I've had three cats, had to let my last little girl go last November.
My fiance has had over a dozen through the years, and she just lost her last one, Tigger, this morning.
Nearly all of them have had some kind of anesthesia at some time and most took 12 hours or more to fully come out of it. My Main Coon, Chester, who left us a year ago, once lost the use of his hind legs for almost a full day, but then recovered. Some vets tend to give a bit more drugs than really needed simply because it is such a real hassle if the animal starts to come out of it during the procedure.
DO monitor your guy, though and there should be a 24-hour emergency vet somewhere you if things start to go downhill. Good on you for taking care of him in his time of need. People who are kind to animals are my kind of people. I would like to meet whoever kicked him in the face.

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