Is it a HIPPA violation for a supervisor to require that I give 48 hours advance notice as well as obtain his express approval before I can go to a medical appointment?

No, it sounds like merely standard company policies, to get permission before taking off work

HIPAA (not HIPPA) "... protects the privacy of individually identifiable health information; the HIPAA Security Rule, which sets national standards for the security of electronic protected health information; and the confidentiality provisions of the Patient Safety Rule, which protect identifiable information being used to analyze patient safety events and improve patient safety."

This has nothing to do with advance notice and approval for medical appointments.

Do you have an employment contract or belong to a Union?

No violations with HIPAA, but you may want to see what your company policy requires.

I know unless it is a emergancy, the company I work for, we are often booked ( scheduled) for a week or more in advance, so we need to often give a week or more notice for anything but something that just comes up and is seroius enough to keep us out of work

I think you just need to give adequate notice before an appointment ( any appointment ) just to make sure that your position will be covered for the length of time you are at your appointment.

This is pretty standard in what ever job you do.Personal details of your appointment are exactly that... personal