Normal Newborn

Dosage Calculation and Medical Mathematics

• Ampicillin Dosage Calculation

  • Prescription: $50\,mg/kg/day$ PO every $6$ hours.

  • Patient Weight: $10\,lbs$.

  • Weight Conversion to Kilograms: $\frac{10\,lbs}{2.2} = 4.54545\,kg$.

  • Total Daily Dosage: $4.54545\,kg \times 50\,mg/kg/day = 227.27\,mg/day$.

  • Individual Dose Calculation (every $6$ hours equals $4$ doses per day): $\frac{227.27\,mg}{4} = 56.818\,mg$.

  • Final Answer (rounded to the nearest 10th): $56.8\,mg$ per dose.

• Newborn Weight Loss Percentage Calculation

  • Formula for Total Weight Loss: $\text{Birth Weight} - \text{Current Weight} = \text{Total Weight Loss}$.

  • Formula for Percentage Loss: $(\frac{\text{Total Weight Loss}}{\text{Birth Weight}}) \times 100 = \text{Percentage Weight Loss}$.

  • Example Calculation:

    • Birth Weight: $8\,lb$ (Converted: $\frac{8}{2.2} = 3.636\,kg = 3636\,grams$).

    • Current Weight at 2 Days: $7\,lb\,4\,oz$ (Converted: $7.25\,lb / 2.2 = 3.295\,kg = 3295\,grams$).

    • Total Loss: $3636\,grams - 3295\,grams = 341\,grams$.

    • Percentage: $(\frac{341}{3636}) \times 100 = 9.4\%$.

Definitions and Scope of Newborn Care

• Timeline of the Newborn Period

  • The newborn period is defined as the timeframe from birth to $28$ days of life.

  • Neonatal transition refers specifically to the first $6$ hours of life.

• Physiologic Adaptation

  • Transitioning from a fetus to a neonate is considered the most complex physiologic adaptation human beings undergo, affecting almost every organ system.

• Interrelated Clinical Concepts

  • Care of the newborn involves several interconnected concepts: Stress, Perfusion, Oxygenation, Coping, Thermoregulation, Cellular Regulation, and Acid-Base Balance.

Key Terminology in Neonatology

• Apgar Score: A rapid assessment tool used to evaluate the newborn's physical condition at $1$ and $5$ minutes after birth.

• Acrocyanosis: A common finding where the newborn's hands and feet appear blue, but the central body is pink.

• Harlequin Sign: A rare vascular phenomenon where one side of the newborn's body turns deep red while the other remains pale, with a sharp midline demarcation.

• Vernix Caseosa: A white, cheese-like substance that protects the fetal skin in utero.

• Mongolian Spots: Blue or purple-tinted pigmented areas commonly found on the lower back or buttocks of newborns with darker skin tones.

• Brown Adipose Tissue (BAT): Highly vascular fat used by newborns for heat production, as they cannot shiver.

• Molding: The shaping of the fetal head to allow it to pass through the birth canal.

• Lanugo: Fine, downy hair often found on the back and shoulders of the newborn.

• Neutral Thermal Environment (NTE): An environment where the newborn can maintain a stable body temperature with minimal oxygen consumption and metabolic rate.

• Cold Stress: Excessive heat loss that forces the newborn to use metabolic mechanisms (like burning BAT) to compensate, potentially leading to respiratory and metabolic complications.

Respiratory and Cardiovascular Adaptations

• Respiratory Changes at Birth

  • The physical "squeeze" of the chest during delivery helps drain fluid from the lungs.

  • The first breath generates positive lung pressure, critical for maintaining functional residual capacity in the alveoli.

  • Factors triggering the first breath: Brief period of asphyxia causing chemical changes, and sensory triggers including temperature change, touch, auditory stimuli, and visual stimuli.

  • Fetal hemoglobin has a significantly greater affinity for oxygen than adult hemoglobin, allowing the fetus to thrive in a relatively lower oxygen environment before birth.

• Cardiovascular Shunt Closures

  • Ductus Arteriosus: Connects the pulmonary artery to the aorta. Functional closure occurs within $24\text{--}72$ hours; anatomical closure takes $2\text{--}3$ weeks. The remnant is the Ligamentum arteriosum.

  • Ductus Venosus: Shunts blood from the umbilical vein to the inferior vena cava, bypassing the liver. Functional closure occurs in minutes to hours; anatomical closure takes $1\text{--}3$ weeks. The remnant is the Ligamentum venosum.

  • Foramen Ovale: An opening between the right and left atria. Functional closure occurs within minutes to hours of the first breath; anatomical closure takes $3\text{--}12$ months. The remnant is the Fossa ovalis.

• Effects of Cord Clamping

  • Clamping the cord immediately reduces preload by blocking approximately $40\%$ of venous return from the placenta via the umbilical vein.

  • It dramatically increases afterload by obstructing the umbilical arteries, which increases peripheral vascular resistance and results in reduced cardiac output.

Thermoregulation and Heat Loss

• Risk Factors for Hypothermia

  • Newborns have a large body surface area relative to their mass.

  • They have a limited amount of subcutaneous fat for insulation.

  • They are unable to shiver to produce heat.

  • Blood vessels are positioned closer to the skin surface.

  • They have proportionally larger heads which contribute to heat loss.

• Mechanisms of Heat Loss

  • Convection: Heat loss from the body surface to cooler surrounding air. (Prevention: Keep away from AC vents, fans, or open windows).

  • Evaporation: Heat loss when water on the skin turns to vapor. (Prevention: Dry the newborn immediately and replace wet blankets with warm, dry ones).

  • Radiation: Heat loss to cooler objects in the vicinity that are not in direct contact. (Prevention: Keep cribs away from outside walls, windows, and doorways).

  • Conduction: Heat loss from the body surface to a cooler surface in direct contact. (Prevention: Use warm blankets or towels to cover scales and changing tables).

Physiologic Functions of Newborn Systems

• The Newborn Liver

  • Iron Storage: Stores enough iron to last approximately $5$ months.

  • Glucose Management: Burns glycogen rapidly after birth to maintain blood sugar once the maternal supply is severed.

  • Blood Clotting: Synthesis of clotting factors requires Vitamin K. Since the newborn gut is sterile and cannot produce Vitamin K, a preventative injection is administered.

  • Bilirubin Processing: Responsible for breaking down old fetal red blood cells for excretion through stool.

• Gastrointestinal and Urinary Systems

  • Newborns can digest simple carbohydrates, proteins, and fats. Peristalsis and swallowing are present at birth.

  • Normal weight loss of $5\text{--}10\%$ is expected during the first week as intake is initially low.

  • Stool Transition: Meconium (thick, tarry black) starts at birth; transitions to green within $2\text{--}3$ days.

  • Bladder volume is between $6\,ml$ and $44\,ml$. The first void should occur within $24\text{--}48$ hours.

  • Newborns are less able to concentrate urine until about $3$ months of age.

  • Observations: Urates (pink or orange crystals) and pseudomenstruation (blood in the diaper of female infants) are normal findings.

Reflexes and Apgar Scoring

• Newborn Reflexes

  • Common reflexes include: Moro (startle), Rooting (searching for nipple), Sucking, Tonic Neck (fencing position), Stepping, Palmar and Plantar grasp, and Babinski (fanning of toes). Nurses must observe for symmetry in these reflexes.

• Apgar Scoring (1 and 5 Minutes)

  • Appearance (Skin Color): $0 =$ Blue/pale; $1 =$ Pink body/blue extremities (acrocyanosis); $2 =$ Completely pink.

  • Pulse (Heart Rate): $0 =$ Absent; $1 =$ Slow (under $100\,bpm$); $2 =$ Over $100\,bpm$.

  • Grimace (Reflex Irritability): $0 =$ No response; $1 =$ Grimace; $2 =$ Cough, sneeze, or cry.

  • Activity (Muscle Tone): $0 =$ Limp; $1 =$ Some flexion; $2 =$ Active motion.

  • Respiration (Crying): $0 =$ Absent; $1 =$ Slow/irregular; $2 =$ Good cry.

Head Injuries and Abnormalities

• Caput Succedaneum

  • Involves soft tissue edema of the scalp caused by physical pressure during head-first delivery.

  • Crosses suture lines.

  • Present at birth and resolves spontaneously within $24\text{--}48$ hours.

• Cephalohematoma

  • Involves a collection of blood between the skull bone and its periosteum due to damaged blood vessels.

  • Does NOT cross suture lines; it is confined to the specific bone.

  • May not be visible at birth; can increase in size over the first few days.

  • Takes much longer to resolve ($3$ weeks to $3$ months) and is a common cause of jaundice due to the breakdown of the trapped blood.

Collaborative and Nursing Interventions

• Standard Newborn Medications

  • Erythromycin Eye Ointment: To prevent ophthalmia neonatorum.

  • Aquamephyton (Vitamin K): To prevent bleeding disorders.

  • Hepatitis B Vaccine: First dose given before discharge.

  • HBIG: Given if the mother is Hepatitis B surface antigen positive.

• Screening Procedures

  • Mandatory screenings include New-born Hearing Test (NHT), Critical Congenital Heart Disease (CCHD), Bilirubin levels, and Phenylketonuria (PKU).

• Circumcision Care

  • Contraindications: Hypospadias, epispadias, or family history of bleeding disorders.

  • Care: Monitor for bleeding, voiding, and pain. Use gauze with Vaseline during diaper changes. Do not wash off the yellow exudate (normal healing process).

• Breastfeeding Indicators

  • A LATCH score is used to assess breastfeeding efficacy.

  • Once the milk supply is established, the newborn should have $6\text{--}8$ wet diapers and $3\text{--}5$ stools every $24$ hours.