Is it a good idea to Anaesthetise your koi when doing a scrape to check for parasites?

Some people say it is important because you prevent injuries to the koi and you have more time to do the job in a relaxed atmosphere without the fish jumping up and down, especially when you are a newbie.

On the other hand, why put the fish under stress of Anaesthetics if you could do a quick scrape and release the fish immediately.

More important, some people say that anaesthetics may also dose the parasite and you will have trouble seeing it because it might lay still or might even be killed by the Anaesthetics?

What is your opinion?