Um, fuck no. Speaking as someone who rather frequently has to schedule a doctor's appointment as soon as there is a available slot (and sometimes on the same day), hell no am I going to ask permission to use the leave I am contractually entitled to. And I would really like to know how you require 48 hours notice for PTO when the most common use for PTO is sick time. "Hey, boss, I was thinking of scheduling a stomach virus on Thursday. Is that convenient?"