Dear jackthedog,
Hydrotherapy will not cause tremors, seizures or other central nervous system abnormalities. You need not feel guilty about your efforts to improve Jack's quality of life and reduce any pain.
Twitching may be related to seizure activity in the brain or perhaps a muscle or nerve disorder. It is unlikely to be related to simple arthritis of joints or vertebrae, but may be due to muscle weakness.
Meloxydyl contains the non-steroidal anti-inflammatory drug "meloxicam" and is similar to "Metacam" which is how it is marketed in the US.
You absolutely have not let Jack down. You are geting him the care he needs. You can't stop his aging: just continue to give him the extra care and love he needs now.
If the "palpitations" you see do not resolve you should go back and if able, use your digital camera to film a few seconds of what exactly he is doing so your vet can see for him/herself.
Do let us know how he's doing and good job on doing what you can to help Jack!
Everyone should do as you are doing!
Sincerely,
Arnold L. Goldman DVM, MS
MedHelp & PDOC
I'd recommend videotaping this on your camera to show your veterinarian, so they can find out what exactly is going on. Mild, fine twitching may be a subtle sign for pain, and video of this will help differentiate seizures from heart problems (causing them to be "syncopal" or pass out) vs. fine muscle twitching.