NEWBORN/NICU REVIEW
THE NORMAL NEWBORN INFANT
Delivery Room Management
1. The cold stressed newborn rapidly depletes essential stores of fat and glycogen. The newborn is prone to heat loss (conductive, convective and evaporative) because of high surface area-body mass ratio. Heat loss in the delivery room can be reduced by the use of radiant warmers, drying and swaddling.
2. Radiant warmers allow the infant to use calories for growth rather than for heat maintenance. Skin temperature is best measured with the skin probe over the EPIGASTRUM. If the probe loses contact with the skin, the warmer produces excessive heat. There is insufficient heat production if the infant or probe is covered by a blanket, placed over the liver, or the skin set point is below the neutral thermal point (the temperature is which the least amount of calories is required for thermoregulation).
3. The Apgar score components: heart rate, respiratory effort, tone, reflex and color.
4. The significance of the ONE and FIVE minute Apgar scores
a. The 1 minute Apgar is not predictive of later neurologic problems. A five minute Apgar of less than 6 is associated with later evidence of neurological injury. The 10, 15, and 20 minute Apgar are the most reliable predictors of outcome especially for IVH and respiratory distress.
b. An Apgar score of 3 or less prolonged for more than 5 minutes is regarded as asphyxia. HOWEVER a low Apgar score in a preterm or SGA infant (6 or 7) is considered normal (they all have low tone by definition).
c. Low Apgar may present in non-asphyxiated infants with depression to maternal medications, trauma, metabolic or infectious disease, CNS, cardiac or pulmonary malformations.
d. A preterm infant usually has an Apgar score of 7 due to decreased tone impaired reflex irritability and irregular respiratory drive.
e. A preterm Apgar of 6 is equivalent to a full term Apgar of 9-10.
5. THE NORMAL NEWBORN CAN FIXATE (but vision is about 20/4000)
Fetal Assessment
1. The non-stress test monitors fetal heart rate reactivity in response to fetal activity, particularly intact fetal brainstem function. Over a 20 minute period, a reactive non-stress test shows at least two accelerations of the fetal heart (fifteen beats/min above baseline lasting at least fifteen seconds. The stress test is used to evaluate uteroplacental insufficiency. An adequate stress test has at least 3 contractions lasting at least 40-60 seconds during a 10-minute time period. If contractions do not occur then the mother is instructed to stimulate her nipples or given oxytocin. No decals should occur.
2. The biophysical profile used by OBs to evaluate fetal well-being prior to birth includes: gross body movements, fetal tone, fetal breathing movements, reactive nonstress test, and qualitative amniotic fluid volume. US is used. 8-10 is considered normal. 4-6 indicates possible fetal compromise and 0-2 predicts high perinatal mortality.
3. Fetal dysrhythmias
a. Normal fetal heart rate is 120-160 bpm.
b. Decelerations
· Early decels are related to the onset of a contraction. The fetal head is compressed which leads to increased intracranial pressure => a vagal response => decrease in FHR. It is usually of no consequence.
· Late decels occur after the contraction. It indicates uteroplacental insufficiency and fetal distress. Management includes changing mother’s position, applying oxygen to the mother, stopping oxytocin if uterine hyperstimulation is suspected, or starting a tocolytic to stop contractions.
· Variable decels can occur before, during or after a contraction. This is secondary to cord compression. It may indicate fetal distress when prolonged and associated with bradycardia. Changing the position of the mother may help.
Transition
1. Physical and behavioral characteristics of the preterm, full term and post-term infants. See new Ballard chart attached.
2. Preterm is defined as <37 weeks gestation. Full term is defined as 37-41 6/7 weeks gestation. Post-term is defined as >42 weeks gestation.
3. SGA is defined as a weight less than the 10th percentile or 2 SD below the mean weight for gestational age. SGA is seen in infants of mothers with hypertension, pre-eclampsia or tobacco use, as well as TORCH infections.
4. AGA is defined as weight in the 10th to 90th percentile.
5. LGA is defined as weight greater than the 90th percentile or 2 SD above the mean weight for gestational age. LGA is seen in infants of diabetic mothers, in Beckwith syndrome, and in hydrops fetalis.
6. Remember, when using the growth curves, plot anthromorphic measures against gestational age.
Routine Care
1. Hemorrhagic Disease of the Newborn
a. Occurs in 1 of every 200-400 neonates not given Vitamin K prophylaxis.
b. Vitamin K is necessary for the function of factors II, VII, IX, X and proteins C and S.
c. The platelet count is normal but the PT is prolonged in disproportion to the PTT. It usually presents within the first 48 hours with bleeding and bruising (skin, GI tract, head bleed).
d. HDN is related to decreased placental transfer of maternal Vitamin K. It can also be related to breast feeding since there is less Vitamin K in breast milk vs. cow’s milk.
e. Treatment: 10 cc/kg of FFP and Vitamin K 1 mg IV.
f. Maternal drugs which predispose to HDN: phenytoin, primodone (similar to phenobarb), methsuximide (anti-epileptic), and Phenobarbital. Drug exposed infants usually present within the first 24 hours of life => if mom is on any of these drugs, she should receive Vitamin K 24 hours PTD and the baby should receive Vitamin K at birth and again 24 hours later.
g. Delayed hemorrhagic disease of the newborn can occur at 4-12 weeks of age. Risk factors include: treatment with antibiotics (which decreased Vitamin K absorption), infants with a malabsorption (liver dx, CF), and breast fed infants who did not receive Vitamin K prophylaxis.
2. Ophthalmia Neonatorum
a. Definition: Inflammation of the conjunctiva within the first month of life.
b. Causes: chemical conjunctivitis, bacterial (Neisseria gonorrhea, Chlamydia trachomatis, Staphylococci, Pneumococci, Streptococci, E. Coli and other GNRs), and herpes virus.
c. Treatments:
1. N. Gonorrhea – conjunctivitis with chemosis, purulent exudates and lid edema starting 1-4 days after birth. There may also be clouding or perforation of the cornea. Complications: scalp infections, anorectal infection, sepsis, arthritis, and meningitis. Treatment includes cefotaxime or ceftriaxone for 7 days if the infection is local. With disseminated disease, treatment extends to 10-14 days.
· In a mom with untreated GC, the infant should receive one dose of abx as well as topical prophylaxis.
· Prophylaxis of ocular gonorrheal infection should include silver nitrate solution in single dose ampules or single-use tubes of ophthalmic ointment containing erythromycin or tetracycline.
2. C. Trachomatis is the MOST COMMON cause of infectious conjunctivitis. It usually presents 5-14 days after birth with minimal swelling and rare corneal involvement. Diagnosis is by DFA, ELISA, or DNA probes. REMEMBER silver nitrate is not adequate prophylaxis for neonatal chlamydial conjunctivitis. Treatment should include 14 days of crythromycin. This can eradicate the organism from the upper respiratory tract and limit the risk of Chlamydial pneumonia.
3. Caloric requirements per kilogram for adequate growth is greater in preterm infants. Preterm infants also have a greater daily fluid requirement per kilogram of body weight than full term infants. Remember that insensible loss is increased with prematurity, phototherapy, and the use of radiant warmers.
4. Most newborns urinate within the first 12 hours of life. 93% urinate by 24 hours, 99% by 48 hours. If a newborn doesn’t urinate within 24 hours, consider the Crede’s maneuver to compress the bladder or catheterization. A workup including serum electrolytes and a U/S should be performed. THE MOST LILKELY EXPLANATION IS AN UNDOCUMENTED VOID IN THE DELIVERY ROOM. Other causes include: UPJ (the most common cause of hydronephrosis), hypovolemia, neurogenic bladder, and posterior urethral valves. (males only)
5. Preterm infants have a lower hematocrit than full term infants. The normal hematocrit for a newborn infant is 56%(51 +/- 4.5). The H/H of a full term newborn is fairly stable for weeks 1-3. After that, the Hgb falls about 1 mg/del per week until the nadir is reached at 7-9 weeks. Also, the timing of the physiologic anemia in the full term infant differs from the preterm infant.
- The Hgb nadir occurs earlier in the preterm infant because of 1) decreased RBC survival, 2) more rapid rate of growth and 3) Vitamin E deficiency which causes shorter RBC survival.
- Term nadir (Hgb=9.5-11) at 8-12 weeks
- Premature nadir of 1200-1500 grams (Hgb=8-10) at 5-10 weeks
- Premature nadir of <1200 grams (Hgb=6.5-9) at 4-8 weeks
***Remember, capillary samples have slightly higher results for the H/H compared with venous samples, sometimes up to 20%!***
6. Blood pressure values vary directly with gestational age, postnatal age of the infant, and birth weight.
7. Bilirubin Metabolism & Jaundice
a. Bilirubin metabolism
1. The heme ring is oxidized in the RES to biliverdin by heme oxygenase. This reaction releases CO and iron. Biliverdin is then reduced to bilirubin by the enzyme biliverdin reductase.
2. Bilirubin is transported to liver cells bound to albumin. Conjugation occurs in the liver by uridine diphospate glucuronyl transferase. Deficiencies of this enzyme lead to Crigler-Naijar Syndrome and Gilbert’s Syndrome and cause hyperbilirubinemia in the newborn.
3. Excretion of conjugated bilirubin takes place in the GI tract and to some extent in the urine. Abnormalities that decrease stooling frequency such as Hirschsprung’s disease lead to unconjugated hyperbilirubinemia.
b. Physiologic Jaundice
1. Full term infant bilirubin peak at 6-8 mg/dl by 3 days of age….a rise to 12 is still considered physiologic.
2. Preterm infant bilirubin peak at 10-12 mg/dl on the 5th day of life with a rise up to 15 mg/dl still considered physiologic.
3. Guidelines for the Use of Phototherapy (see handout).
4. Physiologic Jaundice is due to:
- Increased RBC volume/kilogram and decreased RBC survival
- Increased ineffective erythropoiesis and increased turnover of non-hemoglobin heme proteins.
- High levels of intestinal beta-glucuronidase causing increased enterohepatic circulation.
- Immature conjugation due to decreased
UDPG-T activity in the liver.
c. Nonphysiologic Jaundice
1. Any onset of jaundice before 24 hours of age
2. Any elevation requiring phototherapy
3. A rate of rise greater than 0.5 mg/dl/hour
4. Jaundice persisting after 8 days in the term infant and 14 days in the preterm infant
5. The differential diagnosis of negative Coom’s and direct hyperbilirubinemia includes: 1) hepatitis 2) biliary obstruction 3) sepsis 4) galactosemia 5) alpha-1 antitrypsis deficiency 6) cystic fibrosis 7) hyperalimentation 8) syphilis 9) hemochromatosis
8. Causes of decreased serum thyroxine concentration in term and preterm infants include:
a. Hypothyroxinemia of prematurity is immaturity of the hypothalamic portion of the hypothalamic pituitary thyroid axis. Lack of TRH leads to decreased TSH and T4.
b. Sick euthyroid syndrome – nonthyroidal illness increases reverse triiodothyronine. Deiodination of T4 produces T3 and rT3. In sick preterm infants, the predominant triiodothyronine is rT3, the inactive metabolite of thyroid hormone, which explains the low thyroid hormone activity.
c. In preterm infants, there is an obtunded surge of thyroid hormone activity (compared with full term infants). It spontaneously resolves in 4-8 weeks.
d. Excessive topical application of iodine containing antiseptics is also a potential cause of iodine induced transient hypothyroxinemia.
e. The use of thyroid hormone replacement therapy in premature infants is controversial.
9. PKU screening: the utility and limitations
a. Newborn screening of PKU relies on the detection of elevated levels of blood phenylalanine. Prenatally, fetal phenylalanine crosses the placenta and is metabolized by the mother =>a newborn with PKU will not initially have hyperphenylalaninemia.
b. Phenylalanine levels begin to rise only after feeding has been established and may not be detectable in the first 24 hours=>with infants discharged within the first 24 hours, follow up within 2-3 days including repeat NBS is necessary.
10. The recommended methods of umbilical cord care include local application of triple dye or antimicrobial agents.
11. Most infants stool within 48 hours. The delayed or absent passage of meconium is associated with colonic obstruction due to meconium plug syndrome, Hirshsprung disease, and imperforate anus. It is also due to ileal atresia, malrotation, or maternal use of magnesium sulfate.
12. Bilious vomiting is a common finding in infants with small bowel obstruction.
13. Bottle fed vs. breastfed infants=>differences in stooling and frequency
a. Breastfed infants have stools that are more yellow and seedy.
b. Breastfed infants stool more often than bottle fed infants.
14. The rapid assessment of whole blood glucose concentrations (glucose oxidase test strips) may yield falsely high or low values.
a. Falsely elevated results can be due to high levels of fructose or galactose or a sample contaminated with glucose containing solution.
b. Falsely decreased results usually occur due to shortened retention time on the test strip.
15. Remember, there should be close follow-up with any newborn discharged early.
a. Early hospital discharge is defined as the discharge of a newborn earlier than 48 hours following vaginal delivery and 96 hours following cesarean delivery. (at Duke it is 72 hours – could not find info on this).
b. The most common reason for readmission is hyerbilirubinemia since peak serum bilirubin is not reached until DOL 3.
c. The age of the infant at the time of newborn screening is also critical.
d. Many congenital heart defects (esp. ductal dependent lesions) may not be detected clinically during the first 24 hours of life.
e. With the exception of late onset meningitis, most newborns with bacterial sepsis are symptomatic within 8 hours after birth when respiratory symptoms predominate. (Risk factors for sepsis include: low birth weight, prolonged rupture of membranes, and chorioamnionitis).
f. A newborn should not be discharged until two feeds have been taken with coordinated suck and swallow and at least one stool has passed.
g. All infants discharged early should have follow up within 72 hours.
16. Home birth is associated with many clinical problems, especially Vitamin K deficiency.
a. Vitamin K IM given in the hospital helps prevent hemorrhagic disease of the newborn (see above for further information).