Cerebral intra and extra cellular calcium concentrations in asphyxiated rat fetuses resuscitated with oxygen of different concentrations

Abstract:

OBJECTIVE: To investigate the effects of resuscitation using oxygen of three concentrations on changes of cerebral intraand extracellular calcium, sodium and potassium in asphyxiated fetal rats. METHODS: Fifty-six fetal rats of twenty-day gestational age were randomly divided into five groups: sham operation (control, n=11), room-air resuscitation (n=10), and oxygen-resuscitated group Ｉ, Ⅱ, Ⅲ (n=14, 11, and 10 respectively) of different oxygen-inhaled concentrations and different oxygen timings. The fetal rats in the latter four groups suffered from ischemia and hypoxia in-uteri resulting from interruption of placental circulation. After recirculation, intra- and extra-cellular concentrations of calcium, sodium, and potassium in the brains were measured in each group. RESULTS: Intracellular free calcium concentrations of fetal rat brains in the room air resuscitation group and the oxygen-resuscitated group I (oxygen-inhaled concentration was 92.8%) were (552.08±93.50) nmol/L and (520.61±79.08) nmol/L respectively. They were similar and both significantly higher than those in the control (315.27±86.88) nmol/L (P<0.01). After resuscitation with 65% oxygen, no matter whether it started before (group Ⅱ) or at the beginning of hypoxia (group Ⅲ), their intracellular free calcium concentrations ［(441.46±47.93) nmol/L and (452.93±36.38) nmol/L respectively］ were significantly lower than those in the room-air resuscitation group (P<0.01) and group I (P<0.05), though still higher than those in the control. There was generally no difference in the total concentrations of calcium, sodium, or potassium among all groups. CONCLUSIONS: Resuscitation with oxygen of different concentrations produced different results: Resuscitation with 92.8% oxygen or room air had a similar effect on the parameters measured, indicating that resuscitation of asphyxiated neonates using pure oxygen might not be superior to that using room air; With lower cerebral intracellular calcium concentrations, resuscitation with 65% oxygen might produce a better outcome compared with that using pure oxygen or room air.