Myra H. Wyckoff
THE IMPACT OF NEWBORN RESUSCITATION
The vast majority of newborn infants have a successful transition from intrauterine to extrauterine life without need of assistance; however, approximately 10% require some degree of resuscitative support in the delivery room.1 The presence of certain antepartum, intrapartum, or postpartum risk factors predicts many but certainly not all infants who require help in the delivery room (Table 42-1). Premature, when compared to term infants, are at particular risk for having difficulty with transition following birth. The most common contributing factor for infants in need of resuscitation is asphyxia. Asphyxia is a lack of gas exchange; it results in concomitant hypoxia and hypercapnia and causes a mixed metabolic and respiratory acidosis. The asphyxia can result from either failure of placental gas exchange before birth or deficient pulmonary gas exchange once the newborn is delivered.
Prompt, effective reversal of asphyxia (with a major focus on effective ventilation) can potentially prevent and certainly minimize multiorgan failure, death, and disability. Nearly 1 million newborns worldwide die from birth asphyxia.1 As a result, development of competence in effective newborn resuscitation has the potential to make a profound global impact on the health of children.
ANTICIPATION AND PREPARATION
Anticipation and planning for both expected and unexpected neonatal emergencies is essential for success. If a fetus is at high risk for needing resuscitation in the delivery room, antepartum triage to a center with expertise in high-risk stabilization should be attempted if it is safe to do so. Regardless, every birth should have at least 1 person immediately available to focus solely on the newborn to assess the need for and, when required, initiate resuscitation. That person should then be able to call for additional immediate assistance if necessary. If a high-risk delivery is anticipated, at least 2 or more people with comprehensive resuscitation skills should be present and prepared. Ideally, 1 person should be assigned the task of resuscitation leader who assigns tasks among the available team members before the delivery and helps coordinate the entire resuscitation while limiting his or her own active involvement in the individual tasks in order to maintain focus on communication, coordination, and success of the resuscitation as a whole. Additional personnel must stabilize the airway by maintaining an open airway position of the head. This person may need to intubate and stabilize the endotracheal tube and/or provide assisted ventilation. Others should be assigned to monitor the infant’s condition and keep an accurate written record, to perform cardiac compressions if needed, to establish vascular access, to administer drugs, and to perform other emergency procedures as indicated by the infant’s condition, such as thoracentesis or paracentesis.2 A dedicated, well-trained resuscitation team is ideal for coordination of all these tasks.
Table 42-1. Antepartum, Intrapartum, and Postpartum Factors Associated with Need for Newborn Resuscitation
Obtaining a clear history from the obstetrical team as to why resuscitation providers were called is a critical first step in preparation. At a bare minimum, the resuscitation provider must know how many babies are delivering, the estimated gestational age, and whether meconium is present in the amniotic fluid. If there is time, further history is extremely helpful (see eTable 42.1 ). All equipment that might be needed for a complete resuscitation, including personal protection equipment for the resuscitation providers, must be present, in working order, and ready for use at every delivery (see Table 42-2).1 Appropriate equipment should be immediately checked for presence and function with particular attention to provision of a warm resuscitation environment. Hypothermia of the newborn has been associated with hypoglycemia, metabolic acidosis, and increased mortality (particularly for preterm infants).3 The World Health Organization recommends that in order to minimize heat loss for the newborn, the delivery area temperature should be maintained at 77 °F (25 °C).4 Additional heat loss–prevention strategies include use of maximally powered radiant warmers, warm blankets for drying, and warming aids such as hats and plastic occlusive skin wrap for preterm infants. A functional positive pressure ventilation device with the capability for oxygen delivery, suction devices (bulb syringe as well as wall suction and suction catheters), a functional laryngoscope with appropriate-sized blades, and appropriate endotracheal tubes should be ready. In certain potentially dire circumstances, an umbilical venous line should be prepared and resuscitation medications drawn up and labeled for potential use. For high-risk deliveries that are likely to result in a neonatal intensive care unit admission, additional monitoring equipment, including pulse oximetry, end-tidal carbon dioxide detection, and cardiac monitoring, may be of benefit, as the delivery room can be considered an extension of the neonatal intensive care unit in such circumstances.
INDICATIONS FOR NEED FOR RESUSCITATION
Most term newborns respond to birth with good respiratory effort, a rising or stable heart rate greater than 100 beats per minute (bpm), and movement of the arms and legs with good tone. Preductal oxygen saturations will improve steadily over the first 5 to 10 minutes,5,6 although clinical judgment of pink color can be notoriously problematic.7 Term babies born through clear amniotic fluid who respond vigorously to birth with adequate respiratory effort and good heart rate need only routine care such as provision of warmth (drying) and clearing the airway and can often remain with the mother. Those who are born through meconium, or with poor, gasping, or absent respiratory effort, inadequate heart rates below 100 bpm, or who are born preterm should be taken to the radiant warmer for further assessment and possible resuscitation interventions (Fig. 42-1). Heart rate should be assessed by listening to the precordium with a stethoscope. Palpation of the base of the cord is not as accurate.8 Gasping, apnea and a heart rate below 100 bpm are signs that indicate the need to clear the airway and provide positive pressure ventilation.
Table 42-2. Neonatal Resuscitation Supplies and Equipment
INITIAL STEPS OF NEWBORN RESUSCITATION
All babies should have an immediate assessment and initial steps of resuscitation (provision of warmth, airway opened, and drying and stimulation) provided. If the infant is of term estimated gestational age and vigorous at birth with good respiratory effort, heart rate, and tone, these steps can be done on the mother’s abdomen or chest. If the infant is preterm, nonvigorous, or has anomalies, then he or she should be taken to the prepared radiant warmer for further action. Nonvigorous infants born through meconium stained amniotic fluid are discussed later in this chapter. Infants born through clear fluid should have the following steps taken.
Step 1. Provide warmth: The infant should be received in warm blankets and placed under a preheated radiant warmer. The initial wet blanket must be removed and the infant dried with particular attention to the head. Consider placement of a knit hat.9 If the infant is preterm, consider placing the infant on a portable chemically activated heating pad under a layer of warm blankets.10 If the baby is less than 28 weeks estimated gestational age, place the trunk and extremities into a food-grade resealable polyethylene bag.11 It is useful to measure the infant’s rectal temperature while in the delivery room to guide further intervention in addition to preventing iatrogenic hyperthermia, which is detrimental as well.12
Step 2A. Open the airway: The infant should be placed with the neck in mild extension so that the airway is maximally patent. Sometimes a shoulder roll is helpful to help maintain correct position of the head. Secretions should be quickly and gently suctioned with a bulb syringe or suction catheter from the mouth and then the nose. Care should be exercised to avoid vigorous or deep suction because it can cause vagal stimulation with apnea and bradycardia (the very thing you are trying to avoid!).
Step 2B. Clear the airway of meconium: Depressed infants born through meconium-stained amniotic fluid are at risk for aspiration of the meconium into the lungs, increasing the risk of severe respiratory failure. If a meconium-stained infant is not vigorous at birth, the medical provider should assume that the infant is in secondary apnea and may well have gone through an agonal gasping phase in utero, thus putting him at risk for meconium aspiration pneumonia (eFig. 42.1 ). Such nonvigorous meconium-stained infants should be immediately intubated for meconium suctioning of the airway before stimulation is provided. There is no evidence that routine intrapartum suctioning by the obstetrician is helpful.13 Vigorous meconium-stained infants are unlikely to have gone through an agonal gasping phase in utero, and there is no benefit to intubation and suctioning of such infants.14 Thus, the vigorous meconium-stained infant should be managed in the same manner as one born through clear fluid.
FIGURE 42-1. American Academy of Pediatrics/American Heart Association neonatal resuscitation program algorithm. Note: Routine administration of oxygen has become controversial. (Source: Adapted from KattwinkelJ. Textbook of neonatal resuscitation. American Academy of Pediatrics/American Heart Association, ed. 5th. Elk Grove, IL; 2006, p. 1-11. http://circ.ahajournals.org/cgi/content/full/112/24_Suppl/IV-188)
Step 3. Stimulate: Once the airway is clear, the infant should be dried thoroughly and briefly stimulated by rubbing the back. An infant in primary apnea will respond to almost any form of stimulation. If, however, the baby remains apneic, gasping, or with an inadequate heart rate, the infant is in secondary apnea, and effective positive pressure ventilation must be initiated without delay.
EFFECTIVE POSITIVE PRESSURE VENTILATION
Effective ventilation of the lungs is the most critical step in stabilization of the newborn infant who is not transitioning well at birth. Three different devices (self-inflating bag, flow-inflating bag, and T-piece resuscitator are currently available for ventilation of the newborn in the delivery room, each with its particular positive and negative features. Ventilation can be provided via an appropriately sized face mask or endotracheal tube. In order to provide effective ventilation via face mask, the first step is to make sure the infant is maintained in the open airway position (see eTable 42.2 ). The mask must be appropriately sized to achieve a good seal. It should fit snugly around the mouth, supported by the chin and bridge of nose. The mask should not rest on the eyes because maintenance of pressure to achieve an adequate seal will elicit an adverse vagal reflex. Lack of appropriate airway position and poor seal are common causes of inadequate ventilation and resultant poor response to positive pressure ventilation in the delivery room. The best sign that effective ventilation is underway is a rapid rise in heart rate,15 followed by improvement in color and tone. If there is not rapid improvement, then look for the presence of chest rise with each ventilation and listen for breath sounds. If no chest rise is noted with positive pressure breaths, then attempt the following measures to achieve chest rise, summarized by the acronym MR SOPII (see Table 42-3). Ventilation rates of 40 to 60 breaths per minute are commonly used.16 It is easy for an inexperienced provider to deliver much higher rates than is beneficial, so counting out loud to maintain a steady rhythm of 1 breath per second can be helpful. Initial inflation pressures may be high to inflate the lungs, but after that, it is important to adjust the inspiratory pressure to maintain a heart rate greater than 100 bpm and not overdistend the lungs. The optimum inspiratory pressure, inflation time, and flow rate required to maintain effective ventilation varies.16 If the baby has improved heart rate (> 100 bpm), color, and tone, and begins to breathe spontaneously, then the bagging rate can be gradually discontinued. Decompression of the stomach to prevent gas distention, which can further impede effective ventilation, should be done via placement of an orogastric tube if prolonged bagging is needed. If there is not full improvement, then the infant may need to have the trachea intubated for continued support. If the heart rate remains less than 60 bpm despite what would otherwise appear to be effective ventilation with chest rise, then external cardiac compressions are indicated.
Table 42-3. Strategies to Achieve Chest Rise during Bag Mask Ventilation (MR SOPII)
CONTINUOUS POSITIVE AIRWAY PRESSURE
Use of continuous positive airway pressure (CPAP) in the delivery room for premature infants appears to reduce the need for intubation and surfactant but thus far has not been shown to reduce the potential for chronic lung disease.17CPAP use in the delivery room may increase the risk for pneumothorax. Large randomized studies are ongoing, and as such, the role of CPAP in the delivery room remains unclear. It is important to note that although CPAP may help establish and maintain a functional residual capacity in a stiff, noncompliant lung, thus improving respiratory distress, it should never be used in place of positive pressure ventilation when respiratory effort is poor or absent.
Intubation may be performed for a variety of indications during resuscitation, including meconium suctioning, inadequate response and/or poor chest rise during bag mask ventilation, need for positive pressure ventilation beyond a few minutes, need for external chest compressions, endotracheal delivery of epinephrine if the intravenous route is inaccessible, surfactant administration, and suspected diaphragmatic hernia. For tube size, laryngoscope blade size, and depth of insertion, see Table 42-4. Use of a stylet is an option as long as care is taken that the tip does not protrude beyond the tube and it is secured so that accidental trauma does not occur. Intubation is a skill that takes practice (see eFig. 42.2 ). Once the tube is inserted, the intubator confirms that the tip-to-lip measurement seems reasonable (distance, in cm, equals 6 + the weight in kilograms at the lip has been shown to be a practical starting point)18and attaches an end-tidal carbon dioxide monitor before beginning positive pressure ventilation. An increasing heart rate and end-tidal carbon dioxide detection after several breaths are the primary methods of confirming ventilation.15,19 Secondary confirmation is to see chest rise after beginning positive pressure breaths through the tube, listening for equal breath sounds, and seeing condensation within the tube. Subsequent radiographic confirmation of proper placement is needed. Prolonged or repetitive intubation attempts should be interrupted for reapplication of bag mask ventilation to avoid exacerbation of hypoxia and hypoventilation.
Table 42-4. Laryngoscope Blade Size, Endotracheal Tube Size, and Depth of Insertion for Babies of Various Weights and Estimated Gestational Age (EGA)
Oxygen use during resuscitation remains controversial. Although there is a long history of widespread use of 100% oxygen during resuscitation of newborns, increasing concerns about potential detrimental effects of hyperoxygenation of the newborn have been raised. In utero, the oxygen tension of the fetus is relatively low compared to adult levels. Recent studies have demonstrated healthy term newborns may take 5 to 10 minutes for preductal oxygen saturations to reach 90%.6 Preterm infants are deficient in antioxidant protection and thus face potential adverse effects from high concentrations of inspired oxygen or high blood oxygen tension, such as chronic lung disease and retinopathy of prematurity, respectively. Asphyxiated term infants may suffer additional reperfusion injury in part due to formation of reactive oxygen species after excessive oxygenation during stabilization.20 Pulse oximetry and blended oxygen during resuscitation may help limit excessive oxygen exposure. There is no evidence to suggest that a newborn should have an immediate and sudden increase in blood oxygen saturation immediately at the time of birth. However, there may be critical situations in which additional oxygen is needed to promote adequate pulmonary vasodilation. Randomized controlled trials of resuscitation with varying oxygen concentrations are currently underway.
EXTERNAL CARDIAC COMPRESSIONS
Effective ventilation is typically all that is required for stabilization of most newborns in the delivery room. Hence, cardiac compressions are rarely needed in the delivery room for newborns. Current resuscitation guidelines recommend cardiac compressions for a newborn infant with a heart rate below 60 bpm despite adequate ventilation with supplementary oxygen for 30 seconds.16 Because ventilation is the most effective action in newborn resuscitation and because chest compressions are likely to interfere with effective ventilation, resuscitation providers are strongly encouraged to optimize assisted ventilation with supplemental oxygen (via endotracheal tube if possible) before initiation of chest compressions. Compressions should be delivered to the lower third of the sternum to a depth of approximately one third the anteroposterior diameter of the chest, which should be adequate to produce a palpable pulse.16 The 2-thumb method (shown in eFig. 42.3 ) in which the hands encircle the newborn chest while the thumbs compress the sternum provides the best reliability in achieving the desired depth of compression over time with less fatigue, higher generated blood pressures, and less concerning drift of hand placement that could cause traumatic injury. A compression-to-ventilation ratio of 3:1, such that 90 compressions and 30 breaths are achieved per minute, is currently recommended in order to optimize ventilation. It should be recognized that this compression-to-ventilation ratio is based on accepted consensus rather than evidence. The optimal ratio is unknown. Although vital signs should be checked intermittently, the less interruption of the cardiac compressions, the better perfusion pressure will be maintained.21 Coordinated chest compressions and ventilations should continue until the spontaneous heart rate is 60 bpm or greater.
The goal of cardiac compressions is to perfuse the heart and the brain. When severe asphyxia results in asystole or agonal bradycardia, the newborn myocardium is depleted of energy substrate. Adequate coronary perfusion must be reestablished with oxygenated blood in order to regenerate sufficient adenosine 5′-triphosphate required for effective myocardial function and return of spontaneous circulation. Coronary perfusion pressure is the difference between the aortic diastolic blood pressure and the right atrial diastolic blood pressure. Thus, cardiac compressions plus adequate systemic vascular resistance are needed to generate an adequate diastolic blood pressure in order to achieve return of spontaneous circulation. Given the profound vasodilation that typically results from the significant acidemia induced by asphyxia, a vasopressor agent such as epinephrine will frequently be required to achieve an adequate aortic diastolic pressure for sufficient coronary perfusion.
MEDICATION USE FOR AGONAL BRADYCARDIA/ASYSTOLE
Although based primarily on adult and animal studies, epinephrine has long been the preferred vasopressor agent for treatment of ventilation resistant neonatal cardiac arrest. As mentioned in the previous section, during cardiopulmonary resuscitation, the most important action of epinephrine is to stimulate α-adrenergic receptor–mediated vasoconstriction in order to elevate the diastolic blood pressure and thus the coronary perfusion pressure. Consequently, during neonatal cardiac arrest, if effective ventilation and cardiac compressions have failed to reestablish perfusion, epinephrine should be given rapidly. Current guidelines recommend that if agonal bradycardia (heart rate < 60 bpm) or asystole persists despite 30 seconds of effective positive pressure ventilation, followed by 30 seconds of coordinated cardiac compressions and ventilation, then 0.1 to 0.3 mL/kg of 1:10,000 epinephrine solution should be given rapidly via the intravenous route followed by 0.5 to 1.0 mL of normal saline flush.1 The emphasis on intravenous delivery of epinephrine rather than the previously acceptable endotracheal route mandates that delivery room resuscitation providers be well trained in rapid preparation and placement of umbilical venous catheters. The endotracheal route is no longer considered efficacious or reliable, but if it must be used due to persistent lack of intravenous access, a higher dose (0.3–1.0 mL/kg) of epinephrine should be used in hopes of improving efficacy.23 The higher endotracheal dose should always be drawn up in a larger 3-to 5-mL syringe to help alert the resuscitation team of the route for which the dose is intended, because high doses of epinephrine should not be given intravenously.
Volume infusion should be given only if there is a high suspicion for blood loss as a cause of shock given the clinical circumstances surrounding the delivery (cord avulsion, velamentous insertion of the cord, traumatic abruption, etc) or if the baby appears to be in shock and has not responded to what would otherwise appear to be adequate resuscitation. The best replacement fluid is O-negative blood, but isotonic crystalloid such as normal saline or lactated Ringer solution are acceptable until blood is available. It should be given in 10-mL/kg aliquots slowly over 5 to 10 minutes with assessment for response. It is important to remember, though, that the majority of severely depressed infants have suffered an asphyxial injury and are not hypovolemic. In an asphyxia-induced hypotension and bradycardia model (without hypovolemia), volume infusion during resuscitation increased pulmonary edema, decreased pulmonary dynamic compliance, and did not improve blood pressure either during or after the resuscitation.24 Thus, volume infusions during delivery room resuscitation may be detrimental and exacerbate poor cardiac output when hypovolemia is not present.
There is no evidence to support use of sodium bicarbonate during resuscitation of the newborn. No experimental neonatal animal studies or clinical trials have addressed the specific role of bicarbonate on achieving return of spontaneous circulation. The only randomized trial of sodium bicarbonate infusion in neonates requiring positive pressure ventilation in the delivery room failed to show any benefit on neurologic outcome or survival.25 Animal models and adult studies have demonstrated deleterious effects on physiologic end points after administration of sodium bicarbonate during cardiopulmonary resuscitation, including depression of myocardial function from the osmolar load with severe acidosis, paradoxical intracellular acidosis, and reduced cerebral blood flow. Use of sodium bicarbonate should be discouraged during brief cardiopulmonary resuscitation. Its use in the newborn should be moved to postresuscitation care that can be guided by assessment of acid-base balance.26 Bicarbonate should never be given unless the lungs are being adequately ventilated. Otherwise, acidemia will be increased due to increased respiratory acidosis.
Table 42-5. Apgar Score
ASSIGNMENT OF APGAR SCORES
Virginia Apgar, an obstetrical anesthesiologist, devised a rapid standardized scoring system to assess the clinical status of the infant at birth. She sought to focus the attention of medical providers on the newborn during the critical window of transition from intrauterine to extrauterine life so that they could offer assistance as needed.27 The Apgar score consists of 5 components: heart rate, respiratory effort, muscle tone, reflex irritability, and color (Table 42-5). Each component is given a score from 0 to 2 for a total composite score ranging from 0 to 10. Scores are assigned at 1 and 5 minutes for every delivery. If the 5-minute score is lower than 7, it is suggested to keep assigning scores every 5 minutes until the score is 7 or higher or until resuscitation efforts are withdrawn. A change between the 1- and 5-minute Apgar score is a useful index of the newborn’s response to resuscitation. However, Apgar scores are poor predictors of outcome and should not be used as sole criteria to diagnose asphyxia or hypoxic-ischemic encephalopathy.28
Other conditions that may lead to severe depression or distress at birth and that require early resuscitation include bacterial or viral sepsis, pneumothorax, airway obstruction associated with micrognathia (Pierre Robin constellation), choanal atresia, upper airway tumors or webs, massive cardiomegaly associated with pulmonary hypoplasia, pleural effusions, ascites, and anasarca.2 Many of these conditions interfere with effective ventilation and oxygenation and therefore may require specific interventions, such as insertion of an oral airway, fluid removal from the chest or abdomen, or specific surgical intervention.
If an infant has not responded to what would otherwise appear to be complete and adequate resuscitative measures for over 10 minutes, resuscitation providers may consider discontinuing their efforts.16Current data indicate that after 10 minutes of asystole, there are very few survivors, and those few who do survive bear a heavy burden of profound disability.29