I'm a medical student, we are assured that the hospital can't bill for us. It would be enlightening to see an itemized bill showing that our presence is actually billed for. I've never heard of it happening so I think proof is warranted.
If I remember correctly, the hospital did not bill for him, he billed us separately, but the Hospital condoned this. I'm sure we agreed to it somewhere in the fine print. I'm not trying to vilify student doctors here, I understand 99% of the time they are not billing. But after this experience, we ask.
Ah gotcha. He wasn't a medical student then, most likely a resident. Residents are doctors though, if they perform a service such as anesthesia or other procedure they will likely bill.
For example, an Anesthesia resident will perform all of the procedures and monitor the patient's vital signs and response to the general anesthetics or other drugs. The Attending physician only intermittently checks on the case if the resident needs help or the case becomes too complicated.
If the resident doesn't bill for services performed, such as central line, placement, peripheral line placement, intubation, arterial lines, etc. I'm not sure who would do the billing.