The Sensory Environment of the Intensive Care Nursery



The Sensory Environment of the Intensive Care Nursery


Robert D. White


Sensory development begins early in fetal life in an environment that is quite different from that of the neonatal intensive care unit (NICU). In an uncomplicated pregnancy, the fetus spends the full gestational period in a warm, dark, contained womb that is the source of extensive kinesthetic, auditory, and gustatory stimuli. After a normal birth in most civilizations throughout history, the infant then spends several more months (the “fourth trimester”) in close proximity to its mother, who continues the familiar stimuli from in utero and is the primary source of a gradual increment of new visual, auditory, olfactory, gustatory, and tactile stimuli.


The NICU unavoidably and dramatically alters this normal progression of sensory development. Not only are familiar stimuli replaced by unfamiliar ones, but they also are apprehended by the infant in a much different fashion—auditory stimuli arrive through an air medium rather than the liquid and solid medium of the amniotic fluid and uterus, tactile stimuli are frequently uncomfortable or painful, visual stimuli may have little relationship with a circadian rhythm, and so forth.


In addition, the sensory environment is important not only for the infants in a NICU but also for their parents and caregivers, and many times the needs of these three constituencies are in conflict with one another. In this chapter, we review what is known about how the sensory environment of the NICU affects infants, and later, we describe how this knowledge, along with the needs of parents and caregivers, informs the physical design and operation of the NICU.



Overview


In the last 3 months of gestation, the fetal brain increases in mass by 400%,12 and to an even greater extent in complexity and organization.3 This is comparable to the 400% growth that occurs from term delivery to adulthood, yet we have generally assumed that nearly all learning occurs after birth. In reality, a substantial amount of learning occurs during the third trimester, whether a baby is in or ex utero.


Normal sensory development occurs in a highly programmed, sequential fashion, dependent largely on biologically expected, orderly sensory input. When this input is absent, disordered, or replaced by unexpected stimuli, the result can be abnormal and sometimes permanently impaired development of one or more sensory modalities.15 What follows is a brief overview of how each sensory domain develops in utero as well as how the stimuli differ for infants in the NICU.



Touch and Movement


Touch is the most difficult to describe as a unique sensory modality because elements of movement, pain, temperature sensitivity, and proprioception are all entwined with the tactile experience of the mature individual. Touch is the first sense to develop in the fetus, with reflexive movement to a stimulus seen as early as 8 weeks. Tactile and kinesthetic stimuli are available to the infant throughout pregnancy, and the fetus itself actively initiates such stimulation from a very early stage.


In the NICU, elements of both overstimulation and understimulation can be found, along with randomness and atypical, biologically unexpected stimuli. Taking kinesthetic stimulation as an example, this occurs in utero with the infant in a contained environment, with a liquid-solid interface, and with little influence from gravity. Movements tend to be gentle, often prolonged (as when the mother is walking), and occur with a definite circadian rhythm. In the NICU, however, an infant may spend an extended period of time lying on a flat mattress, interrupted at irregular and unpredictable intervals to be moved suddenly, unnaturally, and sometimes painfully. The NICU infant is constantly “touched” by monitoring devices, indwelling devices, and surfaces that have a much different consistency and impact on the skin than would be experienced in utero. Skin injury is very common in the most premature infants, which may have an additional effect on the sensory experience in the NICU.



Taste and Smell


The senses of taste and smell become functional by 24 to 28 weeks’ postconceptional age19 and soon after reach a level of competence comparable to that of the term infant. Maternal dietary flavors are transmitted to the amniotic fluid and recognized as both flavors and odors by the term newborn, especially in breast milk.16


In the NICU, infants are exposed to a multitude of odors and tastes, mostly unfamiliar and many of them noxious.1 Sometimes, these odors or tastes are associated with other noxious stimuli, and this interaction may affect the infant’s response.10 As with each of the other senses, it seems likely that prolonged skin-to-skin contact with the baby’s mother would mitigate many of these differences between the in utero and NICU environments.



Auditory


The fetus responds to sound by the end of the second trimester,2 and extensive development of the auditory system continues in the third trimester of fetal life. The in utero environment transmits sounds to the fetus through a liquid medium (the amniotic fluid) and, to some extent, through a solid medium as the infant approaches term and remains in more extended contact with the uterus. This environment attenuates sound, especially high-frequency auditory impulses. The sounds experienced by the fetus are primarily those of the mother—both of voice and bodily functions, and it is clear that by term birth, an infant is able to distinguish its mother’s voice from those of other women,7 but not that of its father.8


In the NICU, a cacophony of sounds arrives at the infant’s ear at all hours, transmitted through an air medium that does not attenuate any frequencies. A consistent voice is rarely present, and often, human voices that are meant to be soothing precede and continue through unpleasant stimuli.

Related posts:

  1. Coding and Reimbursement: Principles and Practices
  2. Gastroesophageal Reflux and Gastroesophageal Reflux Disease in the Neonate
  3. Neonatal Apnea and the Foundation of Respiratory Control
  4. White Matter Damage and Encephalopathy of Prematurity

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Jun 6, 2017 | Posted by in PEDIATRICS | Comments Off on The Sensory Environment of the Intensive Care Nursery

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