Carbon dioxide and retinopathy of prematurity in extremely low birth weight infants

Objective: To evaluate the relationship between partial pressure of carbon dioxide (PCO₂) during the first 3 days of life and retinopathy of prematurity (ROP) in extremely low birthweight (ELBW) infants.Patients and methods: A retrospective evaluation of data on ELBW infants were collected over a period of 4 years. Data during the first 72 hours of life was divided into six, 12-hour epochs. The average highest and overall means of PCO₂, PO₂, FiO_2, and glucose were calculated for each epoch. Logistic regression analysis was used to determine the association between PCO₂ and ROP after controlling for covariables.Results: A total of 78 neonates were included: birth weight (BW) (703 ± 157 g) and gestational age (25 ± 1.4 weeks). A total of 45 out of 78 had ROP: stage 1 (N = 8), stage 2 (N = 26), stage 3 (N = 14), and plus (N = 4). The overall mean PCO₂ correlated with ROP in the first 72 hours of life (R = 0.31, p = .0069). This correlation was significant in epochs 2 (p = .049), 4 (p = .008) and 6 (p = .038). The average of the highest PCO₂ also correlated with ROP in the first 72 hours of life (R = 0.38, p = .0007). This correlation was significant in epochs 2 (p = .0115), 4 (p = .0011), 5 (p = .028) and 6 (p = .037). The correlation between the stage of ROP and PCO₂ was significant after controlling for PO₂ and glucose concentrations. Other variables that correlated with ROP were the overall means of FiO₂ (R = 0.23, p = .04), PO₂ (R = 0.39, p = .0005) and glucose (R = 0.39, p = .0004) as well as the average highest concentrations of FiO₂ (R = 0.26, p = .025), PO₂ (R = 0.38, p = .0008) and glucose (R = 0.34, p = .007).Conclusion: After controlling for confounding variables, ROP correlated with the overall means and average highest PCO₂. ROP also correlated with FiO₂, PO₂ and glucose concentrations. Further studies are needed to define the safe PCO₂ range and the effect of PCO₂ on the normal development of the retina.