Cerebral tolerance of hypoxia in growth-retarded and appropriately grown newborn guinea pigs.
To elucidate if there is a reduced perinatal tolerance of hypoxia in growth retardation and approach its pathophysiologic background, newborn guinea pigs of different weights were subjected to standardized hypoxia. Intrauterine growth retardation was induced through uterine artery ligation. After spontaneous delivery experiments were performed within 2 days. After stabilization, hypoxia of stepwise increased severity was instituted. Blood gases, metabolic, cardiovascular, and neurophysiologic [somatosensory-evoked potentials (SEP)] parameters were monitored. A control series in which equally large blood samples were taken at the same intervals was performed. The animals were grouped according to birth weight: greater than or equal to 101 g (n = 10, 12), 71-100 g (n = 11, 10), and less than or equal to 70 g (n = 8, 3) (hypoxic and control series, respectively). Basal SEP latencies did not differ between the groups. Under hypoxia, both the amplitude of the SEP and the time to complete loss of the SEP was reduced in proportion to the degree of growth retardation. The differences between all groups were significant. The animals in the control series did not change their SEP performance significantly. Slight differences in metabolic and cardiovascular parameters between the groups were found not likely to explain the differences in SEP performance. Therefore, it is concluded that a reduced cerebral tolerance of hypoxia prevails in growth-retarded newborn guinea pigs and that this is related to changes in the brain itself. It is also concluded that a relationship exists between the degree of growth retardation and that of reduced cerebral hypoxia tolerance.
Thordstein
M
M
Department of Physiology, Gothenburg University, Göteborg, Sweden.
Kjellmer
I
I
D000818:Animals; D001724:Birth Weight; D001921:Brain / Q000196:embryology* / Q000503:physiopathology; D005073:Evoked Potentials, Somatosensory; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology*; D005865:Gestational Age; D006168:Guinea Pigs; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D011247:Pregnancy