Pediatric Congenital Diaphragmatic Hernia Treatment & Management

Because of associated persistent pulmonary hypertension of the newborn (PPHN) and pulmonary hypoplasia, medical therapy in patients with congenital diaphragmatic hernia (CDH) is directed toward optimizing oxygenation while avoiding barotrauma.

In the delivery room, if the infant is known or suspected to have congenital diaphragmatic hernia, immediately place a vented orogastric tube and connect it to continuous suction to prevent bowel distension and further lung compression. For the same reason, avoid mask ventilation and immediately intubate the trachea. Avoid high peak inspiratory pressures and be alert to the possibility of early pneumothorax if the infant does not stabilize.^[9]

Infants with congenital diaphragmatic hernia may have immature lung development, and animal studies have indicated that surfactant deficiency may be present. However, reports from the Congenital Diaphragmatic Hernia Study Group indicate that administration of exogenous surfactant does not improve survival, need for extracorporeal membrane oxygenation (ECMO), or long-term outcome. Interestingly, this finding is true for both term and preterm infants with congenital diaphragmatic hernia.

Mechanical ventilation strategies are targeted at avoiding high peak inspiratory pressures and synchronizing ventilation with the infant's respiratory effort. In some instances, high-frequency ventilation (HFV) may be helpful in avoiding the use of high peak inspiratory pressures, although this modality is best used at a center with experience in assessing and maintaining optimal lung distension.

Infants with congenital diaphragmatic hernia are critically ill and require meticulous attention to detail for subsequent medical care, including continuous monitoring of oxygenation, blood pressure, and perfusion. A minimal stimulation approach that reduces handling and invasive procedures, such as suctioning, is suggested.

Maintain glucose and ionized calcium concentrations within reference range. If necessary, support blood pressure using volume expansion and inotropic agents. An adequate circulating volume is necessary to maintain right ventricular filling and cardiac output; however, once circulating volume is normalized, repeated boluses of crystalloid solutions, colloid solutions, or both do not provide additional benefit. Inotropic support with dopamine, dobutamine, or milrinone may be helpful in maintaining adequate systemic blood pressure; dobutamine and milrinone may be particularly helpful if myocardial dysfunction is present. Epinephrine infusions may be necessary in severe cases; low-dose epinephrine (< 0.2 mcg/kg/min) may help to promote pulmonary blood flow and improve cardiac output.

The appropriate targets for PaO₂ and PaCO₂ are controversial. PaO₂ concentrations greater than 50 mm Hg typically provide for adequate oxygen delivery at the tissue level. Aiming for higher PaO₂ concentrations may lead to increased ventilator support and barotrauma. Similarly, infants with congenital diaphragmatic hernia often have hypercarbia because of pulmonary hypoplasia. Whether to maintain a low PaCO₂ for pulmonary vasodilation, to allow permissive hypercapnia, or to maintain normocarbia remains controversial. No reliable controlled studies are known, and debate continues in the medical literature. Retrospective studies suggest that gentle ventilation and allowing chronic mild hypercarbia may be associated with improved survival.

Alkalinization was frequently used in the past because of its ability to produce a rapid pulmonary vasodilation. Forced alkalosis can be accomplished either by using hyperventilation to induce hypocarbia or by alkali infusions. However, benefits of alkalosis have never been demonstrated in any prospective clinical trial, and these therapies are considered controversial. In addition, alkalosis may result in undesirable side effects. For instance, hypocarbia constricts the cerebral vasculature and reduces cerebral blood flow. Extreme alkalosis and hypocarbia are strongly associated with later neurodevelopmental deficits, including a high rate of sensorineural hearing loss. Previous studies by Walsh-Sukys and colleagues indicates that the use of alkali infusions may be associated with increased use of ECMO and an increased use of oxygen at age 28 days.^[10]

Inhaled nitric oxide has revolutionized the treatment of PPHN but its benefit in the infant with congenital diaphragmatic hernia remains controversial. Nitric oxide does not reduce mortality or the need for ECMO in infants with congenital diaphragmatic hernia, although it may immediately stabilize infants with critical hypoxemia and reduce the chances of cardiopulmonary arrest.^[11] Inhaled nitric oxide should be used with caution if ECMO is not immediately available. New studies indicate a potential role for long-term low-dose inhaled nitric oxide therapy in the treatment of late or recurrent pulmonary hypertension.

Sedation is an important adjunctive therapy, but the use of paralytic agents remains highly controversial. Although diminished swallowing may be beneficial, paralysis may promote both atelectasis of dependent lung regions and ventilation-perfusion mismatch, as well as generalized edema and decreased chest wall compliance.

Theoretically, fetal surgery for congenital diaphragmatic hernia provides an elegant solution to the difficult problem of congenital diaphragmatic hernia. Unfortunately, this is far from reality. Harrison et al reported the first human fetal surgery for congenital diaphragmatic hernia in 1990. However, a randomized trial published in 1998 showed that in utero repair did not improve survival compared with standard therapy.^[12]

Subsequent trials of fetal intervention focused on occluding the fetal trachea. The fetal lung secretes fluid by active ion transport through gestation, and this lung fluid provides a template for lung growth. Occlusion of the fetal trachea traps this fluid and stimulates lung growth, either by retention of growth factors within the lung or stimulation of local growth factors by the gentle distension provided by the fluid. Unfortunately, a randomized trial in humans found that fetal tracheal occlusion did not improve outcome compared with standard treatment.^[13] Currently, fetal intervention is not indicated in congenital diaphragmatic hernia, although some groups continue to offer it on an experimental basis.

Until recently, specialists believed that reduction of the herniated viscera and closure of the diaphragmatic defect should be emergently performed following birth. However, a delayed surgical approach that enables preoperative stabilization decreases morbidity and mortality. This change in protocol is due to the recent understanding that the medical problems of pulmonary hypoplasia and PPHN are largely responsible for the outcome of congenital diaphragmatic hernia and that the severity of these pathophysiologies is largely predetermined in utero. Herniated viscera in the chest does not appear to exacerbate the pathophysiology as long as bowel decompression with a nasogastric tube is adequate.

Several reports indicate that circulatory stability, respiratory mechanics, and gas exchange deteriorate after surgical repair. The ideal time to repair a congenital diaphragmatic hernia is unknown. Some suggest that repair 24 hours after stabilization is ideal, but delays of up to 7-10 days are typically well tolerated, and many surgeons now adopt this approach. Some surgeons prefer to operate on these neonates when normal pulmonary artery pressure is maintained for at least 24-48 hours based on echocardiography.

Chest tube drainage is necessary when a tension pneumothorax is present; however, whether routine chest drainage following surgical repair has a role is controversial. Some clinicians report improved survival when chest drainage is not used. Others think that balanced intrathoracic drainage, in which a closed gated pressure system is used to maintain intrathoracic pressure within the normal physiologic range, may minimize risk of pulmonary injury and improve respiratory mechanics.

Transplantation of a single lung has been reported in one case. Lung transplantation may allow the remaining hypoplastic lung to grow and to recover from injury while still allowing adequate oxygenation and ventilation. However, this approach has not been widely used because of the substantial problems associated with donor lung availability and immunosuppression.