1099 for CRNA

Are they providing services to your employees, or is your business a health care related business and they are helping you to deliver this services?

If the latter, then I would think that you would issue them a 1099-NEC, because they are "in the business" of providing certain services, and they need to be able to declare income, expenses, and calculate self-employment taxes.

Box 6 is for amounts you, the employer, spend on your employees in regards to health care (like paying for an HRA).

The CRNA are subcontractors.  The business provides anesthesia services.  From what I have researched - Box 6 applies to medical and healthcare payments that you paid to doctors, nurses or other healthcare professionals as  part of your business.

It says on the instructions to Form 1099-Misc, report in box 6 payments to "other supplier or provider of medical or health care services." Anesthesia services would seem to apply here, so it would be appropriate to use the Form 1099-Misc.