Don't know how far in advance you had to make the appointment, but if there is time, you may want to consider the Composure Chews for him. They have a safe calming effect on dogs and cats, meant to be used for groomer and vet visits, among other things. You can get them from Amazon.com

Either way, thinking good thoughts for the vet visit!

http://www.vetriscience.com/composur...dogs-MD-LD.php

http://www.vetriscience.com/sellshee...re%20Chews.pdf

A calming support formula recommended for pets exposed to increased environmental
stressors.
When pets can’t adapt to stress it can lead to anxiety, nervousness, hyperactivity,
frayed nerves, abnormal urine marking, excessive scratching, trembling or
shivering, and destructive or aggressive behavior.
Recommended for:
 Changes to environment
 Company or parties
 Veterinary or grooming visits
 Boarding or holidays
 Boredom or separation anxiety
 Moving or traveling
 Fireworks and thunderstorms