Decreased respiratory tolerance from intermittent asphyxia in rat sucklings.

To study the respiratory tolerance of rat pups to intermittent asphyxia induced by exposure to closed rebreathing, we randomized newborn rats from four litters into two treatment groups. Respiratory tolerance was defined as the time interval during asphyxia until the first episode of 30 seconds of apnea. Rats in the experimental group were asphyxiated once daily during the first 4 days of life. Rats in the control group were asphyxiated once on day 4 of life. Pups exposed to intermittent asphyxia had a significant reduction in respiratory tolerance compared with that of littermates asphyxiated once at the same age. These findings suggest that the ability of the young mammal to withstand re-exposure to asphyxia may be impaired.

The adverse effects of high oral osmolal mixtures in neonates. A review and a study of the osmolality of calcium preparations.

In both animals and humans, there are numerous clinical, physiologic, and morphologic alterations that occur when hypertonic solutions are introduced into the alimentary tract. The most serious adverse effect observed in the human infant is necrotizing enterocolitis. A short in vitro study analyzing osmolalities of drug-formula mixtures at various dilutions, conducted by the authors, showed that an unacceptable degree of high osmolality may be achieved in the preparation of common medications used in newborn nurseries. Although review of the literature confirms that, in general, the osmolalities of mixtures fed to newborns should not exceed 460 mOsm/kg H2O, lower levels would be preferable in ill and low birth weight newborns. When possible, consideration should be given to the use of parenteral medication for the critically ill neonate. Ideally, the osmolalities of mixtures fed to newborns should be measured if they are not known or cannot be calculated.

Impact of intermittent prolonged asphyxia in rat sucklings on growth and development.

Each of four litters of newborn rats was categorized first by sex and then within each litter, each sex-specific group was randomized into three treatment groups: an experimental (asphyxiated on 4 consecutive days from birth), a partial control (asphyxiated once on the fourth day of life), and a control group (never asphyxiated). Asphyxiation was carried out by enclosing pups individually in air tight fixed volume jars until they attained 30 second apnea. Weight and physical and reflex development of the rat pups were assessed daily. The data was analyzed by using ANOVA and ANCOVA to adjust for birth weight.