ch 22a: physiologic and behavioral adaptations of newborn

4 factors that stimulate breathing

chemical, mechanical, thermal, and sensory factors

chemical respiratory stimulation

during labor/contraction = dec BF and O2 to fetus

• transient fetal hypoxia & hypercarbia

↓ Po₂, ↑ Pco₂, ↓ pH → stimulate respiratory center in medulla (breathing)

Cord clamping → ↓ prostaglandins → removes respiratory inhibition

Mechanical factors

vaginal delivery = chest compression =↑inc intrathoracic pressure

birth = released pressure = negative pressure

negative pressure → air drawn into lungs

Crying = distributes air, expands alveoli, keeps them open

thermal factor

baby born = exposure to colder extrauterine temp

Cold stimulates skin receptors

Activates medulla → triggers breathing

sensory

Sensory input: handling, suctioning, drying

Environmental stimuli: lights, sounds, smells

All stimulate respiratory center → breathing initiated

establishing respiration: vaginal vs c/s babies

• at term/during pregananacy

• pre-labor

• during labor

• if c/s?

• which can lead to 2

at term, fetal lungs hold fluids; eventually, air substitute fluids

vaginal thoracic squeeze clears fluid

Pre-labor changes: Less lung fluid production, decreased alveolar fluid.

C-section without labor may lead to retained lung fluid and increased risk of transient tachypnea of the newborn (TTN).

TTN

• looks like

• s/s 4

• resolves?

• intervention

usually shows as signs of respiratory distress

Tachypnea up to 100 bpm

intermittent grunting, nasal flaring, and mild retractions

resolves in 48 to 72 hours

supplemtal O2

Respiratory Patterns/characteristics in Newborns

• rate and rhythm

Normal rate: 30–60 breaths/min.

shallow and irregular

Periodic breathing: Pauses <20 sec are normal during REM sleep; decrease with age.

how do they breath

lung sounds?

• just read

nose breathers: helps coordinate sucking, swallowing, and breathing

Breath sounds should be clear and equal bilaterally

• fine rales normal early on (first few hours).

Abdominal breathing is normal

Signs of respiratory distress 6

abnormal RR apnea/tachynpea: <30 or >60 breaths/min at rest

Seesaw/paradoxical respirations (abdomen rises, chest falls) → abnormal

Nasal flaring

retractions

Grunting

color changes: pallor and central cyanosis

acrocyanosis vs central cyanosis

Acrocyanosis (hands/feet blue) = normal for first 24 hrs

Central cyanosis (lips, mucous membranes blue) = abnormal

• Indicates hypoxemia, poor perfusion, or cardiac issues; Late sign of distress

cardiovascular system

• lung and cirulatory shift

baby’s first breath = dec pulmonary vascular resistance

Pulmonary artery pressure drops → ↓ right atrial pressure

↑ pulmonary blood flow to left atrium → ↑ pressure → functional closure of foramen ovale

ductus arteriosus

• how does it close

• if it doesn’t close?

Inc blood oxygen levels triggers ductus arteriosus constriction

eventually, closes and becomes a ligament

Patent ductus arteriosus can cause heart murmur

Umbilical Vessel, Hypogastric arteries, Ductus Venosus

• Cord clamping = functional closure of:

  • Umbilical arteries

  • Umbilical vein

  • Ductus venosus

• These become ligaments over 2–3 months

• Hypogastric arteries also occlude and become ligaments

heart rate and sounds/murmurs

apical HR: 120 -160 bpm (range 85-180)

• slower in deep sleep; inc when crying

• CONTEXT matters

transient murmurs resolve by 6 months

• Evaluate if murmur + signs (poor feeding, apnea, cyanosis, pallor)

hematopoietic system:

• rbc, hgb, hct

• sampling site

rbc/hgb/hct is higher at birth and decreases over time

rbc: 4.6–5.2 million/mm³

Hemoglobin: 14–24 g/dL → drops to 12–20 g/dL by 2 weeks

hct: 51–56% at birth → rises slightly → 39–59% by 8 weeks

sampling site matters

• Capillary blood yields higher values than venous blood.

fetal polycythemia

• what is it

• causes/rfs(3/4)

hct > 65%

causes

• Delayed cord clamping (DCC)

• Maternal HTN, diabetes

• Intrauterine growth restriction (IUGR)

WBC

• range?

• leukocytosis?

• sepsis may show as what lab?

• later sign?

WBC count at birth: 9-30

Leukocytosis is normal initially

Sepsis: May show ↑ neutrophils — but some infants have no WBC elevation despite symptoms

• high temp/fever is usually a later sign

newborn physical characteristics that puts them at risk for inc heat loss 2

dec subq adipose layer

surface to body mass ratio is greater than adults

Four Modes of Heat Loss

evaporation

conduction

convection

radiation

evaporation

• define

• example/apply to delivery

• Prevention 2

Heat loss when liquid converts to vapor.

Amniotic fluid or bath water drying from skin

prevention

• there has to be water present, so to prevent

  • Dry infant immediately after birth or bathing.

  • Minimize moisture on skin.

radiation

• def

• example

• prev 2

Heat loss to cooler surfaces not in direct contact

Example: Near cold windows or walls.

prev:

• Keep infant away from windows/drafts.

• Avoid placing baby near cold surfaces

conduction

• def, ex, prev (3)

Definition: Heat loss to cold surfaces in direct contact.

Example: Cold scale, blankets, or exam table.

prevention

• Use prewarmed radiant warmers

• Place protective covers on cold surfaces.

• Encourage skin-to-skin contact with mother.

convection

• def

• example

• prevention (2)

Definition: Heat loss to cooler surrounding air.

Example: Cold room air or drafts.

prevention

• Keep room warm

• Wrap infant in warm blankets and hat

thermogenesis in newborns 4

Triggered by cold exposure, but they do not shiver to produce heat

• increase in muscle activity (crying)

• Flexed posture (less surface area exposed)

• Peripheral vasoconstriction (reduces heat loss)

• brown fat

Cold Stress & Hypothermia

• initial signs 3

pale, mottled skin

acrocyanosis

Cold extremities.

body’s response/metabolic effects to hypothermia

• 3 processes

inc risk for 1

inc o2 demand = inc rr ; inc o2 consumption

vasoconstriction = dec pulm perfusion = hypoxemia and acidosis (low o2 and ph)

Hypoglycemia from depleted glucose stores

• inc risk for resp distress

renal system

baby have limited capacity to concentrate urine = frequent urinary output

First void should occur within 24 hrs — notify provider if absent

brick dust and weight loss

BD: uric acid crystals; normal first week; abnormal after

weight loss: 5–10% in first 3–5 days from fluid loss; usually gained in 2 weeks

GI system

• digestion/enzymes

• sucking

• intestinal flora

most digestive enzymes except amylase and lipase

• hence breastmilk/formula

• Newborns digest simple carbs & proteins well

• Limited fat digestion; aided by mammary lipase

mouth should have good latching and sucking/swallowing

• Sucking pads in cheeks; labial tubercles on lips

• coordinated suck-swallow-breathe

intestinal flora

• helps make vit K

• babies have sterile gut: not enough flora/biome for vit k

Gi system: stools

Meconium (green-black, viscous) passed in first 12–24 hrs (by 48 hrs max)

Early feeding → earlier stooling

Transitional stools appear between meconium and milk stools

Breastfed stools: yellow, seedy, more frequent

Formula stools: pale yellow or brown, firmer

hepatic system: general functions 4/5

Iron storage

Glucose & fatty acid metabolism

Bilirubin synthesis

Coagulation

Iron storage

fetal liver begins storing iron in utero

Iron stores last ~4 months in term infants.

• Lower in preterm/SGA infants → depletes sooner.

Breast milk iron = more bioavailable than cow's milk.

coagulation

Liver makes clotting factors activated by vitamin K.

Newborns lack gut bacteria to synthesize vit. K → risk for VKDB.

Vitamin K injection at birth prevents bleeding.

Monitor for bleeding, especially after circumcision.

bilirubin synthesis

• just what rbc breaks down to/types of bilirubin

RBC breakdown → heme → bilirubin (un)conjugated

If it becomes conjugated: water soluble; excreted into urine/feces

if Unconjugated bilirubin = not water-soluble → binds to albumin.

jaundice

• type

• what causes it/patho

can be physiologic or pathologic

usually from excess free bilirubin (not bound to albumin)

physiologic

• is it normal?

• when does it appear?

• peak?

• declines?

normal

Appears after 24 hrs, resolves naturally.

Peaks at 72–96 hrs, declines by week 2.

pathologic

• what is it/dx criteria

• complication

Appears <24 hrs, lasts >2 wks, or TSB >95th percentile.

cross the blood-brain barrier

• neurotoxicity (acute bilirubin encephalopathy/kernicterus

rfs 7

• Preterm

• Breastfeeding: especially if exclusively breastfeeding and weight loss is excessive

• Rh- or ABO incompatibility or other known hemolytic

• Polycythemia

• Asian or Native American race

• Bruising related to birth trauma

• Previous sibling who received phototherapy

rhogam for this

Rhogam covers 12 weeks

• given at 28 weeks and then at term/birth

given early if

• some sort of placental trauma/eruption (can cause maternal and fetal blood to mix) in RH- mom

• leads to antibody reaction and possibly spontaneous abortion

• DV, fall, trauma, MVA etc

• any form of abdominal complaint in rh- mom