Red Cell Distribution Width and RDW-to-Platelet Ratio Patterns Across the Spectrum of Hypoxic-Ischemic Encephalopathy

Background: Red cell distribution width (RDW) and the RDW-to-platelet ratio (RPR) have emerged as readily available hematologic markers reflecting systemic inflammation in neonates with hypoxic-ischemic encephalopathy (HIE); however, their early postnatal trajectories across the clinical spectrum of HIE remain insufficiently characterized. Methods: This retrospective cohort study included 229 term or near-term infants diagnosed with HIE. Among them, 166 infants received therapeutic hypothermia, whereas 63 infants who did not undergo cooling served as the reference group. RDW and RPR values were measured at birth and at 72 h of life (after completion of cooling in the hypothermia group). Results: In the reference group, RDW values significantly decreased at 72 h, reflecting normal postnatal hematologic adaptation. In contrast, the hypothermia group demonstrated a blunted decline, with RDW levels remaining relatively stable over the first 72 h, consistent with a blunted early postnatal RDW decline. RPR values showed a mild, non-significant upward trend during the first 72 h of life; however, exploratory analyses suggested an association between higher RPR levels and increasing HIE severity. Conclusions: Across the spectrum of hypoxic-ischemic encephalopathy, RDW demonstrated a blunted postnatal decline, whereas RPR showed a mild, non-significant increase during the early neonatal period. These readily available hematologic markers may provide complementary insights into early systemic inflammatory and hematologic responses in HIE. Prospective multicenter studies are needed to determine their prognostic value and relationship with clinical and neurodevelopmental outcomes.