I realize that I was mistaken one aspect of this, and apologize to anyone I misled. A provider, not a nurse or MA, has to see the patient in order to bill for a dressing change or suture removal following surgery performed by another practice. This is not due to global surgery rules, but to "incident to" rules, which require (among other restrictions) that a provider in your own practice has assessed the problem and determined the plan of care.
Regarding the global period, CMS is explicit that except in those cases in which two doctors have chosen to arrange a transfer of care, another practice is permitted bill as usual. CMS's Global Surgery Fact Sheet states: "Services of other physicians related to the surgery.... are not included in the global surgery payment... except where the surgeon and the other physician(s) agree on the transfer of care.... Where a transfer of care does not occur, the services of another physician may... be paid separately.... In the same Fact Sheet, they also state: "Where a transfer of care does not occur, occasional post-discharge services of a physician other than the surgeon are reported by the appropriate E/M code. No modifiers are necessary on the claim.... Physicians who provide follow-up services for minor procedures performed in emergency departments bill the appropriate level of E/M code, without a modifier."
I also found an article by Inga Ellzey addressing this: "(Q): What if the patient just comes in for suture removal when the surgery was performed by another practice? Can I bill if the follow-up visit is billed during the postoperative period? How do I bill? Do I use modifiers 54 or 55? (A): Absolutely, you should bill for the services you provide. In most instances, you will not even know what CPT code was billed by the surgeon, how many postoperative days the procedure has, or how many postoperative days remain. Since you are in a different practice, you are not subject to the follow-up or global period of the other provider (eg, performing surgeon). Important: Do not use any modifiers such as 54 or 55 as they are not appropriate for the scenarios discussed above."