Optimal oxygenation of the newborn

Oxygen therapy for newborn infants was introduced in the United States in the 1930s to improve respiratory pattern and to reduce a purported risk of brain damage caused by unrecognized oxygen lack. Post World War 2 incubators were built to maintain high oxygen concentration. Not before the discovery of its relation to retrolental fibroplasia (retinopathy of prematurity, ROP) were questions raised concerning the use of oxygen. in the 1970s the transcutaneous oxygen electrode and in the 1980s pulse oximeters were introduced in neonatal intensive care units and many believed the problems related to oxygen toxicity in the newborn nursery could be eliminated or at least reduced. Although it has been acknowledged for 5 decades that oxygen might be harmful to premature infants it is stili possible that toxic reactions of oxygen are underestimated. in my opinion it is clear that we have a number of unanswered questions. A simple one is to define the normal oxygen saturation in the earliest newborn period. İt has for instance been shown that in very low birth weight infants with gestational age < 30 weeks and weighing < 1000 gram in order to keep SaO2 between 50 and 90% the PaO2 should be kept between 2.5 to 5.5 kPa (18-41 mm Hg). A reasonable paO2 to aim at therefore seems to be around 5.5 kpa, which probably is lower than in most centers.
A recent study from UK by Tin et al indicates that the optimal arterial oxygen saturation of extremely premature infants the first weeks of life perhaps is not known. The normal saturations in term and preterm infants in the first week of life which previously has been identified between 93-100% but this is probably not applicable to the extremely low birth weight infants. The optimal arterial oxygen saturation of growing extremely premature infants is also not known. Existing recommendations are probably valid for the more mature premature infants only. Therefore new recommendations are needed for the most extreme premature infants for instance with gestational ages between 23 and 27 weeks. These infants should perhaps be nursed with lower oxygen saturations than usecl by most nurseries today, at least the first few days of life. Data accumulate indicating that even a hyperoxic exposure during a few minutes after birth may increase the oxidative stress for weeks. Because oxidative stress influences apoptosis and cell growth, this may have long-term consequences on growth and development, and further studies should clarify whether such therapy is carcinogenic as well.

Anahtar Kelimeler

-