Probably brain reversible hypoxia
your child EEG report shows that there is no evidence of epileptics seizure
Second, those alpha and especially theta wave shows for brain hypoxia
due to strong metabolic changes or infections.
can help to exlude infections.I think the cause of that situation can be hypoxia which is reversible.
I would recommend to be carefull and monitore hemodynamics parameters ( such as blood tension, oxygen saturation
Those changes will needs time to disappear , so no further EEG is needed at least for one week.
It is reccomended that a brain MRI is done to see for brain edema
Anyway as you baby is stable now I don't think you have reason to worry because things will go better hours after hours!
Wish my answer had helped you,
Don't hesitate to contact for further questions
Dr Eris Ranxha