Carboxyhaemoglobin levels and free-radical-related diseases in prematurely born infants

Background: Carboxyhaemoglobin (COHb) levels may reflect the level of early oxidative stress which plays a role in mediating free-radical-related diseases in prematurely born infants. Aim: To assess the relationship of COHb levels in the first seven days of after birth to the development of bronchopulmonary dysplasia (BPD) and other free-radical-related diseases. Study design: Retrospective analysis of routinely performed COHb via blood gas samples of infants born at less than 30 weeks of gestation admitted to a tertiary neonatal intensive care unit was undertaken. Subjects: One hundred and four infants were included with a median (range) gestational age of 27.4 (22.4–29.9) weeks and a birthweight of 865 (395–1710) grams. Outcomes: The maximum COHb per infant per day was recorded for the first 28 days and BPD and other free-radical-related diseases including intraventricular haemorrhage (IVH) were noted. The severity of BPD, requirement for home oxygen on discharge and survival to discharge were also recorded. Results: Infants who developed BPD (n = 76) had significantly higher COHb levels in the first seven days [1.7% (0.3–6.8)] compared to those that did not develop BPD [1.6% (0.9–3.8); p = 0.001]. Higher COHb levels in the first seven days after birth were also observed in infants with grade three/four IVH [n = 20; 1.9% (1.0–6.8)] compared to those without [1.6% (0.3–5.6); p < 0.001]. COHb levels, however, were not associated with the duration of ventilation, BPD severity or survival to discharge. Conclusion: Higher COHb levels in prematurely born infants were associated with the development of BPD and IVH.