Resuscitation of Infants With Congenital Diaphragmatic Hernia With an Intact Umbilical Cord

CDH is a severe birth defect, with a prevalence of 1:2000 to 1:3000 live births where a defect in the diaphragm results in, herniation of the abdominal contents into the chest with subsequent compression of the intrathoracic structures. Compression of the intrathoracic structures results in pulmonary and left ventricular (LV) hypoplasia and abnormal development of the pulmonary vasculature in utero. These abnormalities in the development of the heart and lungs in utero, result in persistent pulmonary hypertension of the newborn (PPHN) and respiratory insufficiency after birth. Respiratory insufficiency is managed with intubation and mechanical ventilation. In addition to managing respiratory insufficiency, intubation prevents entrainment of air into the intestines and further compression of the lungs and heart. As part of routine resuscitation in infants with CDH intubation is performed after the delivery personnel separates the baby from the placenta by cutting the umbilical cord. Resuscitation of infants with CDH also involves placement of a nasogastric tube (NG) into the stomach for removal of entrained air and secretions as well as placement of catheters in the umbilical artery and vein for administration of medications (vein) and continuous blood pressure monitoring and sampling of blood (artery). As part of routine practice at our institution, these initial steps of resuscitation are all performed in parallel such that while one team is intubating and initiating ventilation as well as placing the NG tube, another team is placing umbilical lines. This approach has allowed the investigators to obtain arterial blood gas samples in 20 infants with CDH at a median of 4 minutes of life (range 2-9 minutes). When compared to cord blood arterial samples, pCO2 increases by a median of 35mmHg (range 11-77mmHg) from a median cord ABG pCO2 of 55mmHg (range 28-78 mmHg) to 88mmHg (range 65-123 mmHg). In addition to these changes in pCO2 median base deficit changed from -2 ± 0.5350 in the arterial cord blood sample to -7.994 ± 0.8547 in the umbilical arterial blood sample. The resultant respiratory and metabolic acidosis decreased the pH from 7.289 ± 0.01946 in the arterial cord blood sample to 7.036 ± 0.02051 after birth. In addition to the above measures, as part of routine resuscitation, the investigators routinely obtain echocardiographic studies in the first hour of life, to guide pulmonary hypertension management. These studies demonstrate left ventricular (LV) dysfunction and right to left shunting at the ductus arteriosus about 50% of the time. The investigators speculate that the LV dysfunction and increased pulmonary vascular resistance are at least in part due to the acidemia described above. In addition, decreased preload to the LV from right to left shunting at the ductus arteriosus also likely contributes to LV dysfunction. Standard of care for infants with marked abnormalities in gas exchange and LV dysfunction is ECMO rescue early on in the delivery room.

Clamping of the umbilical cord is one of the first interventions that occurs after birth. This separates the infant from the placenta, signifying a landmark period during which the newborn transforms into an independent entity. The transition from a fetus to a neonate at birth represents a critical phase in our life. Early or immediate cord clamping is standard practice where delivery of the fetus is followed by immediate clamping of the umbilical cord (<15 seconds). In 2010, the International Liaison Committee on Resuscitation (ILCOR) recommended that cord clamping could be delayed for at least 1 min. Since then for low risk infants, delayed cord clamping has become routine with the delivering providers delaying clamping of the cord for 1 minute prior to initiating routine newborn care. In these low risk infants there have been many published reports demonstrating benefit with delayed cord clamping. The benefits are primarily attributed to an increase in neonatal blood volume, secondary to placenta-fetal transfusion. More recently the benefits of delayed cord clamping have been demonstrated in higher risk infants. In preterm infants, delayed cord clamping decreased the need for inotropic support after birth, decreased the need for blood transfusions and reduced the incidence of necrotizing enterocolitis and intraventricular hemorrhage. These improvements appear more in line with improvements in cardiac function, which may or may not be associated with an increase in blood volume. More recently, in infants with congenital heart disease delayed cord clamping has been shown to be feasible and decreased the need for packed red blood cell transfusions after birth. Despite the benefits of delayed cord clamping on both the cardiopulmonary transition as well as postnatal outcomes, delayed cord clamping has never been employed in infants with congenital diaphragmatic hernia. This is due to the need for immediate resuscitation after birth and the risk of adverse outcomes by delaying the initiation of postnatal care.

In a recent study doppler ultrasound was used to measure arterial and venous umbilical blood flow during delayed cord clamping in term vaginal deliveries. After birth, the probe was placed in the middle of the umbilical cord and pattern and duration of flow in vein and arteries were evaluated until cord clamping. In 90% of infants, umbilical venous flow was still present at 4 minutes and 36 seconds. In 83% of infants, umbilical arterial flow was still present at 4 minutes and 22 seconds and in 72% of infants bidirectional arterial flow was observed. Bidirectional arterial flow appeared at 45 seconds after birth and persisted for a median duration of 2 minutes and 24 seconds (01:37- 03:52). This study implies that placental gas exchange may remain active for at least 4-5 minutes after birth and suggests that delaying cord clamping for 4-5 minutes while initiating resuscitation may be feasible.

In fetal sheep, the effect of initiation of ventilation with an intact umbilical cord was studied by placing flow probes around the ductus arteriosus, carotid and pulmonary arteries and catheters in the carotid and pulmonary arteries for direct pressure measurements. With clamping of the umbilical cord prior to initiation of ventilation, carotid artery and pulmonary artery pressure increased, carotid artery blood flow increased initially and then decreased and pulmonary artery blood flow and right ventricular output decreased. These changes in carotid and pulmonary pressure and flow were accompanied by a decrease in heart rate. With just 30 seconds of ventilation prior to clamping of the umbilical cord, the fluctuations in heart rate, carotid and pulmonary artery pressure and flow were prevented and the cardiopulmonary transition was much more stable.

The first published report of resuscitation with an intact umbilical cord compared 24 hour hematocrit in premature infants (23 0/7-31 6/7 weeks' GA) randomized to 60 seconds of V (initial continuous positive airway pressure) with addition of positive pressure ventilation if needed - delayed cord clamping (DCC), V-DCC or DCC-only where infants were dried and stimulated by gently rubbing the back if apneic. In this study no differences were seen in the peak hematocrit in the first 24 hours, delivery room interventions, early hemodynamics (cerebral oxygenation by near-infrared spectroscopy, cardiac output and stroke volume by electrical cardiometry, or superior vena cava flow by functional echocardiography), or neonatal outcomes. The onset of breathing was similar between both groups however infants receiving DCC received a greater duration of stimulation than V-DCC. While no benefit was seen with V-DCC, no adverse effects were seen and this study demonstrated the feasibility of resuscitation with the cord intact. In addition the primary outcome measure differed from our question of interest as the infants enrolled in this study were low risk for abnormalities in the cardiopulmonary transition.

In this protocol, the investigators propose initiation of resuscitation during the period of delayed cord clamping in infants with congenital diaphragmatic hernia. This is a feasibility study that will assess tolerance of the participants (pregnant mother and their high-risk infants) to this method of resuscitation as well as the optimal setup and approach to resuscitation. Tolerance to this approach would provide these infants the benefits of delayed cord clamping while allowing for simultaneous resuscitation. The first aim of this study is to assess maternal and fetal tolerance to the procedure and determine the optimal approach to resuscitation. In addition to this the investigators will assess if initiation of resuscitation during the period of delayed cord clamping can stabilize gas exchange and prevent the hypercarbia and acidosis that ensues after birth. Due to the physiologic effects of initiation of ventilation prior to clamping of the umbilical cord the investigators hypothesize that initiation of resuscitation prior to umbilical cord clamping will stabilize the cardiopulmonary transition and will decrease the prevalence of LV dysfunction in this population. The results of this study will lay the foundation for a future multi-center randomized trial and are likely to impact the manner in which newborns with CDH are resuscitated after birth