The Development of Cerebral Oxygenation in Premature Infants
This dissertation recruited 24 premature infants born less than 32 weeks gestational age over a one year time period from October 2010 to 2011. The goals were to longitudinally measure cerebral oxygen saturation, evaluate how environmental variables controlled by nursing, positioning and noise, affect cerebral oxygen saturations, and examine the relationship between cerebral oxygen saturation and two currently measured vital signs.
Using mixed general linear models, findings from this dissertation showed the developmental trajectory of cerebral oxygen saturation values in premature infants' began in the high 70s during the first two days of life and then significantly decreased into the mid-60s over several weeks during hospitalization in a neonatal intensive care unit (NICU). The trajectory of cerebral oxygen saturation during the first week of life in those infants who developed an IVH did not significantly differ from those infants without IVH. At this time, use of cerebral oxygen saturation to identify those infants at risk for IVH during the first week of life cannot be supported, but findings may indicate that cerebral oxygen saturation monitoring could potentially monitor the severity of the impact of IVH later during hospitalization as those infants with an IVH had significantly lower cerebral oxygen saturation values after the third week of life. In this case, cerebral oxygen saturation might help to understand the long-term degree of neurological damage.
Heart rate and peripheral oxygenation were chosen as the two physiologic variables to compare to cerebral oxygen saturation and average cerebral oxygen saturation was lower with higher heart rate and higher with higher peripheral oxygenation. Peripheral oxygenation that is already routinely measured in premature infants appears to not provide an accurate measure of the changes in cerebral oxygen saturation. Cerebral oxygen saturation monitoring is highly suggested for those infants who are at risk for neurological damage such as infants with hypoxic-ischemic encephalopathy or seizures since peripheral oxygenation does not appear to be an appropriate proxy for cerebral oxygenation.
Finally, sound and positioning were chosen to represent two frequently encountered components of the neonatal intensive care environment that also influence infant cerebral oxygen saturation. A peak in sound from the ambient sound level was only 5 decibels and found to not significantly affect cerebral oxygen saturation values. A neutral position considered the gold standard-- supine, head midline--was compared to five other positions widely used by NICU nurses. However, results showed positions with a turned head did not significantly change cerebral oxygen saturation from the neutral position. Yet, differences in cerebral oxygen saturation were found between two lateral positions (left lateral and right lateral, head elevated 15°) with an elevated head measuring lower cerebral oxygen saturation levels.
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