Pediatric Examination and Board Review (200 page)

2.
(C)
Any of these can cause respiratory distress in a newborn. Babies with transient tachypnea generally do not have retractions. Phrenic nerve injury, leading to diaphragm dysfunction, is usually due to a brachial plexus injury (BPI); in this vignette there is no history of a large-for-gestational-age infant, instrumentation at delivery (forceps/vacuum), or shoulder dystocia, all of which are risk factors for BPIs.

3.
(D)
A chest radiograph, evaluation for sepsis, and evaluation for hypoglycemia are all appropriate in this scenario. To rule out congenital cyanotic heart disease, a hyperoxia test is appropriate. To perform a hyperoxia test, obtain a baseline right radial (preductal) arterial blood gas. Next, the patient should be in a head hood with 100% O
₂
for 15 minutes, after which another ABG is obtained. If the Pao
₂
rises above 150 mm Hg, then cyanotic heart disease has been ruled out. Meconium aspiration is associated with an increased risk for pneumothorax but without any clinical signs that would indicate a pneumothorax such as unequal air entry into the lungs, a displaced apical beat, or findings on transillumination, a chest tube thoracostomy is not indicated.

4.
(E)
Any newborn baby with respiratory distress should have a chest radiograph. A sepsis workup should also be done, and the patient should be started on antibiotics, especially because there is a history of prolonged rupture of membranes that places this child at a higher risk for infection. Hypoglycemia can present with a wide range of nonspecific symptoms. In a term baby with respiratory distress, the aim is to maintain the O
₂
saturation at 96-100%.

5.
(E)
The chest radiograph shows bilateral scattered infiltrates. The cardiothymic shadow is normal. This fits best with a picture of pneumonitis, etiology uncertain. TTN usually is associated with perihilar streaking and fluid in the fissures.

6.
(A)
Surfactant administration is recommended for meconium aspiration. Meconium inactivates native surfactant and there is decreased surfactant production following alveolar injury. Inhaled NO is a pulmonary vasodilator. Meconium aspiration syndrome is associated with persistent pulmonary hypertension (PPHN) in many cases. If you are in a hospital where echocardiography cannot be done to rule out cyanotic heart disease, and despite high ventilator settings and other supportive measures the Pao
₂
is low, it is appropriate to start a prostaglandin drip to maintain a patent ductus arteriosus (PDA). Dobutamine and nitrous oxide may be needed if the neonate’s condition continues to deteriorate.

7.
(A)
Before making the diagnosis of PPHN as the cause of hypoxemia/low Pao
₂
in a term baby with respiratory distress, an echocardiogram should be done to rule out cyanotic congenital heart disease.

8.
(A)
After birth, the neonate experiences a rapid decrease in pulmonary vascular resistance. In persistent PPHN, pulmonary pressures remain higher than systemic pressures, resulting in right-to-left shunting at the ductal or atrial level and subsequent hypoxemic respiratory failure. In this patient, bidirectional shunting at the atrial level and bulging of the interatrial septum to the left indicates a high pulmonary pressure compared with systemic pressure.

PPHN generally occurs in a full-term or postterm infant on day of life 1 with hypoxia and cyanosis. The patient can be very labile. The Pao
₂
can increase from 45 to 200 without any change in therapy. If the shunt is at the ductal level, there will be a difference in the pre- and postductal blood O
₂
saturation. This difference in pre- and postductal O
₂
blood saturation is not seen if the shunt is at the atrial level or intrapulmonary.

9.
(E)
Pulmonary vascular resistance is high in the normal fetus because of several factors: low fetal Pao
₂
(normal Pao
₂
of fetus is 30/mm Hg), high fetal Paco
₂
, increased constrictor stimuli like leukotrienes and endothelin, and lack of a dilator stimulus like NO. At birth, mechanical distention of the lung, an increase in Pao
₂
, a decrease in Paco
₂
, and an increase in pH cause decreased pulmonary vascular resistance. Mechanical distention of the lung helps pulmonary vasodilation both mechanically and by the production of endogenous vasodilators.

10.
(C)
Inotropes are used in PPHN to increase the systemic BP so that right-to-left shunting will reverse. Increasing ventilator settings and the MAP will improve oxygenation. Studies in animals have shown that respiratory and metabolic alkalosis lowers pulmonary vascular resistance. Inhaled NO has a rapid and potent vasodilatory effect. Inhaled NO is contraindicated in congenital heart disease that depends on right-to-left shunting across the ductus arteriosus. Therefore, an echocardiogram is essential before starting inhaled NO. Milrinone decreases pulmonary artery resistance and may work additively with inhaled NO. There is no role for furosemide in PPHN. IV sildenafil is a selective pulmonary vasodilator but may cause hypotension and worsen oxygenation when used in conjunction with inhaled NO.

11.
(E)
The normal transition from intrauterine to extrauterine life requires a precipitous drop in pulmonary vascular resistance. Any factor that impairs this normal transition can cause PPHN. The causes of PPHN can be divided into three categories: parenchymal lung disease, idiopathic, and pulmonary hypoplasia. Parenchymal lung disease can be caused by several factors including meconium aspiration syndrome, RDS, and sepsis. Pulmonary hypoplasia can be caused by factors like a congenital diaphragmatic hernia.

12.
(B)
The oxygenation index (OI) is a commonly used calculation to determine the severity of pulmonary hypertension. OI >25 generally is used as a criterion to begin inhaled NO. Worsening (increasing) OI may point toward the need for ECMO.

Oxygenation Index (OI) = [Mean Airway Pressure

                                         × Fio
₂
× 100]/Pao
₂
.

In this patient, OI = [15 × 1.0 × 100]/50 = 30%.

13.
(D)
When a patient acutely decompensates, mechanical causes like ET placement, the presence or absence of pneumothorax, or mechanical factors related to the ventilator should be checked. If mechanical factors are noncontributory, the patient likely has high pulmonary pressure. Any time systemic pressures decreases, there will be right-to-left shunting. Administration of intravascular volume expansion is appropriate to increase the systemic pressure. Surfactant will not help.

14.
(D)
The dose approved by the Food and Drug Administration (FDA) for inhaled NO is 20 ppm. There is a very small subset of patients that do not respond to 20 ppm but respond to 40 ppm. The OI of the patient at this time is 41%. An OI > 40% is predictive of 80% mortality. If the OI for the next few hours remains high, this patient will be a candidate for ECMO.

15.
(C)
Constriction of the fetal ductus arteriosus may lead to PPHN. Of the medications listed, only aspirin does this. Other nonsteroidal anti-inflammatory drugs can also do this.

S
UGGESTED
R
EADING

Hany A. Respiratory disorders in the newborn: identification and diagnosis.
Pediatr Rev.
2004;25:201-207.

Konduri GG. New approaches for persistent pulmonary hypertension of newborn.
Clin Perinatol.
2004;31:591-611.

Steinhorn RH, Farrow KN. Pulmonary hypertension in the neonate.
NeoReviews.
2007;8:e14-e21.

CASE 112: A PREMATURE NEONATE WITH RESPIRATORY DISTRESS SYNDROME AND NECROTIZING ENTEROCOLITIS

A 650-g baby at 26 weeks’ gestation is born to a 20-year-old G2P1 mother by vaginal delivery. Mom presented in preterm labor 6 hours before delivery. The maternal membranes were intact; Mom had no fever. The mother received one dose of betamethasone and one dose of penicillin 4 hours before delivery. Serologic tests for syphilis, hepatitis B surface antigen, and human immunodeficiency virus (HIV) were all negative. The baby is depressed at birth with a heart rate of 100 beats/ minute and is dusky. The respiratory effort is poor. The patient is suctioned and positive pressure ventilation is given for about 1 minute with improvement in heart rate and color. However, the respiratory effort remains poor. The baby becomes dusky each time bagging is stopped, at which time you decide to intubate with a size 2.5 endotracheal tube (ET). The ET is secured with tape and bagging is continued with the ET in place. The color and heart rate improve. The baby now has some spontaneous respiratory effort and begins to move. The baby is taken to the special care nursery. The Apgar scores are 3 and 7 at 1 and 5 minutes, respectively.

SELECT THE ONE BEST ANSWER

1.
Administration of steroids to the mother probably helped the baby

(A) yes

(B) no

2.
What are the problems that you anticipate in the first 24 hours in this premature baby?

(A) fluid/electrolyte imbalance

(B) RDS

(C) sepsis

(D) hypoglycemia

(E) all of the above

3.
After admission to the neonatal intensive care unit (NICU), the baby is put on a ventilator with the following settings: Fio
₂
of 1.0, PIP of 20, PEEP of 5, rate of 40, and I-time of 0.3. The O
₂
saturation is in the mid-90% range. The perfusion is good, the mean BP is 28, the heart rate is 140/minute, and the respiratory rate is 40-50/minute. The baby has mild to moderate subcostal retractions. What is the differential diagnosis of the respiratory distress?

(A) respiratory distress syndrome (RDS)

(B) sepsis