system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When surgeons perform a "36 hour operation" what exactly are they doing?

What exactly are they doing the entirety of those hours? Are they literally just cutting and stitching and suctioning the entire time?  Do they have breaks?
gpt
different doctors and different teams takes turns working on the patient, while others rest. 

Much like in construction, it takes different specialties to do different things. Neurosurgeons stitch together the nerves or separate brain tissue, vascular surgeons cut or reconnect the blood vessels, GI surgeons deal with intenstines, orthopedists deal with bones and joints, oncologist might check things for cancer tumors if that's a concern, etc.

36 hours is not a routine procedure, they might find something unexpected, and then take the time to consult another specialist, or bring in imaging machine to get a better idea of what's going on. 

They might restore blood flow to one part of the body, then wait a bit to see if all works as intended, then proceed to the next part.