Cerebral excitatory amino acids and Na+, K+-ATPase activity during resuscitation of severely hypoxic newborn piglets

We tested the hypothesis that early brain recovery in hypoxic newborn piglets is improved by resuscitating with an O₂ supply close to the minimum level required by the newborn piglet brain. Severely hypoxic 2-5-d-old anaesthetized piglets were randomly divided into three resuscitation groups: hypoxaemic (n = 8), 21% O₂ (n = 8), and 100% O₂ groups (n = 8). The hypoxaemic group was mechanically ventilated with 12-18% O₂ adjusted to achieve a cerebral venous O₂ saturation of 17-23% (baseline; 45±1%, mean±SEM). During the 2h resuscitation period, extracellular aspartate and glutamate concentrations in the cerebral striatum were higher during hypoxaemic resuscitation (p = 0.044 and p = 0.055, respectively) than during resuscitation with 21% O₂ or 100% O₂, suggesting an unfavourable accumulation of potent excitotoxins during hypoxaemic resuscitation. The cell membrane Na⁺,K⁺-ATPase activity of cerebral cortical tissue after 2 h resuscitation was similar in the three groups (p = 0.30). In conclusion, hypoxaemic resuscitation did not normalize early cerebral metabolic recovery as efficiently as resuscitation with 21% O2 or 100% O₂. Resuscitation with 21% O₂ was as efficient as resuscitation with 100% O₂ in this newborn piglet hypoxia model.