What is the differential for neonatal respiratory distress?
Respiratory distress syndrome, Transient tachypnea of the newborn, Sepsis/pneumonia, Pneumothorax, CHF, Hypothermia
What is Intrauterine Oxygenation like in the fetus?
Oxygenated blood from placenta travels to fetus through the umbilical vein. A portion of the oxygenated blood perfuses the liver. Remained bypasses the liver through the ductus venosus and enters the inferior vena cava. One third of vena caval blood crosses the patent foramen ovale (PFO) to the left atrium and is pumped to the coronary, cerebral and upper body circulations. The remaining 2/3 combines with venous blood from the upper body in the right atrium, and is directed to the right ventricle and out the pulmonary artery.
Vasoconstriction of the pulmonary arterioles produces high pulmonary vascular resistance, allowing only 8-10 percent of the blood from the right ventricle to flow through the pulmonary vasculature. The remaining 90-92 percent is shunted through the PDA to the descending aorta.
Oxygenation changes dramatically at birth from a passive, placenta-provided source to an active respiration-based process. Successful transition at birth involves:
(1) Removal of low-resistance placental circulation by cutting the umbilical cord
(2) Initiation of air-breathing
- At delivery, infant’s first breath results in replacement of fluid in lung with air.
- Fluid is squeezed out of lungs during uterine contractions with vagianal delivery and absorbed by pulmonary lymphatics –> delayed absorption can lead to transient tachypnea of the newborn (TTN).
(3) Reduction of the pulmonary arterial resistance
(4) Closure of the PFO and PDA
Infant of a diabetic mother (IDM):
Control of diabetes during pregnancy is an important predictor of fetal outcome, especially with regard to the risk of birth defects:
(1) Incidence of major malformations is directly related to the Hgb A1c level in the first trimester.
(2) Infants born to women with A1C levels greater than 12 have at least a 12-fold increases in major malformations.
An IDM (infant of diabetic mother) is also at risk of being LGA:
(1) High levels of maternal serum glucose stimulate the fetal pancreatic beta cells and the development of hyperinsulinemia.
(2) Insulin the the primary anabolic hormone for fetal growth
(3) High levels in the third trimester result in increased growth of the insulin-sensitive organ systems (heart, liver and muscle) and a general increase in fat synthesis and deposition.
(4) This combination of increased body fat, muscle mass and organomegaly produces a macrocosmic (LGA) infant.
(5) Insulin-insensitive organs, such as the brain and kidneys, are not affected by the elevated insulin levels and have appropriate size for gestational age.
What are risk factors for neonatal respiratory distress?
Infection, Prematurity, Delivery by C section, Maternal diabetes, Maternal drug exposure, Prematurity, PROM (rupture of membranes greater than 18 hrs prior to delivery), Meconium in amniotic fluid.
Cyanosis of the newborn:
Important to first distinguish cyanosis from acrocyanosis!
What are respiratory etiologies of cyanosis of the newborn?
TTN (transient tachypnea of the newborn), RDS, Pneumothorax, Diaphragmatic hernia, Choanal atresia, Pulmonary hypoplasia.
What are cyanotic congenital cardiac defects?
Tetralogy of fallot, Transposition of the great arteries, truncus arteriosus, tricuspid atresia, total anomalous pulmonary venous return and pulmonary atresia.
What are CNS abnormalities related to cyanosis?
Hypoxic-ischemic encephalopathy, Intraventricular hemorrhage, sepsis/meningitis.
What are other causes related to cyanosis?
Infectious, respiratory depression secondary to maternal medications, hypothermia, polycythemia/hyperviscosity syndrome.
What is developmental dysplasia of the hip (DDH)?
Dislocation of the hips is not always detectable at birth. To dec. number of dislocated hips detected later in infancy, the AAP has developed a clinical practice guideline for PCPs. The main components are recognition of risk factors and regular hip examinations to age 18 mo.
What are the clinical features of developmental dysplasia of the hip (DDH)?
Partial or complete dislocation or instability of the femoral head.
What are risk factors for DDH?
Breech position: 30-50 percent occur in infants born in breech position.
Gender: 9 to 1 female predominance.
How do you assign an apgar score for heart rate?
Absent is 0. Below 100 is 1. Above 100 is 2.
How do you assign an apgar score for respiratory effort?
Absent is 0. Weak, irregular, or gasping is 1. Good, crying is 2.
How do you assign an apgar score for muscle tone?
Flaccid is 0. Some flexion of extremities is 1. Well flexed, or active movements of extremities is 2.
How do you assign an apgar score for reflex irritability?
No response is 0. Grimace or weak cry is 1. Good cry or active withdrawal is 2.
How do you assign an apgar score for color?
Blue all over, or pale is 0. Body pink, extremities blue is 1. Pink all over is 2.
Scoring provides a mech. to record fetal-to-neonatal transition. When properly applied, the apgar score is a tool for standardized assessment. The score alone correlates poorly with future neurological outcome of the term infant because it is affected by gestational age, maternal medications, resuscitation, and cardiorespiratory and neurologic conditions. (Poor neurologic outcome is better associated with documented asphyxia)
If infant is crying, what happens to vitals?
HR and RR may be falsely elevated.
In the first hour of life, RR and HR are…
HR: 160-180 bpm
RR: 60-80 bpm
With successful transition, HR will decrease to 120-160 bpm and RR to 40-60 bpm by two hours of life.
What are signs of neonatal respiratory distress?
Tachypnea (greater than 60 bpm), Use of accessory muscles for respiration (nasal flaring, intercostal retractions, grunting), Hypoxia, hypercapnia.
What is acrocyanosis?
Bluish discoloration of hands and feet. Commonly seen in the first few hours following birth. May recur through early infancy when the baby is cold. After 4-5 hours, cyanosis is usually less marked in hands than feet. If acrocyanosis is not resolved within 8 hour for with warming, may be sign of congenital heart disease.
What is LGA?
Large for gestational age. Greater than 90th percentile. Most imp. pathologic etiology is maternal diabetes mellitus. Potential clinical problems include delivery by c-section, forceps, or vacuum extraction, Birth injuries (clavicular fracture, brachial plexus injury, facial nerve palsy), Hypoglycemia.
What is AGA?
Appropriate for gestational age. 10th to 90th percentile.
What is SGA?
Smal for gestational age. Less than 10th percentile. Also called IUGR. An infant its low birth weight may be premature, but low birth weight may also result from many other causes. Potential clinical problems include temperature instability (hypothermia), hypoglycemia (due to inadequate glycogen stores), and polycythemia and hyperviscosity.
The first system for evaluating gestational age was developed by Dubowitz in 1970:
Detailed scoring system based on infant’s external physical characteristics and neurological findings. Requires that infant be alert and active. Results often skewed in very immature or sick infants due to low neurologic scores.
The Ballard assessment, a method developed in 1979 and now more widely used, is a shortened version of the Dubowitz exam:
Standardized score based on specific neuromuscular signs and physical characteristics. Should be performed on every neonate. Most accurate when obtained at 12-24 hours of life.
How do you do the hip exam to assess newborns for developmental dysplasia of the hip (DDH)?
- Remove diaper so it does not constrict movement.
- Do one side at a time.
- Stabilize pelvis with one hand.
- Bend infant’s leg and place finders of hand on greater trochanter, thumb on inside of femur.
- Perform Barlow maneuver.
- Perform Ortolani maneuver.
- Repeat on other side.
What is the Barlow maneuver?
- Movement with leg in adduction
2. Push back to feel if femur head is in the joint or dislocating in and out.
What is the Ortolani maneuver?
- Movement with leg abduction.
- Push out with fingers on greater trochanter to see if clunk is felt (clunk indicates relocation from dislocated position)
What are the most likely diagnosis for an infant in respiratory distress?
Respiratory distress syndrome (RDS), Transient tachypnea of the newborn (TTN), Congestive heart failure (CHF), Sepsis/pneumonia, Hypoglycemia.
What are the less likely diagnosis for an infant with respiratory distress?
Congenital diaphragmatic hernia, Pneumothorax, Meconium aspiration syndrome, transposition of the great arteries (TGA), Hypothermia, Severe coarctation of the aorta.
What is respiratory distress syndrome (RDS)?
Previously known as “hyaline membrane disease”, RDS is caused by a deficiency in lung surfactant. Most common cause of respiratory distress in premature infants.
What are additional risk factors for RDS?
IDM (due to delayed lung maturation), Sibling with history of RDS, Male, Section delivery without labor, Perinatal asphyxia.
What can help distinguish between TTN and RDS?
What is transient tachypnea of the newborn (TTN)?
Delayed clearance of lung fluid after birth causing early onset mild respiratory distress. This is a benign, self-limited disease related to newborn transition. No evidence that TTN predisposes to long-term pulmonary dysfunction. Generally considered a disorder of term infants, but can occur in premature infants. TTN risk factors: Csection delivery, Male, Macrocosmic, IDM.
What is congestive heart failure (CHF) in an infant?
Important cause of tachypnea. Most often caused by a congenital heart defect. There is an increased risk of heart defect in IDMs, and therefore increased risk of CHF. Usually presents with heart murmur.
What is sepsis/pneumonia?
Early signs of neonatal sepsis are subtle and nonspecific and may include symptoms such as poor feeding, lethargy, or irritability. May also present initially with tachypnea and progress to more severe illness rapidly.
What are risk factors for sepsis and pneumonia?
PROM, Group B strep infection transmitted from the mother during labor.
What is hypoglycemia?
May be seen in IDMs due to the chronic hyperinsulinemia state that occurred during gestation. May be more pronounced in premature infants. Tachypnea is a non-specific response to this metabolic derangement.
What is a congenital diaphragmatic hernia?
A congenital malformation resulting from a defect in the development of the diaphragm. Occurs in 1 out of 2,200 to 5,000 live births. Most common type is the Bochdalek hernia (posterolateral hernia), which accounts for majority (greater than 95 percent) of cases:
- Allows passage of abdominal organs into chest cavity and severely impairs lung development.
- Most defects occur on the left side
- Absent breath sounds or presence of bowel sounds on one side of the chest are important diagnostic clues.
What is a pneumothorax?
Caused by a collection of gas in the pleural space with resultant collapse of lung tissue. Common risk factors:
- Mechanical ventilation
- Underlying lung disease (esp. meconium aspiration or severe infant RDS)
- Absence of breath sounds on one side of the chest in combination with respiratory distress is an important clue.
What is meconium aspiration syndrome?
Passage of meconium in utero may indicate fetal stress and hypoxia. Aspiration of meconium may occur in utero with fetal gasping, or at first breath at delivery. Often presents with symptoms of respiratory distress, including tachypnea.
What is transposition of the great arteries (TGA)?
Congenital heart defect in which the aorta and pulmonary arteries are transposed, resulting in respiratory distress and severe cyanosis shortly after birth as PDA closes. IDM is a risk factor. Often associated with other congenital heart defects such as a VSD. Murmur may be heard on physical examination.
What is hypothermia?
Should be considered on the ddx of a tachypneic newborn. May be associated with neonatal sepsis. Small for gestational age and premature infants are more at risk to become hypothermic because of their small body size and relatively large surface area.
What is severe coarctation of the aorta?
May cause respiratory distress if there is severe left ventricular outflow tract obstruction. Classically diminished pulses in the lower extremities and asymmetric blood pressure readings suggest the diagnosis. In severely ill neonates, there may be no differences in pulse because cardiac output is so poor.
Why is a CBC with differential useful when an infant has respiratory distress?
Useful to rule out neutropenia, leukopenia, abnormal immature-to-total neutrophil ratio, an thrombocytopenia as signs of sepsis maybe underlying respiratory distress.
Why are blood and CSF cultures useful when an infant has respiratory distress?
They are critical to the diagnosis and management of sepsis.
Why are arterial blood gases (ABG) helpful when an infant is in respiratory distress?
H-ABGs are helpful in determining the oxygenation (PaO2), ventilation (PaCO2), and acid-base status (pH and HCO3) of the infant.
- If the infant is cyanotic, knowing pCO2 helps elucidate the cause
- If respiratory distress is mild, the infant pink in color, and the infant is not otherwise at risk, blood gas determination is not essential.
Why is pulse oximetry important when an infant is in respiratory distress?
Detects oxygen saturation of blood.
What is the oxygen challenge test (hyperoxia test)?
- Can help differentiate between cardiac and pulmonary etiology in cyanotic infants.
- Oxygen will increase the PaO2 of infant whose cyanosis is caused by a respiratory condition, but not significantly increase PaO2 if cyanosis is caused by a cardiac lesion.
What is important to know about CXR use for infants in respiratory distress?
- Its an integral part of initial assessment of the newborn with respiratory distress
- Size and shape of heart may yield some clues to the diagnosis
- Appearance of the lungs may suggest pneumonia, meconium aspiration, RDS, etc.
- Normal inspiratory films should have eight or more intercostal spaces of lung fields on both sides
What are CXR findings typical of TTN?
- Significant perihilar streaking due to interstitial fluid and engorged lymphatics
- Coarse, fluffy densities that represent fluid-filled alveoli
- Fluid in the pleural space and fissures
What are CXR findings typical of RDS?
Air bronchograms, Diffuse reticulogranular appearance of lung fields (“ground-glass appearance”)
What are CXR findings in infant with diaphragmatic hernia?
Air-filled loops of bowel in left side of chest. Displacement of heart and mediastinum to contralateral side.
What should you know about using an echocardiogram in infants in respiratory distress?
- Gold standard in diagnosis of congenital cardiac lesions and persistent pulmonary hypertension of the newborn
- Indicated when there is persistent cyanosis and no indication of lung disease, or when there are other signs suggesting heart defect, such as a murmur, abnormal electrocardiogram (ECG), or chest Xray showing abnormal cardiac contour.
What should you know about using a glucometer test in infants in respiratory distress?
- The glucometer test is a screening test only, and must not be used to confirm hypoglycemia.
- Confirm glucometer reading with serum or plasma glucose level.
- If low, start treatment immediately; do not deny until laboratory results are available.
How do you best manage Transient tachypnea of the newborn (TTN):
- Monitor to ensure signs of respiratory distress - including tachypnea - resolve.
- If respiratory symptoms do not improve, suspect pneumonia. Orders repeat chest X-ray and start antibiotics.
How do you best manage feeding and respiratory distress?
- Recommendations vary, depending on physician’s experience or the policy of the neonatal unit.
- No evidence from controlled studies that feeding a tachypeic infant by mouth is contraindicated (although many physicians are reluctant to try this because they feel that oral feeding place the infant under greater stress)
- Some infants may need nasogastric feeding/IV fluids if respiratory distress worsens with feeding
- Infants with RR greater than 80 per min will have difficulty with both oral and nasogastric feedings and often require intravenous fluid support.
- Use of a nasogastric feeding tube avoids use of a bottle (after feeding from a bottle, some babies may get frustrated when they breastfeed because the milk does not flow as fast from the breast as from a bottle)
Glucose is the primary substrate for brain metabolism in the neonate, and even asymptomatic hypoglycemia may have negative consequences for long-term neurodevelopment.
What is the goal in treating hypoglycemia?
Maintain glucose levels between 41-50 mg/dL.
What are the threshold values for intervention with hypoglycemia?
Asymptomatic infants and infants at risk for hypoglycemia: less than 35 mg/dL
Symptomatic infants: less than 45 mg/dL
Milk feeding (formula or breast)…
…raises glucose levels, maintains stable levels, and avoids rebound hypoglycemia that is associated with glucose water.
How often should you monitor glucose levels in these kids?
- Monitor glucose levels until levels are stable (greater than 40 mg/dL). If the blood glucose is not greater than 40 mg/dL with the first enteral feeding, initiate IV dextrose infusions.
- Freq. of monitoring depends on severity of hypoglycemia; may range from every 30 minutes to every 3 hrs prior to feeds.
What should you do with premature infants before discharge?
Establish breastfeeding and self-maintenance of body temperature.
What should you confirm before discharging premature infants?
Physical exam without major defects, minimal or no jaundice, no blood group incompatibility, breastfeeding well every two to four hours, six or more wet diapers daily, transition from meconium to seedy, soft, tan-yellow stools, weight loss less than 10 percent, car seat available, good support for mother at home, back to sleep program reviewed, prescription for vitaD completed (for exclusively breastfeeding infants, recommended 200 IU of vitaD daily), follow up visit arranged with PCP, risks of cobedding reviewed.
What are the risks of co-bedding an infant?
Infant may be brought into bed for nursing or comforting but should be returned to their own bassinet or crib when parent is ready to return to sleep. Infant should not be brought into bed when parent is excessively tired or using medication or substances that could impair his or her alertness.