[Changes in vegetative parameters during and after normobaric hypoxic hypoxia in newborn rabbits]

68 awake spontaneously breathing newborn rabbits were investigated in five series; 43 animals were exposed to a hypoxic atmosphere (FiO2 = 0.05) for 3 h during the 1st day of life. Heart rate, rectal temperature and intracranial pressure were recorded. Arterial blood samples were analyzed for pO2, ASTRUP-values, glucose and lactate content; O2-saturation was calculated. The vegetative situation at the end of the hypoxic period was characterized by low heart rate, low body temperatures (less than or equal to 25 degrees C), reduced glucose concentration and a lactate acidosis, compensated by low pCO2 (less than 2 kPa). At the 2nd posthypoxic day all parameters were normalized. If CO2-gas (FiCO2 = 0.05) is added to the hypoxic atmosphere (normocarbic pCO2-values in the arterial blood), the glucose and lactate content remained on the normal level; the diminution of heart rate and rectal temperature was smaller. Under the conditions of severe hypoxia in contrast to the adult rabbits the newborns are able to maintain their life processes for a longer time, but this fact need not be identical with the prevention of posthypoxic brain damage. In the cases of normocarbic pCO2-values, the hypoxic tolerance was elevated in the way of improved O2-delivery to the tissues.