The Premature Infant
Identifying behavioral and physiological cues of pain in premature infants, as well as managing that pain, presents unique challenges. The premature infant is defined as a fetus delivered before completing 37 weeks gestation. The premature infant includes those neonates meeting age of viability for gestational development; in many states that gestational age is 23 weeks. The range of physiological and physical maturity in premature babies is broad and provides significant challenges to the health care provider. Neurodevelopmental maturity by gestational age, physiological maturity of organ systems, and physical maturity of visible structures do not always match the neonate’s actual capacity to send messages, which creates difficulty in identifying and treating pain. It also further complicates education of the parent. The best approach for assessing, identifying and managing this population is through education of the clinician and the family (Ballard et al., 1991).
Physiological maturity increases by gestational age, beginning at the age of viability: 23 weeks. The 23-week-gestation infant’s cardiovascular capacity has a reduced ability to increase contractility of the cardiac tissue, thus a decreased capacity regulates blood flow (Kenner & Lott, 2003). The compensatory response of cardiac tissue causes tachycardia and compromised cerebral perfusion, leading to alterations in blood pressure and mean arterial pressure. Increasing gestational age allows increasing maturity of cardiac musculature, leading to improving cardiac output and perfusion by term gestation. The compromised cardiac output and ensuing alterations in vital signs are interpreted for what they are—unstable vital signs and physiological status, but oftentimes they are not interpreted as vital signals of pain. Tachycardia or hyperthermia are signs of pain in an otherwise stable term newborn—environmental factors for hyperthermia are ruled out and assessment findings lead to an interpretation of pain. Not so for the premature infant. Time spent ensuring cardiac output, volume integrity, and environmental factors delays recognition of pain.
Beginning at the age of viability at 23 weeks gestation, respiratory status of the premature infant requires full respiratory support, including oxygen supplementation. Whereas the full-term infant can exhibit desaturation symptoms during times of pain, the preterm infant again sends misinterpreted cues that delay intervention (Kenner & Lott, 2003; Kenner & McGrath, 2004). In the presence or absence of oxygen supplementation and mechanical support, desaturations in a preterm infant of 23 to 37 weeks gestation directs the clinician to troubleshoot airway and gas exchange. Assessment of patency of invasive airway support, integrity of artificial airways and tubing, percentage of fractioned oxygen support all lead to delays in identifying pain as the mitigating factor for desaturation. The physiological immaturity of the premature infant inhibits its ability to consistently engage in stable gas, which compromises one’s capacity to recognize pain cues using physiological markers.
Physiological immaturity related to gestational age affects the renal and gastrointestinal systems as well as the cardiac and respiratory systems. The renal system and gastrointestinal system are not as reliable or involved in sending signs of pain in a preterm or term infant and typically suffer sequelae of pain stimuli in response to cardiac and respiratory compromise from stimulus (Kenner & Lott, 2003). For the purpose of this discussion, renal and gastrointestinal integrity will not be discussed as physiologically important for pain assessment or management in neonates.
Skeletal and muscular integrity matures with increasing gestational age in terms of mass and neurological maturity. Skeletomuscular immaturity at 23 to 25 weeks gestation limits the neonate’s capacity to generate flexion, experience smooth range-of-motion movements, and display physical signs of pain or discomfort. The premature infant from 23 to 25 weeks by gestation is normally flaccid, with hands and legs splayed away from the body’s core, limiting the clinician’s ability to use posturing as a measure of pain or as exhaustion from pain. With increasing gestational maturity, in about 2-week increments, the neonate becomes increasingly able to voluntarily move to physiological flexion—a sign of skeletomuscular maturity in a term newborn. With increasing gestational age, the assessment of degree of physiological flexion allows the clinician to visually observe the capacity to self-stabilize in response to painful stimuli or the inability to do so (Chang, 2011; Dieckmann, Brownstein, & Gausche-Hill, 2000; Friedrichs, Young, Gallagher, Keller, & Kimura, 1995; Gallo, 2003; Heidari, Nasapour, & Foolardi, 2013; Kenner & Lott, 2003; Kenner & McGrath, 2004; Obeidat, Bond, & Clark Callister, 2009).
Neurodevelopmental immaturity compromises the clinician’s ability to identify pain responses in the neonate. The extremely premature infant, born between 23 and 25 weeks gestation, is still in the organizational stage of neurological development, with neuronal and glial cell migration not yet complete, myelination of neuronal sheaths and synaptic connections also incomplete (Chang, 2011; Dieckmann, Brownstein, & Gausche-Hill, 2000; Friedrichs, Young, Gallagher, Keller, & Kimura, 1995; Gallo, 2003; Heidari, Nasapour, & Foolardi, 2013; Kenner & Lott, 2003; Kenner & McGrath, 2004; Obeidat, Bond, & Clark Callister, 2009). This degree of immaturity does not allow the neonate to express signs of pain; in reality, it is the time of premature life that the experiential stimulus from the hostile NICU environment is hardwiring the brain to not respond to pain. Extra caution must be taken to reduce external stimuli, such as light, noise, and touch, as much as possible, as each are perceived by the extremely premature infant as painful, unpleasant stimuli. Care must be taken to recreate the protective environment of the uterus the neonate should still be growing in to prevent deleterious brain development.
The immature neurodevelopmental status of the neonate born at less than 32 weeks gestation provides the most challenges when assessing and learning to identify signs and symptoms of pain. Not only is the neuronal capacity of the brain limited in its ability to process stimuli and elicit a response, the skeletomuscular maturity is limited as well, which contributes to a decreasing capacity to display outward signs of pain. The use of a maturity tool to determine neuromuscular and physical maturity of neonates beginning with age of viability through term will help the clinician to determine characteristics of maturity to recognize signs of pain more successfully.
The New Ballard Score tool allows the clinician to assess and determine a gestational age by appearance and behavior, to be able to more fully understand the signs and behaviors of the infant so as to identify pain. Having a deeper understanding of the neurobehavioral capacity of the infant allows better identification of pain cues of the premature infant. Assessing the infant and determining a gestational score using the tool provides a foundation of what the infant is capable of. The first part of the tool, as noted in Figure 12.1, directs the clinician to determine neuromuscular maturity by assessing posture, square window, aim recoil, popliteal angle, scarf sign, and heel to ear. A score is assigned based on the infant’s presentation in each category from −1 to 5. Next, the clinician determines physical maturity by assessing skin, lanugo, plantar surface, breast, eye/ear, and gender genitalia. A descriptive finding in each category is determined, with each earning a score from −1 to 5 as well. The resultant scores for neuromuscular maturity and physical maturity are added together for a total score that correlates with gestational age, as noted on the maturity rating box of Table 12.1. The clinician will now be better able to identify subtle signs and symptoms of pain in premature infants.
FIGURE 12.1. Neuromusclar maturity.
TABLE 12.1 Physical Maturity as Determined by the New Ballard Score
Neurobehavioral maturity of an infant progresses in a sequential manner from age of viability to term gestation. The preterm infant has limited capacity to display signs of distress in response to extraneous and negative stimuli. Premature infants have limited reserves for mounting and demonstrating a response. The immature physiological capacity reduces the ability to display or maintain physiological changes in response to painful stimuli. The premature infant is at greater risk of having unrecognized and untreated pain because of an immature capacity to mount and sustain physiological and behavioral signs of pain (Flick & Hebl, 2013).
Premature infants are at the same risk of exposure and experience procedural or postoperative pain as do term infants. The responses are frequently less obvious, less vigorous, and displayed for a shorter length of time, demanding the clinician and family be observant and astute to changes. Encouraging and supporting education of both the clinical caregivers and the family members to know the patient will increase the likelihood that pain is identified and interventions rendered. Encouraging parents to spend time at the bedside, to engage in skin-to-skin care, and to participate in daily rounds increases the parents’ ability to “know” the infant. Ensuring clinician education of assessment practices and use of gestational maturity and pain assessment tools promotes earlier recognition of changes. Implementing and enforcing use of a primary care model of care for clinician practice supports the clinical staff in “knowing” the infant’s individual cues.
Adoption of an appropriate tool is necessary if the premature infant is to enjoy comprehensive pain management. To date, only two pain tools have modifications for use with premature infants—the Premature Infant Pain Profile (PIPP) and the Neonatal Pain, Agitation, and Sedation Scale (N-PASS). Although all tools have been used with some reliability with all newborns, the PIPP and N-PASS tools include metrics specific to the premature infant (Flick & Hebl, 2013). Recognizing that the premature infant will experience a degree of pain related to gravity, when term counterparts are weightless in a fluid-filled environment, helps mitigate external sources of tactile sensory stimuli. Recognizing the premature infant’s limited capacity to mount a response to constant external stimuli that will result in conditioning of the newborn’s fragile and growing neural development is imperative for mitigating pain in the neonate. Recognizing and managing premature infant pain adds a layer of complexity for the clinician in understanding the immaturity of physiological and behavioral responses and then delivering interventions that will be successful.
Interventions for mitigating pain in premature infants must consider the immaturity of the baby’s physiological and behavioral states. Position changes using appropriate products, such as snugglies, beanbags, and gel mattresses, can alleviate gravity-related pain responses. Reduction of external stimuli, such as noise and light, can alleviate physiological stimulation and pain. Keep isolettes covered with thick, light-reflective materials to absorb noise and light. Be mindful not to slam porthole doors, not to tap or write on isolettes, to respond to alarms in a timely manner, keep conversations hushed or removed from the bedside. Keep lights dim and cover the baby’s eyes during procedures that require brighter lighting. Maintain a neutral thermal environment to reduce metabolic needs to allow for a response to pain. Eliminate noxious smells by removing betadine or alcohol pads and swabs from inside the isolette. Promote the use of colostrum for oral care; provide a pacifier for nonnutritive sucking. Encourage parents to practice skin-to-skin care or teach parents to use facilitated tuck or containment holding when visiting. Administer sucrose as indicated. Administer physician-ordered pharmaceuticals as ordered to control pain. Closely observe vital signs and physical behaviors to recognize signs and symptoms of distress early to contribute to a less painful experience for a premature infant who will grow to have a neurologically stable and healthy brain that has no long-term ill effects because of poorly managed pain during the most crucial and sensitive time of his or her life.