I'm thinking it's the sedation also. Once it's cleared out of his system, he should get back to his happy self.

When my husband had surgery, he awoke from the anesthesia laughing and joking. The nurses said that his reaction to the medicine was great because some people wake up yelling and screaming and they also said they had learned to be very fast on their feet because some patients wake up swinging fists in every direction! Maybe kitties have similar reactions ??