Four times general anesthesia here, two of them in the last three month and am still smart enough for university
I know someone who had a terrible accident with his motorcycle and his leg ripped off and shredded.
He has had eighteen, yes, eighteen surgeries for reconstruction under general anesthesia within about three years and he seems pretty smart to me.
He once mentioned that some minor traces from one general anesthesia would remain in a human's body for about one year and that he had accumulated the maximum save amount, so he had to wait for more surgeries for some time.
I don't know if the chemicals used for general anesthesia are much different in other countries, but at least that's how it is in Germany.