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423 Cerebral Oxygen Delivery and Consumption Increase with Postnatal Age in Preterm Infants on Inotropes

BACKGROUND: The effect of inotropic medication on cerebral oxygen metabolism of preterm infants remains unknown. We recently validated the method of Near Infrared Spectroscopy (NIRS) combined with partial jugular venous occlusion to measure cerebral venous saturation (CVSO2) in the newborn lamb brain (separate abstract). Using NIRS, we studied normotensive infants (NT) and infants who were on inotropes (INO, dopamine) for hypotension, and compared their cerebral oxygen delivery (CDO2) and consumption (CMRO2) in the first few days of life.METHOD: Nineteen infants in the NT group and ten infants in the INO group, born at median (range) gestational age of 26 (24–30) weeks, were studied at median (range) postnatal age (PNA) of 17 (2.4–77) hours. Using NIRS (Hamamatsu NIRO-500), cerebral blood flow (CBF) and CVSO2 were measured to compute CDO2 (CDO2 = CBF x cerebral arterial oxygen content), and CMRO2 (CMRO2 = CBF x cerebral arterial minus venous oxygen content).RESULTS: In INO infants, CDO2 increased with PNA (r=0.7, p<0.001), but not so in NT infants. Similarly, CMRO2 in INO infants increased with PNA (r=0.6, p<0.01), but not so in NT infants. Before PNA of 24 hours, median (IQR) CDO2 and CMRO2 in INO infants were 2.0 (1.6–2.4)ml/100g/min and 0.5 (0.4–0.9)ml/100g/min respectively, both lower (p<0.05) than the CDO2 and CMRO2 in NT infants (2.7 (2.3–3.1)ml/100g/min and 0.8 (0.7–1.0)ml/100g/min respectively). However, after PNA of 24 hours, no significant difference in CDO2 and CMRO2 was found between the two groups. There was no difference in cerebral oxygen extraction ((arterial saturation-CVSO2)/arterial saturation) between the two groups at any PNA, implying the increase in CMRO2 in INO infants was not delivery-dependent.CONCLUSION: Infants on inotrope had lower cerbral oxygen delivery and consumption in the first day of life, which increased with postnatal age to equate values in normotensive infants.