Knowledge of the normal physiologic transition from fetal to neonatal life and potential disruptions of this process is vital to a comprehensive understanding of neonatal resuscitation.
Preparation of personnel and equipment prior to resuscitation is essential.
The first steps in resuscitation include stimulating the infant, maintaining a normal body temperature through management of heat gain and loss, and assessment of breathing and heart rate.
Infants who do not establish adequate respirations following the initial resuscitative steps are in secondary apnea. These infants will require respiratory support with positive pressure ventilation.
The adequacy of positive pressure ventilation should be assessed by change in heart rate and chest rise. Ventilation corrective steps should be performed if needed.
Chest compressions are started when the heart rate is below 60 beats per minute despite effective ventilation for 30 seconds and are performed using a 3:1 compression to ventilation ratio. Newborn infants who receive chest compressions have a high incidence of mortality and short-term neurologic morbidity.
Epinephrine should be given to infants who have a heart rate less than 60 beats per minute despite adequate ventilation and chest compressions for 30 seconds. Epinephrine is more effective when given via the intravenous route versus the endotracheal route.
Volume resuscitation is potentially lifesaving in the setting of hypovolemic shock, acute blood loss, or sepsis.
The choice to withhold aggressive resuscitation in the delivery room involves complex ethical considerations and should result from a collaborative decision involving both healthcare providers and parents.
Most babies successfully transition from fetal to neonatal life without any support. Approximately 15% will require some type of resuscitation, although only 5% will require resuscitation beyond drying and stimulation. These percentages may seem small, but with an estimated 3.8 million births in the United States in 2017 and 136 million worldwide, there are 190,000 babies in the United States and 6.8 million worldwide each year who require resuscitative measures beyond the initial basic steps.
Birth attendants with neonatal resuscitation training can decrease neonatal mortality. , Two of the most common neonatal resuscitation training programs are the Neonatal Resuscitation Program (NRP) and Helping Babies Breathe, both from the American Academy of Pediatrics. However, although these programs are a good start, being truly prepared for resuscitation necessitates regular practice of skills. Neonatal death rates are higher at hospitals with a lower number of annual births. A study of rural hospitals revealed that many providers had not performed neonatal resuscitation in the past year. There was also a correlation between frequency of skill performance and comfort level.
Additionally, it is helpful to be aware of the physiology of neonatal transition, resuscitation, and postresuscitation care. This knowledge is particularly important during complex resuscitation when the newborn is not improving after standard resuscitative actions.
The Transition From Fetal to Neonatal Life
The essential step during transition from fetal to neonatal life is ventilation to establish the lungs as the site of gas exchange. In utero, the fetus receives oxygen and nutrients from the placenta through the umbilical vein. The oxygenated blood traverses the ductus venosus, right atrium, patent foramen ovale, left atrium, left ventricle, and aorta to the carotid and coronary arteries supplying the brain and heart. Some of the less oxygenated blood returning to the heart from the superior and inferior vena cava goes to the pulmonary circulation, but most crosses the ductus arteriosus and goes to the lower body and back to the placenta ( Fig. 8.1A ).
At the time of birth, the infant initiates breathing and aerates its lungs because the lungs must now be the site of gas exchange, rather than the placenta. The transition from fluid-filled to air-filled airways is mediated both by active sodium absorption by the respiratory epithelium and the increase in airway pressure that occurs with the onset of breathing. Air replaces fluid, the lung becomes inflated, and the functional residual capacity (FRC), with air and an air–fluid interphase, is created. This, along with the increase in oxygenation that accompanies adequate ventilation, causes a significant decline in pulmonary vascular resistance. If umbilical cord clamping is delayed past ventilation of the lungs, two sources of oxygenated blood (the umbilical vein and pulmonary veins) contribute to left ventricular preload (see Fig. 8.1B ). Subsequently the umbilical cord is clamped and blood stops flowing to the low-resistance placenta, causing an increase in systemic vascular resistance. The pressure in the left atrium then exceeds that of the right owing to both the increased systemic vascular resistance and the increase blood return to the left atrium, which leads to the functional closure of the foramen ovale (see Fig. 8.1C ). The elevated left-sided pressure also causes the flow from right to left across the ductus arteriosus to switch to left to right. The increase in oxygenation causes closure of this shunt during the first days of life in term infants.
Pathophysiology of Perinatal Asphyxia
This process of neonatal transition can be disrupted by alteration of placental blood flow to the fetus or due to neonatal factors impairing the establishment of pulmonary gas exchange, such as impaired ventilation, airway anomalies, birth asphyxia, or parenchymal lung disease (respiratory distress syndrome [RDS] or meconium aspiration syndrome). The term asphyxia describes this lack of sufficient gas exchange resulting in hypoxemia, hypercapnia, and acidosis. The fetus first attempts to redistribute blood flow to vital organs including the brain and heart. However, prolonged asphyxia leads to severe injury to these organs, causing hypoxic-ischemic encephalopathy (HIE).
Asphyxia causes distinctive patterns of breathing and hemodynamic changes. Geoffrey Dawes first described these patterns in 1968 based on his animal model of asphyxia. A similar phenomenon has been described in infants. After a period of acidosis, there is an initial attempt to recover with respiratory efforts to improve gas exchange followed by a period of primary apnea. During primary apnea, bradycardia is observed with preservation of blood pressure by several compensatory mechanisms. Stimulation during this time could result in recovery of normal respirations. As asphyxia progresses without stimulation and recovery, gasping respirations develop, followed by a period of secondary apnea. During secondary apnea, blood pressure drops, resulting in myocardial dysfunction. During this period, positive pressure ventilation (PPV) is required for resuscitation, and stimulation alone is not adequate ( Fig. 8.2 ).
In addition, asphyxia can modify the circulatory changes that occur at the time of birth. Hypoxia and acidosis inhibit the normal decrease in pulmonary vascular constriction and closure of the ductus arteriosus, so right-to-left blood flow continues. There may also be persistence of the right-to-left flow through the foramen ovale due to pulmonary hypertension that causes increased right atrial pressure.
Prompt resuscitation may be able to reverse these alterations, especially if the period of asphyxia was recent and brief. The subsequent portions of this chapter will discuss how to prepare and carry out newborn resuscitation.
The most important part of a successful resuscitation is what happens prior to delivery. Five questions ( Table 8.1 ) with the pneumonic GRASP should be communicated between obstetric and pediatric providers. The team should be informed about gestational age, possible risk factors (such as diabetes, hypertension, and history of prior pregnancy or delivery problems), color of the amniotic fluid, number of fetuses, and plans for placental transfusion. The neonatal providers must have the appropriate resuscitation skills, and all resuscitation equipment should be functional and located nearby. Although risk factors are present in many babies requiring extensive resuscitation, the need for resuscitation can also be a surprise. It is thus important to be prepared at every delivery.
|Gestational age—What is the expected gestational age?|
|Risk factors—Are there any additional risk factors?|
|Amniotic fluid—Is the amniotic fluid clear?|
|Single/multiple—How many babies are expected?|
|Placental transfusion—Are there any plans for delayed cord clamping or cord milking?|
It is essential that the teams responsible for neonatal resuscitation are able to expertly perform their respective tasks and communicate effectively. In a review of 47 cases of perinatal death or permanent disability reported to the Joint Commission under the Sentinel Event Policy, communication, staff competency, and training were identified as the top root causes. The traditional method of neonatal resuscitation certification is the NRP from the American Academy of Pediatrics, which requires providers to complete training every 2 years. However, this program does not ensure competence. The most recent International Liaison Committee on Resuscitation consensus statement that addresses timing for advanced resuscitation retraining presents evidence that there is a decay in skills and knowledge within months after initial training. This statement also states that more frequent training is needed, although the optimal frequency and method of training remain undetermined. Personnel should also be capable of working together as a team. The use of interdisciplinary simulation including mock code drills on a continual basis helps to maintain skills and develop coordination among staff.
One individual whose sole responsibility is the infant and who is capable of initiating resuscitation should attend every delivery. They or another person in the immediate vicinity should be capable of the complete process of neonatal resuscitation. If there are risk factors, at least two people should be at the delivery and prepared to resuscitate the infant. A team briefing should occur prior to the delivery during which the leader is identified, roles of each member are assigned, equipment is checked, and anticipated resuscitation needs are discussed.
Resuscitation equipment should be checked on a regular basis and just prior to each delivery for both availability and function. A standardized equipment checklist can be helpful, and an example of this is provided in the NRP textbook.
Initial Assessment and Management
An initial assessment of the infant should be made upon delivery. The infant can stay with the mother for the resuscitation if he or she appears to be of term gestation, has good tone, and is breathing or crying ( Fig. 8.3 ).
Drying and Stimulation
After the infant is born, the infant should be dried (or if premature, the infant’s body should be placed in a plastic bag or wrap) to prevent evaporative heat loss. Drying also provides stimulation and is often sufficient for an infant that is in primary apnea to begin breathing. Additional stimulation by flicking the soles of the feet and rubbing the back can also be provided. Warmth should be provided by placing vigorous babies skin to skin with their mother or moving them to a radiant warmer.
Thermal Management ( Fig. 8.4 )
Term infants should be placed skin to skin after delivery, if they meet the criteria above or in a radiant warmer to avoid excessive heat loss. They should be dried and the wet blankets should be removed to prevent evaporative heat loss. The temperature of nonasphyxiated infants should be measured and be kept between 36.5°C and 37.5°C because both hypothermia and hyperthermia are associated with increased morbidity and mortality.
Additional measures should be taken if a preterm infant is expected. There was a 28% increase in mortality and 11% increase in late-onset sepsis for each 1°C decrease in temperature at neonatal intensive care unit admission in a 2007 analysis. Prior to the birth of a preterm infant, the temperature in the delivery and resuscitation room should be adjusted so it is 74°F to 77°F (24°C–25°C). There is also evidence that the use of plastic covers or bags and a combination of measures including the addition of plastic caps and thermal mattresses from resuscitation through admission prevents hypothermia in preterm infants and is the recommendation of the NRP.
Respiratory Effort and Heart Rate
The infant’s head and neck should be positioned such that the neck is slightly extended in the “sniffing” position. If the infant is with the mother, a trained observer should be able to see the infant’s nose and mouth, and the head should be turned to one side (see Fig. 8.3 ). The NRP continues to recommend suctioning the mouth before the nose ( M comes before N ) to ensure that oral secretions are not aspirated if the newborn gasps when the nose is suctioned if the infant appears to be having difficulty breathing due to secretions or is apneic, although there is a lack of supportive evidence.
If the infant remains apneic at 30 seconds of life, PPV should be initiated and heart rate should be monitored by either auscultation or placement of electrocardiogram (ECG) leads ; palpation of the umbilical cord may not be reliable, although assessment by auscultation may also be inaccurate. , At the time PPV is initiated, the recommendation by the NRP is to place a pulse oximeter and consider placing ECG leads for monitoring of the infant’s heart rate and oxygen saturation. However, ECG detects the heart rate faster than pulse oximetry, , and pulse oximetry may underestimate the heart rate. , A pulse oximeter can also be used to measure oxygen saturation of an infant who is breathing with a normal heart rate but remains cyanotic, because it has been shown that it is difficult for providers to make an assessment of color. Advantages and disadvantages of various modes of heart rate assessment in the delivery room are shown in Fig. 8.5 .
When the initial steps of resuscitation fail to produce spontaneous respiration, the infant is likely in secondary apnea and will need respiratory support (see Fig. 8.2 ). The provision of ventilation in the delivery room is crucial to a successful resuscitation of a depressed infant. It is through ventilation and establishment of FRC that both the respiratory and cardiovascular changes occur in the transition from fetal to neonatal life.
Positive Pressure Ventilation (PPV)
PPV should be initiated by 60 seconds of life if the baby is apneic, gasping, or has ineffective respirations or if the heart rate is less than 100 beats per minute. Initially, PPV is given by a face mask and a pressure-generating device (discussed in more detail below). There should also be an oxygen blender to titrate the fraction of inspired oxygen, which should be set at 0.21 for term infants and 0.21 to 0.3 for preterm infants. The recommendation is to set the equipment used to provide PPV at a peak inspiratory pressure (PIP) of 20 to 25 cm H 2 O and a positive end-expiratory pressure (PEEP) of 5 cm H 2 O, if the device allows PEEP, and to give breaths at a rate of 40 to 60 per minute, which approximates the normal respiratory rate of a normal term newborn.
The use of PEEP during PPV in resuscitation is common in most centers in the United States. Animal studies suggest that PEEP is beneficial, including in the establishment of FRC. Without PEEP, there is the potential of losing FRC and alveolar collapse with each breath. However, studies in infants have not shown a change in the number of infants requiring intubation when PEEP is added. Nevertheless, it is generally thought that PEEP should be used if available, and the NRP recommends a resuscitation device that is capable of administering PEEP for the resuscitation of preterm infants.
Pressures Delivery Devices
There are several different types of devices used to generate positive pressure in the delivery room. The choice of device is largely made based on availability of equipment. Providers should familiarize themselves with the equipment in each of their workplaces.
Self-inflating bags are intermittently compressed to provide ventilation. They inflate spontaneously after compression. This type of device cannot provide a consistent amount of oxygen, does not provide PEEP unless equipped with a special valve, and cannot be used to provide continuous positive airway pressure (CPAP). It is difficult to accurately provide consistent PIP , and PEEP even with the addition of the valve. The advantage of the self-inflating bag is that is can be used without a source of compressed air. This makes it useful in resource-limited areas.
A source of compressed air is required for flow-inflating bags. These bags also are compressed to provide ventilation, and a lower degree of compression is maintained between ventilations to provide PEEP. The bag then inflates through the flow from the gas source. The pressures delivered are highly dependent on the operator. Many experienced providers like this type of bag because they believe it is possible to feel the compliance of the lungs and adjust the pressures accordingly. However, anesthesiologists ranging from inexperienced residents to experienced pediatric trained attending physicians were unable to identify intermittent occlusion of the endotracheal tube (ETT) when providing ventilation using a flow-inflating bag and test lungs corresponding to that of a term neonate. Flow-inflating bags can be used to provide CPAP.
T-Piece Resuscitation Device
T-piece resuscitation devices also require a gas source. The PIP and PEEP are set using dials, and a hole on the top or side of the device is covered intermittently to provide ventilations. PEEP is delivered when the hole is uncovered. CPAP can be given simply by leaving the hole uncovered. These devices have been shown in many studies to be the most consistent in the delivery of both PIP and PEEP. , Studies of the use of these resuscitation devices in newborn infants requiring PPV have shown a decrease in the need for intubation, , a shorter duration of PPV, and less supplemental oxygen during resuscitation.
Assessment of Efficacy
The best measurement of adequate ventilation is improvement in the heart rate. The NRP recommends assessing the heart rate after 15 seconds of PPV and continuing to use heart rate and chest rise to make repeated assessments. There are several studies indicating that clinician assessment of chest rise as a surrogate for appropriate tidal volume may not be accurate and may result in hypocarbia. Respiratory function monitors can be used to measure and display tidal volume delivery and can aid in the detection of a leak around the mask or an airway obstruction, but they are not widely available. A colorimetric CO 2 detector can also be used to aid in detection of adequate ventilation, and the NRP recommends its use for this purpose.
Providing adequate ventilation with a mask and resuscitation device requires skill. If the infant is not improving with PPV, it is important to assess all components. The mask must be appropriately sized, and a good seal between the mask and the infant’s face must be maintained. One study showed that the typical leak around the mask placed on a manikin was approximately 55% but could be improved with instruction. The two-person ventilation technique, in which one person positions the mask on the face and performs maneuvers to help open the airway if necessary while the other person delivers the breaths, decreases mask leak. The infant must be positioned with the neck slight extended so the airway is open. It is very easy, especially in preterm infants, to overextend or flex the neck and cause airway obstruction. Performing the jaw-thrust maneuver can also aid in maintaining an open airway. The mouth, then the nose, can be suctioned to ensure secretions are not contributing the obstruction. It is also important to make sure that the mouth stays in the open position so that air can easily flow into the oropharynx. Once there is a good mask seal and the airway is open, if PPV is still not effective, the pressure administered can be augmented by increasing the squeeze of the self-inflating or flow-inflating bag or adjusting the dial on the t-piece device.
If appropriate PPV is being delivered after the corrective steps mentioned above and the infant fails to improve or continues to have ineffective respirations, an alternative airway should be placed to provide more efficient and consistent pressure delivery. A secure airway also should be immediately placed before initiation of chest compressions (CCs) if the heart rate is less than 60 beats per minute and is not improving. The 2 common types of alternative airways are ETTs and laryngeal mask airways (LMAs).
Endotracheal Tubes (ETTs)
The intubation procedure requires skill to perform proficiently. Neonatal ETTs are usually uncuffed and straight and range in size from 2.0 to 4.0 mm in internal diameter. The laryngoscope blade used is a straight or Miller blade in sizes 000 to 0 for preterm infants and 0 or 1 for term infants. There are potential complications including bradycardia due to vagal stimulation and trauma to the oral and pharyngeal structures and the trachea. Mask ventilation must be paused for the attempt, and the infant’s heart rate and saturations can decline during attempts. This can be minimized by limiting the duration of the attempt to 30 seconds, and this is now recommended. Videolaryngoscopy can be useful in assisting with ventilation, particularly for experienced providers.
Correct placement of the ETT can be verified by an increase in heart rate, equal breath sounds by auscultation, mist in the ETT, and detection of CO 2 by an end-tidal CO 2 detector. Several studies have shown that the use of a CO 2 detector reduces the time to verification of ETT location. , There is no difference in outcomes with quantitative (such as mainstream or side-steam end tidal CO 2 ) devices or qualitative (colorimetric) devices. Although the tidal volume threshold for detection of CO 2 is sufficiently low to detect CO 2 during PPV using appropriate tidal volume in extremely low birth weight infants, the detector may not show color change if insufficient tidal volume is being provided or cardiac output is low ( Fig. 8.7 ). Tracheal or bronchial obstruction and severe cardiorespiratory compromise (often with extreme prematurity) can result in false negative results with CO 2 detectors in spite of tracheal intubation. ,