Care of the Term Infant

Published on 31/05/2015 by admin

Filed under Neonatal - Perinatal Medicine

Last modified 31/05/2015

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Chapter 1

Care of the Term Infant

The World Health Organization (WHO) defines a term infant as one who is greater than 37 weeks’ gestation. Recent evidence, however, has demonstrated that infants born at 37 weeks’ gestation behave differently from infants delivered at 39 and 40 weeks’ gestation. The more mature term infant (39 or 40 weeks) has fewer respiratory problems, less difficulty with feeding and hyperbilirubinemia, reduced birth injury, a greater ability to respond to infection, and an overall reduction in rates of neonatal complications.

Given that infants born before 37 weeks have even greater liability for problems, the recognition that true term status begins at about 39 weeks’ gestation has led the American College of Obstetrics and Gynecology (ACOG) and the American Academy of Pediatrics (AAP) to recommend that no infants be delivered electively before 39 weeks. ∗†

The mean birth weight of a term infant is approximately 3400 grams, or approximately 7 pounds, 7 ½ ounces. Mean length, which is sometimes difficult to measure accurately, is approximately 52 to 53 centimeters, or 20 inches, and head circumference averages 34 centimeters, or approximately 13.5 inches. Of note is the fact that birth weight in recent years has declined slightly, even though premature births have been declining. ∗

Approximately 10% of all infants need some assistance at birth (e.g., stimulation, oxygen), and approximately 1% need extensive assistance (e.g., positive pressure ventilation, fluids, drugs) at the time of birth. ∗

The Apgar score is a clinical assessment developed by Dr. Virginia Apgar at Columbia University during the early 1950s. Dr. Apgar was a great pioneer for women in medicine, and her development of the Apgar score is just one of her many landmark contributions to medicine. Although she was an anesthesiologist, she was very concerned about the status of newborn infants immediately after delivery. Her score, which was designed to evaluate both the immediate and long-term well-being of a neonate, has been reassessed periodically and still appears to be as valid today as when it was first introduced.

The Apgar score is determined at 1 and 5 minutes of life and consists of the measures listed in Table 1-1. These measures are scored 0, 1, or 2, then totaled.

TABLE 1-1

THE APGAR SCORE

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It is rare for an infant to have an Apgar score of 10 (the highest possible score) in the absence of oxygen administration because the exposure of most newborn infants to the environmental temperature of the delivery room will cause some acrocyanosis of the hands and feet, reducing the potential score to 9. An Apgar score above 7 is considered good, one between 4 and 7 demands close observation, and one that is 3 or lower usually requires some intervention. Even with the changes that have occurred in modern medicine, the Apgar score has retained its value. ∗

One of the other important aspects of the Apgar score is the change between 1 and 5 minutes of life. For vigorous term infants the Apgar score does not change significantly between 1 and 5 minutes of life. Changes in the Apgar score, however, are useful for assessing the response to resuscitation. For example, a newborn infant who has a 1-minute Apgar score of 3 and a 5-minute score of 8 has probably had some terminal difficulty at the time of delivery that has been quickly surmounted. On the other hand, the neonate with Apgar scores of 3 and 4 at 1 and 5 minutes is not responding well and may need further intervention. When an infant’s 5-minute score is 5 or lower, it has become customary to continue to provide Apgar scores every 5 minutes up to 20 minutes of life or until the score is above 7. Slow improvement in an Apgar score may be associated with some element of hypoxia or ischemia during the delivery, but there are many other reasons for low Apgar scores. A low Apgar score at 1 or 5 minutes has a poor positive predictive accuracy for later disabilities.

When called to the delivery of a term infant, the clinician should first make sure that all possible tools that might be needed for resuscitation and maintenance of a thermal neutral environment are ready. Although the great majority of term infants in an uncomplicated pregnancy do not require any intervention, it is important to be prepared for any possibility. In addition, a number of other routine items are necessary. On arrival in the delivery room the following items should be checked:

image The radiant warmer should be turned on, and a temperature probe that can be attached to the skin should be available.

image Several dry towels and blankets should be heated under the radiant warmer for the infant.

image A resuscitation bag or a T-piece device should be available with masks of several sizes. If the gestational age of the infant is known, the most appropriate mask size can be chosen (typically a size 1 for term infants).

image An oxygen source should be available. In most instances resuscitation with 21% oxygen can be used initially if respiratory intervention is required.

image A laryngoscope and endotracheal (ET) tubes should be available. For the term infant, a 0 or 1 laryngoscope blade is appropriate, and a 3.5 FR ET tube should be used. Note: Although it may be easier to insert a smaller ET tube, this approach ignores the fact that work of breathing will be dramatically increased with a tube that is too small for the size of the infant.

image Umbilical catheters, size 3.5 and 5 FR, should be available along with D10W fluid and lactated Ringer’s solution. Feeding tubes should also be available for insertion into the stomach to drain the contents or air.

image A pulse oximeter should be available. In term infants needing resuscitation, the pulse oximeter provides valuable information (heart rate and oxygen saturation levels) regarding whether the interventions are succeeding.

image A medication box should be present with all medications that might be necessary for resuscitation of a neonate. Although the use of medications such as bicarbonate and calcium have fallen out of favor, there are unique situations in which these solutions may be needed as well as pressor drugs, such as epinephrine, Prostaglandin E1 for ductal dilation, and narcotic antagonists such as naloxone. Rarely are any other medications required in the delivery room.

image Suction for the removal of meconium and the emptying of stomach contents must be present.

image An umbilical cord clamp and scissors should be on hand.

image Erythromycin eye ointment should be present for prevention of gonococcal ophthalmia.

image Vitamin K1 for the prevention of vitamin K–dependent hemorrhagic disease of the newborn should be on hand.

Immediately before delivery the fetus is bathed in amniotic fluid and maintained at a temperature identical to that of the mother. Within seconds after birth, however, the neonate is exposed to a temperature drop of approximately 10° C. The fluid bathing the skin starts to evaporate, further depressing body temperature. Exposure to cold stress initiates a metabolic response in which brown fat lining the vertebrae, the kidneys, and the adrenal gland is consumed. Metabolism of brown fat raises body temperature (the neonate does not have a developed shivering mechanism to accomplish an increase in body heat) but also leads to increased acid in the blood. Cooling may also increase pulmonary vascular resistance, resulting in hypoxemia and respiratory distress.

Similarly, excessive heat administration may produce the same kind of changes. Delivery room heat usually comes from keeping a baby under the radiant warmer for a period of time without a temperature probe. In such cases the warmer will continue to emanate heat because it is not being servo controlled to the skin. The increased metabolic rate from the heat exposure can also cause the infant to become tachypneic. In infants with perinatal depression and possible hypoxic ischemic encephalopathy, hyperthermia should be prevented because it may increase the risk of neurodevelopmental disability.

The thermal neutral environment is usually in the range of 36° to 37.5° C skin temperature. Both term and preterm infants suffer similarly when under environmental stress, but the large surface to body mass ratio of the premature infant exaggerates the adverse consequences ( Fig. 1-1).

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Figure 1-1 McCall EM, Alderdice F, Halliday HL, et al. Interventions to prevent hypothermia at birth in preterm and/or low birthweight infants. Cochrane Database Syst Rev 2010 Mar 17;3:CD004210.

Assuming that the obstetrician has clamped the baby’s umbilical cord and the baby appears to be vigorous (i.e., the baby is crying, breathing, centrally pink), the infant should be brought immediately to the radiant warmer and dried thoroughly. A quick weight should be obtained once the baby is dry. All wet blankets and towels should be discarded and the infant clothed in a warmed diaper and dry top. A knit cap should be added to prevent loss of heat from the scalp.

Historically, one of the most important issues with regard to newborn infants was the possibility of developing gonococcal ophthalmia as a result of passing through the birth canal of a mother infected with Neisseria gonorrheae. Gonococcal ophthalmia can produce a severe purulent conjunctivitis that may result in permanent loss of vision and generalized neonatal sepsis. The eye discharge resulting from this infection typically begins during the first 5 days of life.

Eye prophylaxis previously consisted of treatment with silver nitrate drops to the eyes. However, silver nitrate itself causes a significant, though temporary, chemical conjunctivitis. In the past decade it has been replaced by the administration of antibiotic ointment, such as 1% tetracycline or 0.5% erythromycin in single-use ampules.

Neonatal conjunctivitis may be produced by a variety of infectious agents in addition to N. gonorrheae. Chlamydia trachomatis is now the most common form of neonatal conjunctivitis, occurring in approximately 0.5% to 2.5% of all term births in the United States. This infection typically appears between 3 days and 6 weeks of life with an eye discharge, which is occasionally accompanied by pneumonia (10% to 20% of patients). The agents used to prevent N. gonorrheae infection do not prevent chlamydial conjunctivitis.

Other infectious agents capable of causing an eye infection in the newborn infant include Staphylococcus, Group A and B Streptococcus, Pneumococcus, Pseudomonas aeruginosa, and herpes simplex virus. ∗

The use of footprints has been a tradition in hospitals for decades and is mandated in most states. Although the value of footprinting is debatable and the manner in which footprints are obtained is often haphazard, footprints occasionally prove valuable if the identity of the infant in the hospital is in question. Footprinting ideally should be done as soon as possible after delivery, but it can be deferred if the infant develops signs of disease that require intervention or if immediate maternal contact is desired. Footprints should be obtained before the child leaves the delivery room area. The long-term value of footprints is essentially negligible beyond the immediate neonatal period. More sophisticated methods to identify infants using DNA are coming into use.

Studies from a number of investigators in recent years have contradicted the traditional concept that babies become well saturated within a few breaths after birth. In fact, the transition usually requires between 10 and 12 minutes, or longer occasionally, before a term infant’s saturation reaches approximately 93% to 95% ( Fig. 1-2).

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