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Resuscitation and Initial Stabilization
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 only been since the late 20th century 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, ongoing evaluation of the program has resulted in changes when new evidence becomes available. The most recent edition of the NRP textbook, published in 2016, made several revisions, including the use of monitoring in the delivery room and management of infants born through meconium-stained amniotic fluid. 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, completes a thorough review of the literature about each of the relevant questions of resuscitation, which is published and utilized by the different groups that provide recommendations for practice.
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 other events that require resuscitation. 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 gas exchange occurs in the placenta. The transition that occurs at birth requires the neonate to increase heat production, initiate continuous breathing, replace the lung fluid with air, 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 to help fill the lung with air replacing the lung fluid. 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 10%–30% 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 inflation, increased arterial oxygen tension, and local vasodilators. These changes result in a dramatic increase in pulmonary blood flow. Near the end of gestation the placenta contains about 30%–50% of the fetoplacental blood volume. When the umbilical cord remains patent following birth, some of the placental blood volume is transferred into the newborn, leading to higher newborn hematocrit levels and a more stable hemodynamic transition. It has also recently been shown in animal models that when newly born lambs are ventilated prior to cord clamping, hemodynamic parameters such as blood pressure and cerebral blood flow remain more stable after birth. 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 provide 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.
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.
BOX 3.1
Risk Factors Related to Resuscitation at Birth
| 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 minimum requirements for an effective team includes at least three members, one of whom has significant previous experience leading neonatal resuscitations. Preparation involves both the immediate tasks of readying equipment and personnel, as well as the broader 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. Regular simulation and debriefing experiences have been useful in helping keep teams prepared for emergency situations. The use of video debriefing during simulation and real-life resuscitation can help identify areas for quality improvement.
Editorial Comment:
Quality improvement by means of simulation has been implemented in many units with great success. Furthermore, quality improvement aimed at preventing low temperatures on admission to the neonatal intensive care unit have substantially reduced the prevalence of moderate hypothermia (temperature below 36°C) on admission. This may alter mortality and morbidity.
Cord Management
After the infant is delivered, the umbilical cord must be clamped and cut. The recommended timing for clamping the umbilical cord has changed over recent years. The obstetric practice had been to immediately clamp the cord after delivery in an effort to prevent maternal hemorrhage. However, a number of randomized controlled trials have shown that “delayed cord clamping” of at least 60 seconds after birth has benefits for the newborn infant without having adverse effects for the mother. In preterm infants, several studies have shown decreases in the rates of intraventricular hemorrhage, necrotizing enterocolitis, and need for blood transfusion. The most recent metaanalysis of studies comparing delayed cord clamping with immediate cord clamping showed a decrease in mortality in the infants treated with at least 60 seconds of delayed cord clamping. In term infants, delayed cord clamping increases hemoglobin levels and iron stores in the first few months of life. Delayed cord clamping is now recommended by the American College of Obstetrics and Gynecology as well as the NRP. In infants who are depressed at birth, the suggested management is less clear. Some investigators have studied and suggested performing milking of the umbilical cord to increase the transfer of blood from the placenta to the infant. This practice has been equivalent to delayed cord clamping in small studies, but is not currently recommended by any guidelines. Ongoing studies are evaluating the practice of beginning resuscitation with the cord intact for infants who are depressed at birth. There is not sufficient evidence to recommend this practice outside of research protocols.
Editorial Comment:
Delayed or optimal clamping of the cord has been readily accepted and is becoming standard care. Longer-term follow-up is needed, but the data so far are encouraging, and the limited reports demonstrate improved motor function, especially in boys. As noted, questions remain around whether delayed cord clamping in nonvigorous infants is beneficial. Additionally, research is ongoing using a specially designed resuscitation bed that allows neonatal resuscitation simultaneously with delayed cord clamping.
Assessment
Immediately after birth, the infant’s condition is evaluated by general observation as well as measurement of specific parameters to ensure the transition to neonatal life proceeds appropriately. 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 (HR) will remain in the 140s to 160s, and the infant will demonstrate adequate muscle tone with some flexion of the extremities. The 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 spontaneous respiratory effort and HR. These parameters need to be accurately and continually assessed throughout the resuscitation to determine the need for further intervention. HR can be monitored by auscultation or by palpation of the cord pulsations, with auscultation being a more reliable method; however, both methods have been shown to be imprecise and often underestimate the HR. In many situations, the use of a device for more extensive and more accurate monitoring such as a pulse oximeter or electrocardiogram (ECG) monitor can be helpful during resuscitation. A pulse oximeter or ECG monitor can provide the resuscitation team with a continuous audible and visual indication of the newborn’s HR throughout the various steps of resuscitation while freeing a team member to perform other tasks. Studies demonstrated that ECG monitors allow for faster and more accurate HR detection than do pulse oximeters in the delivery room. In addition to measuring HR, the pulse oximeter can be used as a more accurate measure of oxygenation than the evaluation of color alone and can be used to guide the titration of supplemental oxygen. 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. The NRP guidelines currently recommend that whenever an infant requires mask positive pressure ventilation (PPV), a pulse oximeter should be used for additional monitoring of the infant. Additionally, whenever the infant requires prolonged mask PPV, intubation, and certainly chest compressions, ECG leads should be applied to allow reliable, continuous HR monitoring in addition to pulse oximetry.
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, HR, 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: Stimulation 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. The initial screen for neonatal well-being includes checking for spontaneous breathing and tone. As recommended by NRP, an infant who is term, has good tone, and is breathing can continue transitioning with his/her mother, whereas all other infants should be brought to a radiant warmer for further assessment and treatment. When placing the infant on the warmer, the first step is to position the baby in an optimal manner. Appropriate positioning includes placing the infant supine on the warmer with the baby’s head toward the open end of the warmer to allow care providers to have easy access to the infant. In addition, the head should be in a neutral or “sniffing” position to facilitate maintenance of an open airway. Providers may provide gentle stimulation, usually performed simultaneously with drying the infant, to encourage spontaneous breathing; however, this should not delay other interventions if the infant does not respond with a strong cry and spontaneous breathing quickly. The oropharynx may be suctioned if there is excess fluid causing airway obstruction. Care should be taken to avoid excessive suctioning, and the provider must be conscious of the possibility of causing vagal-induced bradycardia while suctioning. A metaanalysis on the benefits of oropharyngeal suctioning demonstrated that in term babies, the available evidence is inconclusive regarding the benefits and harms of routine oronasopharyngeal suction.
An infant born through meconium-stained amniotic fluid is at risk for aspirating meconium and developing significant pulmonary disease known as meconium aspiration syndrome (MAS), 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 MAS. Recognizing that intubation may not be necessary for all infants and that the procedure may be associated with complications, a more selective approach was followed for approximately 15 years where only those infants who were nonvigorous (HR <100, apneic, poor tone) at birth were intubated and underwent tracheal suctioning. More recent, small, randomized trials have evaluated whether tracheal suctioning is beneficial in reducing severe MAS or death in nonvigorous infants. These small trials have demonstrated no difference in the incidence of MAS or death between nonvigorous infants who received tracheal suctioning and those who did not receive routine tracheal suctioning. Acknowledging the lack of evidence for benefit of routine intubation and suctioning and the potential for harm associated with delayed initiation of ventilation and potential complications of intubation, the most recent NRP guidelines do not recommend routine tracheal intubation and suctioning of nonvigorous infants born through meconium-stained fluid. Additional future studies may help clarify this issue further.
Temperature Management
The provision of warmth is crucial for all infants but is particularly important for the extremely preterm infant. Preterm infants are commonly admitted to the neonatal intensive care unit (NICU) hypothermic, with core temperatures well below 37°C. 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. Admission temperature is considered a strong predictor of morbidity and mortality at all gestations, and all attempts should be made to maintain the temperature in the normothermic range. The recommended temperature on admission is between 36.5°C and 37.5°C. Routine documentation of the admission temperature should be standardized in each neonatal unit to ensure ongoing quality of care.
In order to assist infants in maintaining adequate thermoregulation, on arrival to the warmer, all infants should have any wet towels removed and a warmed hat placed on their head to prevent heat loss. 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. The plastic blocks evaporation and minimizes heat loss from convection. A recent metaanalysis examined 18 studies and concluded that the use of plastic wrap or a plastic bag led to increased NICU admission temperatures and fewer infants outside of the normothermic range. Other measures for maintaining infant temperatures include performing resuscitation in a room that is kept at an ambient temperature of approximately 23°C to 25°C (73°F to 77°F), using radiant warmers with servo-controlled temperature probes placed on the infant within minutes of delivery, and the use of prewarmed thermal mattress/heating pads for the tiniest of infants. A metaanalysis has shown that the use of thermal mattresses for infants less than 1500 g is associated with warmer infants and reduced hypothermia on admission to the NICU ; however, one must be careful to avoid hyperthermia when using these mattresses in combination with other strategies to prevent hypothermia. 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; however, it is also important to apply the temperature probe to the infant promptly to avoid overheating the newborn.
Assisting Ventilation
As the newborn infant begins breathing and replaces the lung fluid with air, the lung becomes inflated, and an FRC 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 PPV when the infant shows signs of inadequate lung inflation. The indications for provision of PPV include apnea or inadequate respiratory effort and HR less than 100 beats per minute (bpm). PPV 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 and allows the operator to change pressure delivered easily, but may deliver very high pressure if not used carefully and even with a positive end-expiratory pressure (PEEP) valve does not deliver reliable PEEP. These devices have pressure release valves, but these valves do not always open at the target release pressures. The self-inflating bag is easy to use for inexperienced personnel and will work in the absence of a gas source. An anesthesia bag or flow-inflating bag requires a gas source for use and 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, and 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 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. The face mask must cover the mouth and nose while avoiding the eyes. Masks for infants of all sizes are available, including the smallest of infants. Studies have demonstrated that mask leak and airway obstruction are common challenges encountered, and their recognition is often delayed while providing face mask ventilation. 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 HR and color. The use of a colorimetric carbon dioxide detector during mask ventilation 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 (LMA) device, or an endotracheal tube. These interventions for improving ventilation are summarized in NRP by the pneumonic MR. SOPA ( M ask readjustment, R epositioning, S uction, O pen the mouth, P ressure increase, and A lternate Airway).
The amount of pressure provided with each breath during assisted ventilation is critical to the establishment of lung inflation, FRC 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. During the transition to neonatal life, there are vast changes in compliance and resistance of the lungs, and therefore pressure used to provide the same tidal volume is likely dynamic throughout the resuscitation. A manometer in the circuit during assisted ventilation provides the clinician with an indication of the actual administered pressure, allowing better awareness of the pressures being supplied, although if the airway is blocked, this pressure is not delivered to the lungs. 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. 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. Visible inspection of chest rise can be somewhat subjective, and while it is a good indicator of a patent airway, it is not an accurate gauge of the delivered tidal volume. Choosing the actual initial inspiratory pressure is less important than continuously assessing the progress of the intervention. It has been shown in both manikin and human studies that T-piece resuscitators deliver more consistent peak inspiratory pressure (PIP) and less often deliver inflations of excessive pressure compared to the self-inflating bag. Despite these findings, there is felt to be insufficient evidence to recommend against the self-inflating bag, as clinical outcomes have not been shown to be different between the two devices. Additionally, since the self-inflating bag does not require a gas source, it may be necessary to use in areas with limited resources.
It may be possible to establish FRC without increasing peak inspiratory pressures by providing a sustained inflation. Multiple animal and human studies have assessed sustained inflations of varying pressures (ranging from 20–30 cm H 2 O) and durations (ranging from 10–20 seconds). A recent metaanalysis showed that the use of sustained inflation may be associated with a decreased duration of mechanical ventilation compared with conventional breaths. However, safety of this approach has not been established, and there may, in fact, be considerable harm caused by the practice of providing sustained inflation. Therefore this practice is not recommended.
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 HR, breathing, and color), then the ventilation is most likely inadequate. The 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 NICUs has been associated with a low incidence of chronic lung disease. A recent metaanalysis assessed studies comparing early CPAP with early assisted ventilation with or without surfactant and found that early CPAP was associated with a “small, but clinically significant” reduction in the incidence of bronchopulmonary dysplasia (BPD), death or BPD, and the need for mechanical ventilation as well as surfactant. It is therefore reasonable to begin CPAP for all spontaneously breathing preterm infants soon after birth.
If the infant is not breathing and 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. The NRP recommends placing an endotracheal tube and providing 30 seconds of high-quality ventilation prior to initiating chest compressions in a depressed infant.
The intubation procedure, although potentially critical for successful resuscitation, requires a significant amount of skill and experience to perform reliably and may be associated with serious complications. The procedure entails using a laryngoscope to visualize the vocal cords and passing the endotracheal tube between the vocal cords. The placement of the laryngoscope in the pharynx often produces vagal nerve stimulation, which leads to bradycardia. Assisted ventilation must be paused for the procedure, which, if prolonged, will lead to hypoxemia and bradycardia. Intubation has been shown to increase blood pressure and intracranial pressure. Trauma to the mouth, pharynx, vocal cords, and trachea are all possible complications of intubation. Performing the intubation procedure when the infant already has bradycardia and is hypoxic can lead to further decline in HR and oxygenation. Therefore it is most appropriate to make an attempt to stabilize the infant with noninvasive ventilation prior to performing the procedure, limit each attempt to 30 seconds or less, and stabilize the infant between attempts. If misplacement of the endotracheal tube into the esophagus goes unrecognized, the infant may experience further clinical deterioration. Clinical signs that the endotracheal tube has been correctly placed in the trachea include the following: auscultation of breath sounds over the anterolateral aspects of the lungs (near the axilla), mist visible on the endotracheal tube, chest rise, and clinical improvement in HR and color or oxygen saturation. The use of a colorimetric carbon dioxide detector to confirm intubation decreases the amount of time necessary to determine correct placement of the endotracheal tube and is recommended by the NRP as one of the primary methods of determining endotracheal tube placement.
Given the significant skill required to place an endotracheal tube, another device, the LMA, was developed as an alternative airway that is particularly useful for infants with small chins, cleft lip/palate, or other upper-airway anomalies. The LMA is a small oval mask with an inflatable cuff that sits over the laryngeal opening. The cuff fits on the hypopharynx and occludes the opening to the esophagus, allowing ventilation directed to the larynx. It can be used to provide PPV in apneic infants or for airway control in spontaneously breathing patients. Development of a size 1 LMA allowed for its introduction to neonatal resuscitation in the 1990s and to the NRP guidelines in 2000. Studies have evaluated its use compared to a face mask as a primary ventilation device for PPV in newborns over 34 weeks’ gestation and have shown that it is at least as effective as the face mask for achieving stable vital signs and avoiding the need for intubation. Three small studies have compared the LMA with endotracheal intubation for newborns who have not responded to face mask PPV in the delivery room, and demonstrated similar rates of successful resuscitation between the two devices. Although more studies of the LMA are needed, currently the NRP guidelines suggest the use of the LMA as an alternative to intubation in newborns over 34 weeks’ gestation if face mask ventilation fails, and recommends the LMA when intubation is not feasible.
O’Connell J, Weiner G. Intubating extremely premature newborns: a randomised crossover simulation study. BMJ Paediatr Open. 2017;1(1):e000157.
Editorial Comment:
The laryngeal mask airway (LMA) can achieve effective ventilation during neonatal resuscitation in a time frame consistent with current neonatal resuscitation guidelines. Compared to bag and mask ventilation (BMV), the LMA is more effective in terms of shorter resuscitation and ventilation times and less need for endotracheal intubation; however, there is lack of evidence to support LMA in more premature infants. LMA may be successful when BMV fails and intubation can be avoided. This is a relatively new skill for the neonatal community and requires training and preparation.
The difficulty of intubation and the need for training is highlighted by O’Connell’s study in which 55 physicians and nurses performed four intubations in succession on a high-fidelity extremely low-birth-weight manikin with size 0 Miller and size 00 Miller blades from two different manufacturers. There was no difference in total laryngoscopy time (median 23.7 versus 20.6 seconds) or first-attempt success in <30 seconds (67.3% versus 69.1%) between the size 0 and size 00 blades. With inexperienced operators, the success rate is lower and time to intubation longer.
Oxygen Use
In the past, the use of 100% oxygen for assisted ventilation was routine when neonates required assisted ventilation, as was done in all other types of resuscitation without any specific evidence. Over time, however, the potential toxicity of oxygen, especially through the creation of free radicals, led investigators to study this well-accepted practice. For term or near-term infants, many trials have compared using 100% oxygen to using room air (21%) for neonatal resuscitation. Overall, these trials found that room air was as successful as 100% oxygen in achieving resuscitation, and demonstrated less oxidative stress. Subsequent metaanalyses of up to 10 trials showed that infants resuscitated with room air had less risk of mortality than those resuscitated with 100% oxygen, and also demonstrated a trend toward less risk of severe hypoxic-ischemic encephalopathy (HIE). NRP guidelines currently recommend initiating resuscitation of term and near-term infants (>35 weeks’ gestation) with room air and using a pulse oximeter to allow titration of the oxygen delivered based on target oxygen saturations. These target oxygen saturations can be found in Table 3.1 and were derived from a study of healthy mostly term infants who did not require resuscitation in the delivery room. The values demonstrate that the transition from fetal life normally starts at a relatively low oxygen saturation around 50%–60% and gradually increases to over 90%. For the vast majority of newborns who require respiratory support for stabilization, targeting oxygen levels to mimic healthy transitioning infants is logical. However, for those who are severely depressed and require significant resuscitation, the evidence is less clear. In fact, in some of the initial trials comparing 21% versus 100% oxygen, if infants did not respond to ventilation with 21% oxygen, the amount of oxygen delivered was increased to 100%. It is therefore unknown whether providing less than pure oxygen during times of severely diminished cardiac output is safe. It is recommended that if the infant has significant bradycardia (HR <60 bpm) requiring chest compressions, 100% oxygen be used to ventilate the baby.
TABLE 3.1
Target Oxygen Saturation According to Time After Birth
| Time After Birth (min) | Target SpO 2 (%) |
|---|---|
| 1 | 60–65 |
| 2 | 65–70 |
| 3 | 70–75 |
| 4 | 75–80 |
| 5 | 80–85 |
| 10 | 85–95 |
The best concentration with which to initiate resuscitation for preterm infants is not the same as for term infants. Preterm infants have decreased antioxidant enzyme capacity and may therefore be more susceptible to harmful effects of excessive oxygen exposure. Multiple studies have evaluated starting resuscitation of preterm infants with low oxygen concentrations (≤30%) compared with high initial oxygen concentrations (≥60%). These trials consistently found that infants in the lower oxygen group needed more than 21% oxygen to achieve resuscitation targets. In the largest of these trials in which preterm infants were initially resuscitated with either 21% or 100% oxygen, a subgroup analysis of babies less than 28 weeks’ gestation revealed increased mortality in the infants initially treated with room air. A metaanalysis of studies evaluating infants less than 28 weeks’ gestation demonstrated no difference in overall mortality prior to discharge, BPD, retinopathy of prematurity, intraventricular hemorrhage, or necrotizing enterocolitis between infants resuscitated with an initial low (≤30%) versus high (≥60%) concentration of oxygen. Current NRP guidelines recommend initiating resuscitation of infants less than 35 weeks’ gestation with a low oxygen concentration of 21%–30% and against starting resuscitation with high oxygen (>65%). As with term infants, oxygen delivered should be titrated based on the HR and preductal oxygen saturations obtained using a pulse oximetry probe.
Assisting Circulation
In newly born infants, the need for resuscitative measures beyond assisted ventilation is extremely rare. Additional circulatory assistance can include chest compressions, administration of epinephrine, and volume infusion. In a large urban delivery center with a resuscitation registry, 0.12% of all infants delivered received chest compressions and/or epinephrine from 1991 to 1993, and 0.06% of all infants delivered received epinephrine from 1999 to 2004.
The importance of chest compressions in resuscitation is currently being emphasized in adult and pediatric resuscitation programs. However, because of the unique characteristics of the transitioning newborn infant as discussed previously, ventilation remains the most critical priority in neonatal resuscitation. Chest compressions can be necessary when prolonged cardiorespiratory insufficiency has been present. They are indicated when the HR remains below 60 bpm despite adequate ventilation for 30 seconds. The preferred method of chest compressions is the two-thumb method, which involves encircling the chest with both hands and placing the thumbs on the sternum. The chest is then compressed in a 3:1 ratio coordinated with ventilation breaths to provide 90 compressions to 30 breaths per minute. Chest compressions can be provided from the head of the bed, allowing another team member access to the umbilical cord for venous catheter placement.
Further circulatory support may be necessary if adequate chest compressions do not result in an increase in HR after 60 seconds. Epinephrine is then indicated as a vasoactive substance, which increases blood pressure by alpha-receptor agonist effects, improves coronary perfusion pressure, and increases HR by beta-receptor agonist effects. The strongly recommended method of epinephrine administration is intravenous in a dose of 0.01 to 0.03 mg/kg (0.1 to 0.3 mL/kg of a 1:10,000 solution). Therefore early placement of an umbilical venous catheter during a difficult resuscitation is important for both volume and epinephrine administration. If there is any prenatal indication that substantial resuscitation will be required, the necessary equipment for umbilical venous catheter placement should be prepared before delivery as completely as possible. It is probably advisable to initiate the process of umbilical venous catheter placement when the need for chest compressions arises. Epinephrine may be given by endotracheal tube, but the drug delivery is not as certain, and therefore an increased dose of 0.05-0.1 mg/kg (0.5-1 mL/kg of a 1:10,000 solution) is currently recommended. Epinephrine doses may be repeated every 3 minutes if HR does not increase. Excessive epinephrine administration may result in hypertension, which, in preterm infants, may be a factor in the development of intraventricular hemorrhage. However, the risks are balanced by the benefit of successful resuscitation in an infant who might not otherwise survive.
If the infant has not responded to all of the prior measures, a trial of increasing intravascular volume should be considered by the administration of crystalloid or blood. Situations associated with fetal blood loss are also frequently associated with the need for resuscitation. These include placental abruption, cord prolapse, and fetal-maternal transfusion. Some of these clinical circumstances will have an obvious history associated with blood loss, whereas others may not be readily evident at the time of birth. Signs of hypovolemia in the newly born infant are nonspecific but include pallor and weak pulses. Volume replacement requires intravenous access for which emergent placement of an umbilical venous catheter is essential. Any infant who has signs of hypovolemia and has not responded to other resuscitative measures should have an umbilical venous line placed and a volume infusion administered. The most common volume replacement (and currently recommended fluid) is isotonic saline. A trial volume of 10 mL/kg is given initially and repeated if necessary. If a substantial blood loss has occurred, the infant may require infusion of red blood cells to provide adequate oxygen-carrying capacity. Because not all blood loss is obvious and resuscitation algorithms usually discuss volume replacement as a last resort of a difficult resuscitation, the clinician needs to keep an index of suspicion for significant hypovolemia so that action may be taken to correct the problem as promptly as possible. Therefore in situations where the possibility for hypovolemia is known prior to birth, it would be wise to prepare an umbilical catheter and an initial syringe of isotonic saline, and prepare for the possibility that uncross-matched blood may be required.
Specific Problems Encountered During Resuscitation
Neonatal Response to Maternal Anesthesia/Analgesia
Medications administered to the mother during labor can affect the fetus by transfer across the placenta and directly affecting the fetus or by adversely affecting the mother’s condition, thereby altering uteroplacental circulation and placental oxygen delivery. One of the possible complications of intrapartum medication exposure is perinatal respiratory depression after maternal opiate administration. Because opiates can cross the placenta, the fetus may develop respiratory depression from the direct effect of the drug. Naloxone has been used in the past during neonatal resuscitation as an opiate receptor antagonist to reverse the effects of fetal opiate exposure. However, due to a lack of evidence of beneficial effect and possible adverse effects, naloxone hydrochloride is no longer recommended for use in neonatal resuscitation.
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