Neonatal Resuscitation
Perspective
Approximately 10% of newborns require some resuscitative assistance at birth, and approximately 1% require extensive resuscitative measures.1 Appropriate equipment and preparation, knowledge of neonatal physiology and response to stress, and skill in performing the necessary procedures are essential to successful resuscitation. Preparation for neonatal resuscitation requires an understanding of how it differs from pediatric and adult resuscitation, as follows:
1. Newborns have rapidly changing cardiopulmonary physiology, their own range of normal vital signs (Table 11-1), and unique responses to stress.2,3
2. The approach to newborn resuscitation focuses almost entirely on respiratory, not cardiac, management.2
3. Because of their small size, infants require special equipment.
Pathophysiology
Transition from Fetal to Extrauterine Life
The successful transition from the fetal to the extrauterine environment requires two major cardiorespiratory changes: (1) removal of fluid from unexpanded alveoli to allow ventilation and (2) redistribution of cardiac output to provide lung perfusion. Failure of the development of either adequate ventilation or adequate perfusion leads to shunting, hypoxia, and ultimately reversion to fetal physiology.2
The fetal lung is poorly perfused. Because the pulmonary arterial bed is intensely vasoconstricted, the fetal lung receives only 40% of the right ventricular cardiac output; most of the right ventricular output is shunted from the pulmonary artery through the ductus arteriosus to the descending aorta.4 After the first few breaths, with exposure to alveolar oxygen, pulmonary vascular resistance decreases. The fetal shunt through the ductus arteriosus reverses as systemic vascular resistance increases; then the shunt usually ceases by 15 hours of age as the ductus also constricts. This reversal of flow allows all right ventricular output to perfuse the lungs. If hypoxia or severe acidosis occurs, however, the muscular pulmonary vascular bed constricts again, and the ductus may reopen. The reinstitution of fetal circulation, with its attendant shunting, leads to ongoing hypoxia and is termed persistent fetal circulation.2,4 Resuscitation facilitates the first few breaths, prevents and reverses ongoing hypoxia and acidosis, and assists the newborn in the transition to extrauterine life.
Neonatal Responses
The newborn’s clinical response to severe hypoxia is unique. In utero or intrapartum asphyxia (pathologic lack of oxygen to the fetus before or during delivery) precipitates a sequence of events termed primary apnea and secondary apnea. After initial hypoxia, the infant gasps rapidly, followed by cessation of respirations (primary apnea) and a decreasing heart rate (HR). At this point, only simple stimulation is needed to reverse bradycardia and assist the development of ventilation. With ongoing asphyxia, however, the infant takes several final deep, gasping respirations, followed by cessation of respirations (secondary apnea), worsening bradycardia, and decreasing blood pressure. In secondary apnea, more vigorous and prolonged resuscitation is needed to restore ventilation and an adequate circulation.2
The presence of respirations may not ensure adequate ventilation. In addition, signs of hypoxia (e.g., cyanosis, lethargy, unresponsiveness) may have other causes. Bradycardia in the newborn (HR <100 beats/min) almost always reflects inadequate ventilation and oxygenation. Bradycardia is a major indicator of hypoxia.1,2 Pulse oximetry may assist in determining hypoxemia, but it may take several minutes for a reliable waveform to be achieved.5,6
Hypothermia
The newborn’s inability to maintain body temperature (>36.5° C) has severe physiologic consequences. The newborn cannot generate heat by shivering, cannot retain heat due to low fat stores, and has a relatively large surface-to-volume area. In addition, the newborn is at risk for heat loss because of a high metabolic rate, wet amniotic fluid covering, and exposure to a relatively cool environment, especially in contrast to intrauterine temperature. The body temperature easily and rapidly decreases, and low body temperatures can lead to metabolic acidosis, increased oxygen consumption, hypoglycemia, and apnea.1–3 Drying and warming the newborn are vital to initial resuscitation.
Hypoglycemia
The newborn is at risk for developing hypoglycemia when stressed because of poor glycogen stores and immature liver enzymes. Hypoglycemia is common in premature or small-for-gestational-age infants and in infants born to diabetic mothers. It also develops in response to respiratory illness, hypothermia, polycythemia, asphyxia, and sepsis. Hypoglycemia may be asymptomatic or may cause an array of symptoms, including apnea, color changes, respiratory distress, lethargy, jitteriness, seizures, acidosis, and poor myocardial contractility.7,8 Low blood glucose has been associated with adverse neurologic outcomes in both animal and clinical studies.7 Neonatal hypoglycemia is generally defined as less than 40 mg/dL, although this number is not scientifically proven. Newborns showing symptoms of hypoglycemia together with glucose level less than 40 mg/dL should be treated with intravenous glucose. Of note, bedside glucometers generally result in lower glucose readings than plasma glucose levels by approximately 10 mg/dL.8
Indications for Resuscitation
Any infant born outside of the controlled environment of the delivery room should be considered in need of resuscitation.1–3 Minimal intervention may be required, but a standardized approach as described in this chapter should be followed. Adequate ventilation and warming are essential to a successful resuscitation. Some specific conditions such as the ones presented here increase the likelihood that resuscitation will be required.
Medications given to the mother or illicit drugs taken before delivery can lead to respiratory depression in the newborn. Maternal opioid administration or opioid use should be considered in any newborn with isolated respiratory depression that persists after successful initial resuscitation. As in adults, 0.1 mg/kg of naloxone administered to newborns may reverse respiratory depression caused by opioids. Naloxone may have a shorter half-life than the original maternal opioid; therefore the neonate should be monitored closely for recurrent apnea or hypoventilation, and subsequent doses of naloxone may be required.9,10 However, use of naloxone may precipitate acute withdrawal, seizures, or both in infants who have had prolonged intrauterine opioid exposure, and the overall effect and side effects of naloxone in the newborn are not fully known.9,10 Therefore naloxone is not recommended as a first-line treatment in the initial resuscitation efforts. Support of ventilation may be preferable to reversal with naloxone.
No reliable set of parameters has been identified for newborns who should not receive resuscitative efforts.11 Currently, resuscitation is not recommended for neonates with confirmed gestational age less than 23 weeks; those with birth weight less than 400 g; and those with confirmed anencephaly, trisomy 13, or trisomy 18.11,12 If unsure of gestational age or birth weight limitations, the recommendation is to initiate resuscitation. In the out-of-hospital setting or in the emergency department, every attempt should be made to stabilize the neonate until it is clear that attempted or continued resuscitation would not improve the patient’s chance of survival. Infants with no signs of life (no heart beat and no respiratory effort) after 10 minutes of resuscitation show either a high mortality rate or severe later developmental delay. After 10 minutes of continuous and adequate resuscitative efforts, discontinuation may be justified if there are no signs of life.12,13 It is important to communicate openly with the parent(s) and to acknowledge their opinions regarding risk of morbidity, including participation in the decision of whether or not to continue resuscitation.
Specific Disorders
Meconium in the amniotic fluid is a sign of in utero distress, and the presence of thick or particulate meconium before or at delivery should raise concern about the potential for aspiration. Aspiration of meconium and its consequences can be avoided by rapid intervention. Previous recommendations included suctioning meconium from the infant’s airway after delivery of the head but before delivery of the shoulders (intrapartum suctioning). However, evidence from a large multicenter trial did not show benefit from intrapartum suctioning.14–16 Therefore current recommendations no longer advise routine intrapartum suctioning for infants born to mothers with meconium-stained fluid. The decision to perform endotracheal intubation with tracheal suctioning after delivery of the infant should be made based on the vigor of the infant, rather than on the presence or consistency of the meconium (e.g., thick or particulate vs. thin). Infants with meconium-stained fluid and with any of the following are candidates for tracheal suctioning: (1) absent or depressed respirations, (2) poor muscle tone, or (3) HR less than 100 beats/min.2 In such newborns, a meconium aspirator should be attached to the ETT and connected to wall suction at 100 mm Hg or less. The ETT is withdrawn as suction is being applied. After intubation, the ETT with meconium aspirator serves as the ideal suction catheter. Because of its narrower width, a suction catheter placed in the ETT does not suction meconium effectively. Reintubation and suction should be repeated until the meconium clears. Two passes of intubation and suctioning are usually sufficient. When these steps have been completed, the resuscitation should continue, beginning with the steps at the top of the neonatal flow algorithm (Fig. 11-1). If bradycardia or apnea continues beyond two passes, resuscitation should include bag-mask ventilation and consideration of intubation with ETT to secure the airway.
Preparation
To maximize the effectiveness of resuscitation, the emergency department should have a prestocked drug pack, standardized equipment (Box 11-1), and staff familiar with newborn resuscitation.1,3 The pediatric length-based resuscitation tape (Broselow-Luten tape) has a section that can be used to determine equipment size and drug dosages for newborn resuscitation for infants weighing 3 kg or more.18,19
