Effects of antenatal magnesium sulfate treatment for neonatal neuro-protection on cerebral oxygen kinetics

BACKGROUND: The underlying neuro-protective mechanisms of antenatal magnesium sulfate (MgSO₄) in infants born preterm remain poorly understood. Early neonatal brain injury may be preceded by low cerebral blood flow (CBF) and elevated cerebral fractional tissue oxygen extraction (cFTOE). This study investigated the effect of antenatal MgSO₄ on cerebral oxygen delivery, consumption, and cFTOE in preterm infants. METHODS: CBF and tissue oxygenation index were measured, and oxygen delivery, consumption, and cFTOE calculated within 24 h of birth and at 48 and 72 h of life in 36 infants ≤ 30 wk gestation exposed to MgSO₄ and 29 unexposed infants. RESULTS: Total internal carotid blood flow and cerebral oxygen delivery did not differ between the groups at the three study time-points. Cerebral oxygen consumption and cFTOE were lower in infants exposed to antenatal MgSO₄ (P = 0.012) compared to unexposed infants within 24 h of delivery. This difference was not evident by 48 h of age. Fewer infants in the MgSO₄ group developed P/IVH by 72 h of age (P = 0.03). CONCLUSION: Infants exposed to MgSO4 had similar systemic and cerebral hemodynamics but lower cFTOE compared to nonexposed. These findings suggest reduced cerebral metabolism maybe a component of the neuro-protective actions of antenatal MgSO₄.Michael J. Stark, Nicolette A. Hodyl and Chad C. Anderse