peds - hematology

in peripheral blood smear, RBC size should roughly be that of

small lymphocytes like B and T cells (8 microns)

- if smaller = microcytic

- if larger = macrocytic

due to the shape of RBC, hemoglobin is concentrated

at the edges (giving the donut appearance on peripheral blood smear)

value of peripheral blood smear

confirm CBC values

examine RBC/WBC morphologies

examine for immature precursors (like reticulocytes)

CBC

RBC

WBC

platelets

Hb

Htc

MCV

MCHC

abnormal readings on CBC printout should be confirmed with

peripheral blood smear

high reticulocyte count indicates

active bleeding or destruction of erythrocytes

- indicates that red blood cells are being made

potential causes of high reticulocyte count

hemolysis

blood loss

anemias

low reticulocyte count indicates

bone marrow suppression

normal reticulocyte count

1-2% of TRBC

mature red blood cells lack

nucleus and mitochondria

mature red blood cell shape

biconcave

spherocyte

red blood cell that assumes a spherical shape (lacks characteristic biconcave shape)

reticulocyte appearance

erythrocyte with nuclear fragmentation (mature RBCs do not have nucleus)

normal RBC size

8 microns

3 microns thick at edges, 1 micron thick in center

RBC primary function

respiratory gas exchange

where are hemoglobin oxygen binding sites fully saturated

in the alveoli

how much oxygen normally dissociates from hemoglobin in tissue capillary beds

25%

oxygen dissociation may be affected by

temperature

pH

2,3 BPG

how does 2,3 BPG affect oxygen dissociation

decreases the affinity for oxygen, improving offloading to tissues

- production is increased at higher altitudes at the expense of ATP production during glycolysis

how does temperature affect oxygen dissociation

increased body temperature (fever) favors offloading of oxygen (decreases Hb affinity for oxygen)

how does pH affect oxygen dissociation

lower pH favors dissociation (decreases Hb affinity for oxygen)

how is decreased affinity of hemoglobin for oxygen reflected on a dissociation curve

right shift

- increased temp

- decreased pH

- increased 2,3 - BPG

erythropoietin is made in

kidneys

why are patients with CKD usually anemic

EPO is produced in the kidneys

decreased hemoglobin concentration eventually leads to

tissue hypoxia, which triggers erythropoietin release

normal hemoglobin concentration at birth

16.5 g/dl

normal hemoglobin concentration at 1 month

14 g/dl

normal hemoglobin concentration at 3 to 6 months

11.5 g/dl

normal hemoglobin concentration at 6 months to 2 years

12 g/dl

normal hemoglobin concentration in adult males

15.5 g/dl

normal hemoglobin concentration in adult females

14 g/dl

normal MCV at birth

108

normal MCV at 1 month

104

normal MCV at 3 to 6 months

91

normal MCV at 6 months to 2 years

78 (increases steadily to 90 in adults)

normal MCV in adults

90

anemia is defined as

red blood cell mass 2 STANDARD DEVIATIONS BELOW mean for age, sex, and race

high MCV

macrocytic

low MCV

microcytic

low hemoglobin concentration

anemia

low hemoglobin concentration with normal MCV

normocytic anemia

low hemoglobin concentration with high MCV

macrocytic anemia

low hemoglobin concentration with low MCV

microcytic anemia

low MCHC

hypochromic

high MCHC

Hyperchromic (rare)

anemia may result from

bone marrow suppression

destruction of RBCS

hemorrhage

aplastic anemia

anemia caused by bone marrow suppression

- very low reticulocyte count

most common cause of hypochromic microcytic anemia

iron deficiency anemia

DDx hypochromic microcytic anemia (4)

iron deficiency

thalassemia minor

lead poisoning

chronic infection

MCV calculation

(Htc x 10)/RBC

MCHC calculation

(Hb x 100)/Htc

normal hematocrit

40 to 45%

classic signs of anemia

palor

fatigue

most common pediatric anemia

iron deficiency anemia

iron deficiency anemia

hypochromic microcytic (low MCHC, low MCV, low Hb)

pediatric recommendation for hemoglobin screening

at birth

- again at 4 months if high risk

- if normal, at 12 months during 1 year wellness exam

when is iron deficiency anemia rare in pediatrics

first 6 months

following screening at birth, why is hemoglobin screening not performed again until 12 months

iron deficiency anemias are the most common anemia in children and they are rare in the first 6 months due to adequate levels of iron in breastmilk and formula

- in addition:

- accumulation of maternal Fe occurs mostly during last 3 months of gestation and if the baby is full term there is buffer to utilize Fe stores

- RBCs have 120 day lifespan

when is iron deficiency anemia most likely to be seen in a pediatric patient

10 to 18 months

RBC lifespan

120 days

babies who are exclusively fed cow's milk are likely deficient in

iron

pediatric iron deficiency anemia is most likely to be seen in

children 10 to 18 months of age, especially those who are/were fed cow's milk

folate deficiency anemia

macrocytic anemia

complications of iron deficiency anemia in children

usually asymptomatic but if severe:

- irritability

- decreased IQ

cow's milk should not be given to children under the age of

1

red blood cells in iron deficiency anemia (3)

microcytic

hypochromic

cigar cells

cigar cells

iron deficiency anemia

koilonychia

spooning of fingernails seen in children with iron deficiency anemia

thalassemia minor

Beta-globin chain disorder in which only one gene is defective

usually asymptomatic

results in hypochromic microcytic anemia (can be confused with iron deficiency anemia despite normal iron levels)

thalassemia minor anemia

hypochromic microcytic

Hb in thalassemia minor

low, but greater than 9

thalassemia minor vs iron deficiency anemia: MCV/RBC

MCV/RBC >13.5 suggests iron deficiency

MCV/RBC < 11.5 suggests thalassemia minor

Mentzer index

MCV/RBC

mentzer index useful for distinguishing between

thalassemia minor and iron deficiency anemia

- greater than 13.5 suggests IDA

- less than 11.5 suggests thalassemia minor

ways to distinguish between thal minor and IDA

mentzer index (MCV/RBC)

therapeutic trial of iron

serum iron/TIBC/serum ferritin

therapeutic trial of iron

3 mg/Kg of iron given to patient with hypochromic microcytic anemia, follow up in 6 weeks

if Hb concentration has returned to normal deficiency = IDA

if Hb has not returned to normal, perform Hb electrophoresis

diagnosis of thalassemia minor is made via

hemoglobin electrophoresis

IDA vs Thal minor: serum iron, TIBC, serum ferritin

IDA: low serum iron, high total iron binding capacity, low serum ferritin

thal minor: normal, normal, normal

following a therapeutic trial of iron, if a patient's hemoglobin concentration is still low what is the next step

order hemoglobin electrophoresis

anemia seen in lead intoxication

microcytic hypochromic

basophilic stippling

lead poisoning and thalassemia

pediatric recommendation for lead screening

all children on medicaid at 12 months and 24 months should receive serum lead screen

thalassemia major

Associated with a severe hemolytic anemia (microcytic hypochromic)

minor has a mild hemolytic anemia (microcytic hypochromic)

complete failure of beta globin chain synthesis, aggregation of alpha chains resulting in larger/round RBCs that cant fit through splenic sinusoids and are lysed

associated with bone marrow expansions (most notably of the face) with resulting skeletal deformities

- attempt to compensate for ongoing anemia

Fe is actually elevated and chelation therapy is often required

clinical findings of hemolytic anemias

low Hb

high reticulocyte count

elevated bilirubin/jaundice

dark urine

in hemolytic anemias, hematopoiesis often occurs in

EXTRAMEDULLARY locations

- resulting in enlargement of sites not normally active in hematopoiesis (enlargement of facial bones)

- bone marrow expansion

why does maxillary hyperplasia occur in thalassemia major

bone marrow expansion to compensate for ongoing chronic severe hemolytic anemia

neurological complications of lead poisoning

psychomotor retardation

seizures

encephalopathy

lead levels in children should be less than

10 mcg/dl

GI symptoms of lead poisoning

AP/V

constipation

etiology of pediatric lead poisoning

child beginning to crawl, eating lead paint chips (diagnosis usually involves history of pica)

recent home remodeling

excessive environmental intake (water)

pica

compulsive eating of nonnutritive substances such as clay or ice

lead poisoning on xray

increased density (heavy metals deposit in bones) especially in metaphyses: lead lines

lead lines

increased density in the metaphyses, indicative of lead poisoning

MCV >100

macrocytic anemia

megaloblastic anemia

MCV > 100

causes of macrocytic anemia

Folate and B12 deficiency

phenytoin use (induces folate deficiency)

folate deficiency in children may result from excessive consumption of

goat's milk (low in Fe and B9)

patients taking phenytoin long term may become deficient in

folate

hereditary spherocytosis

autosomal dominant RBC membrane defect of spectrin, causing RBC to lose their characterisitc biconcave shape

why is spherocytosis of concern

the loss of biconcave shape prevents RBC from passing through splenic sinusoids, resulting in hemolysis