We would recommend doing the hydrafacial first, and then waiting a few days to have the prp. The reason is that while the hydrafacial is not invasive in any way, with all of the suction and the acids used in the treatment, it would be best to give the skin a short break before adding on additional treatments.
You could complete both treatments , HF & MN @ the same appointment time. However for the optimum results I would recommend doing the PRP MicroNeedling 1st , then follow up with a relaxing calming HydraFacial about 7-10 days post PRP . This will also allow the HF to remove any dead skin that can slough off after the PRP treatment.