The Healthy Newborn - Lecture Notes
Module 7: The Healthy Newborn
Chapter 21: The Normal Newborn: Adaptation and Assessment
Introductory Concepts
Chemoreceptors:
Function: Sense decreased levels of O2 (PO2) and increased levels of carbon dioxide (PCO2) associated with birth.
Outcome: Stimulates the respiratory center located in the medulla of the brain.
Factors Influencing Respiration:
Chemical Factors: Changes in blood gases stimulate respiration.
Mechanical Factors:
Squeezing during delivery relieves pressure and allows for chest recoil, creating negative pressure in the thoracic cavity.
The recoil promotes the initiation of breath.
Thermal Factors:
Skin sensors relay thermal changes to the brain, stimulating breathing.
Sensory Factors:
Various tactile stimuli from sound, light, smell, and pain influence breathing initiation.
Initiation of Respiration
Surfactant:
Definition: A slippery combination of lipoproteins detectable by 28 weeks of gestation.
Function: Reduces surface tension within the alveoli; prevents alveolar collapse during exhalation.
Impact: Without adequate surfactant, the infant faces increased work to breathe due to alveolar collapse after each breath.
Cardiac Adaptations at Birth
Ductus Arteriosus:
Function: Allows blood to flow directly from the pulmonary artery to the aorta.
Changes at Birth: Pressures in the heart reverse post-birth, resulting in the ductus arteriosus closing.
Foramen Ovale:
Only opens from right to left in fetal circulation, facilitating blood bypass of the lungs.
Ductus Venosus:
Closes shortly after birth due to increased oxygenation and the metabolism of prostaglandins.
Neurological Adaptation and Thermoregulation
Factors Affecting Thermoregulation:
Negative Effects:
Thin skin and proximity of blood vessels to the surface increase heat loss.
Positive Effects:
Flexed position, minimal subcutaneous fat, and a large surface area help retain heat.
Heat Loss Mechanisms:
Evaporation: Loss of moisture during bathing, birth, and from wet linens.
Conduction: Contact with cold objects (e.g., scales, restraint boards).
Convection: Drafts from open doors or air conditioning.
Radiation: Heat loss from the infant to colder surfaces nearby.
Nonshivering Thermogenesis
Primary Source of Heat Production:
Thermal receptors in the skin detect a drop in temperature leading to norepinephrine release.
Norepinephrine stimulates brown fat metabolism, producing heat.
Blood warms up as it passes through the metabolizing brown fat, redistributing throughout the body.
Effects of Cold Stress
Cold stress can lead to:
Increased oxygen needs
Decreased surfactant production, potentially causing respiratory distress
Hypoglycemia
Metabolic acidosis
Increased risk of developing jaundice.
Hyperthermia in Newborns
Description: Increased metabolic rate resulting in heightened oxygen and glucose demand.
Implications: Significant insensible fluid losses occur due to peripheral vasodilation.
Monitoring: Utilize temperature probes with prolonged exposure under warmers.
Gastrointestinal Adaptations
Gastrointestinal Capacity: At birth, the stomach capacity approximates 6 mL/kg.
Gastrocolic Reflex: Activation of bowel activity stimuli.
Stomach Comparison:
More elongated than in adults, infants are more susceptible to dehydration during diarrhea.
Defecation: Meconium stool typically passed within the first 12-48 hours.
BREASTFEDvs. Formula-fed BM Characteristics.
Hepatic System Functionality
Key Functions:
Maintains blood glucose levels
Conjugates bilirubin
Begins glycogen storage by the liver
Regulation of glucose for sustaining:
Stress from labor/delivery
Breathing and thermoregulation
Physical movement
Normal Blood Glucose Levels:
Day 1: 40-60 mg/dL
Over Day 1: 50-90 mg/dL
Clinical Risks:
Preterm or small for gestational age (SGA) infants are more susceptible to hypoglycemia.
Bilirubin: A byproduct of hemoglobin breakdown can cause delayed jaundice due to an immature liver.
Hyperbilirubinemia and Jaundice
Physiological Jaundice: May develop as a natural consequence of the newborn’s adaptations but typically presents after 24 hours.
Pathological Jaundice: Manifestations that occur within the first 24 hours necessitate investigation for possible underlying issues.
Breastfeeding and Jaundice:
Breastfeeding jaundice arises from insufficient intake.
Breastmilk jaundice appears later and occurs 3-5 days postpartum.
Urinary System and Functionality
Nephron Formation: Completed by 34 to 36 weeks gestation but not functional until after birth.
Water Sensitivity: Newborns lose 5-10% of body weight due to diuresis in the initial days.
Acid-Base Balance Issues: Increased risk of acidosis due to amino acid reabsorption inefficiencies and bicarbonate loss.
Immune System Functionality
Immunity Types:
IgG: Crosses the placenta in the third trimester for protection against gram-negative bacteria.
IgM: Develops rapidly upon exposure to antigens and is present in breastmilk for gut protection.
IgA: Also crosses via breastmilk to protect against GI and respiratory infections.
Assessment of the Newborn
Vital Signs:
Temperature:
Normal range: 36.5°C-37.5°C (97.7°F-99.5°F), preferably taken axillary.
Abnormal readings indicate the need for further investigation regarding environmental rejection or infection.
Pulse:
Normal 120-160 beats/min.
Variations: Tachycardia or bradycardia present concerning underlying health issues.
Respiration:
Normal rate: 30-60 breaths/min. Indicators for assessment include the presence of nasal flaring, grunting, and retractions.
Physical Measurements
Weight: Normal range is 2500-4000 g.
Length: Typical range is 48-53 cm.
Head Circumference: Ranges from 32-36 cm.
Chest Circumference: Typical is 30.5-33 cm, usually about 2 cm less than head circumference.
Newborn Behavior and Reflex Assessment
Posture & Movement:
Infants should exhibit flexed posture, move symmetrically, resist extension, and demonstrate normal muscle tone.
Abnormal findings may suggest neurological or muscle disruption.
Skin Assessment:
Expected color is pink or tan with the prevalence of variations such as milia, erythema toxicum, and mottling.
Neurological Reflexes
Babinski Reflex: Stroking the foot elicits toe flaring and dorsiflexion of the big toe.
Moro Reflex: Infant's arms extend outward when the head drops back.
Rooting Reflex: Touching the cheek leads the infant to turn its head toward the stimulus indicating hunger.
Sucking Reflex: Present when the mouth is stimulated.
Assessment of Hepatic Function
Jaundice Detection:
Monitor for progression, typically beginning at serum bilirubin levels of 5-6 mg/dL, following a cephalocaudal progression.
Newborn Maturity Rating & Classification
Neuromuscular Maturity Points: Evaluating arm recoil, leg positioning, and posture gives insight into gestational maturity.
Physical Maturity Points: Assess skin condition, lanugo, ear shape, and breast/bud development for growth assessment.
Post-Delivery Nursing Procedures
Immediate Care:
Use clean gloves, dry infant thoroughly, place under warmer or on mother's chest for warmth and stimulation.
APGAR Scoring:
A scoring system that assesses heart rate, respiratory effort, tone, reflex response, and color with points assigned from 0-2.
Drug Information for Newborns
Vitamin K (Phytonadione): Administered intramuscularly to prevent bleeding due to inherent deficiency.
Erythromycin Ophthalmic: Administered shortly after birth to prevent conjunctivitis from gonorrhea exposure.
Additional Newborn Care Instructions
Cold Stress Prevention: Techniques to regulate ambient temperature and dry infant are critical to reduce heat loss.
Skin Care: Encourage hygiene practices while avoiding irritation, especially around the diaper area.
Cord Care: Monitor for infection or bleeding and maintain dryness post-delivery as part of ongoing care.
Discharge Criteria
Must include:
Normal vital signs, feeding, urinary/stool output, and no complications, while providing follow-up information for pediatric care.