Therapeutic Measures Used to Manage Infants With or Prevent Chronic Lung Disease of Infancy
Prenatal steroids
A single course of prenatal glucocorticoids administered to women who are at high risk for premature
delivery results in a significant decrease in the mortality rate and in the morbidity associated with
prematurity.
Gentle ventilation
Despite development of numerous sophisticated ventilators for the newborn, there is still no clear
advantage to any one approach. The general approach is a ventilatory mode that prevents
atelectasis, sustains or maintains functional residual capacity, uses a minimal tidal volume, and
permits the infant to trigger his or her own ventilation as much as possible. Every effort should be
made to minimize high peak inspiratory pressures, high mean airway pressures, and overdistention
of the lungs. For example, high-frequency ventilation, low tidal volumes, and permissive
hypercapnia are commonly used.
Low inspired
Every effort should be made to administer only the lowest concentration of oxygen that is necessary.
oxygen
concentrations
Nasal continuous
Early application of nasal CPAP in high-risk respiratory distress syndrome and infants with chronic
positive airway
lung disease of infancy (CLDI) is highly recommended during postnatal care.
pressure
(CPAP)
Fluid restriction
Because fluid overload is a causative factor associated with CLDI, fluid limitation may be helpful.
However, care should be taken to avoid being overly aggressive when limiting fluids, because
undernutrition is also associated with the development of CLDI.
Vitamin A
Vitamin A is an essential nutrient for maintaining the epithelial cells of the tracheobronchial tree.
Caffeine
Early initiation of caffeine in those at risk for CLDI has been shown to shorten the course of
respiratory support and the incidence of CLDI.
Diuretics
In infants with severe CLDI, pulmonary edema is a major component. There is clear evidence that
either daily or alternate-day therapy with furosemide improves lung mechanics and gas exchange
in infants with established CLDI.
Bronchodilator
Increased airway resistance is highly associated with CLDI. Short-term therapy with inhaled or
therapy
parenteral beta2-adrenergic agonists is occasionally administered to infants with CLDI.
Airway clearance
Routine suctioning is beneficial.
therapy
Postnatal
The administration of postnatal corticosteroids to preterm infants has been shown to reduce lung
corticosteroids
inflammation and the incidence of CLDI. Postnatal corticosteroids are also believed to increase
surfactant synthesis, enhance beta-adrenergic activity, increase antioxidant production, stabilize
cell and lysosomal membranes, and inhibit prostaglandin and leukotriene synthesis. Side effects
include increased incidence of hyperglycemia and infection.
Prenatal
Per Surfactant Administration Protocol, Protocol 33.5
Surfactant
Case Study Chronic Lung Disease of Infancy
Admitting History and Physical Examination
An 1100-gram baby boy was born at 28 weeks’ gestation to a mother who received no prenatal care. The mother had used cocaine and marijuana and may have had a vaginal infection during her pregnancy. Because of the baby's clinical presentation, mechanical ventilation was started moments after birth. Exogenous surfactant was given to improve lung compliance and avoid a prolonged ventilator course.
The infant worsened over 24 hours. He was diagnosed with respiratory distress syndrome and group B streptococcal pneumonia. An intravenous line and umbilical artery catheter were placed. Antibiotics were started. He required higher concentrations of oxygen, positive inspiratory pressures (PIPs) greater than 30 cm H2O, and higher levels of positive end-
expiratory pressure (PEEP) to maintain oxygenation and adequate tidal volume.
He was placed on high-frequency oscillatory ventilation for 4 days and was eventually transitioned back to conventional ventilation. He was placed on high-flow nasal cannula oxygen at day 14. However, at day 20 he became tachypneic, with grunting and retractions, requiring an increase in FIO2. A respiratory viral panel showed he was positive for influenza A, a
virus contracted from his maternal grandmother who had been visiting the nursery. He developed pneumonia, requiring another intubation and ventilator support. At this time the clinical team was concerned that the infant has the potential to develop chronic lung disease of infancy (CLDI).
At 4 weeks, the baby was still on a pressure-cycled mechanical ventilator with the following settings: PIP +25 cm H2O, respiratory rate (RR) 35 breaths/min, inspiratory time (TI) 0.45, FIO2 0.60, and PEEP +7 cm H2O. His pulmonary mechanics
showed increased airway resistance and decreased lung compliance. He demonstrated coarse bilateral crackles and some wheezes. Thick, clear mucus was suctioned. The chest radiograph showed patchy atelectasis and areas of pulmonary
fibrosis. His arterial line ABGs on an FIO2 of 0.60 were pH 7.31, PaCO2 55 mm Hg, 27 mEq/L, PaO2 50 mm Hg, and SaO2 of 84%. The doctor wrote the following order in the baby's chart: “Respiratory therapy to assess patient and begin to
wean from ventilator.”
The respiratory therapist charted the following assessment.
Respiratory Assessment and Plan
S N/A
O Marginal pulmonary mechanics—decreased compliance and increased airway resistance. Coarse crackles and wheezes. CXR: Suggests CLDI with scattered areas of atelectasis and
hyperinflation. ABGs on ventilator and FIO2 0.60: pH 7.31, PaCO2 55, 27, PaO2 50, and
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SaO2 84%.
A
•Stiff lung with airway obstruction (pulmonary mechanics) suggests CLDI
•Chronic ventilatory failure with moderate hypoxemia (ABGs)
•Excessive bronchial secretions (crackles and suctioning results)
•Possible bronchospasm (wheezes—maybe caused by bronchial secretions)
•Appears ready for slow weaning trial
P Wean slowly per Mechanical Ventilation and Ventilator Weaning Protocol (decrease mandatory respiratory rate slowly; decrease need for pressure; transition to pressure support ventilation). Continue Oxygen Therapy Protocol (FIO2 to meet SpO2 goals). Continue suction
PRN. Trial Bronchodilator Therapy Protocol (in-line neb with 0.25 mL of albuterol in 2.0 mL normal saline q4h) to assess effectiveness. Continue to monitor closely and assess frequently.
Over the next 10 weeks, the baby slowly improved. Five days before discharge, the mother was trained on respiratory and nursing procedures for home care. Over the next 4 years, the child's lungs continued to improve even though he had recurrent pneumonia and was seen monthly in the ED during the first 6 months. On one occasion, he was readmitted to the hospital for a week; he recovered and is now doing well. He is of normal weight and height for his age, runs and plays well with other children, and is about to enter preschool.
Discussion
Several comments should be made regarding this challenging pulmonary disorder of the newborn. First, infants with CLDI have limited pulmonary reserves. Their lungs are seriously damaged, scarred, and fibrotic. They have increased airway resistance and decreased lung compliance. Because their lung tissues are constantly being bombarded by inflammatory stimuli, their hearts and lungs have a limited ability to recover from stress. These infants may be slow to recover from procedures such as tracheal or nasopharyngeal suctioning. They are also prone to gastroesophageal reflux disease (GERD) and microaspiration. Therefore health care personnel should perform all therapeutic procedures as quickly and efficiently as possible.
Second, every attempt should be made to wean the baby off the ventilator because ventilator pressures, rates, and high oxygen concentrations are the main factors causing the pulmonary damage. The longer the baby is on the ventilator, the more the lungs are being damaged. Some neonatal intensive care units are now implementing criteria for extubation readiness testing to regularly assess infants for extubation, hoping to shorten their days on the ventilator.
Because chronic ventilatory failure with hypoxemia commonly occurs in infants with chronic CIDI, the respiratory therapist should not hurry to decrease the infant's PaCO2 to the “normal” range of 35 to 45 mm Hg. Infants in the acute and
chronic stages of CLDI often have a high PaCO2 and normal pH (compensated). A PaCO2 of 50 to 60 mm Hg may be tolerated well. Therefore the therapist must be prepared to accept chronically high PaCO2 levels. As the baby's lungs
deteriorate, moreover, the ability of blood to flow easily through the lungs progressively declines. As the condition worsens, the work of the right side of the heart increases. If the CLDI does not resolve, pulmonary hypertension and cor pulmonale may develop and require treatment.
CLDI is a disorder that requires a great deal of parental education and support at the time of the baby's discharge from the hospital. Therefore the importance of comprehensive home medical and respiratory care and regular assessment of their child's respiratory status must be stressed to the family. The respiratory therapist can be instrumental in working with the family both in the hospital and in the home to ensure the parents are prepared to support the infant's respiratory care needs. For example, the parents must understand the procedures of oral and nasal suctioning, and aerosolized medication administration at home. Feeding problems and GERD are very common in these infants. Infants with CLDI who have been discharged from the hospital commonly return to the hospital once or twice a year in acute respiratory distress. The majority of infants with severe CLDI will develop some degree of airway hyperresponsiveness or reactivity. Although CLDI infants have asthma-like symptoms as they age, they are less likely to demonstrate significant response to bronchodilators because of their fixed airway narrowing and bronchomalacias. Inhaled or chronic low-dose systemic steroid therapy may be necessary. Therefore the importance of comprehensive home medical and respiratory care and regular assessment of their child's respiratory status must be stressed to the family.
Self-Assessment Questions
1.Which of the following is(are) associated with the cause of chronic lung disease of infancy?
1.History of RDS
2.Low positive pressure mechanical ventilation
3.High concentrations of oxygen
4.Infant's weight greater than 2000 grams
a.2 only
b.1 and 3 only
c.2, 3, and 4 only
d.1, 3, and 4 only
2.The anatomic alterations of the lungs associated with chronic lung disease of infancy are: 1. Increased alveolar-capillary membrane thickness
2. Atelectasis
3.Excessive bronchial secretions
4.Consolidation
a.2 and 4 only
b.3 and 4 only
c.1, 2, and 3 only
d.1, 2, 3, and 4
3.In what is referred to as the “new” chronic lung disease of infancy (new CLDI), the major anatomic pathologic process is a decrease in alveolar number, called:
a.Patches of atelectasis
b.State IV CLDI
c.Alveolar hypoplasia
d.Canalicular period of fetal development
4.Which of the following arterial blood gas values are associated with severe chronic lung disease of infancy?
1.Decreased pH
2.Increased PaCO2
3.Normal pH
4.Decreased
a.2 and 3 only
b.1 and 4 only
c.2, 3, and 4 only
d.1, 2, and 4 only
5.Which of the following clinical manifestations are associated with chronic lung disease of infancy?
1.Crackles
2.Intercostal retractions
3.Hypoxemia
4.Wheezes
a.1 and 4 only
b.2 and 3 only
c.1, 2, and 3 only
d.1, 2, 3, and 4
1Permissive hypercapnia defined: Mechanical ventilation was traditionally applied with the goal of normalizing arterial blood gas values, particularly the arterial carbon dioxide tension (PaCO2). However, this is no longer the primary objective
of mechanical ventilation. Today, the emphasis is on maintaining adequate gas exchange while—and, importantly— minimizing the risks of mechanical ventilation. Common strategies used to reduce the risks of mechanical ventilation include (1) low tidal volume ventilation to protect the lung from ventilator-associated lung injury in patients with acute lung injury (e.g., ARDS) and (2) reduction of the tidal volume, respiratory rate, or both to minimize intrinsic positive endexpiratory pressure (i.e., auto-PEEP) in patients with obstructive lung disease (e.g., COPD). Although these mechanical ventilation strategies may result in an increased PaCO2 level (hypercapnia), they do help protect the lung from barotrauma
(i.e., physical damage to lung tissues caused by excessive gas pressures). The lenient acceptance of the hypercapnia is called permissive hypercapnia. In most cases, the patient's PaCO2 is adequately maintained by an increased ventilatory
rate that offsets the decreased tidal volume. The PaCO2, however, should not be permitted to increase to the point of severe acidosis. The most current consensus suggests it is safe to allow pH to fall to as low as 7.20 (http://www.ARDSNet).
2It has long been known that mechanical ventilation can produce a variety of lung injuries referred to as ventilatorinduced lung injury (VILI), pulmonary volutrauma, or pulmonary barotrauma. VILI is defined as stress fractures of the pulmonary capillary endothelium, epithelium, and basement membrane and, in severe cases, lung rupture. Lung ruptures can lead to leakage of fluid, protein, and blood into tissue and air spaces or leakage of air into tissue spaces. This condition can be followed by an inflammatory response and possibly a reduced defense against infection. Pulmonary volutrauma is defined as damage to the lung caused by overdistention by a mechanical ventilator set for an excessively high tidal volume. Pulmonary barotrauma is defined as damage to the lungs caused by rapid or extreme pressures generated by mechanical ventilation. Predisposing factors for VILI, pulmonary volutrauma, or pulmonary barotrauma include (1) mechanical ventilation with high peak inspiratory volumes and pressures, (2) mechanical ventilation with a high mean airway pressure, (3) structural immaturity of lung and chest wall, (4) surfactant insufficiency or inactivation, and (5) preexisting lung disease. Fortunately, newborn mechanical ventilator strategies today minimize lung injuries by keeping exhaled volumes low, accepting higher PCO2 levels, or switching to high-frequency ventilation when positive inspiratory
pressures exceed safe limits. Pulmonary air leak syndrome (see Chapter 38, Pulmonary Air Leak Syndrome), however, can still occur in certain clinical scenarios, especially when very high ventilator pressures are used or in the delivery room with aggressive ventilation during resuscitation.
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C H A P T E R 4 1
Congenital Diaphragmatic Hernia
CHAPTER OUTLINE
Anatomic Alterations of the Lungs Etiology and Epidemiology
Overview of Cardiopulmonary Clinical Manifestations Associated With Congenital Diaphragmatic Hernia General Management of a Congenital Diaphragmatic Hernia
Case Study: Diaphragmatic Hernia Self-Assessment Questions
CHAPTER OBJECTIVES
After reading this chapter, you will be able to:
•List the anatomic alterations of the lungs associated with congenital diaphragmatic hernia.
•Describe the causes of congenital diaphragmatic hernia.
•List the cardiopulmonary clinical manifestations associated with congenital diaphragmatic hernia.
•Describe the general management of congenital diaphragmatic hernia.
•Describe the clinical strategies and rationales of the SOAP presented in the case study.
•Define key terms and complete self-assessment questions at the end of the chapter and on Evolve.
KEY TERMS
Atelectasis
Bochdalek Foramen
Bochdalek Hernia
Congenital Diaphragmatic Eventration
Congenital Diaphragmatic Hernia (CDH)
Echocardiogram
Extracorporeal Membrane Oxygenation (ECMO)
Hemothorax
Inhaled Nitric Oxide (iNO) Therapy
Morgagni Hernia
Pneumothorax
Posterolateral Diaphragmatic Hernia
Prenatal Ultrasound
Pulmonary Hypertension
Pulmonary Hypoplasia
Scaphoid Abdomen
Total Absence of the Diaphragm
Anatomic Alterations of the Lungs
During normal fetal development, the diaphragm first appears anteriorly between the heart and liver and then progressively grows posteriorly. Between the eighth and tenth week of gestation, the diaphragm normally completely closes at the left Bochdalek foramen, which is located posteriorly and laterally on the left diaphragm. At about the tenth week of gestation (about the same time the Bochdalek foramen is closing), the intestines and stomach normally migrate from the yolk sac. If, however, the bowels reach this area before the Bochdalek foramen closes, a hernia results—a congenital diaphragmatic hernia (CDH) (also called Bochdalek hernia or posterolateral diaphragmatic hernia). Thus the Bochdalek hernia is an abnormal hole in the posterolateral corner of the left diaphragm that allows the intestines —and in some cases the stomach—to move directly into the chest cavity and compress the developing lungs.1
As shown in Fig. 41.1, the effects of a diaphragmatic hernia are similar to the effects of a pneumothorax or
hemothorax—that is, the lungs are compressed. As the condition becomes more severe, atelectasis and complete lung collapse may occur. When this happens, the heart and mediastinum are pushed to the right side of the chest. In addition, long-term lung compression in utero causes pulmonary hypoplasia, which is most severe on the affected (ipsilateral) side but also occurs on the unaffected (contralateral) side.
FIGURE 41.1 Diaphragmatic hernia.
This pathologic process causes a marked reduction in the number of bronchial generations and alveoli per acinus. Concomitant increased muscularity of the small pulmonary arteries may contribute to the increased pulmonary vascular resistance and pulmonary hypertension commonly seen in these patients. Respiratory distress usually develops soon after birth. As the infant struggles to inhale, the increased negative intrathoracic pressure generated during each inspiration causes even more of the intestines to be sucked into the thorax. Further compression of the lungs and heart occurs as the infant cries and swallows air, causing the intestine and stomach to distend further.
Finally, as a consequence of the hypoxemia associated with a diaphragmatic hernia, these babies often develop hypoxiainduced pulmonary arterial vasoconstriction and vasospasm, which also produce a state of pulmonary hypertension.
The major pathologic or structural changes associated with diaphragmatic hernia may include the following:
•Failure of the Bochdalek foramen of the diaphragm to close
•Migration of intestines and stomach into the thorax
•Atelectasis
•Complete lung collapse
•Mediastinal shift to the unaffected side of the thorax
•Reduction in the number of bronchial generations and alveoli per acinus
•Pulmonary hypoplasia
•Transient pulmonary hypertension
Etiology and Epidemiology
The overall incidence of CDH is 1 in 2500 to 3500 live births. The baby is usually mature, and two-thirds are male. About 90% of CDHs occur on the left side through the Bochdalek foramen. The mortality rate for infants with CDH, including spontaneous abortions, stillbirths, and prehospital deaths, is about 50% to 60%. The prognosis depends on (1) the size of the defect, (2) the degree of hypoplasia, (3) the condition of the lung on the unaffected side, and (4) the success of the surgical diaphragmatic closure. Most cases of CDH are now diagnosed by prenatal ultrasound, allowing the infant to be delivered at a hospital where surgical repair of the diaphragmatic hernia can occur very shortly after birth. A few pediatric centers are performing high-risk prenatal surgery (in-utero) to repair the diaphragm.
Overview of Cardiopulmonary Clinical Manifestations Associated With Congenital Diaphragmatic Hernia
The following clinical manifestations result from the pathologic mechanisms caused (or activated) by atelectasis (see Fig. 10.7)—a common anatomic alteration of the lungs associated with diaphragmatic hernia (see Fig. 41.1).
Clinical Data Obtained at the Patient's Bedside
The Physical Examination
Vital Signs
Increased Respiratory Rate (Tachypnea)
Normally, a newborn's respiratory rate is about 40 to 60 breaths/min. When a diaphragmatic hernia is present, the respiratory rate is generally well over 60 breaths/min. Several pathophysiologic mechanisms operating simultaneously may lead to an increased ventilatory rate:
•Stimulation of peripheral chemoreceptors (hypoxemia)
•Relationship of decreased lung compliance to increased ventilatory rate
•Stimulation of central chemoreceptors
Increased Heart Rate (Pulse) and Blood Pressure
Clinical Manifestations Associated With Greater Negative Intrapleural Pressures During Inspiration
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•Intercostal retraction
•Substernal retraction
•Nasal flaring
Chest Assessment Findings
•Diminished or absent breath sounds over the affected side
•Bowel sounds over the affected side
•Apical heartbeat heard over the unaffected side (usually right)
Expiratory Grunting
Cyanosis
Barrel Chest Deformity
When the intestines are in the chest and distended with gas, the baby often demonstrates a barrel chest deformity.
Scaphoid Abdomen
Depending on the degree of intestinal displacement into the thorax, the infant's abdomen often appears flat or concave.
Clinical Data Obtained from Laboratory Tests and Special Procedures
Pulmonary Function Test Findings
(Extrapolated Data for Instructional Purposes) (Primarily Restrictive Lung Pathophysiology)
The anatomic alterations of the lungs associated with CDH primarily cause a restrictive lung pathophysiology. For example, in moderate to severe cases, the following lung volumes and capacities may be lower than normal.
RV
IRV
VC
FRC
TLC
↓
↓
↓
↓
↓
Arterial Blood Gases1
Mild to Moderate Diaphragmatic Hernia
Acute Alveolar Hyperventilation With Hypoxemia2 (Acute Respiratory Alkalosis)
pH
PaCO2
PaO2
SaO2 or SpO2
↑
↓
↓
↓
↓
(but normal)
2See Fig. 5.2 and Table 5.4 and related discussion for the acute pH, PaCO2, and changes associated with acute alveolar hyperventilation.
Severe Diaphragmatic Hernia
Acute Ventilatory Failure With Hypoxemia3 (Acute Respiratory Acidosis)
pH4
PaCO2
4
PaO2
SaO2 or SpO2
↓
↑
↑
↓
↑
(but normal)
3See Table 5.5 and related discussion for the acute pH, PaCO2, and changes associated with acute ventilatory failure.
4When tissue hypoxia is severe enough to produce lactic acid, the pH and values will be lower than expected for a particular PaCO2 level.
1NOTE: A critically ill newborn is likely to have an umbilical arterial catheter in place for arterial blood gas (ABG) sampling. In older critically ill infants and children, an arterial line may be placed for frequent ABG sampling. For intermittent sampling, because of the difficulty of obtaining ABG samples from newborn and pediatric patients, capillary
blood gas (CBG) samples may be used to determine the pH, PaCO2, and (i.e., the acid-base and ventilation status only). Capillary PO2 values are unreliable and should not be used for clinical analysis. The standard way to evaluate the oxygenation status in these infants is pulse oximetry (SpO2) (see Chapter 33, Newborn Assessment and Management).
Oxygenation Indices5
QS/QT
DO26
VO2
O2ER
↑
↓
N
N
↑
↓
6Because the newborn normally has a higher hemoglobin level at birth (16.8 to 18.9 g/dL), the DO2 may actually be greater than indicated by PaO2 or SpO2 alone (see Chapter 5, Blood Gas Assessment).
Increased Opacity (Ground-Glass Appearance, Especially in Areas That Are Compressed)
A typical radiograph shows fluidand air-filled loops of intestine in the chest and a shift of the heart and mediastinum to the unaffected side. Atelectasis and complete lung collapse may be present. The lungs may appear hypoplastic and may not expand to meet the chest wall. A nasogastric tube (in the patient's stomach, it is hoped!) may be seen on the chest radiograph. It is used to decompress the abdominal viscera. The presence of a diaphragmatic hernia on a chest radiograph usually confirms the need for surgery (Fig. 41.2).
FIGURE 41.2 Chest radiograph of a left diaphragmatic hernia.
General Management of a Congenital Diaphragmatic Hernia
Severe diaphragmatic hernia used to be considered one of the most urgent neonatal surgical emergencies. Current practice is to make sure the patient has a stable cardiorespiratory status before undergoing surgical repair.
As soon as the diagnosis of a diaphragmatic hernia is made, a double-lumen oral gastric tube should be inserted with intermittent or low continuous suction. This reduces the amount of gas in the stomach and bowels and thereby reduces lung compression. Oxygen therapy should be started immediately (see Oxygen Therapy Protocol, Protocol 33.1). The infant also may be placed in the semi-Fowler position, which reduces intrathoracic pressure and facilitates the downward positioning of the abdominal viscera. Placing the infant on the affected side aids expansion of the good lung. The infant must not be manually ventilated with a bag and mask because of the danger of air swallowing.
The infant must, however, be intubated and ventilated. Mechanical ventilation should be applied with low peak airway pressures (less than 30 cm H2O) and rapid respiratory rates. A typical set of ventilator parameters would be peak
inspiratory pressure (PIP) +18 to +26 cm H2O, respiratory rate 20 to 40, FIO2 1.0, positive end-expiratory pressure (PEEP) +5 to +8 cm H2O, and inspiratory time (TI) 0.4. High-frequency oscillatory ventilation and high-frequency jet ventilation are
other successful ventilation techniques to achieve adequate oxygenation and carbon dioxide elimination while keeping airway pressures lower (see Mechanical Ventilation and Ventilator Weaning Protocol, Protocol 33.4).
Because the infant's lungs are fragile and rupture easily, the incidence of pneumothorax is high. Therefore the physician may need to insert one or more chest tubes during mechanical ventilation, if a pneumothorax occurs.
Paralysis with muscle relaxants and sedation are helpful at times. Paralysis eliminates air swallowing, which helps keep the gastrointestinal contents compressed. Suctioning may be necessary to maintain the infant's airways (see Airway Clearance Protocol, Protocol 33.2).
Occasionally, certain pharmacologic agents may be administered to offset the infant's pulmonary hypertension. Such drugs include tolazoline, prostacyclin, prostaglandin E1, sildenafil, and inhaled nitric oxide (iNO), in combination with different inotropes, such as dopamine and dobutamine. The physiologic action of iNO is believed to be similar to that of the vasoactive substance, endothelium-derived relaxing factor. The use of iNO has significantly reduced the need for ECMO therapy.
The surgical procedure entails repositioning the abdominal contents into the abdomen and closing the diaphragmatic defect. In some infants the peritoneal cavity may be too small to contain the abdominal contents. In these cases, after the repair is completed, the surgeon will place a patch to close the surgical site. After surgery, the baby is placed back on the ventilator and weaned per ventilator protocol. Mechanical ventilation with PEEP and continuous positive airway pressure (CPAP) are commonly required to offset the atelectasis and hypoplasia associated with the disorder. Often, the lung on the affected side is hypoplastic, and days or weeks of therapy may be required for full expansion to occur (see Lung Expansion Therapy Protocol, Protocol 33.3).
Extracorpeal Membrance Oxygenation (ECMO) may be indicated to treat circulatory and respiratory complications after surgery for infants who do not respond favorably to conventional medical therapy. While on ECMO, the infant is put on ventilation with only 10 breaths/min to keep the lungs inflated.
Case Study Diaphragmatic Hernia
Admitting History and Physical Examination
A full-term baby boy was delivered at 2:25 a.m. without complications to a mother who had received no prenatal care. After delivery, however, the baby made one cry and quickly became blue and limp, started to have bradycardia, and became
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apneic. The baby's 1-minute Apgar score was 3 (heart rate 1, respiration 0, tone 1, reflex irritability 1, color 0). The nurse handed the baby to a student intern, who immediately began manual ventilation. Both the respiratory therapist and the nurse noted that the baby's abdomen was scaphoid; the therapist stated that the baby might have a diaphragmatic hernia and that bagging should be stopped immediately. Moments later, the neonatologist entered the room, confirmed the scaphoid abdomen, noted that the lungs were very stiff in response to the bagging, and ordered a stat intubation with a 3.5-mm tube and a chest radiograph.
The infant was then transferred to the neonatal intensive care unit. The chest radiograph confirmed a left diaphragmatic hernia and hypoplastic left lung. At this time, a nasogastric tube was inserted and suction was begun. Initial ABGs were pH
7.19, PaCO2 63 mm Hg, 23 mEq/L, PaO2 37 mm Hg, and SaO2 56%. The baby was sedated and placed on a pressure-
limited mechanical ventilator. An intravenous line and umbilical artery catheter were then secured. The initial ventilator settings were respiratory rate 30 breaths/min, TI 0.5, PEEP +5, PIP + 25, and FIO2 1.0. No breath sounds could be heard
over the infant's left chest.
The neonatologist diagnosed pulmonary hypertension of the newborn by echocardiogram. The respiratory therapist then adjusted the ventilator settings as follows: respiratory rate 35 breaths/min, TI 0.4 second, PEEP +6, PIP +28 cm H2O,
and FIO2 1.0. A second set of ABGs taken 15 minutes later showed pH 7.29, PaCO2 49 mm Hg, 23 mEq/L, PaO2 44 mm Hg, and SaO2 74%.
The baby was started on iNO with little improvement in oxygenation. The team assumed this poor response was a result of the severe pulmonary hypoplasia. He was then placed on ECMO, with the ventilator set to minimal settings. Even though the ECMO was doing all the oxygenation, the baby's lungs were expanded by the ventilator 10 times a minute. Four days later, his pulmonary artery pressure was determined to be low enough for surgery. The diaphragmatic hernia was repaired, and the baby was returned to the unit. He was continued on a ventilator and ECMO.
The ventilator settings 3 days later were respiratory rate 10/min, TI 0.6, PIP +20, PEEP +5, and FIO2 0.45. His vital signs
were heart rate 145 beats/min, blood pressure 70/45 mm Hg and mean arterial pressure (MAP) of 53 mm Hg, (In pediatrics, MAP is utilized routinely to evaluate blood pressure), respiratory rate 65 breaths/min (between ventilator breaths), and temperature 37°C (98.6°F). His skin was pink and normal. Good breath sounds were auscultated over the right lung, fine and coarse crackles could be heard over the left lung.
His ABGs at this time were pH 7.36, PaCO2 44 mm Hg, 24 mEq/L, PaO2 73 mm Hg, and SaO2 94%. The baby's
chest radiograph showed good lung expansion on the right side. Although the upper half of the left lung was well expanded, atelectasis and hypoplasia were still seen over the lower half of the left lung. A small amount of thin, clear secretions was suctioned from the baby's endotracheal tube three or four times an hour.
At that time the respiratory therapist wrote the following assessment in the infant's chart.
Respiratory Assessment and Plan
S N/A
O Vital signs: On ECMO HR 145, BP 70/45 (53), RR 65 (10 mechanical breaths), T 37°C (98.6°F). Skin: Pink and normal. Breath sounds: Right lung normal; left lung coarse crackles.
•ECMO dependent on ventilator at minimal settings but improving (vital signs, skin color, ABGs)
•Mild amount of large and small airway secretions (fine and coarse crackles)
•Atelectasis and hypoplasia of the left lower lobe (CXR)
•May be ready to wean from ECMO—check with physician
P Mechanical Ventilation and Ventilator Weaning Protocol (continue to wean per protocol —wean pressures first, then FIO2). Lung Expansion Therapy Protocol (continue PEEP or CPAP
per Mechanical Ventilation and Ventilator Weaning Protocol). Airway Clearance Protocol (continue suction PRN). Oxygen Therapy Protocol (keep SpO2 at 97% as the FIO2 is decreased.
Do not decrease FIO2 more than 0.10 per hour).
ECMO was discontinued. The baby continued to improve over the next 5 days. On day 6, he was off the ventilator and discharged from the hospital 2 weeks later. The baby continued to develop normally over the next 4 years; at the time of this writing, he was about to enter kindergarten.
Discussion
This case nicely illustrates the importance of good assessment skills. Most diaphragmatic hernias are identified before the baby is born by high-resolution ultrasound of the maternal abdomen, visualizing the fetus in utero during routine prenatal care. Unfortunately, this mother had no prenatal care, and as a result the baby's diaphragmatic hernia was a surprise. Fortunately, the respiratory therapist and nurse in this case quickly and correctly identified the possibility of the diaphragmatic hernia by noting the scaphoid abdomen. Had the student intern continued to bag the baby manually, more gas would have entered the stomach and intestines, compressing and compromising the infant's lungs even more. The atelectasis (see Fig. 10.7) caused by the enlarged intestines was objectively confirmed on the chest radiograph. The Lung Expansion Therapy Protocol was clearly justified to offset the atelectasis after the diaphragmatic hernia was repaired (see Lung Expansion Therapy Protocol, Protocol 33.3).
This case further illustrates that the first objective in the management of the infant born with a diaphragmatic hernia is correction of the pulmonary hypertension. Often, as in this case, treatment requires that the infant be given ECMO and other cardiorespiratory stabilization treatments for several days before surgery. After the pulmonary hypertension is controlled, the second objective is surgical repair of the hernia. Mechanical ventilation with PEEP is usually required after surgery to correct the atelectasis and hypoplasia associated with the disorder. Typically, weaning involves decreasing the FIO2 while monitoring the baby's pulse oximetry. Ideally, the ventilator pressures are decreased first, followed by the
ventilatory rates. Permissive hypercapnia is routinely used, with a target PaCO2 of 55 mm Hg or less. An infant on a respiratory rate of 20 breaths/min, a peak inspiratory pressure of +20 cm H2O or less, and a PEEP of +5 to 6 cm H2O or
less is usually ready for extubation. Infants who survive congenital diaphragmatic hernia require follow-up pulmonary care for the first years of life because they handle pulmonary infections poorly, owing to their smaller than normal lungs as a result of the prenatal lung hypoplasia.
Self-Assessment Questions
1.The Bochdalek foramen closes at the:
a.Fourth to sixth week of gestation
b.Sixth to eighth week of gestation
c.Eighth to tenth week of gestation
d.Tenth to twelfth week of gestation
2.Which of the following are associated with a congenital diaphragmatic hernia? 1. Females affected more than males
2.Left side (90%)
3.A scaphoid abdomen at birth
4.Bowel sounds on the affected side of chest
a.1 and 3 only
b.2 and 4 only
c.2, 3, and 4 only
d.1, 2, 3, and 4
3.Which of the following arterial blood gas values is(are) associated with mild to moderate congenital diaphragmatic hernia?
1.Increased pH
2.Increased PaCO2
3.Increased PaO2
4.Increased
a.1 only
b.1 and 4 only
c.2, 3, and 4 only
d.1, 2, and 4 only
4.Which of the following clinical manifestations is(are) associated with a congenital diaphragmatic hernia?
1.Diminished or absent breath sounds
2.Bowel sounds over the affected side
3.Pulmonary hypertension
4.Atelectasis
a.3 and 4 only
b.1 and 2 only
c.1, 2, and 3 only
d.1, 2, 3, and 4
5.Treatment of congenital diaphragmatic hernia may include:
1.Inhaled nitric oxide
2.ECMO
3.Surgical repair
4.High-frequency ventilation
a.1 and 4 only
b.2 and 3 only
c.1, 3, and 4 only
d.1, 2, 3 and 4
1About 90% of CDHs are Bochdalek hernias. Rare CDHs include Morgagni hernia, which compromises approximately 9% of CDHs, total absence of the diaphragm, and congenital diaphragmatic eventration of the diaphragm. Morgagni hernias are characterized by herniation through the foramina of Morgagni, which are located immediately adjacent to the xyphoid process of the sternum. Most Morgagni hernias occur on the right side of the body and depending on the amount of liver involvement, tend to have a higher mortality rate and require more extracorporeal membrane oxygenation (ECMO) support than left-sided CDH infants. A congenital diaphragmatic eventration is abnormal elevation of part or all of an otherwise intact diaphragm into the chest cavity. This rare form of CDH occurs when a region of the diaphragm is thinner (commonly caused by an incomplete muscularization of the diaphragm), which in turn allows the abdominal viscera to protrude upward.
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C H A P T E R 4 2
Congenital Heart Diseases
CHAPTER OUTLINE
Patent Ductus Arteriosus (PDA)
Anatomic Alterations of the Heart
Etiology and Epidemiology
Diagnosis
Clinical Manifestations
Treatment
Atrial Septal Defect (ASD)
Anatomic Alterations of the Heart
Etiology and Epidemiology
Diagnosis
Clinical Manifestations
Treatment
Ventricular Septal Defect (VSD)
Anatomic Alterations of the Heart
Etiology and Epidemiology
Diagnosis
Clinical Manifestations
Treatment
Tetralogy of Fallot (TOF)
Anatomic Alterations of the Heart
Etiology and Epidemiology
Diagnosis
Clinical Manifestations
Treatment
Transposition of the Great Arteries (TGA)
Anatomic Alterations of the Heart
Etiology and Epidemiology
Diagnosis
Treatment
Hypoplastic Left Heart Syndrome (HLHS)
Anatomic Alterations of the Heart
Etiology and Epidemiology
Diagnosis
Treatment
Case Study: Transposition of the Great Arteries
Self-Assessment Questions
CHAPTER OBJECTIVES
After reading this chapter, you will be able to:
•List the anatomic alterations associated with common congenital heart diseases.
•Describe the etiology and epidemiology of common congenital heart diseases.
•Describe the testing of newborns to rule out “critical congenital heart defects” before hospital discharge.
•List the cardiopulmonary clinical manifestations associated with common congenital heart diseases.
•Describe the general management of the common congenital heart diseases.
•Describe the clinical strategies and rationales of the SOAPs presented in the case study.
•Define key terms and complete self-assessment questions at the end of the chapter and on Evolve.
27 mEq/L, PaO
27, PaO
changes associated with acute alveolar hyperventilation.
changes associated with acute ventilatory failure.
values will be lower than expected for a particular PaCO
(i.e., the acid-base and ventilation status only). Capillary PO
23 mEq/L, PaO2 37 mm Hg, and SaO2 56%. The baby was sedated and placed on a pressure-
23 mEq/L, PaO2 44 mm Hg, and SaO2 74%.
24 mEq/L, PaO2 73 mm Hg, and SaO2 94%. The baby's
24, PaO2 73, SaO2 94%. CXR: Right lung normal; atelectasis
