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Chapter 17 Pediatric and Geriatric

Hematology

PEDIATRIC HEMATOLOGY

Dramatic changes occurs in the bloodand bone marrow of the newborn infant

during the first hours and days after

birth, and there are rapid fluctuations inthe quantities of hematologic elements

Significant hematologic differences areseen between term and preterm infants

and among newborns, infants, young

children, and older children

Prenatal Hematopoiesis

Begins in the first weeks of embryonicdevelopment

Three phases of development:a) Mesoblastic (yolk sac)b) Hepatic (liver)c) Myeloid (bone marrow)

First cells produced in the developingembryo are primitive erythroblasts

formed in the yolk sac

By the second month of gestation,hematopoiesis ceases in the yolk sac,

and the liver becomes the center for

hematopoiesis, reaching its peak activity

during the third and fourth gestationalmonth

During the fourth and fifth gestationalmonths, the bone marrow emerges as a

major site of blood cell production, and

it becomes the primary site by birth

Hematopoiesis of the New Born

Active bone marrow is referred to as thered marrow

Inactive fatty bone marrow is referred toas the yellow marrow

In a full term infant, hepatichematopoiesis has ceased and continues

to develop in the bone marrow

Postembryonic extramedullaryhematopoiesis is abnormal in a full term

infant

In a premature infant, the center ofactivity of hematopoiesis are frequently

seen in the liver and occasionally

observed in the spleen, lymph nodes or

thymus

Pediatric Developmental Stages

Neonatal period: first 4 weeks of life Infancy: first year of life Childhood: age 1 to puberty(8 to 12yo) Pediatric patients has higher normal

values on hematologic test

NRBC are usually found on peripheralblood smears of babies

Gestational Age

Full term: 37 to 42 weeks Premature or preterm: less than 37

weeks

Postterm: 42 weeks Low birth weight (micropreemies): 24 to26 weeks

Birth Weight Classification

Appropriate size for gestational age Small for gestational age (2.5 kg or less) Very low birth weight (1.5 kg or less) Extremely low birth weight (0.5 kg or

less)

Large for gestational age (4kg or more)Red Blood Cell Values at Birth

Neonatal hematologic values areaffected by the gestational age of the

infant, the age in hours after delivery,

the presence of illness and the level of

support required

The presence of fetal hemoglobin (HbF),bilirubin, and lipids in newborn can also

interfere with hematology testing

Red Blood Cell Count

RBC count is increased during the 1st 24hours of life, and remains steady for 2

weeks, then slowly declines, this is

called polycythemia of the newborn

Polycythemia of the newborn can beexplained by in utero hypoxia

Physiologic anemia is seen in 5 to 8weeks of life

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RBC reaches its lowest count at 7 weeksof age

Hemoglobin reaches its lowestconcentration at 9 weeks of age

Erythrocyte Morphology of the Neonate

Erythrocyte remains macrocytic fromthe first 11 weeks of gestation until day

5 of postnatal life

Orthochromic normoblasts frequentlyare observed in the full term infant on

the first day of life but disappear within

postnatal days 3 to 5

NRBC may persist longer than a week inimmature infants

Average number of NRBCs ranges from 3to 10 per 100 WBCs in a normal full

term infant to 25 NRBCs per 100 WBCsin a premature infant

The presence of NRBCs for more than 5days suggests hemolysis, hypoxic stress

or acute infection

Additional erythrocytic differences(biconcave disk relative to

stomatocytes):

a) Neonates (43% disk, 40%stomatocytes)

b) Adults (78% disk, 18%stomatocytes)

c) Premature infants (40% disk,30% stomatocytes, 27%

additional poikilocytes)

Reticulocyte Count

90% reticulocytes during 12 weeks ofgestation

15% reticulocytes during 6 monthsgestation

4% to 6% reticulocytes at birth Reticulocytosis persist for 3 days after

birth, then declines abruptly to 0.8%

reticulocytes on postnatal day 4 to 7

At 2 months the number of reticulocytesincrease slightly, followed by a slight

decline from 3 months to 2 years, when

adult levels of 0.5% to 1.5% are attained

Reticulocyte count of premature infantsis typically higher that that of term

infants

Significant polychromasia is indicativeof postnatal Reticulocytosis

Hemoglobin

Full Term Infants

At birth HbF constitutes 70% to 80% ofthe total hemoglobin

HbF declines from (90% - 95%) at 30weeks to 7% at 12 weeks after birth

HbF stabilizes at 3.2 + 2.1% at 16 to 20weeks after birth

The switch from HbF to HbA isgenetically controlled and determined

by gestational age

Capillary samples from new born havehigher hemoglobin concentration than

venous samples, which can be attributedto circulatory factors

The average Hb for a full term infant atbirth is 16.5 to 12.5 g/dl

Less than 14 g/dl are consideredabnormal for full term infants

Average Hb value for a preterm infantwho is small for gestational age is 17.1

g/dl

Hb values less than 13.7 g/dl isconsidered abnormal for preterm infants

Physiologic Anemia for Neonate

Hb concentration of term infantsdecreases during the first 5 to 8 weeks

of life, a condition known as physiologic

anemia od infancy

Infants born prematurely alsoexperience a decrease in Hb

concentration, which is termed

physiologic anemia of prematurity

Contributing to the physiologic anemiais the shortened life span of the fetal RBC

Chromium labeled newborn RBCsestimate a survival time of 60 to 70 days

Life span of RBCs in premature infants isabout 35 to 50 days

The more immature the infant, thegreater the degree of reduction

Hemodilution related to the increasedblood volume that accompanies the

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rapid weight gain can be seen in the first

few months of life is not thought to paly

a key role in anemia

Hb levels of premature infants aretypically 1g/dl or more bellow the

values of full term infants

Very low weight infants show aprogressive decline in Hb, RBC count,MCV, MCH, MCHC, and have a slower

recovery than other preterm and term

infants

Hematocrit

The average Hct at birth for full terminfants is 53%

Newborn with increased Hct, especiallyvalues greater than 65% experience

hyperviscousity of the blood

Hct increases approximately 5% duringthe first 48 postnatal hours followed by

a slow linear decline to 46% to 62% at 2

weeks and 32% to 51% between the

second and fourth months

Normal adult values of 47% (males) and42% (females) are achieved during

adolescence

Very low birth weight preterm infantsare frequently anemic at birth

Red Blood Cell Indices

Mean Cell Volume

Erythrocytes of newborn infants aremarked macrocytic at birth

Average MCV for full term infants is 110+ 15 fL

A sharp decrease occurs during the first24 hours of life

MCV continues to decrease to 90 + 12fLin 3 to 4 months

The more premature the infant, thehigher the MCV

A newborn with an MCV of less than 94fL should be evaluated for a-thalassemia

or iron deficiency

Mean Cell Hemoglobin

MCV is 30 to 42 pg in healthy neonates MCV is 27 to 41 pg in premature infants

Mean Cell Hemoglobin Concentration

Average MCHC is 33 g/dl for infants andadults

Red Blood Cell Distribution Width

RDW is markedly elevated in newborns,with a range of 14.2% to 19.9% in the

first 30 days of life then it graduallydecreases and reaches normal adult

levels in 6 months

Anemia in Infants and Children

Iron Deficiency Anemia

Most common pediatric hematologicdisorder

Most frequent cause of anemia onchildhood

Prevalence is still 2% in toddlers 1 to 2years of age and 3% in children 3 to 5

days of age

Ancillary Tests for Anemia in Infants and

Children

Haptoglobulin level is low as to beundetected in neonates

Transferrin levels are also low inneonates, increasing rapidly after birth

and reaching normal adult values in 6months

Serum ferritin and serum iron are highat birth, rise during the first month, drop

to their lowest level between 6 months

and 4 years of age and remain low

through out childhood

White Blood Cell Values in the Newborn