Developmental Care—Understanding and Applying the Science

Introduction

The complexity of managing the high-risk neonate and the convalescing premature infant is multifaceted. The number of surviving extremely low–birth-weight (22–25 weeks of gestation) infants has increased over the past decade, yet despite advances in lifesaving technologies, approximately 50% of these survivors are still at significant risk of morbidity or severe pulmonary and neurodevelopmental compromise. Prematurity often thrusts these vulnerable infants on very different developmental trajectories than their term counterparts. High rates (17%–59%) of severe neurodevelopmental disabilities have been reported in short-term follow-up studies, with some improvements noted in sequential studies. Long-term adverse outcomes after extreme prematurity include intellectual disability (5%–36%), cerebral palsy (9%–18%), blindness (0.7%–9%), and deafness (2%–4%). Additional deficits have also been reported in cognition, behavior, sensory processing, and autism spectrum disorders.

Striving for best patient outcomes is the goal of every neonatal intensive care unit (NICU), including minimization of neurodevelopmental issues that are onerous for families, healthcare, school systems, and the general public. Immature brain development and the ability of the infant to mitigate the stressors of the extrauterine environment depend on mindful caregiving and healthy social and parental engagement. Caring for a premature infant or high-risk neonate is not always instinctive in the face of significant medical complexity and can present challenges for staff and parents. This chapter will discuss theories and conceptual models of delivering developmental care in the NICU, as well as evidence-based interventions and practice applications. Although this chapter centers on the premature infant, all high-risk neonates (i.e., narcotic exposed, neonatal encephalopathy, etc.) are included in the general applications and benefits of developmental care.

Defining Developmental Care

Developmental care is the deliberate effort to bring all aspects of nurturing and lifesaving medical care harmoniously together by recognizing and responding to the individual needs of each and every infant. Developmental care theories and paradigms stress the importance of understanding the impact of the NICU environment on the developing infant and the benefit of adaptations to maximize short- and long-term developmental outcomes. Over the years, developmental care has evolved to include philosophical and conceptual models that enhance neurosensory and emotional development and promote parent–infant attachment opportunities. Parent engagement and education are prioritized as key aspects of developmentally supportive care. Interventions center around: decreasing stress and pain, modifying environmental stimuli (visual, auditory, tactile, and vestibular sensory input), supporting optimal positioning, protecting sleep, facilitating provision of mother’s milk, and, cue-based care and feeding. The synergistic effects of combining multiple evidence-based developmental care principles within a family-centered model of care maximize optimal outcomes for both infants and families. While researchers continue to develop practices and guidelines surrounding developmental care, most agree that pursuing an individualized, personalized approach to care should be a shared objective among neonatal clinicians.

The Evolution of Neonatal Neurodevelopmental Care

In the latter part of the 19th century, a particular interest in the care of newborns emerged in Europe. In the United States, a focus on pathophysiology of the newborn arose in the early 20th century. The term neonatology was coined by Dr. Alexander Schaffer in 1960. Since then, many advances in the clinical management of specific neonatal health conditions and improved technology have enhanced neonatal survival outcomes. Pediatrician Dr. T. Barry Brazelton first studied infant development in the early 1960s. His work was instrumental in guiding the medical community to appreciate that children have varying “temperaments” and emotional needs that impact behavior, development, and caregiver attachment. His focus on the assessment of behaviors and emotional needs of his patients created a paradigm shift in the way the medical community approached caring for children. Likewise, through years of research and dedication, his passion for promoting the bidirectional relationship between child and parent became embedded in the study of developmental pediatrics. While Dr. Brazelton and colleagues focused their research on the newborn and early child development, Dr. Heidelise Als may have been the first clinician to scrutinize early preterm development focusing on the most vulnerable newborn populations and their families.

Dr. Als and her colleagues evaluated the premature infant nervous system’s acceptance of sensory input and the interaction between infant behaviors and the environment. This specific approach led to the development of the conceptualized synactive theory. The tenets of synactive theory and the work of Als have served as the foundation for understanding the importance of analyzing the premature infant’s responses to the outside environment. Through detailed observation, they analyzed the infant’s functioning across five identified subsystems: autonomic, motor, state, attentional/interactive, and self-regulation. These subsystems represent the hierarchical nature of premature infant behaviors with autonomic stability as the foundation of all systems. When stability in the autonomic subsystem is disrupted, the infant will not achieve higher levels of engagement. Each system is dynamically interdependent on one another in determining the infant’s ability to interact with the world. After studying thousands of infants, the Newborn Individualized Developmental Care and Assessment Program (NIDCAP) was developed. This program emphasized training clinical staff on “naturalistic observation” of infant behaviors during routine care and how to provide effective interventions.

The pioneering work of Dr. Als and colleagues paved the way for a deeper appreciation of how the environment impacts brain development and the need for modifications. There is now abundant evidence that preterm infants have an increased incidence and wide spectrum of altered neurodevelopmental outcomes that may be linked to perinatal factors. Environmental stressors of the NICU have been shown to disrupt infant physiologic stability and impact neurodevelopmental outcomes across the life span. As subsequent research emerged, neonatal units have attempted to adapt the environment to minimize stress placed on infants and their families. Clinicians gradually became aware of the importance of observing the effect of their interactions on the infant’s sensory system and the need to prevent sensory overload during caregiving. Als coined this concept, “reflective caregiving.” She also reinforced the importance of strengthening the bidirectional relationship between the parent and infant as an important core measure of caregiving.

Studies have documented significant improvements in infant outcomes and parent satisfaction utilizing the NIDCAP approach. However, various metaanalyses and systematic reviews have yielded conflicting findings sparking published rebuttals. One explanation is that researchers have acknowledged that the strategies outlined in NIDCAP have become so integrated into the standard care in most NICUs that it is difficult to obtain a true control group. Accepting varying levels of evidence, Als’ work, along with the NIDCAP Federation, has impacted the care of premature infants all over the world.

“One Brain for Life......Everything Matters” Dr. Heidelise Als

Brain Development: The Foundation of Behavior

Behavior is an expression of brain function. From primitive reflexes to volitional movements, complex neuronal activity is responsible for these visible outward signs of the developing brain. Between 24 and 40 weeks’ gestation, the brain undergoes a critically sensitive and significant period of growth. The germinal matrix, present until 36 weeks postmenstrual age (PMA) and responsible for glial cell differentiation, is experiencing rapid proliferation and movement of neurons. Excitatory and inhibitory neurons will migrate from their sites of origin on the endogenous paths outlined for them. This “neurogenic determinism” occurs in the natural maturational process; however, it is susceptible to epigenetic influences. Sensory motor experiences will influence the proliferation of neurons, synaptic connections, speed of myelination, and eventual planned pruning of the unused neural pathways. It is estimated that 70% of neurons in the developing cortex will succumb to apoptosis between 28 and 40 weeks PMA if pathways are not established. During this critical period of brain growth, extrauterine influences will have a significant effect on neurologic mapping and how these experiences become biophysical or biochemical pathways in the brain.

The combination of altered endogenous and exogenous influences (epigenetics) can negatively impact developmental trajectories in terms of delayed maturation or specific injury. The premature infant in this critical period is very competent in the intrauterine environment but is extremely mismatched with nature when born prematurely and thus extremely vulnerable to the outside influences of everyday life in the NICU. Exposure to these clinical elements is life sustaining yet brain altering in both positive and negative ways.

Extensive research in preterm birth survivors, as well as in animal models, has established a direct correlation between the degree of prematurity and loss in cortical volume with poorer neurodevelopmental outcomes. The risk of cerebral palsy increases with decreasing gestation from approximately 1% at 34 weeks to 20% at 26 weeks or less of gestation. Understanding the impact that prematurity, brain insult, genetic variations, and repeated stress have on the developing brain is essential in identifying and implementing strategies for mitigating negative effects and long-term sequelae. Despite the exposure to the stressors of the extrauterine world, infants may respond differently to the same experiences, which leaves researchers continuing to search for a link between epigenetics, buffering agents, genetic predisposition, and resiliency.

New research is evolving to examine and understand behavioral epigenetics or experiences that impact gene expression ( Fig. 8.1 ). Extreme prematurity and prolonged medical stays are considered adverse life experiences despite the fact that they are also lifesaving experiences. Studies examining the role of perinatal and postnatal stress in relation to dysregulation of the hypothalamic–pituitary–adrenal (HPA) system and deoxyribonucleic acid (DNA) expression may identify the genetic mechanisms behind stress. Repeated stress on the infant is hypothesized to overactivate the HPA axis, resulting in excessive amounts of cortisol in the bloodstream. Cortisol has been implicated in the destruction of telomeres. Repeated stress results in telomere erosion, which has been correlated to chronic stress and life adversity in childhood and adult studies. Recently, the study of telomere length in very preterm infants has been investigated, with results indicating similar erosion or shortening, thus implicating the early cellular impact of repeated stress.

In longitudinal studies examining telomere integrity in older children and adults, parent responsiveness has been shown to have a significant positive impact. This has led researchers to question the role of parental, responsive caregiving, and the buffering effects this has on reducing chronic stress when applied early in the neonatal period. The most investigated developmental care strategy that demonstrates epigenetic protective mechanisms is skin-to-skin care (SSC). Future studies are needed to examine the impact of other stress-reducing interventions initiated early in the NICU course and the long-term impact on telomere length and adverse neurodevelopmental outcomes.

Promoting Neuroprotection

The immature brain is vulnerable and susceptible to the constant relay of sensory stimuli such as light, touch, sound, smell, temperature, and pain. Every encounter with the premature infant activates sensory pathways. Implementing developmentally supportive neuroprotective interventions helps defend against neuronal injury often incurred by the cumulative effects of the NICU environment. Developmental strategies to promote neuroprotection include recognition and timely responses to infant cues, protecting deep sleep, supportive containment, facilitated flexion (tucking), midline positioning, SSC, environmental modifications, positive touch, and parental engagement. These interventions will be further discussed in detail.

The Eco-Bio-Developmental Framework

The triad of unique early life stressors, including repetitive and cumulative stress, parental separation, and pain, have been identified as “toxic stress” and significantly disruptive to the neurodevelopmental process. The effects of toxic stress are conceptualized in the eco-bio-developmental framework as frequent and extended activation of the infant’s stress response and continual release of stress hormones. The way care is delivered impacts the premature infant on many levels. Infant stress can manifest as physiological instability, motoric disorganization, irritability, hyper- or hyporesponsiveness, poor state regulation, diminished interactive and attentional abilities, and lack of self-regulation. Procedural care and undermanaged pain along with insufficient parental, or “human” nurturing contact, can overload the immature nervous system and the HPA axis, leading to an exaggerated sympathetic “fight” state. This exaggerated state results in an overproduction of the stress hormone cortisol. Ironically, heightened states of cortisol over time can eventually lead to hyporesponsivity to stress and sensory stimulation, resulting in a blunted effort on the infant’s part to later attend and respond to typical and expected environmental influences such as positive touch. The influence of vagal tone and the autonomic nervous system, with continual activation of the “fight-or-flight response,” is known as the Polyvagal theory, and may be predictive of adverse behavioral, cognitive, and motor outcomes at 3 years of age. Chronic repetition of stressful and painful input leads to changes in brain activity and ultimately brain architecture, resulting in long-term alterations in behavior.

Parents of NICU infants are more likely to experience significant life stressors before their child is born. These significant life stressors, known as adverse childhood experiences, may result in diminished emotional resources and coping abilities needed to withstand the financial, situational, emotional, and mental stressors that often accompany their child’s course. It is imperative that NICUs have programs to assist families not only financially but with the emotional support needed to face the unpredictable journey that lies ahead of them.

Trauma-Informed Care

The trauma-informed care model attempts to explain these collective toxic stress-evoking experiences and identify interventions that NICUs should adopt to support infants and effective family coping. Understanding real and perceived stressors that families experience as a result of their infant’s vulnerable condition helps prevent unnecessary repetitive stress and promote feelings of “safety, security, and connectedness” between the infant and caregiver. Modifications of the stress response come from deliberate and intentional efforts to provide care by buffering environmental stressors for both infant and parent, thus minimizing further adverse experiences.

Intentional caregiving, the deliberate act of thoughtful engagement in all interventions and interactions, forms the basis of trauma-informed care. Mindful interventions on the part of all practitioners has been shown to reduce the effects of noxious stress, thus mitigating long-term consequences on both infant and caregiver. Parents of premature infants are often not ready or able to manage the overwhelming or traumatic circumstances they encounter. Parents may feel additional emotional stress, depression, anxiety, ambiguity about their child’s future, financial pressures, and posttraumatic stress than parents of term infants. Family dynamics are substantially affected throughout the NICU experience as well as afterwards. Parents often leave with mental health issues triggered or intensified by their infant’s experience. Weaving tenets of trauma-informed care principles into the culture of care diminishes stress on caregivers as well as infants and families.

The Importance of Touch and Social Connectedness

“The first love of the human infant is for his mother” Harry Harlow

Over the years, the importance of maternal engagement, touch, and human connectedness have been shown to bolster cortical growth and synaptic connections and is a basic human need. Classic Harlow monkey studies of the 1950s and 1960s demonstrated the importance of soft physical touch over nutrition as the rhesus monkeys sought the comfort of their soft terrycloth-simulated mothers over food. Additionally, when the monkeys were physically isolated or experienced deprivation from physical contact, they demonstrated rocking and self-stimulating behaviors as well as aggression and “autistic-like” outbursts. Harlow concluded that human contact is critical for comfort and social-emotional development.

Studies of Romanian orphans have yielded similar conclusions. In the 1980s and 1990s, thousands of orphans received only custodial care because of overcrowding and lack of financial resources. Many of these children suffered social isolation and lack of intimate, loving touch and attention. They were later diagnosed with “failure to thrive” and presented with diminished social, emotional, and cognitive behaviors. The impact of social deprivation was physically captured on their magnetic resonance images (MRIs), which showed 30% less cortical volume compared to their typically developing 3-year-old peers who experienced routine family interactions. Follow-up studies found that the subgroup of children who went into highly committed and nurturing foster care along with early-intervention programming before 2 years of age showed significant improvements in their white matter and improved social and cognitive outcomes. In contrast, children who remained in the orphanages until later years had poorer outcomes. These findings suggested that neural plasticity could be achieved through promotion of high-quality caregiver–infant attachments and early-intervention programming.

In the 1990s, the Humane Neonatal Care Initiative advocated that premature infants needed nurturing touch and engagement with their families not only for its medical advantages, but because it was “humane”. In their groundbreaking research on SSC (mother and infant in direct contact) and infant–mother bonding, Klaus and Kennell recognized that “humane touch” was essential for healing and a “right” of every infant. The works of Brazelton, Kennell, Klaus, and others have significantly contributed to social bonding theories and the importance of maternal touch and engagement. Recent research has investigated the epigenetic influences of early tactile experiences and found significant effects on the biological formation of social bonds, as well as reduction of infant pain and stress regulation. Early parent engagement and bonding opportunities such as SSC are now cornerstones of care in the postnatal period, including the NICU environment.

Skin-to-Skin Care

SSC, also known as kangaroo care, offers the most favorable extrauterine environment for the premature infant. It is the “normal environment” and the optimal venue for delivery of care. The process of SSC involves the diaper-clad infant being held directly on a parent’s bare chest in an upright prone position. Parental–infant SSC safeguards the premature infant from the deleterious consequences of separation, promotes optimum brain growth, encourages attachment, and fosters infant self-regulation. It has been shown to be a neuroprotective intervention that diminishes infant and parental stress. Studies have shown that brain maturation and plasticity is enhanced when parent infant SSC is offered 6 hours per week for 8 weeks. Parents also experience positive physiologic effects by offering SSC to their premature infants, such as enhanced parent–infant attachment and improved perceptions of parental competence. Parental attachment and satisfaction are augmented with maternal–infant during SSC, while paternal depression is decreased. SSC accelerates brain development, encourages healing and growth, optimizes parent–infant bonding, and decreases infections and length of hospital stay, thereby serving as the foundation for neuroprotective developmental care in the NICU. SSC has become standard in most NICUs. Refer to Fig. 8.2 .

Clinical Application : Both mothers and fathers should engage in SSC. Even though there are very few contraindications to providing SSC, infants should continue to be monitored closely and use a three-person team to assist intubated infants and families with transfer and positioning. Physicians may advise about medical appropriateness for SSC and promote the benefits to parents in daily rounds to convey the importance SSC on both medical and emotional well-being of the infant and parent. Theoretically, SSC care should rarely be limited, but there may be exceptions.

Benefits of Loving Touch

In addition to SSC, studies have highlighted the relationship between massage or moderate-pressure touch therapy and improved infant and mother outcomes. Parental anxiety while in the NICU has been linked to compromised neurodevelopmental outcomes in very low–birth-weight infants. Recent studies have revealed encouraging evidence that mothers who provided infant massage showed less psychological distress and anxiety and improved attachment. Oxytocin, the neuropeptide that regulates emotions and feelings associated with love and safety, has a strong role in communicating the intention of touch. Loving, nurturing touch and physical proximity have been shown to increase circulating oxytocin in term infants and improve social attachment. Although increased circulating oxytocin has not been established in preterm infants at this time, noted improvements in behavioral responsiveness were seen when infants were socially engaged with their mothers, even at very young gestational ages (25–28 weeks). Implications of these findings reinforce the importance of establishing social bonds and appropriate touch early in the developmental sequence. Additional benefits of massage will be discussed later in this chapter. Refer to Fig. 8.3 .

The Neonatal Integrative Model of Developmental Care

Models of developmental care have evolved over the years, leading to a currently proposed model of wide acceptance known as the Neonatal Integrative Model of Developmental Care. The Neonatal Integrative Model of Developmental Care guides clinical practice in NICUs around the world because it suggests practical application integrating evidence and theory. The seven neuroprotective core measures of the IDC model may be envisioned as overlapping lotus petals. Refer to Fig. 8.4 . The core measures are:

• 1.

  the healing environment

• 2.

  partnering with families

• 3.

  positioning and handling

• 4.

  safeguarding sleep

• 5.

  minimizing stress and pain

• 6.

  protecting skin

• 7.

  optimizing nutrition

An Introduction to The Seven Core Measures

The Neonatal Integrative Model of Developmental Care weaves the seven core measures into all aspects of NICU care for vulnerable preterm infants and their families. The core measures offer clinical direction for NICU staff to provide neuroprotective family-centered developmental care to preterm infants and their families. Infants display identifiable behaviors or responses that may be considered quantifiable signs of core measure outcomes and detailed guidelines for interventions that strive to achieve the designated improvements or outcomes. Included are examples of the seven core measures along with recommendations for clinical application of important concepts of each identified area.

Understanding Effects of Room Design

The single-family room (SFR) NICU was designed to improve medical and neurodevelopmental outcomes. SFRs enhance medical and neurodevelopmental outcomes for premature infants, foster parental interactions, and improve regulation of the environment, especially sound and light. Improvements in parent and staff satisfaction have been reported with the SFR concept. Basic amenities a SFR should include are parent sleep space, individually controlled lighting, and private/secure storage for personal belongings. The availability of SFRs encourages parental presence and infant interactions. Increased developmental support and maternal involvement, as evidenced by the provision of more SSC and direct infant care, was linked to increased weight at discharge, improved weight gain, fewer medical procedures, enhanced attention, and decreased stress and pain in SFR NICUs. Privacy is improved in SFRs as well as increased availability of mother’s milk. Exposure to human speech during the neonatal period, especially the mother’s voice, adds linguistic value that can be crucial for the initial wiring of the brain for language acquisition.

There are numerous benefits of SFRs; however, there is emerging confounding evidence that suggests that SFRs may not consistently lead to optimal neurodevelopmental outcomes across all infant populations. For example, it has been found that former premature infants at 2 years of age had compromised language development when compared with infants in open-bay units. Abnormal language development may result from prolonged hospitalization in a SFR where lack of regular human speech is diminished if parents are not consistently present, thus increasing long periods of social isolation.

Clinical Application : There are multiple factors that interact that may create either a positive healing environment or a neurotoxic environment. Light and sound are elements in the NICU that are easily modified in SFRs and have an important impact on neurodevelopmental outcomes. Clinicians should direct families to talk, read, and sing to their infants. Parents should be encouraged to stay with their infant as much as possible to fully participate in care in order to strengthen parental confidence and connectedness.

Facilitating Noise Reduction and Promoting Auditory Development

The structural development of the human ear is complete by 24 weeks of gestation and becomes consistently functional after 28 weeks of gestation. Between 26 to 30 weeks of gestation, hair cells in the cochlea are adapted for exact frequencies and can transform acoustic vibrations into electrical stimuli that travel to the brainstem. Hearing accuracy becomes nearly comparable with adult levels by 42 weeks of gestation. Because the sensory receptors in the cochlea cover an area in the cortex much denser than in other sensory zones, it is highly vulnerable to afferent input. Modulating auditory input is essential in diminishing sensory overload and avoiding damage to the developing neural centers.

The American Academy of Pediatrics (AAP) recommends sound levels less than 45 dB ; however, levels have been found to range between 7 dB to 120 dB. Excessive environmental noise exposure in the developing premature infant leads to physiological instability, damaged hearing, poor neurodevelopmental outcomes, increased days on oxygen, and increased length of hospitalization. Noise disturbs the autonomic nervous system, slows advancement to full enteral feeding and weight gain, and interrupts the sleep cycle. High-frequency noise that reaches the immature cochlea may damage auditory pathways and impair language development. Hearing loss is found in premature infants at a rate of 2% to 10% compared with 0.1% in the pediatric population. Aside from excessive auditory input, hearing loss is associated with the synergistic use of aminoglycosides and incubator treatments, apneic spells, hypothermia, hyperbilirubinemia, and hypoxemia.

Modifying the level of noise that reaches infants has been investigated. Sound levels are decreased when noise meters are used or when implementing a “quiet hour.” In a small study examining a novel intervention, extremely low–birth-weight infants were randomized to wearing silicone earplugs or to a control group without plugs. Earplugs were placed at the time of randomization and used continuously until the infants attained 35 weeks PMA or were discharged (whichever happened first). Medical or social visits with family warranted removal of the earplugs. The control group received standard care. Mental Developmental Index (Bayley II) mean scores at 18 to 22 months corrected gestational age were significantly higher in infants with earplugs than in the control infants.

Deprivation of biological maternal sounds that a developing fetus would normally hear in utero cause loss of significant acoustic input during a critical period of brain development. Parent communication and voice exposure is critical to infant auditory development. Researchers found that when premature infants born between 25 and 32 weeks of gestation were randomized in their first month of life to hear audio recordings of their mother’s voice and heartbeat, they had a significantly larger auditory cortex bilaterally compared with infants who heard only typical NICU environmental sounds, demonstrating experience-dependent auditory plasticity.

Clinical Application : Healthcare professionals should observe sound levels in the NICU, including the inside of incubators, and demonstrate mindful strategies to lessen noise such as lowering voices, decreasing volume of televisions, addressing alarm violations promptly and silencing them quickly, and closing incubator and cabinet doors with care. Use of overhead paging systems should be avoided, and alternative noiseless staff communication technologies should be employed. SSC provides an opportunity for an infant to hear parental biological sounds such as heartbeats or breathing sounds. Infants benefit from hearing conversations with human sounds and conversation. Parents should be encouraged to read aloud to their children and provide audio recordings of their voices for staff to play at appropriate decibel levels when they are not available.

Controlling Lighting and Visual Development

The visual system is the last sensory system to mature. Bright light and direct visual stimulation are often overwhelming. An understanding of neurodevelopmental vision progression will expose potential issues for vulnerable infants. At 25 weeks’ postconceptual age (PCA), light stimulates the blink reflex, and neurons of the visual cortex appear. The pupillary light response may be elicited at 27 weeks’ PCA, and vision is only a basic photometric reaction at this time. Between 30 and 32 weeks’ PCA, a bright light stimulates the eyelids to close promptly. The premature infant can focus at 32 weeks and briefly track objects around 33 weeks, while showing visual preferences closer to 34 weeks.

Lighting may enhance healing as well as potentially harm the growth and development of premature infants. Artificial and natural light transmits impressions, allows visual work of clinicians, impacts neonatal physiology and maturation, controls circadian rhythms, and provides neonatal therapy. Cycled lighting should begin at 28 weeks PCA and be graded in terms of intensity and duration. In patient care areas, ambient lighting should have reasonable flexibility to address individualized needs of each infant and caregivers, and be easily adjusted by the healthcare team and families. Natural light offers significant psychological value for clinicians and families. In patient areas with access to natural light, be careful when infants are positioned close to windows because issues with radiant heat loss or gain and glare may occur.

Clinical Application : When performing a procedure or an examination, the infant’s eyes should be shielded because premature infants may not have a mature pupillary reflex, so intense light may be unpleasant and damaging to the developing retina. Also, use ambient lighting instead of overhead bright light to create natural circadian cycling. Open-bay units present challenges for controlling light on the individual infant and require novel strategies and modifications.

Protecting and Promoting Olfaction and Gustation

Both olfactory and gustatory systems have important roles in feeding, metabolism, and digestion as well as caregiver–infant attachment and pain management. The olfactory system emerges between 8 to 11 weeks of gestation and is well developed by 24 weeks. Taste receptors begin to emerge around 7 to 8 weeks of gestation and are fully functional by 18 to 20 weeks. Taste receptors are located throughout the entire oral–pharyngeal cavity, including the tongue, palate, pharynx, esophagus, and epiglottis. When ingestion occurs, combined signals from olfactory and gustatory receptors communicate flavor to the brain. A fetus can detect flavors early in utero and have shown preferences to sweet solutions over bitter. Fetal swallowing has been shown to increase in frequency with the introduction of sweet solutions into the amniotic fluid and decrease with bitter solutions. This preference for flavor is also observed in 28-week preterm infants after birth, because they have been shown to recognize and prefer their mother’s scent when presented with pads impregnated with maternal versus donor breast milk. This sensory recognition benefits oral feeding, behavioral state regulation, and formation of affective neurological pathways. Both olfaction and gustation are important in activation of anticipatory pathways that prepare the body for feeding and digestion known as the cephalic phase response. This response increases gut motility and secretion of hormones and digestive enzymes that regulate blood glucose and enhance digestion. Infants who require prolonged tube feedings demonstrate decreased time to full oral feedings and reduction in hospital stay when routinely exposed to maternal breast milk taste and odor three times a day between 28 to 34 weeks gestation.

In terms of sensory modalities and pain management, the benefits of SSC and maternal breast milk decrease pain responses because of the olfactory properties in the familiar scent of the mother. The use of sucrose or breast milk mitigates pain responses during routine skin-breaking procedures including intravenous line placement and blood draws. Sensorial stimulation (SS) combines tactile, gustatory, auditory, and visual techniques that minimize pain responses. A systematic review of 16 studies found that SS was more effective than sucrose alone in reducing pain. Researchers are currently investigating the role of olfaction as a novel nonpharmacological agent that may contribute to this combined benefit of reducing pain.

Regarding negative olfactory and gustatory experiences, exposure to detergents and disinfectants in the intensive care unit have resulted in decreased oxygenation and are noxious to the maturing infant. Bitter medications, vitamins, hydrolyzed formulas, and gastroesophageal reflux negatively impact the afferent perceptions of smell and taste.

Clinical Application : Staff and parents should refrain from using scented lotions and other olfactory irritants. Allow hand sanitizer to dry before touching the infant or entering the incubator. Avoid scented bathing products and strong detergents. Provide a scented cloth from the mother (or father) in the isolette or crib. Encourage gentle application of colostrum or maternal breast milk to lips, and use during oral care. Incorporate sensory stimulation and provisions for the introduction of milk scent and taste surrounding early gavage feedings as part of prefeeding readiness routines. Combining sensory modalities of touch, taste, smell, and sound can promote positive associations supporting feeding progression, pain management, and bonding opportunities.