This course is designed to provide an overview of Congenital Diaphragmatic Hernia (CDH), a congenital defect affecting approximately one infant per 2400 live births in the United States. Definitions will be provided in order to clarify concepts associated with Congenital Diaphragmatic Hernia. The etiology and pathophysiologic process will be outlined along with the medical and surgical management of CDH. Associated anomalies, Perinatal and delivery room management, nursing care of the infant with CDH and parent teaching will be explored.
Course Objectives:
Upon completion of this course the student will be able to:
• Define Congenital Diaphragmatic Hernia
• List at least 2 associated anomalies of CDH
• Discuss the prenatal diagnosis and assessment of CDH
• List at least 3 goals of Perinatal management for the infant with CDH
• Review delivery room management of the neonate with CDH
• List at 2 interventions essential to the immediate stabilization of the neonate in the delivery room.
• Review the pathophysiology of CDH.
• State the effects of CDH on the pulmonary system
• Describe the medical management of CDH
• Describe the surgical repair undertaken in CDH
• Identify the role of the nurse in the care and treatment of the neonate with CDH
What is Congenital Diaphragmatic Hernia?
Congenital Diaphragmatic Hernia is a congenital defect of the diaphragm that results in an abnormal opening in the diaphragm that allows bowel loops and other abdominal organs to herniate into the chest cavity. Hypoplasia of the lung on the affected side is often seen.
Defining Congenital Diaphragmatic Hernia:
This relatively common birth defect results when the diaphragm does not completely close during fetal development. The defect is thought to result from a failure of the pleural-peritoneum canals to completely close between the 8th-10th weeks of gestation. The cause of this improper fusion of structures during fetal development is unknown. Some are associated with a genetic defect, but most occur as an isolated event with no gene abnormality identified. Approximately 40-50% of fetuses with CDH will present with other anomalies. The most common associated anomaly is a cardiac defect.
The size of the defect can vary, ranging from very small to complete agenesis of the diaphragm and can occur as either a right or left-sided defect. The most common type is the Bochdalek’s hernia, which is a posterolateral defect; however, the defect can occur at multiple sites unilaterally or bilaterally. Anteromedial (Morgagni’s foramen), hiatal, and diaphragmatic eventration (central weakening of the diaphragm) are other types of CDH.
Bochdalek’s hernias, the most common type, usually are left-sided but can occur on the right. Left-sided hernias occur five times more often than right sided. 90% of posteriolateral hernias occur on the left side, 5% on the right and occasionally on both sides. One theory as to why the defect is more common on the left side is that the liver obstructs herniation through a right-sided defect. It is also hypothesized that because the right side of the diaphragm closes earlier than the left, the diaphragm is not closing during the time the bowel returns to the peritoneum from its normal embryological rotation in the yolk sac, thus limiting the chances of the bowel herniating through a defect.
The abnormal opening is the defining feature of CDH; however, the opening is not the cause of the symptoms that are seen. The mortality that is seen with this defect results from a simple problem that leads to devastating consequences. The intestinal migration into the chest cavity as it returns from its normal embryological rotation into the umbilical cord results in compression of the developing lung. This compression leads to an abnormally small and abnormally developed lung. Pulmonary hypoplasia results in inadequate ventilation and progressive pulmonary hypertension. The major morbidity that is seen in infant’s presenting with CDH results from the abnormal development of the lung.
The abnormal opening is know to occur during the 8th-10th week of gestation, however the actual herniation of the abdominal contents may not occur until later in gestation. The timing of the herniation can determine the degree of pulmonary hypoplasia ultimately determining the clinical presentation and survival.
Survival Rate:
Approximately 60% of infant’s brought to term will survive; however this is an optimistic number given the fact that the current prenatal termination rate is estimated to be 15%.
Approximately 750 infants die from CDH yearly in the United States. (As a comparison, 150 die from Wilm’s Tumor and <100 die from Gastroschisis).
It is difficult to determine postnatal outcomes prior to delivery. One method is to evaluate the extent of herniation. With a left sided defect, prognosis is based on whether the herniation involves the intestine only, intestine, bowel, and stomach or intestine, bowel, stomach, spleen and liver. The more abdominal contents involved result in a poorer prognosis.
With a right-sided herniation, almost all will present with a portion of the liver in the chest cavity. More than 50% of the liver in the chest is considered a poor sign.
Some defects occur with the abdominal contents secluded in a sac. This is impossible to diagnose on ultrasound, but indicates a remnant of diaphragm was present. The resulting pathophysiology is less severe with this type of herniation.
Two theories exist in regards to this type of herniation; 1) that the defect occurred later in gestation or 2) that the diaphragmatic remnant holds back abdominal contents. The end result is that less lung is affected which improves prognosis.
Diagnosis:
Prior to the late 1970’s, definitive prenatal diagnosis was not possible. Prenatal diagnosis is common today as a result of improvements in ultrasonography. Ultrasound imaging can show the following signs of CDH as early as 15 weeks:
· Visualization of abdominal contents in chest cavity
· Mediastinal and cardiac shifts away from affected side
· Fetal Hydrops
· Polyhydramnios (due to obstruction of the fetal esophagus resulting in impaired swallowing of amniotic fluid. This finding has been linked to a poor prognosis).
Low levels of maternal serum Alpha Fetoprotein have been associated with CDH however are also associated with other defects as well, therefore are not a definitive test but should lead to further investigation.
Ultrasound imaging remains unable to accurately predict the extent of pulmonary hypoplasia, which is a significant predictor of postnatal survival in this group of infants.
Associated Anomalies:
Associated anomalies occur commonly (40%) in CDH. Most of the associated anomalies do not affect survival and include:
Atrioseptal Heart Defect
Malrotation of the intestine
Meckel Diverticulum
Undescended Testes
Unilateral Kidney
Other more serious anomalies include:
Serious Heart Defects (10%)
Hypoplastic Left Heart Syndrome is the most common cardiac defect associated with CDH
Chromosomal Anomalies (10-34%)
Turner Syndrome (Monosomy X)
Edward Syndrome (Trisomy 18)
Patau Syndrome (Trisomy 13)
Pathophysiology:
The pathophysiology of CDH begins when the diaphragm does not close normally during the 8th-10th week of gestation. This defect results in an abnormal opening that allows the fetal abdominal contents to migrate into the chest cavity. Compression of the developing lung leads to pulmonary hypoplasia and pulmonary hypertension. Morbidity and mortality are dependent on the size of the defect and the resulting herniation, which determines the degree of pulmonary hypoplasia.
Early herniation leads to changes in the architecture of the lung on the affected side. Changes include fewer airways, fewer alveoli, a smaller pulmonary artery, and a small pulmonary vascular bed. Gas exchange is impaired as a result.
The leading cause of inadequate oxygenation in the infant with CDH, however, is not the small lung area, but results from Persistent Pulmonary Hypertension of the Newborn (PPHN). PPHN is the most common problem associated with CDH in the early postnatal period and is a clinical state with many root causes.
Adequate oxygenation of the newborn is dependent on inflation of the lungs, closure of the fetal shunts, a decrease in pulmonary vascular resistance, and an increase in pulmonary blood flow. Pulmonary vascular resistance usually decreases with the first breath of life. When this does not occur, pulmonary blood flow is impeded and the transition from fetal to neonatal circulation is impeded. PPHN presents as severe pulmonary hypertension with pulmonary artery pressure elevation equal to or greater than systemic pressure resulting in large right-to-left shunts through the Foramen Ovale and Ductus Arteriosus.
PPHN can affect any newborn, but is more common and more severe in the newborn with CDH. This is a result of the small pulmonary vascular bed, and an increased muscularization and thickening of the walls of the arteries that is found in infants with CDH. This fixed component can improve over time, but is slow to resolve. A reactive component also is present due to the changing resistance of the pulmonary arterioles that is caused by loss of lung volume, hypoxia, infection, inflammation and idiopathic reasons.
PPHN usually resolves over time, but makes the management of the newborn with CDH very difficult. Over treatment can lead to more problems and under treatment can lead to an increase in PPHN.
Another confounding factor leading to respiratory distress in this group of infants is dysfunction of the surfactant system. Several components necessary for a mature surfactant system have been found to be missing in these infants. Surfactant reduces the surface tension of the alveoli, which increases lung compliance, provides alveolar stability, and decreases opening tension. Additionally, it enhances alveolar fluid clearance and decreases precapillary tone.
Additionally, because the bowel is located in an abnormal location, the normal rotation of the bowel did not occur and the infant will also have non-rotation or malrotation of the bowel, which can lead to digestive problems once feedings are established.
Prenatal Management:
The incidence of CDH in the United States is twice that of childhood cancer with a cost of health care for infants with this defect estimated to be at least $230 million. Postnatal surgery is effective in repairing the defect, however, the complications that are responsible for the mortality and morbidity associated with CDH including pulmonary hypoplasia, respiratory failure and PPHN are not preventable with postnatal surgery. Over the last few decades, research has focused on means to correct the defect in utero and/or prevent the resulting lung hypoplasia caused by this space-occupying lesion. Fetal surgery has been attempted to prevent the complications of Congenital Diaphragmatic Hernia. The goal of prenatal surgery has been to increase lung development and prevent PPHN. Two procedures that have been attempted include:
Prenatal repair of CDH early in gestation:
Fetal surgery was performed to repair the CDH. Direct repair of the defect was performed through a hysterotomy.
The fetus without liver involvement required a thoracotomy incision and a substernal incision. The surgery resulted in the reduction of the viscera, closing of the diaphragmatic defect and enlarging the abdomen. The defect was repaired and compensatory lung growth resulted; however when compared with fetus’s receiving postnatal treatment only, the survival rate was not improved.
Treatment of infants with liver involvement was also attempted; however reduction of the liver back into the abdomen resulted in obstruction of the umbilical venous blood flow and fetal death.
Fetal surgery is no longer the standard of care.
Occlusion of fetal trachea:
Fetal tracheal obstruction in animals has been shown to improve pulmonary hypoplasia. The fetal lung produces lung fluid throughout gestation. This fluid exits through the trachea into the amniotic fluid. Preventing this fluid to exit has been shown to increase lung growth.
Occlusion of the fetal trachea in animal models either with a plug, intratracheal balloon or external clip resulted in increased fluid levels in the lungs with an increase in lung growth noted.
In human trials, increased morbidity was seen as result of the required hysterotomy. Preterm labor and delivery were the primary cause of morbidity. Fetal tracheal damage also resulted when the external clips were used. As a result, this procedure is no longer considered an option.
To decrease morbidity that resulted from hysterotomy, video assisted fetal endoscopy (FETENDO) was developed which allowed tracheal plugging without a hysterotomy, however, preterm labor and delivery continued to be a problem even with this minimally invasive technique. Additionally, other complications resulted such as tracheal dissection, reoccurrence of the herniation and increased morbidity from Gastroesophageal reflux.
Delivery of the infant that had prenatal plugging required a Cesarean delivery with modification to maintain fetoplacental circulation to allow for the removal of the plug or balloon. This technique is called Ex Utero Intrapartum Treatment (EXIT) strategy. While the umbilical circulation is still maintaining the infant, the balloon is popped or the clips are removed with an endoscope. The infant is then intubated, given surfactant and mechanically ventilated. Complete delivery then ensues.
This treatment is still considered a potential, but is not currently the standard of practice. It does however offer hope for the fetus that has high-risk CDH, but efficacy must be proven with properly conducted randomized, controlled trials.
Perinatal management for CDH includes:
Prevention of preterm delivery, which is a potential secondary to polyhydramnios. Polyhydramnios is a uterine irritant. Prevention would involve early diagnosis and follow-up at a high-risk perinatal center. Bed rest may be advised along with the use of prenatal steroids to improve lung development. Magnesium Sulfate or Terbutaline decreases uterine irritability and is used to delay preterm labor.
Planned delivery at a high-risk neonatal center. These infants require intensive resuscitation and continued intensive care. Transport to a high risk neonatal center increases the risk to the infant and increases the risk of developing retractable PPHN, therefore, proper identification of CDH in utero and planned delivery at a high risk Perinatal center with a level III neonatal unit may increase the chance of survival.
Consideration of prenatal steroid administration:
Maternal treatment with Betamethasone has been shown to accelerate surfactant production by the fetal lung reducing the incidence of neonatal respiratory distress in premature infants without CDH. A single course of antenatal glucocorticoid therapy, 12 mg of Betamethasone IM followed by a second dose after 24 hours if baby is undelivered, given to the mother, has been shown to improve neonatal outcomes in infants less than 30 weeks’ gestation. Repeat treatment: 12 mg IM dose once every 7 days if infant remains undelivered and infant is at substantial risk for respiratory distress resulting from prematurity (generally less than 34 weeks gestation).
Late prenatal corticosteroids are unlikely to provide significant benefit to fetuses with CDH because they most likely do not have decreased surfactant production.
Current recommendations from the 2000 National Institute of Health conference on antenatal steroid treatment support treatment of all infants between 24 and 34 weeks of gestation if delivery is expected before 34 weeks.
Clinical Manifestations:
The most severely affected infants will present with severe respiratory distress and evidence of Persistent Pulmonary Hypertension of the Newborn (PPHN). These infants are at high risk of developing a pneumothorax as a result of the hypoplastic lung.
Clinical presentation at the delivery will include the following:
Scaphoid (concave) abdomen (This finding is a result of the abdominal contents residing in the chest cavity).
Respiratory distress
Cyanosis
Asymmetric chest movements (secondary to the hypoplastic lung).
Absent breath sounds on the affected side (secondary to the hypoplastic lung).
Shifted heart sounds
Bowel sounds in the chest
Diagnosis is confirmed by chest x-ray revealing a mass with an air-filled bowel on the affected side.
Delivery Room Management:
Immediate stabilization is crucial in the management of any infant; however the infant with CDH requires additional stabilization that takes precedence. Immediate intubation is essential. Bag and mask ventilation must be avoided to prevent dilation of the stomach and intestines, which could further compromise pulmonary function. A large size oro-/nasograstric tube must also be placed immediately to minimize the effect of air in the intestines. The goal of initial stabilization is respiratory stability and prevention of bowel distention. Additional resuscitative measures following Neonatal Resuscitation Program guidelines for airway, breathing, circulation and thermoregulation are appropriate for the infant with CDH.
Treatment/Nursing Care:
Congenital Diaphragmatic Hernia has been described as a physiologic emergency rather than a surgical emergency. The critical concern is the avoidance of or improvement of PPHN. Removal of the abdominal contents from the chest cavity is not emergent. Delayed surgical intervention is currently the standard of care for infants with CDH. In the past, this disorder was considered a surgical emergency, but it is now known that early surgical repair does not alter the outcome. The standard of care is to stabilize the infant and manage the associated pulmonary dysfunction prior to surgical intervention. Surgical intervention can be delayed from a few days to up to two weeks, depending on the infant. The goal of the medical management is to stabilize the pulmonary dysfunction and decrease the pulmonary hypertension. The goal of the respiratory management is to provide adequate ventilation and oxygenation but to avoid causing permanent lung damage.
Treatment for the infant with CDH may consist of:
Gentle ventilation:
Decreased inflation pressure or high frequency ventilation (HFOV)
Tolerance for hypercapnea and hypoxemia
Gastric decompression:
Oro/nasogastric tube to low continuous suction is used to decrease the amount of air entering the intestines and obstructing the lung.
Inhaled Nitric Oxide:
Nitric Oxide (NO) is a powerful vasodilator that is minimally toxic. Low doses of Nitrous oxide blended with oxygen in the inspiratory limb of mechanical ventilators effectively reduces pulmonary vascular resistance and decreases extra pulmonary right-to-left shunting at the ductus arteriosus and foreman ovale. It acts to dilate the pulmonary vascular bed and decrease the PPHN. When effective, it improves oxygenation quickly.
Nitric oxide is administered via inhalation and initially delivered at 20 parts per million (ppm). The goal is to decrease the dose to 2 ppm when tolerated.
Late or protracted pulmonary hypertension occurs in a subset of infants with CDH. Inhaled NO has been effectively delivered via nasal cannula to these infants no longer requiring mechanical ventilation. The dose usually administered via nasal cannula is 10 ppm which results in a nasopharyngeal concentration of 1-5 ppm.
Pressors:
Pressors are used to increase systemic blood pressure to decrease the effect of PPHN. PPHN presents as severe pulmonary hypertension with pulmonary artery pressure elevation equal to or greater than systemic pressure resulting in large right-to-left shunts through the Foramen Ovale and Ductus Arteriosus.
The goal of utilizing pressors is to increase the systemic pressure to a level that will help to override the resistance from the pulmonary bed, to decrease the right-to-left shunting through the ductus arteriosus and foreman ovale and increase the pulmonary blood flow. The most common pressors include:
Dopamine:
Increases peripheral vascular resistance
2mcg/kg/min to a max of 20mcg/kg/min
Continuous infusion
Dobutamine:
Increases cardiac contractility
2mcg/kg/min to a max of 20mcg/kg/min
Continuous infusion
Note: Both Dopamine and Dobutamine may be used concurrently to maximize the effects and increase the systemic pressure.
Surfactant Administration:
Recent studies indicate that a primary surfactant deficiency is unlikely in the infant with a CDH.
Some infants with CDH are not receptive to exogenous surfactant
The usual dose of 4ml/kg may be too high based on the infant’s reduced tidal volume.
Current studies show no benefit to surfactant administration and some indicate a potential for worse outcomes in the treated infants.
Arterial and central venous lines for monitoring and fluid infusion:
Umbilical arterial line are optimal for pressure monitoring
Umbilical venous lines with double lumen are optimal for fluid resuscitation and ongoing fluid maintenance.
Sedation:
Minimal handling (the goal is to decrease agitation to minimize effects of PPHN).
Supportive positioning (Position infant with affected side down to aid ventilation of the “good” lung. Also position infant in a nesting position to decrease agitation).
Parent education:
Parents receiving the diagnosis of Congenital Diaphragmatic Hernia initially experience emotional distress, which has been shown to impair optimum learning. Studies of prospective parents of an infant with a fetal anomaly revealed their inability to assimilate all the information given to them in one session. Parents have indicated that both visual and auditory learning is important and have suggested that written material and drawings would be useful in helping parents retain and review information. Keeping this in mind, the following information needs to be given to the parents prenatally:
Description of Congenital Diaphragmatic Hernia
Explanation of what to expect in the delivery room
Tour of neonatal unit
Explanation of what to expect upon admission to NICU and first day of life including intubation, ventilation, antibiotics, umbilical venous/arterial lines, IV therapy, gastric decompression and cardiac monitoring.
Education upon admission to NICU:
Reinforce information given prenatally as noted above
Discuss plan of care
Pre-operative Education:
Update parents to plans for surgery and what to expect post-operatively
Post-operative Education:
Update parents about infant’s status post-operatively and review any new equipment, medication, or therapies that have been added to infant’s care.
Discharge Education:
General Infant Care
Car seat Safety
Care for the infant with reflux (as appropriate)
Care for the infant on oxygen therapy (as appropriate)
Extracorporeal Membrane Oxygenation (ECMO):
ECMO is defined as a modified heart-lung machine combined with a membrane oxygenator to provide cardiopulmonary support for patients with reversible pulmonary failure such as PPHN.
The first successful use of ECMO in a full term newborn with CDH was in 1976 at the University of California, Irvine Medical Center.
ECMO is offered as a lifesaving technology for infants with respiratory failure that is not responsive to maximal medical therapy.
ECMO allows time for the lung to recover from the underlying disease process and for reversal of pulmonary hypertension.
ECMO is an option for the infant with CDH that does not respond to conventional medical treatment. The infant is placed on ECMO to allow for the pulmonary hypertension to resolve. Once the pulmonary hypertension is stabilized, surgery is performed and conventional treatment resumes.
The infant must meet certain criteria to be eligible for ECMO. Each ECMO center has its own criteria, but general inclusion and exclusion criteria include:
Term or near-term infant (Gestational age > 34 weeks)
< 10-14 days of mechanical ventilation at time of ECMO (This is because chronic lung injury induced by prolonged ventilation and high oxygen concentrations will not improve within the time period that ECMO can be used safely.)
No significant coagulopathy (This is because systemic heparinization is required during ECMO and preexisting coagulopathy can result in excessive bleeding.)
No major intracranial hemorrhage
Reversible lung disease
No uncorrectable congenital heart disease or lethal congenital anomalies
No evidence of irreversible brain damage
Complications of ECMO include:
Intracranial hemorrhage (resulting from the systemic heparinization)
Non-hemorrhagic infarction of the central nervous system
Since the advent of nitrous oxide therapy for the infant with PPHN, the use of ECMO has declined. It is no longer a first line therapy.
ECMO is an invasive procedure that is currently used now as a rescue intervention for the patient with CDH. (Cumulative survival statistics for the patient with CDH treated with ECMO is 53%)
Consultation with cardiology, genetics, neurology and other subspecialties as appropriate.
Primary goals of treatment for the infant with CDH include:
Preserving the lung the infant was born with
Minimizing trauma to the lung
Providing supportive care until the PPHN resolves
Surgical correction once stabilized
Surgical Repair:
Surgical repair for Congenital Diaphragmatic Hernia consists of reducing the herniated abdominal contents from the chest and closing the defect. If the defect is large, a prosthetic patch is needed to repair the diaphragm, which is a marker of more severe disease. These infants are at high risk for gastroesophageal reflux and future herniation as the patch does not grow with the infant. In some cases, the abdominal cavity is too small to accommodate the abdominal contents. In these cases, closure of the abdomen is not possible and a prosthetic patch is closed over the top of the abdominal contents leaving a ventral hernia, which will need to be repaired at a later time.
Post-operative care is essentially the same as for any infant having surgery with the primary concern being ventilation and oxygenation. Preventing the reoccurrence of PPHN is a primary goal.
Long-term Outcomes:
Outcomes are quite variable depending on the extent of the defect and resulting pulmonary hypoplasia and Persistent Pulmonary Hypertension of the Newborn. The typical course for these neonates is difficult requiring many interventions. Neurodevelopmental delays, chronic lung disease, nutritional deficiencies, feeding problems, and Gastroesophageal reflux are all potential long-term problems.
References
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