The High-Risk Newborn and Family

Late-Preterm Infant

Within the past two decades, several significant changes have occurred in neonatal care. Early postpartum discharge for term and preterm infants gained popularity as health care institutions attempted to cut health care costs. Another change occurred in newborn care, as infants who appeared to be “near” term began to be treated much like term infants, thus avoiding the costs of neonatal intensive care for infants who appeared to be healthy. Experts have recommended that infants born between 34 and weeks of gestation be referred to as late-preterm infants rather than near-term infants (Engle, 2006; Engle, Tomashek, Wallman, et al, 2007). Late-preterm infants may be able to make an effective transition to extrauterine life; however, such infants, by nature of their limited gestation, remain at risk for problems related to feeding, neurodevelopment, thermoregulation, hypoglycemia, hyperbilirubinemia, sepsis, and respiratory function (Bakewell-Sachs, 2007; Darcy, 2009). In one study children born at 34 to 36 weeks were more than three times as likely as children born at term to be diagnosed with cerebral palsy (CP) (Petrini, Dias, McCormick, et al, 2009). It is now estimated that late-preterm infants represent 70% of the total preterm infant population and that the mortality rate for this group is significantly higher than that of term infants (7.9 versus 2.4 per 1000 live births, respectively) (Tomashek, Shapiro-Mendoza, Davidoff, et al, 2007). Because late-preterm infants’ birth weights often range from 2000 to 2500 g (4.4 to 5.5 lb) and they appear relatively mature in comparison to smaller preterm infants, they may be cared for in the same manner as healthy term infants, while risk factors for late-preterm infants are overlooked. Late-preterm infants are often discharged early from the birth institution and have a significantly higher rate of rehospitalization than term infants (Escobar, Clark, and Greene, 2006). Discussions regarding high-risk infants in this chapter also refer to late-preterm infants who are experiencing a delayed transition to extrauterine life.

The Association of Women’s Health, Obstetric and Neonatal Nurses has published the Late Preterm Infant Assessment Guide (Askin, Bakewell-Sachs, Medoff-Cooper, et al, 2007) for the education of perinatal nurses regarding the late-preterm infant’s risk factors and appropriate care and follow-up care (Table 10-1).

Classification of High-Risk Newborns

High-risk infants are most often classified according to birth weight, gestational age, and predominant pathophysiologic problems. The more common problems related to physiologic status are closely associated with the infant’s state of maturity and usually involve chemical disturbances (e.g., hypoglycemia, hypocalcemia) and consequences of immature organs and systems (e.g., hyperbilirubinemia, respiratory distress, hypothermia). Box 10-1 outlines specific terminology describing the developmental status of the newborn.

Formerly, weight at birth reflected a reasonably accurate estimation of gestational age; that is, if an infant’s birth weight exceeded 2500 g (5.5 lb), the infant was considered to be mature. However, accumulated data have shown that intrauterine growth rates are not the same for all infants and that other factors (e.g., heredity, placental insufficiency, and maternal disease) influence intrauterine growth and the infant’s birth weight. From these data a more definitive and meaningful classification system that encompasses birth weight, gestational age, and neonatal outcome has been developed. It has also been determined that the lowest perinatal mortality occurs in the infant who weighs between 3000 and 4000 g (6.4 and 8.8 lb) and whose gestational age is more than 36 weeks and less than 42 weeks (Walsh and Fanaroff, 2006). (See Fig. 8-2 for size comparison of newborn infants.)

Many perinatal problems can be anticipated before delivery. Prenatal testing and labor monitoring have reduced the incidence of perinatal mortality, and specialized care of the distressed newborn is improving the survival rate. If the infant is likely to require special therapy at or soon after birth, plans can be made for the delivery to take place at a hospital with the facilities to provide such care. This eliminates delay in initiating needed care and averts some of the hazards associated with transporting the sick newborn. Prenatal evaluation of fetal well-being and advanced surgical and anesthetic techniques have made intrauterine treatment of certain pathologic conditions possible, thus enhancing the neonate’s chances for survival (Reed and Blumer, 2006).

Organization of Services

The most efficient organization of services is a regionalized system of facilities within a designated geographic area. Neonatal intensive care facilities may provide three prescribed levels of care with special equipment, skilled personnel, and ancillary services concentrated in a centralized institution (American Academy of Pediatrics and American College of Obstetricians and Gynecologists, 2007):

Transporting High-Risk Newborns

When an at-risk infant is identified or anticipated, arrangements are made for care in the intensive care facility. The uterus is the ideal transport unit for the infant with anticipated difficulties; therefore, whenever possible, take the mother where special care is available for her delivery.

Some infants develop difficulties after a seemingly normal pregnancy and uncomplicated labor. Because it is impossible to always predict when infants will require intensive care, a coordinated system is needed to ensure them an optimum opportunity for survival. Each hospital that delivers infants should be able to provide for appropriate neonatal stabilization and arrange for transport to a tertiary care facility. The infant must be kept warm, be adequately oxygenated (including intubation if indicated), have vital signs and oxygen saturation monitored, and, when indicated, receive an intravenous (IV) infusion. The infant is transported in a specially designed incubator unit that contains a complete life-support system and other emergency equipment that can be carried by ambulance, van, plane, or helicopter.

The transport team may consist of one or more of the highly trained persons from the NICU: a neonatologist (or a fellow in neonatology), a neonatal nurse practitioner, a respiratory therapist, and one or more nurses. The professional assigned to accompany the infant must be constantly alert to every change in the infant’s condition and able to intervene appropriately. The neonate who must be moved from one place to another within the hospital (e.g., to surgery, or from delivery room to nursery) is transported in an incubator or radiant warmer and accompanied by the necessary personnel and equipment.

Safety Measures

The increased sophistication of supportive technology, including delivery systems, monitors, ventilator devices, and warmers, is both boon and bane. Although built-in safety systems and better engineering have made these devices more reliable and easier to use, our increasing reliance on them carries with it the additional risks of electrical biohazards and inaccurate function. Additionally, untrained or inexperienced operators confer an extra element of risk. Parents need instruction regarding safety precautions and observations. They are usually uncomfortable around the equipment and atmosphere of an intensive care unit and therefore appreciate an explanation of the purposes and functions of the devices and pertinent safety aspects. Although most NICUs are closed units, parents must also learn about specific safety measures designed to prevent neonatal abduction. Most institutions have their own protocols for preventing such an occurrence. (See Protect from Infection and Injury, Chapter 8.)

Respiratory Support

The primary objective in the care of high-risk infants is to establish and maintain respiration. Many infants require supplemental oxygen and assisted ventilation. All infants require appropriate positioning to ensure an open airway and to maximize oxygenation and ventilation. Oxygen therapy is provided on the basis of the infant’s requirements and illness (see Respiratory Distress Syndrome, p. 347, and Oxygen Therapy, p. 352).

Thermoregulation

Concurrent with the establishment of respiration, the most crucial need of the low-birth-weight (LBW) infant is provision of external warmth. Prevention of heat loss in the distressed infant is absolutely essential for survival, and maintaining a neutral thermal environment is a challenging aspect of neonatal intensive nursing care. Heat production is a complicated process that involves the cardiovascular, neurologic, and metabolic systems, and the immature neonate has all the problems related to heat production that are faced by the full-term infant. (See Thermoregulation, Chapter 8.) However, LBW infants are placed at further disadvantage by a number of additional problems. They have an even smaller muscle mass and fewer deposits of brown fat for producing heat, lack insulating subcutaneous fat, and have poor reflex control of skin capillaries.

Protection from Infection

Protection from infection is an integral part of all newborn care, but preterm and sick neonates are particularly susceptible. Thorough, meticulous, and frequent hand washing is the foundation of a preventive program. This includes all persons who come in contact with infants and their equipment. After handling another infant or equipment, no one should ever touch an infant without first washing hands.

Personnel with infectious disorders are either barred from the unit until they are no longer infectious or are required to wear suitable shields, such as masks or gloves, to reduce the likelihood of contamination. Standard Precautions as a method of infection control are instituted in all nursery areas to protect the infants and staff. (See Chapter 27.)

Readmission of infants from home or admission of infants delivered in unsterile conditions or infants suspected of having communicable illnesses is handled per institutional protocol. Such infants should at least be initially physically isolated from other highly susceptible high-risk infants. (See American Academy of Pediatrics and American College of Obstetricians and Gynecologists [2007] for further infection control recommendations, including nursery care of infants with specific communicable diseases.)

Hydration

High-risk infants often receive supplemental parenteral fluids to supply additional calories, electrolytes, and/or water. Adequate hydration is particularly important in preterm infants because their extracellular water content is higher (70% in full-term infants and up to 90% in preterm infants), their body surface area is larger in comparison to their weight, and the capacity for osmotic diuresis is limited in their underdeveloped kidneys. Therefore these infants are highly vulnerable to fluid depletion.

Parenteral fluids may be given to the high-risk neonate via several routes depending on the nature of the illness, the duration and type of fluid therapy, and unit preference. Common routes of fluid infusion include peripheral, peripherally inserted central venous (or percutaneous central venous), surgically inserted central venous or arterial, and, at times, umbilical venous or umbilical arterial catheterization. The preferred sites for peripheral IV infusions in neonates are the peripheral veins on the dorsal surfaces of the hands or feet. Alternative sites are scalp veins and antecubital veins. Special precautions and frequent observations (at least once every hour) must accompany the use of peripheral lines with hypertonic solutions (dextrose 10% to 12%) and parenteral hyperalimentation solutions. In many neonatal centers the percutaneous central venous catheter, also commonly called the peripherally inserted central venous catheter, is used for IV hydration therapy and medication administration because of less expense and decreased neonatal trauma, and because of the ease of insertion (Bradshaw, Turner, and Pierce, 2006).

In most facilities NICU nurses insert peripheral IV catheters and maintain the infusions. IV fluids must always be delivered by continuous infusion pumps that deliver minute volumes at a preset flow rate. Secure the catheter to the skin with transparent tape or a specialized IV dressing, taking care not to cause undue pressure from the needle hub and tubing. Because ELBW and VLBW infants are highly vulnerable to any fluid shifts, infusion rates are carefully regulated and checked hourly to prevent tissue damage from extravasation, fluid overload, or dehydration (Kerr, Starbuck, and Block, 2006). Pulmonary edema, congestive heart failure, patent ductus arteriosus (PDA), and intraventricular hemorrhage (IVH) may occur with fluid overload. Dehydration may cause electrolyte disturbances (particularly sodium), with potentially serious central nervous system (CNS) effects.

Small, fragile peripheral blood vessels are subject to rupture and subsequent infiltration. This situation is compounded by the use of infusion pumps that continue to infuse fluid into surrounding tissues. Observations are especially important when using hypertonic solutions (calcium, sodium bicarbonate, parenteral hyperalimentation) and IV drugs (antibiotics and vasoactive drugs such as dopamine and dobutamine), which can cause serious tissue damage. With flexible catheters and small IV catheter shields, arm boards and limb restraints are usually unnecessary. If used, restraints should be checked frequently to ensure that no harm to the patient’s extremity occurs and that peripheral circulation is adequate.

Infants who are ELBW, tachypneic, receiving phototherapy, or in a radiant warmer have increased IWL that require appropriate fluid adjustments. Nurses must monitor fluid status by taking daily (or more frequent) weights; accurately monitoring intake and output of all fluids, including medications and blood products; monitoring urine specific gravity as well as urine glucose and protein; and evaluating serum electrolyte levels. ELBW infants often require more frequent monitoring of these parameters because of their excessive transepidermal fluid loss, immature renal function, and propensity to dehydration or overhydration. Intolerance of even dextrose 5% is not uncommon in the ELBW infant, with subsequent glycosuria and osmotic diuresis. Alterations in behavior, alertness, or activity level in these infants receiving IV fluids may signal an electrolyte imbalance, hypoglycemia, or hyperglycemia. The nurse is also observant for tremors or seizures in the VLBW or ELBW infant, since these may be a sign of hyponatremia or hypernatremia.

A common problem observed in infants who have an umbilical arterial catheter in place is vasoconstriction of peripheral vessels, which can seriously impair circulation. The response is triggered by arterial vasospasm caused by the presence of the catheter, the infusion of fluids, or injection of medication. Blanching of the buttocks, genitalia, or legs or feet is an indication of vasospasm. The problem is recognized promptly and reported to the practitioner. The nurse must also observe for signs of thrombi in infants with umbilical venous or arterial lines. The precipitation of microthrombi in the vascular bed with the use of such catheters is commonly manifested by a sudden bluish discoloration seen in the toes, called “cath toes.” The problem is promptly reported to the practitioner because failure to alleviate the pathologic condition may result in permanent injury to the toes, foot, or leg.

Circulatory effects are observed first in the toes but may extend to include the legs and buttocks. The toes first flush and then turn a mulberry color; if the condition is not corrected, there may be serious complications involving the loss of a limb. The infant with an umbilical venous or arterial catheter should also be observed closely for catheter dislodgment and subsequent bleeding or hemorrhage; urinary output, renal function, and gastrointestinal function are also evaluated in these infants. Although the intent of such catheters is to effectively deliver IV fluids (and sometimes medications) and to obtain arterial blood gas samples, they are not without inherent complications.

Nutrition

Optimum nutrition is critical in the management of ELBW, VLBW, and LBW preterm infants, but difficulties arise in providing for their nutritional needs. The various mechanisms for ingestion and digestion of foods are not fully developed. The more immature the infant, the greater the problem.

Feeding Resistance

Any feeding technique that bypasses the mouth precludes the opportunity for the affected child to practice sucking and swallowing, or the opportunity to experience normal hunger and satiation cycles. Infants may demonstrate aversion to oral feedings by such behaviors as averting the head to the presentation of the nipple, extruding the nipple by tongue thrust, gagging, or even vomiting.

Developmental delays have occurred in perceptual-motor performance among infants with feeding refusal as measured by standard tests, although intellectual function remains within normal limits. Other observations include disinterest in or active resistance to oral play, diminished spontaneity and motivation, and shallow interpersonal relationships, probably related to the absence of some early incorporative patterns of normal oral experiences. The longer the period of nonoral feeding, the more severe the feeding problems, especially if this period occurs during a time when the infant progresses from reflexive to learned and voluntary feeding actions. During infancy the mouth is the primary instrument for reception of stimulation and pleasure.

Infants identified as being at risk for feeding resistance should receive regular oral stimulation based on the child’s developmental level. Those who exhibit feeding aversion should begin a stimulation program to overcome resistance and acquire the ability to take nourishment by the oral route. Because management requires long-term commitment, successful implementation of a plan for oral stimulation depends on maximum parental involvement and promotion of primary nursing. Key components and interventions are in Box 10-4.

Skin Care

The skin of preterm infants is characteristically immature. Because of its increased sensitivity and fragility, no alkaline-based soap that might destroy the “acid mantle” of the skin is used. The increased permeability of the skin facilitates absorption of ingredients. All skin products (e.g., alcohol or povidone-iodine) are used with caution. The skin is rinsed with water afterward because these substances may cause severe irritation and chemical burns in LBW infants.

The skin is easily excoriated and denuded; therefore take care to avoid damage to the delicate structure. The total skin is thinner than that of full-term infants and lacks rete pegs, appendages that anchor the epidermis to the dermis. Therefore there is less cohesion between the thinner skin layers. Adhesives used after heel sticks or to secure monitoring equipment or IV infusions may excoriate the skin or adhere to the skin surface so well that the epidermis can be separated from the dermis and pulled away with the tape. The use of a zinc oxide–based tape such as Hy-Tape is encouraged to minimize epidermal stripping; the tape is flexible, waterproof, and, washable. The use of skin barriers protects healthy skin and helps excoriated skin heal.

Use scissors very carefully to remove dressings or tape from the extremities of very small and immature infants because it is easy to snip off tiny extremities or nick loosely attached skin. Avoid solvents to remove tape because they tend to dry and burn the delicate skin. Guidelines for skin care are given in the Nursing Care Guidelines box.

During skin assessment of preterm infants, nurses are alert to the subtle signs that indicate zinc deficiency, a common problem in these infants. Breakdown usually occurs in the areas around the mouth, buttocks, fingers, and toes. In VLBW infants it may also occur in the creases of the neck, wrists, and ankles and around wounds. Zinc deficiency is most likely to appear in infants with sepsis, those experiencing nasogastric losses, or those who have had surgery. Report suspicious lesions to the practitioner so that zinc supplements can be prescribed. In most preterm infants the skin barrier properties resemble those of the term infant by 2 to 3 weeks postnatal age, regardless of gestational age at birth.

Although no studies comparing the effectiveness of different commercially available neonatal bedding have been done, a number of products are useful in minimizing skin problems. The Nursing Care Guidelines box gives general information about bedding. Particularly vulnerable areas of the skin, such as bony prominences, can be protected with transparent dressings. Gel pads or mattresses can also be used to prevent pressure ulcers (Association of Women’s Health, Obstetric and Neonatal Nurses, 2007).

Skin injuries have been reported during use of phototherapy blankets. Caution is warranted in using these products with extremely preterm infants or infants with birth trauma, poorly perfused skin, or hypotension. Manufacturers of phototherapy blankets recommend the following during therapy: monitor skin color, observe for rashes or excoriation, keep skin clean with warm water, promptly clean perineum after stooling, reposition every 2 hours, carefully monitor cleanliness and skin integrity, and avoid direct contact of blanket with infant’s skin.

Administration of Medications

Administration of therapeutic agents, such as drugs, ointments, IV infusions, and oxygen, requires judicious handling and meticulous attention to detail. The computation, preparation, and administration of drugs in minute amounts often require collaboration between nurses, physicians, and pharmacists to reduce the chance for error. In addition, the immaturity of an infant’s detoxification mechanisms and inability to demonstrate symptoms of toxicity (e.g., signs of auditory nerve involvement from ototoxic drugs such as gentamycin) complicate drug therapy and require that nurses be particularly alert for signs of adverse reaction. (See Administration of Medication, Chapter 27.)

Nurses should be aware of the hazards of administering bacteriostatic and hyperosmolar solutions to infants. Benzyl alcohol, a common preservative in bacteriostatic water and saline, is toxic to newborns and should not be used to flush IV catheters or to dilute or reconstitute medications. It is recommended that medications with preservatives such as benzyl alcohol be avoided. Nurses must read labels carefully to detect the presence of preservatives in any medication administered to an infant.

Hyperosmolar solutions present a potential danger to preterm infants. Hyperosmolar solutions given orally to infants can produce clinical, physiologic, and morphologic alterations, the most serious of which is NEC. Oral or parenteral medications should be sufficiently diluted to prevent complications related to hyperosmolality.

Take caution to reduce adverse effects of medication administration in preterm infants. Strategies to heighten awareness and decrease unnecessary morbidity in such infants include having two registered nurses double check the dosages of potentially lethal medications (high-risk medications) and providing calculators in neonatal units to perform dosage calculations, double check unit dose medications, and check medications that are reconstituted by the nurse. Some other precautions are to have readily available quick-reference guides to weight-specific medication doses and appropriate dosages for preterm infants and to provide tables with medication cross-reactivity and incompatibility. One NICU developed a distinct neonatal formulary to reduce medication errors. Another strategy was to develop computerized guidelines for managing dose ranges based on the neonate’s most recent weight so medications ordered outside the appropriate dose range could be reevaluated by the pharmacist and practitioner This concept was also applied to computer-generated emergency medication sheets, which are updated weekly (Lucas, 2004).

Information technology (e.g., computerized practitioner order entry and clinical participation by a clinical pharmacist) is available to reduce medication errors, yet this technology does not provide the entire solution (Taylor, Loan, Kamara, et al, 2008). The human factor involved in many root-cause analyses for medication errors involves systems and the humans involved in those systems. Nurses, physicians, and pharmacists are at times affected by internal and external environmental factors that lead to a medication error: excessive workload; distractions such as a monitor alarm or questions asked during medication administration; boredom; work hours (nighttime or daytime); lack of updated, consistent drug information; ambiguous drug labeling; and dosage calculation errors (Lefrak, 2002). The variables involved are numerous and multifaceted yet can be decreased by simple cautionary measures, extensive education, and verification of medication orders written.

Developmental Outcome

Neonatal intensive care and rapid improvements in technology are associated with improved survival of critically ill newborn and preterm infants. Survival rates have increased to 93% for VLBW infants (1001 to 1500 g [2.2 to 3.3 lb]), 85% for ELBW infants (751 to 1000 g [1.6 to 2.2 lb]), and about 50% for infants weighing 501 to 750 g [1.1 to 1.6 lb] (Msall and Tremont, 2000). With decreasing mortality, morbidity rates have remained stable. At highest risk for unfavorable outcomes are preterm infants compromised during the neonatal period by respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD, or chronic lung disease), NEC, sepsis, anemia, IVH, hydrocephalus, meningitis, or seizures (McGrath, Sullivan, and Lester, 2000; Vohr, Widen, Cone-Wesson, et al, 2000). These serious sequelae of prematurity correlate with the degree of immaturity, demonstrating the relationship of increasing morbidity with decreasing gestational age. A greater incidence of CP, attention deficit hyperactivity disorder, visual-motor deficits, mild to severe cognitive disabilities, hearing loss, speech and language impairment, and neuromotor problems has been reported in outcome studies of preterm infants (van Baar, van Wassenaer, Briet, et al 2005; Wilson-Costello, 2007; Hack and Costello, 2008). Reduced language and visual-motor skills have been reported in former LBW infants at 7 years of age (Pietz, Peter, Graf, et al, 2004).

An increased need for special school services, especially in reading and math, has been reported in former LBW infants at 12 years of age (Luu, Ment, Schneider, et al, 2009). Another longitudinal study of 532 VLBW infants from four countries found that, when evaluated between 8 and 11 years of age, more than half of all cohorts required special educational assistance and/or repeated a grade (Saigal, den Ouden, Wolke, et al, 2003). Neurodevelopmental impairment also occurs in preterm infants who have been spared the complications of IVH, sepsis, and hypoxemia, moving through the NICU with seemingly few problems. Conversely, some preterm infants do well and function at age level without evidence of neurobehavioral limitations. Improved developmental outcomes are more likely for these survivors of early gestation and LBW when emphasis is placed on providing the finest medical and nursing care within a developmentally supportive framework. This philosophy requires caregivers to evaluate their own knowledge, skills, and attitudes and expand their thinking beyond the traditional medical and nursing models of care.

Facilitating Parent-Infant Relationships

Because of their physiologic instability, preterm infants are immediately separated from their mothers and surrounded by a complex, impenetrable barrier of glass windows, mechanical equipment, and special caregivers. Increasing evidence indicates that the emotional separation that accompanies the physical separation of mothers and infants interferes with the normal maternal-infant attachment process, discussed in Chapter 8. Maternal attachment is a cumulative process that begins before conception, strengthens by significant events during pregnancy, and matures through maternal-infant contact during the neonatal period.

When an infant is sick, the necessary physical separation appears to be accompanied by an emotional estrangement in the parents, which may seriously damage the capacity for parenting their infant. This detachment is further hampered by the tenuous nature of the infant’s condition. When survival is in doubt, parents may be reluctant to establish a relationship with their infant. They prepare themselves for the infant’s death while continuing to hope for recovery. This anticipatory grief (see Chapter 23) and hesitancy to embark on a relationship are evidenced by behaviors such as delay in giving the infant a name, reluctance to visit the nursery (or focusing on equipment and treatments rather than on their infant when they do visit), and hesitancy to touch or handle the infant when given the opportunity.

Comprehensive management of high-risk newborns includes encouraging and facilitating parental involvement rather than isolating parents from their infant and associated care (Box 10-7). This is particularly important in relation to mothers; to reduce the effects of physical separation, mothers are united with their newborns at the earliest opportunity (Fig. 10-6). Preparing the parents to see their infant for the first time is a nursing responsibility.

Before the first visit, the nurse prepares parents for their infant’s appearance, the equipment attached to the child, and the general atmosphere of the unit. The initial encounter with the intensive care unit is stressful, and the frightening array of people, equipment, and activity is likely to be overwhelming. A book of photographs or pamphlets describing the NICU environment (infants in incubators or under radiant warmers, monitors, mechanical ventilators, and IV equipment) provides a useful and nonthreatening introduction to the NICU.

Encourage parents to visit their infant as soon as possible. Even if they saw the infant at the time of transport or shortly after birth, the infant may have changed considerably, especially if there are a number of medical and equipment requirements associated with the infant’s hospitalization. At the bedside the nurse should explain the function of each piece of equipment and the role it plays in facilitating recovery. Explanations may often need to be patiently repeated because parents’ anxiety over the infant’s condition and the surroundings may prevent them from really “hearing” what is said. When possible, some items related to therapy can be removed; for example, phototherapy can be temporarily discontinued and eye patches removed to permit eye-to-eye contact.

Parents appreciate the support of a nurse during the initial visit with their infant, but they may also want some time alone with the infant. It is important during the early visits to emphasize the positive aspects of their infant’s behavior and development so that parents can focus on their infant as an individual rather than on the equipment that surrounds the child. For example, the nurse may describe the infant’s spontaneous behaviors during care, such as grasp, sucking, and movement, or make comments about the infant’s biologic functions. Most institutions promote family-centered care and have open visiting policies so that parents and siblings can visit as often as they wish.

Parents vary greatly in the degree to which they are able to interact with their infant. Some may wish to touch or hold their infant during the first visit, whereas others may not feel comfortable enough to even enter the nursery. Parents may not be receptive to early and extended infant contact because they need time to adjust to the impact of an infant with birth problems and must be helped to grieve before they can accept their infant.

The parents’ inability to focus on their infant is a clue for the nurse to assist the parents in expressing feelings of guilt, anxiety, helplessness, inadequacy, anger, and ambivalence. Nurses can help parents deal with these distressing feelings and recognize that they are normal responses shared by other parents. It is important to point out and reinforce the positive aspects of parents’ behavior and interactions with their infant.

Ward’s (2001) research of parental needs in the NICU demonstrates the importance of nurses providing accurate information to the parent regarding treatment plan and procedures; answering parents’ questions honestly; actively listening to parents’ concerns, fears, and expectations; and helping parents understand infant responses to hospitalization.

Most parents feel shaky and insecure about initiating interaction with their infant. Nurses can sense parents’ level of readiness and offer encouragement in these initial efforts. Parents of preterm infants follow the same acquaintance process as do parents of full-term infants. They may quickly proceed through the process or may require several days, or even weeks, to complete it. Parents begin by touching their infant’s extremities with their fingertips and poking the infant tenderly, and then proceed to caresses and fondling (Fig. 10-7). Touching is the first act of communication between parents and child. Parents need to be prepared for their infant’s exaggerated and generalized startle responses to touch so that they will not interpret these as negative reactions to their overtures. It may be necessary to limit tactile stimuli when the infant is critically ill and labile, but the nurse can offer other options, such as speaking softly or sitting at the bedside.

Parents of acutely ill preterm infants may express feelings of helplessness and lack of control. Involving the parent in some type of caregiving activity, no matter how minor it may seem to the nurse, enables the parent to take on a more active role. Examples of such caregiving for the acutely ill infant who cannot be held and is seemingly not responding positively include moistening the infant’s lips with a small amount of sterile water on a cotton-tipped swab or slipping the diaper from under the infant when it is wet or soiled.

The nurse encourages parents to bring in clothes, a toy, a stuffed animal, or a family snapshot for their infant, and the nurse can help parents set goals for themselves and for the infant. Parents may become involved by reading a children’s storybook or nursery rhymes in a soft, soothing voice. The nurse encourages parents to visit at times when they can become involved in their infant’s care (Figs. 10-8 and 10-9).

Throughout the parent-infant acquaintance process, the nurse listens carefully to what the parents say to assess their concerns and their progress toward incorporating their infant into their lives. The manner in which parents refer to their infant and the questions they ask reveal their worries and feelings and can serve as valuable clues to future relationships with the infant. The alert nurse is attuned to these subtle indications of parents’ needs, which provide guidelines for nursing intervention. Often all that the parents need is reassurance that they will have the nurse’s support during caregiving activities and that the behaviors about which they are concerned are normal reactions and will disappear as the infant matures (e.g., an exaggerated Moro reflex or inability to coordinate swallowing).

Parents need guidance in their relationships with their infant and assistance in their efforts to meet their infant’s physical and developmental needs. The nursing staff must help parents understand that their preterm infant offers few behavioral rewards and show them how to accept small rewards from their infant. They need reassurance that avoidance behaviors are not a reflection on their parenting skills. Teach parents to recognize their infant’s cues regarding stimulation, handling, and other interaction, especially aversive behaviors that indicate a need for rest. Nurses need to include parents in planning their infant’s care.

Above all, nurses must encourage and reinforce parents during their caregiving activities and interactions with their infant to promote healthy parent-child relationships. It is also helpful for the parents to have contact and communication with the infant’s primary nurse and associate primary nurse (according to unit model of nursing care). This decreases the amount of different information given to parents and often instills confidence that, although the parents cannot be at their infant’s bedside 24 hours a day, they can call competent and caring nurses to inquire about the infant’s status. Periodic parent conferences involving the primary practitioner, primary nurse, and associate primary nurse serve to clarify misunderstandings or problems related to the infant’s condition. Other members of the NICU team, such as the perinatal social worker, lactation consultant, discharge coordinator, or surgeon, may become involved as necessary.

Discharge Planning and Home Care

Parents become apprehensive and excited as the time for discharge approaches. They have many concerns and insecurities regarding the care of their infant. They fear the child may still be in danger, that they will be unable to recognize signs of distress or illness, and that the infant may not be ready for discharge. Nurses need to begin early to assist parents in acquiring or increasing their skills in the care of their infant. Appropriate instruction must be provided and sufficient time allowed for the family to assimilate the information and learn the continuing special care requirements. Where rooming-in or other live-in arrangements are available, parents can stay for a few days and nights and assume the care of their infant under the supervision and support of the nursery staff.

There should be appropriate medical and nursing follow-up care, including developmental follow-up, and referrals to services that can benefit the family. Parents of preterm infants should also receive information about immunizations, including respiratory syncytial virus (RSV) prophylaxis, as well as other discharge planning information. Home health agencies provide nursing supervision, counseling, and referrals for nursing visits. With early discharge, many hospital-based home health care agencies become involved in the follow-up monitoring and care of the NICU “graduate” in the home. For an infant being discharged with equipment such as an oxygen tank, apnea monitor, or even a ventilator, discharge planning requires multidisciplinary, collaborative practice to ensure that the family has not only the appropriate resources but also the available assistance for dealing with the infant’s needs. Many communities have organized support groups, including those discussed previously, those designed for parents of infants who require special care because of specific defects or disabilities, and those for parents of multiple births. (See Chapter 3.)

Car seat safety is an essential aspect of discharge planning. It is recommended that infants less than 37 weeks of gestation have a period of observation in an appropriate car seat to monitor for possible apnea, bradycardia, and decreased Sao₂ (Bull, Engle, and American Academy of Pediatrics, 2009). One study found that mean oxygen saturation levels decreased from 97% to 94% for both term and preterm infants who were observed in their car seats; 12% of the preterm infants in the study had significant apneic or bradycardic events in their car seats (Merchant, Worwa, Porter, et al, 2001). Despite this evidence, a Cochrane review of predischarge car seat testing failed to find evidence that such testing prevents morbidity or mortality (Pilley and McGuire, 2006) (see Family-Centered Care box).

Several car seat models can be adapted for small infants with the placement of blanket rolls on each side of the infant, but never behind, to support the head and trunk. For adequate support without slumping, the seat back-to-crotch strap distance must be 14 cm (5.5 inches) or less. A small rolled blanket may be placed between the crotch strap and the infant to reduce slouching. If the child’s head drops forward because the position of the seat is upright, a roll cloth or blanket may be placed in the vehicle seat crease and under the safety base so the infant reclines at no more than a 45-degree angle. A car seat restraint without a shield is recommended; if the infant needs to be supine, a crash-tested car bed may be used (Bull, Engle, and American Academy of Pediatrics, 2009).

The rear-facing position provides support for the head, neck, and back, thereby reducing the stress to the neck and spinal cord in a vehicle crash. It is recommended that, before discharge from the hospital, the preterm infant have an evaluation in the designated car seat restraint by a staff member who is knowledgeable in car seat restraint positioning. Parents should learn how to properly restrain the child in the car seat for safe transportation (Bull, Engle, and American Academy of Pediatrics, 2009).

Additional guidelines are available from the American Academy of Pediatrics, including a videotape for the safe transportation of preterm and LBW infants. (See Chapter 12 for a discussion of infant car restraints and American Academy of Pediatrics website [www.aap.org] for a list of appropriate car seats for infants.)

An important part of discharge planning and care of the preterm infant is nutrition for continued growth; thus choice of feeding must be carefully addressed. Human milk should be fortified according to the infant’s corrected age and physiologic needs. An enriched postdischarge formula (usually 22 kcal/oz) has been recommended for preterm infants born at less than 36 weeks to meet appropriate growth standards (see Table 10-4) (Lucas, Fewtrell, Morley, et al, 2001; Carver, Wu, Hall, et al, 2001). However, a Cochrane review of studies examining growth in preterm infants fed an enriched postdischarge formula did not find strong evidence of enhanced growth and development compared with infants fed standard formula (Henderson, Fahey, and McGuire, 2007).

The term vulnerable child syndrome is applied to physically healthy children who are perceived by their parents to be at high risk for medical or developmental problems. The syndrome has been observed in parents of children who had an illness or injury from which they had not been expected to recover. The family continues to perceive the child as fragile, vulnerable, and “different” and as having needs that warrant special status in the family, which adversely affects the child’s and family’s behavior. The parents may lack confidence in their parenting ability that persists beyond the illness. The parents may also become overly indulgent and have difficulty setting limits, resulting in interference with normal development. Consequently, the child becomes dependent, demanding, and out of control. Overprotection and frequent visits to the health care provider are characteristic.

Problems that may arise in the high-risk newborn include overfeeding, underfeeding, feeding resistance, aversion to human touch or interaction, and difficulty separating the child from the parent. To help parents deal with the stress of home care for the infant, nurses can help families discuss their fears and anxieties, which are exaggerated in parents of preterm infants, and encourage them to create a normal routine in caring for the infant. Parents need to learn the normal developmental delays expected of formerly preterm infants and the importance of setting disciplinary limits and schedules. Continued explanations and clarification of the infant’s true health status and ongoing support of the parents’ efforts are important aspects of follow-up care.

Neonatal Loss

The precarious nature of many high-risk infants makes death a real and ever-present possibility. Although infant mortality has been reduced sharply with improved technology, the mortality rate is still greatest during the neonatal period. Nurses in the NICU are the persons who must prepare the parents for an inevitable death and facilitate a family’s grieving process after an expected or unexpected death.

Critical Thinking Exercise—Neonatal Loss

The loss of an infant has special meaning for the grieving parents. It represents a loss of a part of themselves (especially for mothers), a loss of the potential for immortality that offspring represent, and the loss of the dream child that has been fantasized throughout the pregnancy. The parents have a sense of emptiness and failure. In addition, when an infant has lived for such a short time, they may have few, if any, pleasant memories to serve as a basis for the identification and idealization that are part of the resolution of a loss.

To help parents understand that the death is a reality, it is important that they be given the opportunity to hold their infant before death and, if possible, be present at the time of death so their infant can die in their arms if they choose.

Parents should have the opportunity to actually “parent” the infant in any manner they wish or are able to before and after the death. This may include seeing, touching, holding, caressing, and talking to their infant privately. The parents may also wish to bathe and dress the infant. If parents are hesitant to see their dead infant, it is advisable to keep the body in the unit for a few hours, since many parents change their minds after the initial shock of the death.

Parents may need to see and hold the infant more than once—the first time to say “hello” and the last time to say “good-bye.” If parents wish to see the infant after the body has been taken to the morgue, the infant should be retrieved, wrapped in a blanket, rewarmed in a radiant warmer, and taken to the mother’s room or other private place. The nurse should plan to stay with the parents but also provide them an opportunity for private time alone with their dead infant if they wish. Individual grief responses of the mother and father should be recognized and handled appropriately. Gender differences and cultural and religious beliefs will affect the parents’ grief responses (Dyer, 2005).

Some units have implemented a hospice approach for families with infants for whom the decision has been made not to prolong life and who are receiving only palliative care. A special “family” room is set aside and contains all supportive equipment needed for the care of the infant. It also provides a homelike atmosphere for the family. All hospice services are available to the family, and the infant remains under the care and supervision of a primary nurse on the NICU staff. (See Chapter 23, End-of-Life Care, for further discussion of hospice care.)

A photograph of the infant taken before or after death is highly desirable. Parents may wish to have a special family portrait taken with the infant and other family members. This often helps personalize the experience and make it more tangible. The parents may not wish to see the photograph at the time of death, but the chance to refer to it later will help to make their infant seem more real, which is a part of the normal grieving process. A photograph of their infant being held by the hand or touched by an adult offers a more positive image than a morgue type of photograph. Many NICUs have a bereavement or memory packet made up for the grieving parents, which may include the infant’s handprints and footprints, a lock of hair, the bedside name card, and, if appropriate to the family’s religious beliefs, a certificate of baptism. The photographs and other personal effects of the deceased infant were perceived as critically important in the grieving process by one group of parents in a survey. Parents often indicated that the photographs were helpful in remembering the infant’s actual appearance during this stressful period (Anderson, 2001; Gold, Dalton, and Schwenk, 2007). Naming the deceased infant is an important step in the grieving process. Some parents may hesitate to give the newborn a name that had been chosen during the pregnancy for their special “baby.” However, it helps to have a tangible person for whom to grieve. In supporting parental responses to the loss of a child, care providers must understand and respect the cultural and religious practices.

A primary nurse who is familiar to the family should be present during the discussion about the dead or dying infant. A Resolve Through Sharing or bereavement counselor is often involved in helping the family through this difficult period. The nurse should talk with parents openly and honestly about funeral arrangements because few of them have had experience with this aspect of death. Many funeral homes now offer inexpensive arrangements for these special cases. Someone from the NICU should take the responsibility for acquiring this information. It is often helpful to parents for the NICU to have a list of local funeral homes, services offered, and prices. Families need to be informed of the options available, but a funeral is preferable because the ritual provides an opportunity for parents to feel the support of friends and relatives. A clergyman of the appropriate faith may be notified if the parents wish. Issues regarding an autopsy or organ donation (when appropriate) are approached in a multidisciplinary fashion (primary practitioner and primary nurse) with respect, tact, and consideration of the family’s wishes. (See also “Grief and Perinatal Loss” in Merenstein and Gardner, 2006.)

Before the parents leave the hospital, the nurse should provide them with the telephone number of the unit (if they do not have it) and invite them to call any time they have any further questions. Many intensive care units make it a point to contact the parents after a neonatal death to assess the parents’ coping mechanisms, evaluate the grieving process, and provide support as needed. Several organizations are available to offer support and understanding to families who have lost a newborn, including the Compassionate Friends* and Aiding Mothers and Fathers Experiencing Neonatal Death (AMEND).† (See Chapter 23 for further discussion of the family and the grieving process.)

Nurses who care for critically ill infants also experience grief. NICU nurses may feel helpless and sorrowful. It is important that such grief be allowed and that nurses attend the funeral or memorial service as a part of working through the grieving process. Nurses may fear that showing emotion is unprofessional and that the expression of grief demonstrates “loss of control”; these fears are unfounded. Studies have demonstrated that to continue to be effective managers and providers of care, nurses must be allowed to grieve and support each other through the process (Jansen, 2003).

Education regarding bereavement, end-of-life care, and culturally sensitive care of families and their dying infants may help nurses comfort families during this stressful period (Engler, Cusson, Brockett, et al, 2004).

Etiology

A variety of maternal and pregnancy-related complications increase the risk of preterm delivery; however, the actual cause of prematurity is not known in most instances. The incidence of prematurity is lowest in the middle to high socioeconomic classes, in which pregnant women are generally in good health, are well nourished, and receive prompt and comprehensive prenatal care. The incidence is highest in the lower socioeconomic classes, in which a combination of deleterious circumstances is present. Other factors, such as multiple pregnancies, pregnancy-induced hypertension, and placental problems that interrupt the normal course of gestation before completion of fetal development, are responsible for a large number of preterm births.

The outlook for preterm infants is largely, but not entirely, related to the state of physiologic and anatomic immaturity of the various organs and systems at the time of birth. Infants at term have advanced to a state of maturity sufficient to allow a successful transition to the extrauterine environment. Infants born prematurely must make the same adjustments but with functional immaturity proportional to the stage of development reached at the time of birth. The degree to which infants are prepared for extrauterine life can be predicted to some extent by estimated gestational age. (See Clinical Assessment of Gestational Age, Chapter 8.) An understanding of prenatal development provides some concept of the status of the systems, at various stages of development, that must cope with functional changes that occur with birth.

Characteristics

Preterm infants have a number of distinct characteristics at various stages of development. Identification of these characteristics provides valuable clues to the gestational age and hence to the physiologic capabilities. The general, outward physical appearance changes as the fetus progresses to maturity. Characteristics of skin, general posture and tone, distribution of hair, and amount of subcutaneous fat provide clues to a newborn’s physical development. Observation of spontaneous, active movements and response to stimulation and passive movement contributes to the assessment of neurologic status. The appraisal is made as soon as possible after admission to the nursery because much of the observation and management of infants depend on this information.

On inspection, preterm infants are very small and appear scrawny because they lack or have only minimum subcutaneous fat deposits and have a proportionately large head in relation to the body, which reflects the cephalocaudal direction of growth. The skin is bright pink (often translucent, depending on the degree of immaturity), smooth, and shiny (may be edematous), with small blood vessels clearly visible underneath the thin epidermis. The fine lanugo is abundant over the body (depending on gestational age) but is sparse, fine, and fuzzy on the head. The ear cartilage is soft and pliable, and the soles and palms have minimum creases, resulting in a smooth appearance. The bones of the skull and the ribs feel soft, and before 26 weeks the eyes may be fused. Male infants have few scrotal rugae, and the testes are undescended; the labia minora and clitoris are prominent in females. Fig. 10-11 compares the features of full-term and preterm infants.

In contrast to full-term infants’ overall attitude of flexion and continuous activity, preterm infants are inactive and listless. The extremities maintain an attitude of extension and remain in any position in which they are placed. Physiologically immature, many preterm infants are unable to maintain body temperature, have limited ability to excrete solutes in the urine, and have increased susceptibility to infection. A pliable thorax, immature lung tissue, and an immature regulatory center lead to periodic breathing, hypoventilation, and frequent periods of apnea. These infants are more susceptible to biochemical alterations such as hyperbilirubinemia and hypoglycemia (see Chapter 9), and they have a higher extracellular water content that renders them more vulnerable to fluid and electrolyte imbalance. Preterm infants exchange fully half their extracellular fluid volume every 24 hours compared with one seventh of the volume turnover in adults.

The soft cranium is subject to characteristic unintentional deformation (dolichocephaly) caused by positioning from one side to the other on a mattress. The head looks disproportionately longer from front to back, is flattened on both sides, and lacks the usual convexity seen at the temporal and parietal areas. This positional molding is often a concern to parents and may influence their perception of the infant’s attractiveness and their responsiveness to the infant. Frequent repositioning of the infant and positioning on a gel mattress can reduce or minimize cranial molding.

Late-preterm infants may not have the immature appearance so commonly observed in preterm infants born at a lower gestational age (<34 weeks’ gestation). However, late-preterm infants are at risk for the development of some of the same physiologic adaptation problems as their preterm counterparts: respiratory distress syndrome, hyperbilirubinemia, thermoregulation difficulties, hypoglycemia, and feeding problems.

Therapeutic Management

When delivery of a preterm infant is anticipated, the intensive care nursery is alerted and a team approach implemented. Ideally, a neonatologist or a neonatal nurse practitioner, a staff nurse, and a respiratory therapist are present for the delivery. Infants who do not require resuscitation are immediately transferred in a heated incubator to the NICU, where they are weighed and where IV access, oxygen therapy, and other therapeutic interventions are initiated as needed. Resuscitation is conducted in the delivery area until infants can be safely transported to the NICU. Ongoing care is described elsewhere in the chapter.

Nursing Care Management

As with therapeutic management, individualize nursing care for each infant. See appropriate discussions under Nursing Care of High-Risk Newborns for details of care.

Pathophysiology

AOP reflects the immature and poorly refined neurologic and chemical respiratory control mechanisms in preterm infants. These infants are not as responsive to hypercarbia and hypoxemia, and their neurons have fewer dendritic associations than those of more mature infants. The respiratory reflexes of these infants are significantly less mature, which may be a contributing factor in the etiology. Overall weakness of the muscles of the thorax, diaphragm, and upper airway may also contribute to apneic episodes in the preterm infant. In addition, apnea is characteristically observed during periods of REM sleep. A variety of factors, including infection, intracranial hemorrhage (ICH), or PDA, can make apnea worse. Secondary causes of apnea should be investigated in infants with new-onset apnea or when there is a significant change in the frequency or severity of apneic episodes. Apnea in full-term infants should always be considered secondary and the cause investigated.

Clinical Manifestations

Factors that contribute to apnea in preterm neonates should be investigated and treated. Apnea can be anticipated in infants with a variety of conditions (Box 10-8); conversely, one of these disorders may be suspected in infants with persistent apneic spells. Although apnea is an expected event in preterm neonates, it should not be designated as being benign until all other causes have been ruled out. The observation of apnea is a reason to screen for any of the causes listed in Box 10-8.

Therapeutic Management

Administration of caffeine is often effective in reducing the frequency of primary apnea-bradycardia spells in newborns. Caffeine acts as a CNS stimulant to breathing. Neonates receiving caffeine must be closely observed for symptoms of toxicity. Caffeine has come to the forefront of pharmacologic therapy for AOP because it has fewer side effects than previously used aminophylline or theophylline, requires dosing once daily, has more predictable plasma concentrations, has slower elimination, and has a wider therapeutic range (trough, 5 to 20 mcg/ml). Caffeine citrate (Cafcit) has been approved for use in preterm infants with AOP. It is available in injectable and oral form. Weight and urinary output should be closely monitored because caffeine acts as a mild diuretic.

Nasal CPAP and, more recently, nasal intermittent positive pressure ventilation have been used as an adjunct treatment for AOP. CPAP acts to maintain airway patency; hence it is most effective for obstructive or mixed apnea.

Nursing Care Management

Management of apnea consists of monitoring respiration and heart rate routinely in all preterm infants and preventing contributing conditions. Cardiorespiratory monitors alert the staff to cessation of respiration according to a preset delay time—usually 15 to 20 seconds. Effective monitoring devices do not eliminate the need for alert nursing observation. Nursing observation combined with monitoring is the most effective means of identifying neonatal apnea.

If begun early, gentle tactile stimulation (e.g., rubbing the back or chest gently, turning the infant to a supine position) will stop most apneic spells. If tactile stimulation fails to reinstitute respiration, flow-by oxygen and suctioning of the nose and mouth may be required. If breathing does not begin, the chin is raised gently to open the airway, and sufficient pressure is applied with a resuscitation mask and bag to lift the rib cage. The infant is never shaken. After breathing is restored, the infant is assessed for possible precipitating factors, such as unstable temperature, abdominal distention (if not observed earlier), and supplemental oxygen (if any) being delivered before the episode. The use of pulse oximetry has helped detect the onset of an apneic episode.

It is important that nurses maintain a careful record of episodes of apnea, including the number of apneic spells, the infant’s appearance during and after the episode, and whether the infant self-recovers or whether tactile stimulation or other measures are needed to restore breathing. Subsequent investigation into the possible cause of the apneic episode is vital to the care of the preterm infant because it may signal an underlying condition such as sepsis or NEC.

Persistent and repeated periods of apnea may be treated by mechanical ventilation or CPAP. Various methods devised to provide an intermittent stimulus for breathing, such as oscillating beds and water beds, have achieved variable success in the treatment of AOP.

Pathophysiology

Preterm infants are born before the lungs are fully prepared to serve as efficient organs for gas exchange. This appears to be a critical factor in the development of RDS. RDS results from a combination of structural and functional immaturity of the lungs.

Because the final unfolding of the alveolar septa, which increases the surface area of the lungs, occurs during the last trimester of pregnancy, preterm infants are born with numerous underdeveloped and many uninflatable alveoli. In addition, the fetal chest wall is highly compliant because of the predominance of cartilage rather than bone; and the diaphragm, the dominant respiratory muscle, is prone to fatigue.

Functionally, the fetal lungs are deficient in surfactant, a surface-active phospholipid secreted by type II cells in the alveolar epithelium. Surfactant is first produced at about 24 weeks of gestational age, but the type II cells in the lung do not fully mature until about 36 weeks of gestation (Fig. 10-12). Acting much like a detergent, this substance reduces the surface tension of fluids that line the alveoli and respiratory passages, resulting in uniform expansion and maintenance of lung expansion at low intraalveolar pressure. Immature development of these functions produces consequences that seriously compromise respiratory efficiency. Deficient surfactant production causes unequal inflation of alveoli on inspiration and the collapse of alveoli on end expiration. Without surfactant, infants are unable to keep their lungs inflated and therefore exert a great deal of effort to reexpand the alveoli with each breath. It has been estimated that each breath requires as much negative pressure (60 to 75 cm H₂O) as the initial lung expansion at birth. With increasing exhaustion they are able to open fewer and fewer alveoli. This inability to maintain lung expansion produces widespread atelectasis.

PATHOPHYSIOLOGY REVIEW

In the absence of alveolar stability (normal functional residual capacity) and with progressive atelectasis, pulmonary vascular resistance (PVR) increases, whereas with normal lung expansion it would decrease. Consequently, there is hypoperfusion to the lung tissue, with a decrease in effective pulmonary blood flow. The increase in PVR causes partial reversion to the fetal circulation, with a right-to-left shunting of blood through the persisting fetal communications—the ductus arteriosus and foramen ovale.

Inadequate pulmonary perfusion and ventilation produce hypoxemia and hypercapnia. Pulmonary arterioles, with their thick muscular layer, are markedly reactive to diminished oxygen concentration. Thus a decrease in oxygen tension causes vasospasm in the pulmonary arterioles that is further enhanced by a decrease in blood pH. This vasoconstriction contributes to a marked increase in PVR. In normal ventilation with increased oxygen concentration, the ductus arteriosus constricts and the pulmonary vessels dilate to decrease PVR (Fig. 10-13).

Prolonged hypoxemia activates anaerobic glycolysis, which produces increased amounts of lactic acid. An increase in lactic acid causes metabolic acidosis; inability of the atelectatic lungs to blow off excess carbon dioxide produces respiratory acidosis. Lowered pH causes further vasoconstriction. With deficient pulmonary circulation and alveolar perfusion, Pao₂ continues to fall, pH falls, and the materials needed for surfactant production are not circulated to the alveoli.

Pulmonary edema observed in the early stages of RDS also contributes to impaired gas exchange. Factors believed to facilitate this fluid accumulation in the lungs include renal immaturity or insufficiency resulting from hypoxemia, high fluid intake and PDA, left ventricular dysfunction associated with papillary muscle necrosis, low serum protein concentration and low colloid osmotic pressure, increased alveolar surface tension that enhances the shift of interstitial fluid to alveolar spaces, oxygen toxicity, and high plasma vasopressin.

Pulmonary interstitial emphysema (PIE) may develop in preterm infants with RDS and immature lungs as a result of overdistention of distal airways. This condition further complicates adequate oxygenation in the immature airways (see Air Leak Syndromes, p. 358).

Deficiencies in other systems contribute to respiratory distress. For example, a high threshold of the respiratory center to afferent stimuli and weak or absent gag and cough reflexes reflect the immaturity of the nervous system. In addition, the persistence of fetal hemoglobin, so beneficial in prenatal existence, may place the infant at a disadvantage during respiratory distress. Although the binding power of fetal hemoglobin for oxygen is much greater than that of adult hemoglobin, this increased affinity also causes less oxygen to be released to the tissues at normal oxygen tension. In the newborn the arterial oxygen concentration must fall to a lower level for bound oxygen to be released from fetal hemoglobin.

A hyaline membrane is formed as hypoxemia and the increased pulmonary vascular pressure cause transudation of fluid into the alveoli. Necrotic cells from damaged alveoli plus the fibrin in the transudate form a membranous layer that lines the alveoli and inhibits gas exchange. The hyaline membrane contributes to respiratory difficulties by greatly diminishing lung distensibility, or compliance, the elastic quality of lung tissue that permits expansion in response to a given amount of applied pressure during inspiration. Affected lungs are stiffer and require far more pressure than do normal lungs to achieve an equal amount of expansion. Table 10-7 summarizes the major factors that produce RDS in immature infants.