You are asked to attend an emergent cesarean section delivery of a 40 weeks' gestation infant with non-reassuring heart tones. Mother is a 30 year old gravida 1 married woman who was admitted in active labor four hours ago. She had good prenatal care starting at 6 weeks gestation and her pregnancy has been uncomplicated. Prenatal labs are as follows: A+, antibody negative, rubella immune, VDRL non-reactive, Gonococcus negative, Chlamydia negative, HIV negative, Hepatitis B surface antigen negative, and Group B Strep negative. Prior to delivery, mother received general anesthesia, fentanyl and IV fluids, but no other medications. Membranes are ruptured at the time of delivery revealing bloody amniotic fluid, but no meconium. The obstetrician suspects placental abruption.
At delivery, you receive a floppy, apneic, and blue term male infant. You bring him to the warming table where he is quickly positioned, dried, stimulated and given free-flow oxygen. At 30 seconds of life, he remains apneic and cyanotic. His heart rate is 30 beats per minute. You administer positive pressure ventilation with 100% FiO2 and note good chest wall rise with each positive pressure breath. The infant continues to be apneic and bradycardic with a heart rate of 40 bpm. Chest compressions are begun and positive pressure ventilation is continued. Following 30 seconds of coordinated ventilation and chest compressions, his heart rate is still 40 bpm. You intubate the infant while the nurse draws up 0.1 cc/kg of 1:10,000 concentration of epinephrine to be given via the endotracheal tube. There is no improvement in his heart rate following administration of epinephrine. You then catheterize the umbilical vein and give the second dose of epinephrine intravenously. The infant remains bradycardic. Positive pressure ventilation and chest compressions are continued as you reassess the infant. Good breath sounds are heard bilaterally, but his skin remains pale and mottled and pulses are difficult to palpate. Suspecting hypovolemia, you then administer 10cc/kg of normal saline through the umbilical vein catheter over 5 minutes. The infant's heart rate rises to 150 and his color gradually improves. You check the security of the endotracheal tube and umbilical catheter and prepare for transport to the newborn intensive care unit.
The transition from intrauterine to extrauterine life occurs without incident in approximately 90% of all births. However, 10% of newborns will require some assistance with breathing at birth, while 1% will need extensive resuscitative measures in order to survive. Worldwide, the outcome of more than 1 million newborns per year may be improved with the use of neonatal resuscitative measures.
In utero, the lungs do not perform gas exchange and accordingly, pulmonary blood vessels are markedly constricted. Oxygenated blood flows from the placenta through the umbilical vein to the right heart where the majority of the blood is shunted to the aorta through the foramen ovale and patent ductus arteriosus. Seconds after birth, three major changes occur in the newborn in order to transition to extrauterine life. First, fluid in the alveoli is absorbed into lung tissue and is replaced by air. Next, the umbilical cord is clamped, disconnecting the infant from the low resistance placental circulation and increasing systemic blood pressure. Lastly, the pulmonary vasculature relaxes in response to increased oxygen levels in the lungs causing a dramatic increase in pulmonary blood flow. The right to left shunt through the patent ductus arteriosus decreases, becoming bi-directional and the foramen ovale functionally closes in association with the increase in blood return to the left atrium. Infants who fail to complete the transition to extrauterine life may exhibit cyanosis, bradycardia, hypotension, depressed respiratory drive and/or poor muscle tone (1).
Although it is impossible to consistently predict the need for active newborn resuscitation, many antepartum and intrapartum maternal and obstetrical conditions are associated with increased risk to the newborn. Antepartum risk factors include: maternal diabetes, hypertension (pregnancy induced or chronic), chronic maternal illness, anemia or isoimmunization, previous fetal or neonatal death, bleeding in the second or third trimester, maternal infection, polyhydramnios, oligohydramnios, premature rupture of membranes, post-term gestation, multiple gestation, size-dates discrepancy, maternal drug therapy, maternal substance abuse, fetal malformation, diminished fetal activity, no prenatal care and maternal age <16 or >35 years. Intrapartum risk factors include: emergency cesarean section, forceps or vacuum-assisted delivery, breech or other abnormal presentation, premature labor, precipitous labor, chorioamnionitis, prolonged rupture of membranes, prolonged labor, prolonged second stage of labor, fetal bradycardia, non-reassuring fetal heart rate patterns, use of general anesthesia, uterine tetany, narcotics administered to mother within 4 hours of delivery, meconium-stained amniotic fluid, prolapsed cord, abruptio placentae, and placenta previa.
A team approach should be applied to all potential newborn resuscitations. Appropriate preparation for an anticipated high-risk delivery requires detailed communication between the mother's caregivers and the newborn resuscitation team. At least one person capable of initiating resuscitation should attend every delivery and be responsible for the care of the infant. Resuscitations involving assisted ventilation and chest compressions require at least two experienced persons. Three or more trained persons would ideally be available for an extensive resuscitation requiring medication administration.
The need for resuscitation should be determined immediately after birth. Most term newborn infants who transition normally to the extrauterine environment (with crying, pink color and good tone) can remain with the mother to receive routine care. Indications for further assessment under a radiant warmer include meconium in the amniotic fluid or on the skin, absent or weak responses, persistent cyanosis and preterm birth. Following this initial assessment, all subsequent assessments are based on the triad of breathing, heart rate and color. Regular respirations are adequate if they can maintain a heart rate of >100 bpm and good (pink) color. Gasping, apnea and central cyanosis generally indicate the need for additional interventions. A newborn's heart rate can be assessed by either auscultating the precordium or counting pulsations through palpation of the base of the umbilical cord. Heart rate should be >100 bpm in the uncompromised newborn. A newborn's color is best determined by examining the face, trunk, and mucous membranes. An uncompromised infant will maintain pink mucous membranes without supplemental oxygen. Cyanosis of the distal extremities or acrocyanosis, is a normal finding at birth and should not be used to determine the need for supplemental oxygen.
For the infant who is not vigorous at delivery, the basic steps in newborn resuscitation include providing warmth, positioning and clearing the airway, drying and stimulating the infant and providing supplemental oxygen as needed. Warming the infant immediately after birth will decrease cold stress and oxygen consumption. This can be done by simply placing the infant under a radiant warmer, quickly drying the skin, removing wet linens and wrapping the infant in pre-warmed blankets. The airway is cleared first by positioning the infant supine or lying on its side with the head in a slightly extended position. If airway secretions are concerning, the infant can be suctioned, mouth first, then nose, with a bulb syringe or suction catheter. Additional stimulation may be provided by gently rubbing the back or flicking the soles of the feet if an infant fails to initiate effective respirations following drying and suctioning. 100% free-flow oxygen should be administered by mask or oxygen tubing to the breathing newly born infant with cyanosis, bradycardia or other signs of distress. These initial steps should be performed during the first 30 seconds of life and the infant should then be reevaluated for breathing, heart rate and color (1,2).
If the infant continues to be apneic, is gasping, has a heart rate of less than 100 bpm and/or has persistent central cyanosis despite 100% free flow oxygen, then positive pressure ventilation with a bag and mask should be administered. Adequate ventilation is the most important and most effective step in cardiopulmonary resuscitation of the compromised newborn infant. Before assisting ventilation with a bag and mask, the proper size mask must be selected, the airway must be clear, and the baby's head should be positioned. The mask should cover both nose and mouth to achieve a tight seal with the face. Noticeable chest wall rise, bilateral breath sounds and improved color and heart rate are indications that ventilation is adequate. Breaths should be delivered at a rate of 40 to 60 per minute. After 30 seconds of proper ventilation, breathing, heart rate and color should be reevaluated. If the baby is breathing spontaneously and the heart rate is greater than 100 bpm, positive pressure ventilation can be stopped. However, if the infant's heart rate is greater than 60, but less than 100 bpm, then positive pressure ventilation must be continued.
If the infant's heart rate remains less than 60 bpm following the initial 30 seconds of positive pressure ventilation, it is likely that blood oxygen levels are low and myocardial contractility (and cardiac output) is poor. Chest compressions must be started and assisted ventilation continued until the myocardium recovers adequate function. Two people are required to administer chest compressions: one to administer compressions and one to continue ventilation. To perform chest compressions, enough pressure is applied to the lower third of the sternum to depress the sternum to a depth of approximately one third of the anterior-posterior diameter of the chest then released to allow the heart to refill. Poor technique may result in liver laceration and/or rib fracture. Three compressions should be administered for every one assisted ventilation so that 90 compressions plus 30 breaths are given each minute. Reevaluation of respiration, heart rate and color should be done after 30 seconds of coordinated ventilation and chest compressions. If the heart rate is above 60 bpm, then chest compressions can be stopped, but assisted ventilation should continue until the heart rate is greater than 100 bpm and there is spontaneous breathing. However, if the infant is not improving, that is, the heart rate remains below 60 bpm despite 30 seconds of well coordinated ventilation and chest compressions, then epinephrine should be given.
Epinephrine is a cardiac stimulant that increases contractility (inotropy) and heart rate (chronotropy) while causing peripheral vasoconstriction (alpha adrenergic effect). The recommended dose is 0.1 to 0.3 ml/kg of a 1:10,000 solution (equal to 0.01 to 0.03 mg/kg). It can be administered through an endotracheal tube for absorption by the lungs into the pulmonary veins, which drain directly into the heart. Alternatively, epinephrine can be given into a catheter placed in the umbilical vein. This route will likely deliver more effective blood levels of the drug, but additional time is required to insert the catheter. Thirty seconds following administration, an increase in heart rate to more than 60 bpm should be observed. If the heart rate remains depressed (<60 bpm) repeat doses of epinephrine may be given every 3 to 5 minutes. In the meantime, good chest movement, equal bilateral breath sounds, and well coordinated chest compressions to an appropriate depth must all be ensured. If the infant displays pallor, poor perfusion and/or there is evidence of blood loss, hypovolemic shock should be considered in the infant who has not responded to resuscitative efforts.
The recommended solution for acutely treating hypovolemia in the newly born infant is normal saline. Alternative acceptable solutions include Ringer's lactate and O-negative blood. Volume expanders must be given intravenously, usually through an umbilical vein catheter, although the intraosseous route can also be used. The initial dose is 10ml/kg given over 5 to 10 minutes. Repeat doses may be needed if large volume blood loss has occurred. If the heart rate is detectable but remains below 60 bpm after administering adequate ventilation, chest compressions, epinephrine, and volume expanders, the possibility of metabolic acidosis should be considered. Moreover, mechanical causes of poor response including airway malformation, pneumothorax, and diaphragmatic hernia or congenital heart disease should also be considered.
If the heart rate remains absent after 15 minutes of resuscitative efforts (establishing an airway, delivering positive pressure ventilation, administering chest compressions, administering epinephrine, addressing the possibilities of hypovolemia, acidosis, congenital airway malformation or congenital heart disease) discontinuation of resuscitation may be appropriate (2).
Apgar scores are commonly recorded as part of the delivery record. Apgar scores of 8 and 9 at 1 and 5 minutes, respectively, are normal. Scores are given as noted in the table below. A one minute Apgar score of 8 is usually due to a zero score for color since truncal cyanosis is still present at one minute. A 5 minute Apgar score of 9 is normal because acrocyanosis of the feet persists for some time past five minutes. Low Apgar scores at five and ten minutes may reflect birth depression and/or need for resuscitation
Apgar Scoring
Questions
1. What antepartum and intrapartum risk factors are seen in the case presented?
2. Name three major physiologic changes that must occur in the newborn shortly after birth in order to transition to extrauterine life.
3. What three elements of the newborn physical examination are reassessed every 30 seconds during resuscitation until the infant is stable?
4. Ideally, how many caregivers should be available for the resuscitation presented in the case vignette?
5. What is the most important step in cardiopulmonary resuscitation of the compromised newborn infant?
6. What are the indications for beginning assisted ventilation with a bag and mask? At what rate?
7. How can you assess whether or not assisted ventilation is adequate?
8. When should chest compressions be administered? At what rate?
9. What injuries are associated with chest compressions?
10. What is the recommended dose of epinephrine for neonates? By which routes can it be given?
References
1. Kattwinkel J (ed). Textbook of Neonatal Resuscitation, 4th Edition. 2000, Elk Grove Village, IL: American Academy of Pediatrics, American Heart Association..
2. Niermeyer S, et al. International Guidelines for Neonatal Resuscitation: An Excerpt From the Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science. Pediatrics 2000;106(3):E29.
Answers to questions
1. Antepartum risk factors: None. Intrapartum risk factors: emergency cesarean section, non-reassuring fetal heart tones, use of general anesthesia, narcotics administered to mother within 4 hours of delivery, and abruptio placentae.
2. Fluid in alveoli is absorbed and air fills the air sacs, umbilical cord is clamped disconnecting the infant from the placental circulation and pulmonary vasculature must relax allowing increased pulmonary blood flow and decreased right-to-left shunting.
3. Breathing, heart rate and color.
4. Three or more trained persons would ideally be available for an extensive resuscitation requiring medication administration.
5. Ventilation of the lungs is the most important and most effective step in cardiopulmonary resuscitation of the compromised newborn infant.
6. If the infant continues to be apneic, is gasping, has a heart rate of less than 100 bpm and/or has persistent central cyanosis despite 100% free flow oxygen, then positive pressure ventilation with a bag and mask should be administered. Breaths should be delivered at a rate of 40 to 60 per minute.
7. Noticeable chest wall rise, bilateral breath sounds and improved color and heart rate are indications that ventilation is adequate.
8. If the infant's heart rate remains less than 60 bpm following the initial 30 seconds of positive pressure ventilation, chest compressions must be started and assisted ventilation continued. Three compressions should be administered for every one assisted ventilation so that 90 compressions plus 30 breaths are given each minute.
9. Liver laceration and rib fracture.
10. The recommended dose is 0.1 to 0.3 ml/kg of a 1:10,000 solution (equal to 0.01 to 0.03 mg/kg). It can be administered through an endotracheal tube or through an umbilical vein catheter.