The transition from fetal to neonatal life is a dramatic and complex process involving extensive physiologic changes that are most obvious at the time of birth. Individuals who care for newly born infants during these first few minutes of neonatal life must monitor the progress of the transition and be prepared to intervene when necessary. In the majority of births, this transition occurs without a requirement for any significant assistance. However, when the need for intervention arises, the presence of providers who are skilled in neonatal resuscitation can be life saving. Each year approximately 4 million children are born in the United States and more than 30 times as many are born worldwide. It is estimated that approximately 5% to 10% of all births will require some form of resuscitation beyond basic care, thereby making neonatal resuscitation the most frequently practiced form of resuscitation in medical care. Throughout the world, approximately 1 million newborn deaths are associated with birth asphyxia. Although it cannot be expected that neonatal resuscitation will eliminate all early neonatal mortality, it has the potential for helping save many lives and for significantly reducing associated morbidities.
Attempts at reviving nonbreathing infants immediately after birth have occurred throughout recorded time with references in literature, religion, and early medicine. Although the organization and sophistication has changed, the basic principle and goal of initiating breathing has remained constant throughout time. It has just been over the last 20 years that the process of neonatal resuscitation has been more officially regimented. Resuscitation programs in other areas of medicine were initiated in the 1970s in an effort to improve knowledge about effective resuscitation and provide an action plan for early responders. The first of such programs was focused on adult cardiopulmonary resuscitation. These programs then began increasing in complexity and becoming more specific to different types of resuscitation needs. With the collaboration of the American Heart Association and the American Academy of Pediatrics, the Neonatal Resuscitation Program (NRP) was initiated in 1987 and was designed to address the specific needs of the newly born infant. Since the origination of the NRP, on-going evaluation of the program has resulted in changes when new evidence becomes available. The most recent edition of the NRP textbook published in 2011 made several revisions including specific recommendations for the preterm infant. Various groups throughout the world also provide resuscitation recommendations that may be more specific to the practices in certain regions. An international group of scientists, the International Liaison Committee on Resuscitation (ILCOR), meets on a regular basis to review available resuscitation evidence for all the different areas of resuscitation and puts forth a summary of its review.
The overall goal of the NRP is similar to other resuscitation programs in that it intends to teach large groups of individuals of varying backgrounds the principles of resuscitation and to provide an action plan for providers. Similarly, a satisfactory end-result of resuscitation would be common to all forms of resuscitation, namely to provide adequate tissue oxygenation to prevent tissue injury and restore spontaneous cardiopulmonary function. When comparing neonatal resuscitation with other forms of resuscitation, several distinctions can be noted. First, the birth of an infant is a more predictable occurrence than most events that require resuscitation in an adult, such as an arrhythmia or a myocardial infarction. Although not every birth will require “resuscitation,” it is more reasonable to expect that skilled individuals can be present when the need for neonatal resuscitation arises. It is possible to anticipate with some accuracy which neonates will more likely require resuscitation based on perinatal factors and thus allow time for preparation. The second distinction of neonatal resuscitation compared with other forms of resuscitation involves the unique physiology involved in the normal fetal transition to neonatal life. The fetus exists in the protected environment of the uterus where temperature is closely controlled, continuous fetal breathing is not essential to provide gas exchange, the lungs are filled with fluid, and the gas exchange organ is the placenta. The transition that occurs at birth requires the neonate to increase heat production, initiate continuous breathing, replace the lung fluid with air/oxygen, and significantly increase pulmonary blood flow so that gas exchange can occur in the lungs. The expectations for this transitional process and knowledge of how to effectively assist the process help guide the current practice of neonatal resuscitation.
Fetal Transition to Extrauterine Life
The key elements necessary for a successful transition to extrauterine life involve changes in thermoregulation, respiration, and circulation. In utero, the fetal core temperature is approximately 0.5° C greater than the mother’s temperature. Heat is produced by metabolic processes and is lost over this small temperature gradient through the placenta and skin. After birth, the temperature gradient between the infant and the environment becomes much greater and heat is lost through the skin by radiation, convection, conduction, and evaporation. The newly born infant must begin producing heat through other mechanisms such as lipolysis of brown adipose tissue. If heat is lost at a pace greater than it is produced, the infant will become hypothermic. Preterm infants are at particular risk because of increased heat loss through immature skin, a greater surface area to body weight ratio, and decreased brown adipose tissue stores. Preterm hypothermic infants who are admitted to the nursery have decreased chances of survival. Routine measures during neonatal resuscitation, such as the use of radiant warmers and drying the infant are aimed at preventing heat loss. For the preterm infant, special measures for temperature management, such as the use of plastic wrap as a barrier to evaporative heat loss, are necessary to ensure adequate thermoregulation.
The fetus lives in a fluid-filled environment and as lung development occurs, the developing alveolar spaces are filled with lung fluid. Lung fluid production decreases in the days prior to delivery and the remainder of lung fluid is resorbed into the pulmonary interstitial spaces after delivery. As the infant takes the first breaths after birth, a negative intrathoracic pressure of approximately 50 cm H 2 O is generated. The alveoli become filled with air, and with the help of pulmonary surfactant, the lungs retain a small amount of air at the end of exhalation known as the functional residual capacity (FRC). Although the fetus makes breathing movements in utero, these efforts are intermittent and are not required for gas exchange. Continuous spontaneous breathing is maintained after birth by several mechanisms including the activation of chemoreceptors, the decrease in placental hormones, which inhibit respirations, and the presence of natural environmental stimulation. Spontaneous breathing can be suppressed at birth for several reasons, most critical of which is the presence of acidosis secondary to compromised fetal circulation. The natural history of the physiologic responses to acidosis has been described by researchers creating such conditions in animal models. Dawes described the breathing response to acidosis in different animal species. He noted that when pH was decreased, animals typically have a relatively short period of apnea followed by gasping. The gasping pattern then increases in rate until breathing ceases again for a second period of apnea. Dawes also noted that the first period of apnea or primary apnea could be reversed with stimulation, whereas the second period of apnea, secondary or terminal apnea, required assisted ventilation to establish spontaneous breathing. In the clinical situation, the exact timing of onset of acidosis is generally unknown and, therefore, any observed apnea may be either primary or secondary. This is the basis of the resuscitation recommendation that stimulation may be attempted in the presence of apnea, but if not quickly successful, assisted ventilation should be initiated promptly. Without the presence of acidosis, a newborn may also develop apnea because of recent exposure to respiratory-suppressing medications such as narcotics, anesthetics, and magnesium. These medications, when given to the mother, cross the placenta, and depending on the time of administration and dose, may act on the newborn.
Fetal circulation is unique because gas exchange takes place in the placenta. In the fetal heart, oxygenated blood returning via the umbilical vein is mixed with deoxygenated blood from the superior and inferior vena cava and is differentially distributed throughout the body. The most oxygenated blood is directed toward the brain, while the most deoxygenated blood is directed toward the placenta. Thus, blood returning from the placenta to the right atrium is preferentially streamed via the foramen ovale to the left atrium and ventricle, and then to the ascending aorta, providing the brain with the most oxygenated blood. Fetal channels, including the ductus arteriosus and foramen ovale, allow blood flow to mostly bypass the lungs with their intrinsically high vascular resistance, which will receive only approximately 8% of the total cardiac output. Thus, the fetal circulation is unique in that the pulmonary and systemic circulations are not equal as occurs after these channels close. In the mature postnatal circulation, the lungs must receive 100% of the cardiac output. When the low resistance placental circulation is removed after birth, the infant’s systemic vascular resistance increases while the pulmonary vascular resistance begins to fall as a result of pulmonary expansion, increased arterial oxygen tension, and local vasodilators. These changes result in a dramatic increase in pulmonary blood flow. The average fetal oxyhemoglobin saturation as measured in fetal lambs is approximately 50%, but ranges in different sites within the fetal circulation between values of 20% to 80%. The oxyhemoglobin saturation rises gradually over the first 5 to 15 minutes of life to 90% or greater as the air spaces are cleared of fluid. In the face of poor transition secondary to asphyxia, meconium aspiration, pneumonia, or extreme prematurity, the lungs may not be able to develop efficient gas exchange, and the oxygen saturation may not increase as expected. In addition, in some situations the normal reduction in pulmonary vascular resistance may not fully occur, resulting in persisting pulmonary hypertension and decreased effective pulmonary blood flow with continued right to left shunting through the aforementioned fetal channels. Although the complete transition from fetal to extrauterine life is complex and much more intricate than can be discussed in these few short paragraphs, a basic knowledge of these processes will contribute to the understanding of the rationale for resuscitation practices.
Environmental Preparation
The environment in which the infant is born should facilitate the transition to neonatal life as much as possible and should readily accommodate the needs of a resuscitation team when necessary. Hospitals may vary in the approach to the details of how to prepare for resuscitation. For example, some hospitals may have a separate room designated for resuscitation where the infant will be taken after birth, others bring all the necessary equipment into the delivery room when resuscitation is expected, and some have every delivery room already equipped for any resuscitation. Wherever the resuscitation will take place, a few key elements should be ensured. The room should be warm enough to prevent excessive newborn heat loss, bright enough to assess the infant’s clinical status, and large enough to accommodate the necessary personnel and equipment to care for the baby.
When no added risks to the newborn are identified, the term birth frequently may occur without the attendance of a specific neonatal resuscitation team. However, it is frequently recommended that one individual be present who is only responsible for the infant and can quickly alert a neonatal resuscitation team if necessary. Even the best neonatal resuscitation triage systems will not anticipate the need for resuscitation in all cases. Using a retrospective risk assessment scoring system, Smith and colleagues found that 6% of newborns requiring resuscitation would not be identified based on risk factors. Antenatal determination of neonatal risk allows the neonatal resuscitation team to be present for the delivery and to be more thoroughly prepared for the situation. Preterm infants require resuscitation more frequently than term infants and, therefore, require the presence of a prepared neonatal resuscitation team at the delivery. Any situation in which the infant’s respirations may be suppressed or the fetus is showing signs of distress should signal the need for a neonatal resuscitation team. A list of factors that may be associated with an increased risk of need for resuscitation can be found in Box 3-1 . Hospitals may vary to some extent about which conditions require presence of the neonatal resuscitation team at delivery.
| Maternal factors | Fetal factors | Placental factors |
|---|---|---|
| Diabetes mellitus Preeclampsia Chronic illness Poor prenatal care Substance abuse Uterine rupture General anesthesia Chorioamnionitis | Preterm birth Known fetal anomalies Multiple gestation Hydrops fetalis Oligohydramnios Polyhydramnios Intrauterine growth restriction Signs of fetal distress Decreased fetal movement | Placenta previa Placenta accreta Vasa previa Placental abruption Premature rupture of membranes |
The composition of the neonatal resuscitation team will also vary tremendously among institutions. Probably the most important factor in how well a team functions is how well the group has prepared for the delivery. When there is a high index of suspicion that the newborn infant will be born in a compromised state, the minimally effective team should have at least three members, including one member with significant previous experience leading neonatal resuscitations. Preparation involves both the immediate tasks of readying equipment and personnel, as well as the more broad institutional preparation of training team members and providing appropriate space and equipment. Teams that regularly work together and divide tasks in a routine manner will have a better chance of functioning smoothly during a critical situation. Although much attention has been raised in the literature regarding teamwork and team and leadership training, minimal evidence is available to recommend a specific team composition or training approach.
Assessment
Immediately after birth, the infant’s condition is evaluated by general observation as well as measurement of specific parameters. Typically after birth, a healthy newborn will cry vigorously and maintain adequate respirations. The color will transition from blue to pink over the first 2 to 5 minutes, the heart rate will remain in the 140s to 160s, and the infant will demonstrate adequate muscle tone with some flexion of the extremities. The overall assessment of an infant who is having difficulty with the transition to extrauterine life will often reveal apnea, bradycardia, cyanosis, and hypotonia. Resuscitation interventions are based mainly on the evaluation of respiratory effort and heart rate. These parameters need to be continually assessed throughout the resuscitation. Heart rate can be monitored by auscultation or by palpation of the cord pulsations with auscultation being a more reliable method. In many situations, the use of a device for more extensive monitoring such as a pulse oximeter can be helpful during resuscitation. A pulse oximeter can provide the resuscitation team with a continuous audible and visual indication of the newborn’s heart rate throughout the various steps of resuscitation while allowing all team members to perform other tasks. In addition, the pulse oximeter can be used as a more accurate measure of oxygenation than the evaluation of color alone. It has been well established that color alone is an unreliable measure to accurately assess the infant’s oxygen saturation, especially where the room lighting is suboptimal. Whenever interventions beyond brief mask positive pressure ventilation are required, a pulse oximeter should be considered for additional monitoring of the infant.
The overall assessment of a newborn was quantified by Virginia Apgar in the 1950s with the Apgar score. The score describes the infant’s condition at the time it is assigned and consists of a 10-point scale with a maximum of 2 points assigned for each of the following categories: respirations, heart rate, color, tone, and reflex irritability. The score was initially intended to provide a uniform, objective assessment of the infant’s condition and was used as a tool to compare different practices, especially obstetrical anesthetic practices. Despite the intent of objectivity, there is often disagreement in score assignment among various practitioners. Low scores have been consistently associated with increased risk of neonatal mortality, but have not been predictive of neurodevelopmental outcome. Interpreting the score when interventions are being provided may be difficult and current recommendations suggest that clinicians should document the utilized interventions at the time the score is assigned.
Initial Steps: Temperature Management and Maintaining the Airway
In the first few seconds after birth, all infants are evaluated for signs of life and a determination of the need for further assistance is made. This is done both formally, as described in the NRP, and informally as the initial care providers observe the infant in the first few moments of life. When the determination that further assistance and formal resuscitation is necessary, the infant is then placed on a radiant warmer and positioned appropriately for resuscitation to proceed. Appropriate positioning includes placing the infant supine on the warmer in such a way that care providers have easy access, traditionally with the baby’s head toward the open end of the warmer. In addition, the head should be in a neutral or “sniffing” position to facilitate maintenance of an open airway. Frequently, the oropharynx contains large amounts of fluid which can be removed by suctioning with a standard bulb syringe.
An infant born through meconium-stained amniotic fluid is at risk for aspirating meconium and developing significant pulmonary disease known as meconium aspiration syndrome, which may also be accompanied by persistent pulmonary hypertension. For many years, routine management of all infants with meconium-stained amniotic fluid included endotracheal intubation and tracheal suctioning in an attempt to remove any meconium from the trachea and prevent the development of meconium aspiration syndrome. Recognizing that intubation may not be necessary for all infants, while the procedure may be associated with complications, a more selective approach was proposed and evaluated. A metaanalysis of studies that have evaluated this question supported the notion that universal endotracheal suctioning does not result in a lower incidence of meconium aspiration syndrome when compared with selective endotracheal suctioning. The likelihood that an infant with meconium-stained amniotic fluid will develop meconium aspiration syndrome is increased in the presence of fetal distress. The selective approach to endotracheal suctioning requires a quick evaluation of the infant after delivery. If the infant is vigorous with good respiratory effort, normal heart rate and tone, the steps of resuscitation should proceed as usual. However, if the infant is not vigorous, has poor respiratory effort, a heart rate less than 100 beats per minute (bpm) and/or decreased tone, endotracheal intubation and tracheal suctioning are performed as quickly as possible.
The provision of warmth is particularly important for the extremely preterm infant. Preterm infants are commonly admitted to the neonatal intensive care unit (NICU) with core temperatures well below 37° C, and in a population-based analysis of all infants less than 26 weeks’ gestation, greater than one third of these preterm infants had admission temperatures less than 35° C. More disturbing is the fact that infants with such admission temperatures survived less often than those with admission temperatures greater than 35° C. Vohra and colleagues have shown that admission temperatures may be improved in infants less than 28 weeks’ gestation by immediately covering the infant’s body with polyethylene wrap prior to drying the infant. With this approach, the infant’s head is left out of the wrap and is dried, but the body is not dried prior to wrap application. Other measures for maintaining infant temperatures include performing resuscitation in a room that is kept at an ambient temperature of approximately 25° C to 26° C (77° F to 79° F), using modern radiant warmers with servo controlled temperature probes placed on the infant within minutes of delivery, and the use of accessory prewarmed mattress/heating pads for the tiniest of such infants. It is important to note that as a required safety feature, radiant warmers will substantially decrease their power output after 15 minutes of continuous operation in full power mode. If this decrease in power is unrecognized, the infant will be exposed to a much cooler radiant temperature. By applying the temperature probe and using the warmer in servo mode, the temperature output will adjust as needed and the power will not automatically decrease.
Assisting Ventilation
As the newborn infant begins breathing and replaces the lung fluid with air, the lung becomes inflated and a functional residual capacity is developed and maintained. With inadequate development of FRC, the infant will not adequately oxygenate, and if prolonged, the infant will develop bradycardia. The steps involved in performing resuscitation include providing assisted positive pressure ventilation when the infant shows signs of inadequate lung inflation. The indications for provision of positive pressure ventilation include apnea or inadequate respiratory effort, poor color, and heart rate less than 100 bpm. Positive pressure ventilation can be delivered noninvasively with a pressure delivery device and a face mask or invasively with the same pressure delivery device and an endotracheal tube. Pressure delivery devices can include self-inflating bags, flow-inflating or anesthesia bags, and T-piece resuscitators, each with its own advantages and disadvantages. A self-inflating bag requires a reservoir to provide nearly 100% oxygen, may deliver very high pressure if not used carefully, but is easy to use for inexperienced personnel and will work in the absence of a gas source. These devices have pressure blow-off valves, but these valves do not always open at the target blow-off pressures. An anesthesia bag or flow-inflating bag requires a gas source for use, allows the operator to “instinctively” vary delivery pressures, but requires significant practice to develop expertise with use. A T-piece resuscitator is easy to use, requires a gas source for use, delivers the most consistent levels of pressure, but requires intentional effort to vary pressure levels. The flow-inflating bag and T-piece resuscitator allow the operator to deliver continuous positive airway pressure (CPAP) or positive end expiratory pressure (PEEP) relatively easily.
A level of experience is required to perform assisted ventilation using a face mask and resuscitation device, especially for an extremely low-birth-weight infant. It is important to maintain a patent airway for the air to reach the lungs. The procedure of obtaining and maintaining a patent airway includes, at minimum, clearing of fluid with a suction device, holding the head in a neutral position, and sometimes lifting the jaw slightly anteriorly. The face mask must make an adequate seal with the face for air to pass to the lungs effectively. No device will adequately inflate the lungs if there is a large leak between the mask and the face. Until recently, there were no masks that were small enough to provide an adequate seal over the mouth and nose for the tiniest infants. Such masks are now readily available and facilitate bag and mask resuscitation of very small infants. Signs that the airway is patent and air is being delivered to the lungs include visual inspection of chest rise with each breath and improvement in the clinical condition, including heart rate and color. The use of a colorimetric carbon dioxide detector during bagging will allow confirmation that gas exchange is occurring by the observed color change of the device or alerting the operator of an obstructed airway with lack of such color change. It is important to remember that these devices will not change color in the absence of pulmonary blood flow, as occurs with inadequate cardiac output. At times, multiple maneuvers are required to achieve a patent airway, such as readjusting the head and mask positions, choosing a mask of more appropriate size, and further suctioning of the pharynx. Alternate methods of providing a patent airway include the use of a nasopharyngeal tube, a laryngeal mask airway device, or an endotracheal tube.
The amount of pressure provided with each breath during assisted ventilation is critical to the establishment of lung inflation and therefore adequate oxygenation. Although it is important to provide adequate pressure for ventilation, excessive pressure can contribute to lung injury. Achieving the correct balance of these goals is not simple and is an area of resuscitation that requires more study. A specific level of inspiratory pressure will never be appropriate for every baby. Initial inflation pressures of 25 to 30 mm Hg are probably adequate for most term babies. The current NRP textbook recommends initial pressures of 20 to 25 mm Hg for preterm infants. The first few breaths may require increased pressure if lung fluid has not been cleared, as occurs when the infant does not initiate spontaneous breathing, and infants with specific pulmonary disorders, such as pneumonia or pulmonary hypoplasia, also frequently require increased inspiratory pressure. It has been shown that using enough pressure to produce visible chest rise may be associated with hypocarbia on blood gas evaluation and excessive pressure may decrease the effectiveness of surfactant therapy. It may be possible to establish FRC without increasing peak inspiratory pressures by providing a few prolonged inflations (3 to 5 seconds inspiration) , although the use of prolonged inflations has not been associated with better outcomes than has conventional breaths during resuscitation. Choosing the actual initial inspiratory pressure is less important than continuously assessing the progress of the intervention.
Current neonatal resuscitation guidelines recommend using visual assessment of chest wall movements to guide the choice of inflating pressure during positive pressure ventilation (PPV) in the delivery room. The accuracy of this assessment has not been tested. Poulton et al compared the assessment of chest rise made by observers standing at the infant’s head and at the infant’s side with measurements of tidal volume. Airway pressures and expiratory tidal volume (V[Te]) were measured during neonatal resuscitation using a respiratory function monitor. After 60 seconds of PPV, resuscitators standing at the infant’s head (head view) and at the side of the infant (side view) were asked to assess chest rise and estimate V(Te). These estimates were compared with V(Te) measurements taken during the previous 30 seconds. Agreement between clinical assessment and measured V(Te) was generally poor. During mask ventilation, resuscitators were unable to accurately assess chest wall movement visually from either head or side view.
A manometer in the circuit during assisted ventilation provides the clinician with an indication of the actual administered pressure, although if the airway is blocked, this pressure is not delivered to the lungs. The most critical component of continued assessment is evaluation of the infant’s response to the intervention. If after initiating ventilation, the condition of the infant does not improve (specifically improved heart rate, breathing, and color), then the ventilation is most likely inadequate. Two most common reasons for inadequate ventilation are a blocked airway or insufficient inspiratory pressure. The blocked airway frequently can be corrected with changes in position or suctioning, whereas inadequate pressure is corrected by adjusting the ventilating device.
In addition to consideration of inspiratory pressure, use of continuous pressure throughout the breathing cycle seems to be beneficial for the establishment of FRC and improvement in surfactant function. This is accomplished during assisted ventilation with the use of PEEP or CPAP when additional inspiratory pressure is not needed. In the absence of PEEP, a lung that has been inflated with assisted inspiratory pressure will lose on expiration most of the volume that had been delivered on inspiration. This pattern of repeated inflation and deflation is frequently thought to be associated with lung injury. In preterm infants, a general approach of using CPAP as a primary mode of respiratory support in neonatal intensive care units has been associated with a low incidence of chronic lung disease. The recently published SUPPORT trial found no significant difference in death or bronchopulmonary dysplasia between infants randomly assigned CPAP beginning in the delivery room versus those who received intubation and early surfactant.
If assisted ventilation is necessary for a prolonged period of time or if other resuscitative measures have been unsuccessful, ventilation should be provided via an endotracheal tube. If it has been difficult to maintain a patent airway by ventilating with a face mask, the appropriately placed endotracheal tube will provide a stable airway. This will allow more consistent delivery of gas to the lungs and, therefore, provide for the ability to establish and maintain FRC. At this time, intubation is required for administering surfactant and may be used to administer other medications necessary for resuscitation. Finally, for depressed infants born through meconium-stained amniotic fluid, intubation is performed for suctioning of the airway.
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