Retinopathy of prematurity: the effects of oxygen saturation targets in at-risk neonates

Retinopathy of prematurity (ROP) is a potentially blinding disorder, known to be associated with preterm birth, low birth weight, and the use of oxygen. An optimal oxygen saturation range of 85-93% is often targeted to minimize the risk of either hypoxia or hyperoxia. Yet maintaining premature infants within the targeted range can be difficult. Many infants spend significant amounts of time both above 93% and below 85%. The potential effect of this time out of the targeted range on the development of ROP and the risk of death is unknown. Using a longitudinal, retrospective, descriptive design, weekly 24-hour histograms of saturation levels were collected during a three year period for each infant at risk for ROP from the time of admission for each infant and coded for the percentage of time spent >93% or ≤ 85%. Data were entered longitudinally until retinal maturity/ROP occurred (N=241ROP study) or until death/discharge (N=250 survival study). Infants were excluded from both studies if ROP was present prior to admission, or death/discharge occurred without an eye exam or data collection. Survival analysis using a discrete-time hazard model was used to explain the risk of developing ROP (Stage 1 or ≥ Stage 2) or death, associated with the time above and below the targeted range, controlling for the effects of gestational age and birth weight using logistic regression. All models included a cubic time trend to reflect the average change in probability of developing ROP, or a quadratic time trend for the risk of death. For every 2.7% of the time the infant spent ≤ 85%, the risk for ROP increased by 48 iv (p<0.038), and the risk of death increased by 11% (p<.001). The percentage of time an infant spent >93% decreased their risk of ROP and death. For every 10% of time spend >93%, the risk of ROP decreased 21%, and the risk of death decreased 11%. These data raise concerns about the appropriateness of current saturation targets. The upper limit of time for saturations >93% to be beneficial remains unknown and needs further research.