Description

• Congenital diaphragmatic hernia (CDH) is a failure of a portion of the fetal diaphragm to fully develop. The defect allows abdominal contents to enter the thorax, often interfering with normal lung growth.
• CDH can present as a neonatal life-threatening emergency.

Etiology/Risk Factors

• Cause remains unknown
• There does appear to be a genetic link and an increased risk if a sibling or a parent had the condition.

Physiology/Pathophysiology

• CDH results from a failure of fusion of peripheral and central elements of the diaphragm.
• Respiratory. Pulmonary hypoplasia occurs secondary to compression by abdominal contents. There is an abnormal division of airways that results in a decreased number of bronchi, alveoli, and pulmonary arterial branches. Additionally, there is surfactant deficiency and premature muscularization of pulmonary vessels. Severity is related to the time during gestation when herniation occurred (usually during the 8th week).
  • Mechanical abnormalities result from the herniation of abdominal contents shifting into the mediastinum; causes the mediastinum to shift to the opposite side of the defect.
  • Circulating vasoactive mediators increase, as does the body's sensitivity. This further worsens the pulmonary hypertension associated with CDH.

Anesthetic Goals/Guiding Principles

• Reduction in the herniated viscera and closure of the diaphragmatic defect should be emergently performed following birth. However, surgical treatment can be delayed to stabilize infants with pulmonary hypoplasia and persistent pulmonary hypertension of the newborn (PPHN). Preoperative stabilization with delayed repair has become the standard of care.
• Physiologic considerations include hypoxemia, hypercarbia, acidemia, pulmonary hypertension and associated right-to-left shunting, possible pneumothorax, and malrotation.
• Goals
  • Adequate gas exchange and prevention of worsening metabolic or respiratory acidosis while avoiding ventilator-associated lung injury.
  • Avoidance of aspiration
  • Adequate pain control
  • Maintain normothermia, volume status, and electrolyte balance.

Symptoms

• Cyanosis
• Tachycardia
• Tachypnea, retractions, grunting, severe respiratory distress
• A small subset of patients (~5%) present primarily with bowel obstruction and minimal respiratory distress.

Treatment History

• Minimally invasive fetal surgeries have been attempted (e.g., tracheal balloon occlusion) to promote the growth of hypoplastic lung tissue, but it has not shown improved survival.
• Ex utero intrapartum therapy (EXIT) procedures may be performed for severely hypoplastic lungs with very large CDH.
• ECMO. Morbidity occurs secondary to anticoagulation and intracranial bleeding. Indications include
  • Estimated gestational age >35 weeks
  • Absence of intracranial hemorrhage
  • Absence of uncorrectable cyanotic congenital heart disease
  • Absence of uncorrectable associated anomalies
  • Parental consent
• Nitric oxide can promote smooth muscle relaxation and short-term improvements in arterial oxygenation. Its use is controversial; it may be helpful in the initial stabilization, but does not reduce the need for ECMO or decrease mortality.
• Permissive hypercapnia to a PaCO₂ of 60 mm Hg may decrease ventilator support and barotrauma as well as dilate the pulmonary vasculature; in the setting of pulmonary hypoplasia, this can be beneficial. However, it remains controversial.
• High frequency oscillatory ventilation (HFOV). May be utilized if conventional ventilation fails to reverse hypercapnia and hypoxemia. It avoids injury to the lung and preserves end expiratory lung volume without overdistension.

Medications

• Sedation and muscle relaxation are used in intubated patients to avoid ventilator dyssynchrony and decrease the release of catecholamines, which may increase pulmonary vascular resistance.
• IV fluids and total parenteral nutrition (TPN) should be continued in the OR.

CONCOMITANT ORGAN DYSFUNCTION

• CNS: Neural tube defects or hydrocephalus
• Craniofacial, extremity, or spinal abnormalities
• Genitourinary anomalies (6–8%)

Circumstances to delay/Conditions

Surgical treatment can be delayed to stabilize pulmonary hypoplasia and PPHN.

Classifications

• The Bochdalek hernia, also known as a posterolateral diaphragmatic hernia, can occur on the left or right. It accounts for >95% of cases.
• Morgagni's hernia, also known as a retrosternal or parasternal hernia can occur through this right, anterior defect (known as the foramen of Morgagni). Infants may be asymptomatic; however, repair is still recommended to avoid the risk of a strangulated intestine. Accounts for ~2% of cases.
• Diaphragmatic eventration describes cranial displacement of part, or all, of an otherwise intact diaphragm into the chest cavity. This rare type of CDH occurs due to incomplete muscularization of the diaphragm or failure of phrenic nerve innervation, and can be found unilaterally or bilaterally. Minor forms of diaphragm eventration are asymptomatic; however, severe cases will present with respiratory distress similar to Bochdalek hernia.

Bed Acuity

NICU or PICU

Medications/Lab Studies/Consults

• Blood gas analysis to assess oxygenation and ventilation, as well as possible postoperative acidosis.
• CBC to evaluate hematocrit after surgical blood loss and intraoperative volume shifts.
• Ventilator settings: Low peak pressures to avoid injury to the normal lung.
• Pneumothorax on the unaffected side should be suspected if the infant is hypotensive and hypoxic.

Complications

• Hypoventilation
• Pneumothorax
• Metabolic acidosis
• Hypothermia
• All the above conditions could lead to right-to-left shunting either through the ductus arteriosus or an abnormal shunt (e.g., ASD, etc).

• Retinopathy of Prematurity
• Pneumothorax

ICD9

756.6 Anomalies of diaphragm

ICD10

Q79.0 Congenital diaphragmatic hernia

Ranu Jain , MD