Hyperoxia in pediatric cardiopulmonary bypass patients is associated with adverse effects, including reoxygenation injury, increased mortality, heightened inflammatory response, and cerebral injury. Although prior research has demonstrated a correlation between these adverse effects and hyperoxia during cardiac surgery, definitions of “hyperoxia’ vary across the literature. This scoping review synthesizes findings from PubMed, CINAHL, Embase, and Web of Science to categorize the adverse effects of hyperoxia based on age range, presence of cyanosis, and PaO₂ levels. The results highlight the need for standardized oxygenation management protocols in pediatric bypass procedures and a consistent definition of “hyperoxia” for cyanotic and acyanotic patients.