Surgeon allegedly bashed at Melbourne hospital may be left with 'devastating' brain damage.

The surgeon who was allegedly bashed at a Melbourne hospital on Tuesday night faces serious brain damage if he survives the assault, a colleague has claimed.

Heart surgeon Patrick Pritzwald-Stegmann was working at Box Hill Hospital when he was allegedly hit from behind by a man he’d reportedly told to stop smoking in a non-smoking area on the premises.

The father of two is now in a critical condition with a “devastating” brain injury, according to Royal Australasian College of Surgeons chair of trauma Dr John Crozier.

"The probability of death from a single punch, I think, is very high at this stage," Dr Crozier tells the Daily Mail Australia.

If Dr Pritzwald-Stegmann does survive, Dr Crozier believes it is "almost certain" he will never work again as a doctor.

"This is the point of greatest potential in a surgical career. This is a devastating tragedy on so many planes."

On Wednesday night, a 22-year-old man was arrested and questioned by police about the one punch assault and is expected to appear in Melbourne Magistrates Court later on Thursday.

The Australian Medical Association has condemned the attack, saying violence has become a common occurrence in hospitals.

"You should be able to turn up to work and not be abused, threatened or assaulted," president of AMA Victoria Lorraine Baker said in a statement.

Dr Pritzwald-Stegmann is married to a Melbourne lawyer, and the couple has two daughters.

With AAP.