He's at work. He's the person controlling the flow of pharmaceuticals into the person being operated on, and at any moment things could go horribly wrong because of the surgeon, the nursing staff, dumb luck, or nature. There are times to text and there are times not to text. An operating room absolutely belongs in the latter category.
The length of time an operation might take is immaterial. He was on the clock while a person's life was effectively in his hands. If he's texting, or looking at pictures of his kids, or signing up on a charity list to feed orphans in the war torn regions of the world, then he's not doing his job. Period. There is a reason malpractice insurance exists, and this guy is seriously raising the rates.
But hey, it's not like anyone died, right? Let's forget it and move on, because personal and professional responsibility isn't what this is all about.