ch 17

Introduction

• neonatal period: the first 28 days of life

Physiologic Transitioning

• “golden hour of life” = the first hour of life

• A newborn's most rapid and critical transitions after birth happen in four connected areas: the respiratory system, the circulatory system, thermoregulation, and their ability to stabilize their blood glucose levels

Respiratory System Adaptations

• At birth, the responsibility for gas exchange shifts from the placenta to the newborn’s lungs

  • transition includes lung aeration, starting pulmonary gas exchange, and converting fetal circulation to adult circulation.

• Lung aeration: the process of filling the newborn’s lungs with air for the first time after birth

  • The newborn's first breath is a gasp, increasing transpulmonary pressure and pulling the diaphragm downward.

  • this creates functional residual capacity (the ability to retain air in the lungs after exhaling) allowing pulmonary gas exchange to begin

  • As the lungs expand with air, tidal volume increases, allowing more air into the lungs

• factors triggering breathing: hypercapnia (high CO₂), hypoxia, and acidosis from labor as well as pressure changes, noise, light, temperature changes, touching, compression of the fetal chest during the birthing process, and low O₂ blood concentrations

• Surfactant : a surface tension–reducing lipoprotein found in the lungs that prevents alveolar collapse at the end of expiration, lung atelectasis, and loss of lung volume

  • lines the alveoli to lower the pressure required to open the alveoli

  • production starts at ~26 weeks gestation and reaches maturity levels at ~35 weeks

• the chest wall is floppy due to high cartilage and underdeveloped muscles, making accessory muscles for breathing ineffective

• If amniotic fluid is removed too slowly or incompletely from airways after birth, tachypnea (above 60 bpm) occurs

  • happens during c-sections, fast deliveries, or sedation of the newborn (less thoracic compression)

  • thoracic compression is needed to prevent this

Lungs

• must occur for lungs to maintain respiratory function:

  • Initiation of respiratory movement

  • Expansion of the lungs

  • Establishment of functional residual capacity

  • Increased pulmonary blood flow

  • Redistribution of CO

Respirations

• 30-60 bpm; shallow and irregular with short periods of apnea (less than 15 seconds)

  • should not be labored

  • periodic breathing: cessation of breathing lasting 5-10 seconds without changes in color or heart rate

  • Apneic periods lasting more than 20 seconds with cyanosis, pallor, and HR changes require further evaluation

• Signs of respiratory distress: central cyanosis, tachypnea, expiratory grunting, sternal retractions, and nasal flaring

CV System

Fetal to Neonatal Circulation Changes

• clamped umbilical cord → first breath is taken → lungs begin to function → increased systemic (blood to body) vascular resistance, decreased right-sided heart pressures (blood from body to lungs), decreased pulmonary (blood to lungs) vascular resistance, increased pulmonary blood flow

  • increased systemic pressure → left-sided heart pressures increases (blood from lungs to body)

  • pulmonary vascular resistance decreases at birth → pulmonary blood flow increases and oxygen exchange occurs in the lungs

  • Onset of respirations causes a rise in PO2 in the lungs and a decrease in pulmonary vascular resistance

• newborn’s first breath → air pushes into the lungs → triggers an increase in pulmonary blood flow and pulmonary venous return to the left side of the heart → pressure in the left atrium becomes higher than in the right atrium

• The two umbilical arteries and one umbilical vein begin to constrict at birth because, with placental expulsion, blood flow ceases and peripheral circulation increases

HR

• ~110 to 160 bpm the first few mins after birth, but decreases to an average of 120 to 140 bpm

Hematologic System Adaptations

Blood Volume

• depends on the amount of blood transferred from the placenta at birth

• Waiting to clamp the umbilical cord increases blood volume available to perfuse the lungs of the newborn after birth

  • current recommendation: delay cord clamping until 30-60 seconds after birth

  • provides higher hemoglobin levels, prevents iron-deficiency anemia at 3-6 months of age, improves myelin brain volume to 12 months of age, improves neurodevelopmental outcomes at 4 years of age

  • Cord clamping should not delay newborn resuscitation or care when the mother or baby’s safety is at risk.

Blood Components

• Fetal RBCs are better at grabbing oxygen even when there isn’t much oxygen around — better than adult RBCs.

  • “they have a greater affinity for oxygen at a lower oxygen pressure than adult RBCs”

• newborn RBC count gradually increases as cell size decreases since the cells are adapting to the higher oxygen levels outside the womb

• newborn RBCs lifespan: 80-100 days (adults = 120 days)

• Newborns have higher hemoglobin levels right after birth, peaking at 4–6 hours, then gradually decreasing over the next 12–18 hours and months.

  • This is due to a natural decline in RBC mass, known as physiologic anemia of infancy.

• Leukocytosis (elevated WBCs) is present as a result of birth trauma soon after birth.

• newborn platelet count and aggregation ability are the same as those of adults

Body Temperature Regulation

• newborn temp ranges from 97.9-99.7°F (36.6°C to 37.6°C)

• first line prevention for mild hypothermia in low-risk newborns: skin-to-skin care

Heat Loss

• predisposing factors: thin skin with blood vessels close to the surface, lack of shivering ability until 3 months old, limited use of voluntary muscle activity or movement to produce heat, large surface area-to-body mass ratio, lack of subq fat, little ability to conserve heat by changing posture (fetal position)

• Conduction: the transfer of heat between two objects when they’re in direct contact with each other

  • ex: when the newborn touches a cold mattress, blanket, cold hands, or metal scale

• Convection: heat loss from the body surface to cooler surrounding air or to air circulating over a body surface

  • ex: a cold breeze that flows over the newborn which carries heat away, a cool room, cool corridors, or outside air currents.

• Evaporation: heat loss when a liquid is converted to vapor.

  • may be sensible (sweating) or insensible (skin and respirations)

  • ex: amniotic fluid covering the newborn is evaporating into the air, bathing a newborn

• Radiation: the loss of body heat to cooler, solid surfaces that are in proximity but not in direct contact with the newborn

  • ex: newborn is placed in a single-wall isolette next to a cold window, newborns bare skin is exposed in an environment with cooler objects

Overheating

• signs: flushed face and restlessness

• predisposing factors: limited insulation and sweating ability

• primary heat regulator is in the hypothalamus and the CNS

  • the immaturity of the newborn’s CNS makes it difficult to create and maintain this balance

• causes: isolette that’s too warm or left too close to a sunny window, too many clothing or blankets

• increases fluid loss, RR, and the metabolic rate considerably

Thermoregulation

• thermoregulation: the balance between heat loss and heat production; related to the newborn’s rate of metabolism and oxygen consumption

• cold environment → increases norepinephrine → triglycerides stimulate brown fat metabolism → blood is warmed as CO increases

• neutral thermal environment (NTE): an environment in which body temp is maintained without an increase in metabolic rate or oxygen use

  • rates of oxygen consumption, heat (energy) expenditure, water loss, and metabolism are minimal

  • promotes growth & stability and allows the newborns body to conserve energy for basic bodily functions

  • newborns need a higher environmental temp to maintain NTE

    • decreased environmental temp → more oxygen consumption → tachycardia → metabolic rate increases

• nonshivering thermogenesis: brown fat (adipose tissue) is oxidized in response to cold exposure

  • the newborn’s primary method of heat production

• brown fat: a unique tissue that can convert chemical energy directly into heat when activated by the SNS

  • produced during the 3rd trimester

  • brown coloring is derived from the fat’s rich supply of blood vessels and nerve endings

  • found between the scapulae, axillae, at the nape of the neck, in the mediastinum, and in areas surrounding the kidneys and adrenal glands

• cold stress: excessive heat loss that requires a newborn to use compensatory mechanisms (nonshivering thermogenesis, tachypnea) to maintain core body temp

  • body temp decreases → newborn becomes less active, lethargic, hypotonic, and weaker

  • risk occurs particularly within the first 12 hours of life, especially for preterm babies

  • can lead to hypoglycemia, metabolic acidosis, jaundice, and respiratory distress

Hepatic System Function

• newborn liver function include blood coagulation, iron storage, carb metabolism, and conjugation of bilirubin

Iron Storage

• Maturity, birth weight, and hemoglobin level determine the iron status of the newborn

• adequate maternal iron intake during pregnancy means sufficient iron has been stored in the newborn’s liver for use during the first 6 months of age

Carb Metabolism

• Newborns must learn to regulate their blood glucose concentration and adjust to an intermittent feeding schedule

• Hypoglycemia is one of the most frequent problems encountered

• long-term consequences: neurologic damage, seizures, developmental delays, personality disorders

• Initiating early breastfeeding or bottle-feeding helps stabilize the newborn’s blood glucose levels

Bilirubin Conjugation

• Newborns produce bilirubin twice as fast as adults up until 10-14 days after birth

• even in healthy term newborns, very high bilirubin levels during the first week of life can cause bilirubin encephalopathy, a permanent and devastating form of brain damage

GI System Adaptations

• At birth, stomach content pH is mildly acidic, reflecting the pH of the amniotic fluid

• Bowel sounds are normally heard shortly after birth but may be hypoactive on the first day.

Mucosal Barrier Protection

• The intestinal mucosal barrier remains immature for 4-6 months after birth

• function of the mucosal barrier: prevents the penetration of harmful substances (bacteria, toxins, and antigens) present within the intestinal lumen

• bacterial colonization of the gut is dependent on oral intake (breast milk or formula), usually occurring within 24 hours of age and is required to produce vitamin K

• Human breast milk provides a passive mechanism with antibodies

Stomach and Digestion

• The newborn stomach is capable of holding up to 30 mL of fluid

• bottle-fed newborns: small, frequent feedings

• breastfed newborns self-regulate how much they consume

• Coaxing an infant to take more milk leads to overfeeding

• immature cardiac sphincter and nervous control of the stomach → uncoordinated peristaltic activity and frequent regurgitation

• immature pharyngoesophageal sphincter and absence of lower esophageal peristaltic waves → regurgitation

• Avoid overfeeding and stimulate frequent burping to minimize regurgitation

• Most digestive enzymes are available at birth = newborn can digest simple carbs and protein

  • low amylase and lipase levels at birth → limited ability to digest complex carbs and fats → newborn excretes a fair amount of lipids → fatty stools

• term newborns lose 5-10% of their birth weight as a result of insufficient caloric intake within the first week after birth (normal)

  • gaining weight requires an intake of 108 kcal/kg/day from birth to 6 months of age

Bowel Elimination

• Meconium is composed of amniotic fluid, shed mucosal cells, intestinal secretions, and blood

  • greenish black, tarry consistency, and usually passed within 12-24 hours of birth

• feedings are initiated → transitional stool develops (greenish brown to yellowish brown, thinner in consistency, and seedy in appearance)

  • breastfed transitional stools = light mustard with seedlike particles

  • formula-fed transitional stools = tan or yellow in color and firmer

• the earlier the stool, the less bilirubin buildup

• milk stool = the last development in the stool pattern

  • breastfed stool = yellow-gold, loose, stringy to pasty in consistency, and typically sour-smelling

  • formula-fed stools = vary depending on formula but may be yellow to greenish and loose, pasty, or formed in consistency, and an unpleasant odor

Renal System Changes

• glomeruli and nephrons are functionally immature at birth → reduced GFR and limited ability to concentrate urine → newborn is susceptible to dehydration and fluid overload (keep this in mind when giving IV therapy to a newborn)

  • limited ability to concentrate urine until 3 months of age

    • before 3 months of age, newborn voids frequently and the urine has a low specific gravity

  • GFR reach full adult values by 1 year of age

• 5-6 voids daily indicates adequate fluid intake

Immune System Adaptations

• Newborns receive IgG antibodies from their mothers through the placenta, offering some protection until about 6 months of age, but they are still vulnerable to infection since they cant mount long-lasting responses due to their immature immune system

• breastfed newborns receive antibodies from breast milk, including IgA, IgE, IgG, and IgM

• Healthy infants produce their own antibodies starting at 2-3 months of age

Natural Immunity

• does not require previous exposure to the microorganism or antigen to operate efficiently

• made of physical barriers (skin, mucous membranes), chemical barriers (gastric acids, digestive enzymes), and resident nonpathologic organisms

• involves the ingestion and killing of microorganisms by phagocytic cells.

Acquired Immunity

• involves two primary processes:

  • production of antibodies (immunoglobulins) that target specific antigens

  • formation of activated lymphocytes designed to destroy foreign invaders

• absent until after the first invasion by a foreign organism or toxin

• newborn depends highly on IgG, IgM, IgA

  • IgG = shapes the infant’s gut bacteria and immunity

    • the major and most abundant immunoglobulin

    • the only antibody that can pass through the placenta (starting at 20-22 weeks gestation)

    • produces antibodies against bacteria, bacterial toxins, and viral agents

  • IgA = believed to protect mucous membranes from viruses and bacteria

    • major source = human breast milk

      • contributes to the colonization of the infant gut microbiome

    • does not cross the placenta

    • max levels are reached during childhood

    • predominantly found in the gastrointestinal and respiratory tracts, tears, saliva, colostrum, and breast milk

  • IgM = the first immunoglobulin to respond to infection; protects from bloodborne infections

    • found in blood and lymph fluid

    • does not cross the placenta

    • levels are generally low at birth unless a congenital intrauterine infection is present

Integumentary System Adaptations

• the skin limits the loss of water, prevents absorption of harmful agents, and protects thermoregulation, fat storage, and against physical trauma

  • begins developing midgestation and is fully formed by ~32 weeks gestation

• the skin is sensitive, fragile, has a neutral pH, lower lipid content, thinner, and higher water content when compared with adults

  • vulnerable to injury and infections, especially if preterm (ex: use of tapes and monitors, improper handling)

Neurologic System Adaptations

• continues to develop until 1 year of age

• The brain increases its size threefold during the first year of life

• newborn’s sensory capabilities include:

  • Hearing and touch are well developed

  • Taste - ability to distinguish between sweet and sour by 72 hours old

  • Smell - ability to distinguish between mom’s breast milk and breast milk from others

  • Vision - incomplete at birth; maturation is dependent on nutrition and visual stimulation

    • can focus only on close objects (6-10 in away) with a visual acuity of 20/640

    • demonstrate a preference for looking at faces

Congenital Reflexes

• congenital reflexes are the hallmarks of maturity of the CNS, viability, and adaptation to extrauterine life.

• reflexes: involuntary muscular response to a sensory stimulus

  • presence and strength is key sign of neurologic development and function

  • Many disappear with maturation, though some remain throughout adulthood

• major reflexes = gag, Babinski, Moro, and Galant

• minor reflexes = finger grasp, plantar grasp, rooting, sucking, head righting, stepping, and tonic neck

• Absent or abnormal reflexes, persistence of a reflex past the age when it is normally lost, or redevelopment when older may indicate neurologic pathology

Behavioral Adaptations

Behavioral Patterns

First Period of Reactivity

• begins at birth and may last from 30 mins to 2 hours

• newborn is alert, moving, and may appear hungry

  • allows parents to interact with them

• characterized by myoclonic movements of the eyes, spontaneous Moro reflexes, sucking motions, chewing, rooting, and fine tremors of the extremities

  • provides a good opportunity for initiating breastfeeding

• RR and HR are elevated but gradually begin to slow as the next period begins

Period of Decreased Responsiveness

• happens at 30-120 mins of age

• period of sleep or decreased activity/responsiveness

• Movements are less jerky and less frequent (muscles become relaxed)

• HR and RR rates decline

• difficult to arouse or interact with the newborn; no interest in sucking is shown

• quiet time can be used for both parent and newborn to remain close and rest together after labor and the birthing experience

Second Period of Reactivity

• begins as the newborn awakens and shows an interest in environmental stimuli

• typically lasts 2-8 hours

• HR, RR, and peristalsis increase

  • newborn may pass meconium or void during this period

• motor activity, muscle tone, and muscular coordination increase

• interaction between mom and newborn should be encouraged if mom has rested

Behavioral Responses

• neurobehavioral response: how they react to the world around them

• comprises predictable periods that are probably triggered by external stimuli

• Expected newborn behaviors: orientation, habituation, motor maturity, self-quieting ability, and social behaviors

• a deviation in behavioral responses may indicate a complex neurobehavioral problem

Orientation

• definition: the response of newborns to stimuli (new stimulus increases alertness)

• reflects newborn’s response to auditory and visual stimuli, demonstrated by their movement of head and eyes to focus on that stimulus

• Newborns prefer the human face and bright shiny objects by staring intently which helps them become familiar with their surroundings

Habituation

• definition: the newborn’s ability to process and respond to visual and auditory stimuli

  • a measure of how well and appropriately an infant responds to the environment

• the ability to block out external stimuli after the newborn has become accustomed to the activity

• provides a useful indicator of neurobehavioral intactness

• Memory Tip: Habituation = “Habits form” → Baby learns to ignore what doesn’t matter or isnt threatening

Motor Maturity

• depends on gestational age and evaluates posture, tone, coordination, and movements

• enables newborns to control and coordinate movement

• When stimulated, newborns with good motor organization show rhythmic and spontaneous movements which indicate that the CNS is processing stimuli appropriately

  • ex: bringing the hand up to the mouth

Self-Quieting Ability (aka self-soothing)

• refers to newborns ability to quiet and comfort themselves, usually by hand-to-mouth movements and sucking, alerting to external stimuli, and motor activity

Social Behaviors

• includes cuddling and snuggling into the arms of the parent when the newborn is held

• cuddliness is important to parents because they frequently measure their ability to care for their newborn by the newborn’s acceptance or positive response