Acid–Base Status and Cerebral Oxygenation in Neonates: A Systematic Qualitative Review of the Literature

Introduction Blood gas analysis is utilized to assess parameters of oxygenation and ventilation, including acid–base status [pH value, base excess (BE) or base deficit (BD), and bicarbonate (HCO₃)], to evaluate systemic metabolism status. Acid–base imbalances can have complex effects on the organism, potentially impacting oxygen delivery to tissue. Cerebral oximetry is a non-invasive monitoring technique using near-infrared spectroscopy (NIRS) for the continuous measurement of cerebral tissue oxygenation. The relationship between the acid–base status and cerebral tissue oxygenation in neonates remains unclear. This systematic qualitative review aims to analyze current knowledge of the potential correlations between different acid–base status parameters and cerebral tissue oxygenation measured via NIRS in neonates. Methods: A systematic search of PubMed and Ovid Embase was performed, focusing on cerebral oxygenation, neonates, and acid–base status. Risk of bias was assessed using the ‘‘Risk of Bias for Non-randomized Studies of Exposures’’ (ROBINS-E) instrument. Results: Fifty studies that measured parameters of the acid–base status and cerebral tissue oxygenation in the neonatal period were identified. Seven studies demonstrated a correlation between pH and cerebral tissue oxygenation, while eleven studies found no such correlation. Five studies demonstrated a correlation between the BE/BD and cerebral tissue oxygenation, while six studies found no such correlation. Three studies demonstrated a correlation between HCO₃ and cerebral tissue oxygenation, while five studies found no such correlation. Discussion: Associations between acid–base status parameters and cerebral tissue oxygenation remain controversial. However, studies with the lowest risk of bias mainly demonstrated no significant correlation between any of the acid–base status parameters and cerebral tissue oxygenation.