Siamese cat biting and scratching.

Question
Hello Becky, This morning I had Co-Co our 4yr10m old siamese to the vets for his claws to be clipped. I held him whilst the vet cut his nails.
I brought him back home and went back to work, when I got home about 5.30 this evening, Coco allowed me to stroke him as gentle as always then he started sharpening his claws on the furniture and I said "No you bad cat!" in a slow low pitched voice.  Coco allowed me to stroke him and then he started to grab my arm, scratching and clawing and he has bitten me and drawn blood.  I am naturally very upset by this incident as Co-Co is soft as muck, and we can do all sorts with him and he loves it.I would really be grateful for some kind of illumination on his behaviour.
I have had siamese cats for years and my last cat Quinn died two years ago at the age of 21yrs. Coco doesnt appear to be stressed as he is not spraying or chewing wool, he is very happy, but obviously I have done something to upset him, and all I can think of is the travel in the car to the vets, the appointment, his claws clipped and then the return journey home.  Incidentally I am a receptionist in a small animal veterinary surgery.
Would you be so kind as to reply as soon as you are able please as I need my mind putting at ease.
Kind regards-Kim

Answer
Hi Kim!

I think you hit the nail on the head. It sounds like he is quite upset about his little trip to the Vet today.  Cats do not like change, and Siamese especially are very prone to showing their displeasure.  I think he was still a bit peeved and took it out on your arm!  

By the way, do you have a scratching post?  Cats do need something to scratch on.  My cats use a floor to ceiling model and NEVER scratch on my furniture.  Just thought I'd suggest that.

I really think by tomorrow he will be back to his old self.

God Bless,
Becky