Abstract
BACKGROUND: Sick preterm infants are often on inotropic medication to maintain mean arterial blood pressure (MAP). The effect of inotropes on cerebral oxygen metabolism 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 to measure CVSO2 and cerebral blood flow (CBF), we aimed to compare cerebral oxgyen consumption (CMRO2) between normotensive infants and those who were on inotropes.
METHOD: Twenty-nine infants born at median (range) gestational age of 26 (24–30) weeks were studied at median postnatal age of 17 (2.4–77) hours. Nineteen infants were normotensive (NT) and ten were on inotropes (INO, dopamine) for hypotension. Using NIRS (Hamamatsu NIRO-500), replicate measurements of CBF and CVSO2 were grouped into 20-minute bins and averaged. CMRO2 was determined by CBF and cerebral oxygen extraction (CMRO2 = CBF x cerebral arterial minus venous oxygen content).
RESULTS: CMRO2 was lower (p<0.05) in the INO infants compared to NT infants, with median (IQR) of 0.63 (0.46–0.95)ml/100g/min and 0.85 (0.74–0.96)ml/100g/min respectively. CVSO2 was higher in the INO infants compared to NT infants (p<0.05), implying less cerebral oxygen extraction in INO infants. There was no significant difference in MAP and CBF between the NT and INO groups. CBF positively correlated with CSVO2 (r=0.61, p<0.001) in NT infants. In contrast, no correlation existed between CBF and CSVO2 in the INO infants.
CONCLUSION: Infants on inotropes have lower CMRO2, lower cerebral oxygen extraction, and uncoupling of cerebral perfusion and oxygen extraction. The aetiology of the lower cerebral oxygen demand in these infants and its relationship with the initial hypotension remain to be clarified.
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Wong, F., Barfield, C. & Walker, A. 421 Preterm Infants on Inotropes Have Lower Cerebral Oxygen Consumption Measured by Near Infrared Spectroscopy. Pediatr Res 58, 426 (2005). https://doi.org/10.1203/00006450-200508000-00450
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DOI: https://doi.org/10.1203/00006450-200508000-00450