Association of Day-1 Hemoglobin Oxygen Affinity (p50) with Severe Intraventricular Hemorrhage in Preterm Infants.

OBJECTIVE

The partial pressure of oxygen at which hemoglobin is saturated at 50% (p50) reflects the balance between oxygen loading and tissue unloading. This study was conducted to ascertain if a lower p50 is linked to a greater incidence of severe intraventricular hemorrhage (IVH) in preterm infants.

METHODS

This retrospective cohort study included very preterm infants (≤ 32 weeks' gestation) admitted to the neonatal intensive care unit between January 1, 2020 and December 31, 2023. p50 was obtained from the first arterial blood gas, measured within 12h after birth. IVH was graded using cranial ultrasonography according to the Papile classification; severe IVH was defined as grades III-IV. Multivariable logistic regression models adjusted for gestational age, sex, early-onset sepsis, and invasive ventilation exposure were used to ascertain role of hemoglobin p50 for predicting severe IVH in very preterm infants.

RESULTS

Out of 290 eligible infants [mean (SD) gestational age: 28.4 (2.6) weeks; mean (SD) birth weight: 1210 (365 g], 230 (79%) had no IVH, 26 (9%) had mild IVH, and 34 (12%) had severe IVH. The median day-1 p50 decreased with increasing IVH severity (no IVH: 21.5 mmHg; mild IVH: 18.7 mmHg; severe IVH: 16.0 mmHg; P < 0.001). In adjusted models, lower day-1 p50 was independently associated with severe IVH (adjusted odds ratio 1.38 per 1 mmHg decrease; 95%CI 1.09-1.82; P = 0.012).

CONCLUSIONS

Lower day-1 p50 is independently associated with severe IVH in very preterm infants.