Topic 4: Iron Deficiency Anemia Flashcards
why does an iron deficiency lead to decreased heme production?
heme is the iron-containing component of the hemoglobin protein that’s made via heme synthesis pathway
Fe is a substrate for the enzyme ferrochelatase in the final step of heme synthesis
deficiency of iron will impair this process and result in decreased heme production
what compensatory mechanisms does the body have during anemia to maintain oxygen delivery to tissues?
- increase in cardiac output
- increased oxygen extraction by tissues
- right shift of oxyhemoglobin curve - this graph measures hemoglobin oxygen
saturation as a function of the partial pressure of oxygen
a right shift decreases hemoglobin’s affinity for oxygen and allows for increased oxygen unloading from hemoglobin
if anemia develops rapidly (like from hemorrhage) the patient will be symptomatic but if anemia onset is gradual, these compensatory mechanisms will be able to maintain oxygen delivery
what is anemia?
a condition in which there is a reduction in RBC number or hemoglobin concentration
what are the causes of iron deficiency?
- blood loss
- decreased nutritional intake
- increased iron requirement
what is blood loss often due to?
- menses, trauma, hematemesis
- frequent blood donation
- occult GI bleeding
- parasitic hookworm in tropical areas
what populations have an increased iron requirement?
- children
2. pregnant women
Why do iron-deficient patients develop anemia?
Iron is a required substrate in the synthesis of heme, which is a major component of hemoglobin. If iron is deficient, hemoglobin synthesis will be impaired
Anemia occurs when the hemoglobin concentration drops below the normal reference range.
what are common symptoms of IDA?
fatigue, weakness, lightheadedness, shortness of breath on exertion, and exercise intolerance
craving for ice = pagophagia
pallor, dry skin, spoon nails (koilonychia)
what is Plummer-Vinson syndrome?
chronic iron deficiency anemia associated with glossitis and esophageal web with accompanying dysphagia and fatigue
at risk for developing squamous cell carcinoma of the esophagus
treatment: iron supplement and esophageal dilation to alleviate dysphagia
how are Hb and hematocrit levels on the CBC of an IDA patient effected?
hemoglobin and hematocrit are decreased
how is the RBC count on the CBC of an IDA patient effected?
RBC is also decreased, since the main problem is that it’s hard to make red cells
how is the size of RBC of IDA patient effected?
microcytic and MCV is low too (<80)
because there’s a problem making Hb
how is RDW in IDA effected?
RDW is increased
RDW measures how much the red cells vary in size
in IDA there are some little cells and some bigger cells and the RDW is high = anisocytosis
anisocytosis happens in IDA because each new wave of red cells produced is smaller than the last
how is the reticulocyte count in IDA effected?
decreased
you can’t make enough red blood cells because there’s not enough iron around
what iron studies can definitively confirm IDA?
CBC isn’t enough because it may have similarities to ACD
- serum iron
- TIBC
- serum ferritin
- % transferrin saturation
how is the serum iron in IDA effected?
decreased
non-diagnostic alone because iron is decreased in both iron deficiency and anemia of chronic disease
how is the TIBC in IDA effected?
TIBC increases
this is a measure of how many binding sites are available for iron on the transferrin molecule
in iron-deficiency anemia, since there is little iron around, the TIBC goes up
how is the serum ferritin in IDA effected?
decreased ferritin levels
ferritin is an iron storage protein that is proportional to total body iron stores
low ferritin is virtually diagnostic for iron deficiency
sometimes though, ferritin can be elevated in conditions like systemic inflammation so a normal or high ferritin level doesn’t rule out IDA
so if ferritin is low, definitely IDA
but if ferritin is normal or high, you don’t know if it’s IDA or not
how is % transferrin saturation effected in IDA?
it’s decreased
since there is little iron around, the percent of transferrin binding sites that are saturated with iron is low
Which parameter on iron panel is most reliable for determining iron deficiency?
Serum ferritin is most reliable because low levels are highly specific for iron deficiency
what does an IDA blood smear show?
- less RBCs = lots of white space between cells
- RBCs look paler due to decreased Hb content = hyperchromic
- anisocytosis
- elliptocytes
- reactive thrombocytosis may be present
how do you evaluate chromasia of RBC?
chromasia = amount of Hb in RBC
look at the zone of central pallor which should be 1/3 of cell diameter
in IDA, zone of pallor is increased
what is anisocytosis?
that a patient’s red blood cells are of unequal size
can you see anisocytosis in blood smear of IDA?
yup
there are some little cells (these are the newer ones) and some larger ones (these are older, and are bigger because there was more iron around then)
what is the feared cause of IDA in older males or post-menopausal women
occult gastrointestinal bleeding from a gastrointestinal malignancy such as colon cancer
should be evaluated with a colonoscopy to rule out any potential bleeding or masses
how do you treat IDA?
figure out the underlying cause
once the cause of iron deficiency is identified, treatment is targeted towards the underlying etiology in addition to supportive treatment, including iron replacement
when would iron supplement be given via IV instead of orally?
given to patients who cannot tolerate oral iron or those with inflammatory bowel disease, gastric bypass surgery, or malabsorption syndromes
what impairs absorption of iron if it’s given orally?
Calcium, phytates, and tannates
so iron shouldn’t be given with milk, eggs, or cereal
what enhances iron absorption if it’s given orally?
iron absorption is enhanced in an acidic environment
so it’s usually given with vitamin C or orange juice
what are some side effects of oral iron supplements?
- gastrointestinal upset
- constipation,
- dyspepsia
- nausea
