Cerebral intracellular calcium concentrations in asphyxiated rat fetuses resuscitated with oxygen.

Objective: To investigate the effects of resuscitation with three different oxygen concentrations on cerebral intra-and extra-cellular calcium, sodium and potassium changes in asphyxiated rat fetuses. Methods: Fifty-six fetal rats of gestational age of 20 days were randomly assigned into five study groups: sham operation group (control, n=11), room-air resuscitation group (n=10), and 3 oxygen-resuscitated groups (n=14), 11, and 10 respectively). Different inhaled oxygen concentrations and different timings of oxygen delivery were assigned. Except for control all fetal rats were rendered ischemic and hypoxic in utero by interrupting the placental circulation. After re-circulation, intra- and extra-cellular concentrations of calcium, sodium, and potassium in the brains were measured for each individual group. Results: The mean intracellular free calcium concentration of fetal rat brains was similar for the room-air resuscitation group (552.1+/-93.5 nmol/L) and the group resuscitated with 92.8% oxygen (520.6+/-79.1 nmol/L), and both were significantly higher than in the control (315.3+/-86.9 nmol/L) (P<0.001). After resuscitation with 65 %, oxygen, be it instituted before or immediately after hypoxia, their mean intracellular free calcium concentrations in the brain cells (441.5+/-47.9 and 452.9+/-36.4 nmol/L respectively) were significantly lower than those in the room-air resuscitation (P<0.01) and 92.8 % oxygen group (P<0.05), though still higher than in the control (P>0.05). There was no difference in the total concentrations of calcium, sodium, or potassium among all groups. Conclusion: Resuscitation with 92.8 % oxygen or room air exerted a similar effect on the parameters measured, indicating that resuscitation of asphyxiated neonates using 100% oxygen might not be superior to using room air. Resuscitation with 659% oxygen resulted in lower cerebral intracellular calcium concentrations and might produce a better outcome than using 100 % oxygen or room air.