long it has been present
end result is a decrease in O2 carrying capacity of the blood
-perfusion to nonvital tissue is compromised to sustain perfusion of vital organs
-initially patients may be asymptomatic
What are the common symptoms of anemia?
fatigue, dizziness, weakness, SOB, tachycardia
decreased mental acuity
pallor, cold extremities
What are the components involved in the diagnosis of anemia?
medical history
physical examination
laboratory evaluation
What kind of stuff should be collected in a medical history if anemia is suspected?
past & current Hb & bloodwork if available
comorbid conditions
occupational, environmental & social history
transfusion
family history
medications
What are some things to look for during a physical examination if anemia is suspected?
pallor
postural hypotension, tachycardia
neurologic findings (B12 deficiency)
jaundice (hemolysis)
bleeding gums, blood in stool, urine, epistaxis
What kind of laboratory evaluations should be conducted if anemia is suspected?
complete blood count (CBC)
-Hb
-hematocrit (packed cell volume)
-RBC count
-RBC indices (MCV, MCH, MCHC)
RBC morphology
reticulocyte count
iron studies (ferritin, serum iron, TIBC)
peripheral blood smear
stool for occult blood
bone marrow aspiration and biopsy
What are the RBC indices?
MCV=mean corpuscular volume
-avg RBC volume
MCH=mean corpuscular hemoglobin
-avg mass of Hb divided by RBCs
MCHC=mean corpuscular hemoglobin concentration
-avg Hb conc within volume of RBC
RDW=red blood cell distribution width
-higher RDW common in mixed anemias
-marker of variation in RBC width/size
What is the Hb level that can diagnose a man or woman with anemia?
men: <130g/L
women: <120g/L
What are the specific types of anemia?
deficiency-related anemias
-iron, vit B12, folate
hemolytic anemia
sickle cell anemia
anemia related to other diseases/conditions
aplastic anemia
What is the most common nutritional deficiency worldwide?
iron deficiency
What are the symptoms associated with iron deficiency anemia?
symptoms of pallor
cardiovascular
respiratory
cognitive complications
decreased QoL
What is iron deficiency anemia?
a negative state of iron balance in which daily iron intake are unable to meet RBC and other body tissue needs
-accounts for 50% of anemia cases
What are the causes of iron deficiency anemia?
lack of dietary intake
-vegetarians/vegans, poor diet
blood loss
-menstruation, GI (peptic ulcer), trauma
decreased absorption
-celiac disease, medication, gastrectomy, regional enteritis
increased requirement
-infancy, pregnant/lactating women
impaired utilization
-hereditary, iron use
What is the pneumonic to remember the causes of iron-deficiency anemia?
NIMBLE
need (increased need in pregnancy, children, etc)
intake is low (malnutrition)
malabsorption
blood
loss
excessive donation
Why do we treat iron deficiency anemia?
mortality:
-rarely a direct cause of death
-moderate-severe iron deficiency anemia can cause hypoxia (aggravate underlying pulmonary/CV disorders)
morbidity:
-symptoms can be disruptive, impair daily functioning, etc
-slowed growth rate in children, decreased ability to learn, lower IQ
-splenomegaly may occur with severe, persistent, untreated iron deficiency anemia
elderly:
-anemia associated with: risk of hospitalization and mortality, decreased QoL, decreased physical functioning
pregnancy:
-anemia during pregnancy increases risk for: LBW, preterm delivery, perinatal mortality
Describe iron distribution in the body.
body contains ~3-5g, of which 2g are found in Hb
significant amount is stored as ferritin or aggregated ferritin in the liver, spleen, bone marrow
small fraction in plasma, of which most is bound to transferrin
iron stores are usually well preserved
How is iron metabolism regulated?
hepciding
Describe iron absorption.
Fe 3+ ionized in stomach and reduction to Fe 2+
Fe 2+ absorbed from duodenum & upper jejunum by active transport
binding to transferrin
incorporation into Hb or storage as ferritin
What are the different iron studies?
serum iron
ferritin
TIBC
Tsat
What is serum iron?
concentration of iron bound to transferrin
-best interpreted in context with TIBC
-subject to individual diurnal variation
-may remain in normal range when iron stores are dropping
What is ferritin?
storage iron
most sensitive but non-specific and is elevated in inflammatory conditions, liver disorders, etc
What is TIBC?
indirect measurement of iron-binding capacity of transferrin, performed by adding and excess of iron to plasma to saturate and then removing the excess
serum transferrin receptor levels, which reflect the amount of RBC precursors available for active proliferation are increased in iron deficiency anemia
What is Tsat?
% transferrin saturation
a measure of how much serum iron is actually bound
serum iron/TIBC x 100
Describe the labwork we would expect to see with iron deficiency anemia.
decreases in:
-ferritin
-serum iron
-transferrin saturation
-Hb and Hct
increases in:
-TIBC
RBC morphology:
-microcytic (decreased MCV)
-hypochromic (decreased MCHC)
What are the types of iron sources?
heme iron
-derived from animal proteins
-better absorbed, more consistent absorption
-less affected by dietary factors
non-heme iron
-plant sources
-fruits and vegetables, nuts, grains, iron-fortified food
-requires acidic GI pH for absorption
What can decrease the absorption of iron?
phytates (grains, brans)
polyphenols/tannins (coffee/tea)
calcium
H2RAs, PPIs
gastrectomy/bariatric surgery/achlorhydria
What can increase the absorption of iron?
increased stomach acidity
eating heme and non-heme sources at the same time
cook with cast-iron or stainless steel pots/pans
What is the RDA of iron during pregnancy?
27mg
What are the symptoms of iron deficiency anemia?
typical anemia symptoms
other symptoms:
-brittle, spoon-shaped nails
-pica (appetite for non-nutritive substances)
-pagophagia (consumption of icy drinks)
-smooth tongue
What is the first-line dosage form of iron for the treatment of iron deficiency anemia?
oral (tablets or liquid)
-safe, convenient, cheap
parenteral only to be used if needed