Can a heartrate quickly and dramatically change during surgery?

Yes, of course especially if a patient is having a cardiac arrest.

It depends on what caused the heightened rate to begin with. If it is something that is immediately removed, rather than wearing off over time, you can see a sudden change in heart rate. And normal laws of physics and medicine don't apply to Jack Bauer, after all, he is the only person who can survive nerve gas that kills on skin contact OR inhalation simply by putting the hood up on his hoodie.

Oops. My mistake. Wrong Jack. Guess I don't know Jack.

@hossman Who cares, I laughed anyway.

Surgery is the science of cutting into people and as we all know science makes ANYTHING possible. So yeah, it could happen. Does it happen? Has it happened? Mayhaps. Seriously though, the fact that it’s surgery makes the answer pretty obvious. You could cut half the tendons and if he’s under just the right amount of anethesia all that would do is cause the heart to beat half as fast, and maybe leak.

Chemicals and brain activity control heart rate so being unconcious would be a factor. Pain, distress and loads of stuff could cause heart rate to increase but there’s just as much chemicals that slow your heart down so again: anything is possible. The sky is no limit, it just turns into space.