Development of Cerebral Blood Flow and Oxygenation
As infants grow and develop, cerebral blood flow increases.[23–26] At birth, all infants transition to inhaling oxygen into the lungs and transporting the oxygen by a beating heart to the entire body because the placenta is no longer attached. Decreased pulmonary pressure allows the lungs to inflate, and increased systemic pressure results from increased blood flow.[27] Once the placenta is removed from circulation, an infant must maintain temperature and meet metabolic demands that require two to three times as much oxygen than in utero.[28] Because cerebral blood flow supplies the brain with oxygen and nutrients, cerebral oxygenation is considered an appropriate measurement for cerebral blood flow as long as adequate oxygen can reach the circulation.
Research has shown that cerebral blood flow decreases for approximately the first 2 hours after birth and then remains stable at this low flow for the next 24 hours, although for unknown reasons.[29] After the first day of life, cerebral blood flow gradually increases inconsistently over time possibly because of postnatal growth, increased blood pressure, blood viscosity, or oxygenation.[26] Yet how cerebral oxygenation develops over time is unknown. The fluctuations in cerebral blood flow place premature infants at risk for IVH,[21] particularly in the first week of life, and PVL. As cerebral blood flow increases oxygen delivery to meet higher oxygen demands, cerebral oxygenation will also increase. In addition to changes related to chronological age, significant changes of circulation and adaptation expand. Patent ductus arteriosus,[30] respiratory distress requiring respiratory support,[29] or infection can also effect cerebral blood flow.[31] As a result, cerebral oxygenation levels may continue to change after the first week of life as premature infants continue to stabilize.
NAINR. 2011;11(3):153-159. © 2011 Elsevier Science, Inc.
Cite this: Cerebral Oxygenation Monitoring - Medscape - Sep 01, 2011.
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