pediatric fundamentals growth and development drs. greg and joy loy gordon january 2005

Pediatric Fundamentals

Growth and Development

Drs. Greg and Joy Loy GordonJanuary 2005

Pediatric Fundamentals - Growth and Development

Maturational change in form and function

Prenatal GrowthGestational age (wks) Mean birth wt (Gm)

25 85028 100030 140033 190037 290040 3500

Postnatal GrowthBirth weight doubles by 5 months

triples by 1 yearBirth length doubles by 4 years


Maturational change in form and function

Percent body waterTerm newborn 801 year old 70Adult 60

Surface area:Weightpremature > full term > infant > childgreater surface area

greater evaporative heat lossrapid hypothermia if unprotected

Girls Boys

Puberty onset 11 years 11½ years

Peak growth Tanner stage 3 Tanner stage 4


Metabolism of one calorie of energy consumes one ml of H2O,

so fluid requirements thought to reflect caloric requirement:

Body weight (kg) Calories needed (kcal/kg/day) = Fluid requirement (ml/kg/day)

0-10 100

10-20 1000 + 50/(kg>10)

> 20 1500 + 20/(kg>20)

Dividing by 24 (hours/day) yields the famous

4:2:1 Rule for hourly maintenance fluid:

4 ml/kg/hr 1st 10 kg +

2 ml/kg/hr 2nd 10 kg +

1 ml/kg/hr for each kg > 20

Fluid requirements


Airway/respiratory system

Gas exchange first possible approximately 24 weeks gestationSurfactant production appears by approximately 27 weeks

produced of Type II pneumocytesexogenous form available

Number (and size) of alveoli increase to age 8 years(size only after 8 years)

First breaths of airpneumothorax or pneumomediastinum less than 1%several hours to reach normal lower lung fluid levels

some expelled during birth canal compressiontransient tachypnea of newborn (TTN)

increased incidence after C-section


Respiratory rate/rhythmpauses up to 10 seconds normal in prematures

without cyanosis or bradycardiaAge (years) Normal Rate1 - 2 20 - 402 - 3 20 – 307 - 8 15 - 25

Obligate nose breathing

especially prematures

able to mouth breath if nares occluded

80% of term neonates

almost all term infants by 5 months


Airway differences – infant vs adultepiglottis and tongue relatively largerglottis more superior, at level of C3 (vs C4 or 5)cricoid ring narrower than vocal cord aperture

until approx 8 years of age 4.5 mm in term neonate11 mm at 14 years


Cardiovascular system

In utero circulationplacenta ->umbilical vein (UV)-> ductus venosus (50%) -> IVC -> RA ->foramen ovale (FO) ->LA -> Ascending Ao ->SVC -> RA ->tricuspid valve ->RV (2/3rds of CO) -> main pulmonary artery (MPA) ->ductus arteriosus (DA) (90%) ->descending Ao ->umbilical arteries (UAs)->


Transition to postnatal circulation


Loss of large low-resistance peripheral vascular bed, the placenta

(UV, UAs constrict over several days)

With first air breathing

marked drop in pulmonary vascular resistance with

greatly increased pulmonary blood flow

LA pressure > RA pressure

closes FO

Elevated PaO2 constricts DA

hours to days

Hgb F impairs postnatalO2 delivery

Higher newborn resting cardiac index

with decreased ability to further increase



Normal murmurs

up to 80% of normal children

vibratory Still’s murmur

basal systolic ejection murmur

physiologic peripheral pulmonic stenosis (PSS)

venous hum

carotid bruit

S3

Murmur only in diastole = abnormal


Gastrointestinal notes

Gastric pH higher at birth; decreases over several weeksYoung infants

diminished lower esophageal sphincter tone50% have daily emesis (usually remits by 18 months)more show reflux if esophageal pH monitoredonly 1 in 600 develop complications of reflux

Physiologic jaundiceColic < 3 monthsUmbilical hernia

commonfrequently resolve spontaneously

Teethprimary: 7 months to 2 or 3 yearspermanent: 6 years to 20 years


Renal system

Urine production begins first trimester

Newborn

GFR

low (correlates with gestational age/size in prematures)

rises sharply first 2 weeks

adult values by age 2 years

limited concentrating ability (600 vs adult 1200 mOsm/kg)

ability to dilute urine relatively intact


Hematologic system

Infant Hgb F – higher O2 affinity

Hgb A production largely replaces Hgb F by 4 months

Hgb/Hct decrease to nadir at about age 2 months

exaggerated in prematures (low total body Fe stores)

Blood volume (ml/kg)

Prematures 105

Term newborn 85

Adult 65


General pharmacotherapeutic note:

On a per kg basis compared to adults

Expect lower doses in infants and

Higher doses in children


Neuro notes

Nervous system anatomically complete at birth except:

Myelination

rapid for 2 years

complete by 7 years

Posterior fontanelle closed by 6 weeks

Anterior fontanelle closed by 18 months

Primitive reflexes disappear in few months


Developmental pediatrics

History and physical notes

Newborn – pregnancy and delivery

Infancy – developmental milestones

Toddler – poor localization of symptoms and very suggestible

(e.g., pharyngitis or pneumonia presenting as

abdominal pain or distress)

Older child – involve in discussion/decision

Preadolescent and older – consider interview without parents

Exam

opportunistic approach in infants and young children

observation essential

distraction useful


Developmental pediatrics

Approach to patient depends on stage of developmentStranger anxiety 7 months 25%

9 50 12 75

Toddlersmagical thinking (belief that own thought or deed causes external events)temper tantrums (aggravated if tired, ill, uncomfortable)

Toilet trainingability develops by 18 monthsusually complete by 2 to 3 years (day before night)bedwetting

15 - 20 % at 5 years with gradual decrease to 1% at 15 years

6 -11 years - concrete operations phasecan consider different points of viewdevelop explanation based on observationbeginning logical reasoning but still tend to dogmatic

11 and older - development of abstract thinkingAdolescent - increasing need for autonomy, participation in care

http://metrohealthanesthesia.com/edu/ped/pedspreop3.htm


For more info regarding age-related preparation of the

pediatric patient for anesthesia see:

http://metrohealthanesthesia.com/edu/ped/pedspreop3.htm

pediatric fundamentals growth and development drs. greg and joy loy gordon january 2005

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