Spanish SS doctors make house calls (normally GPs and Pediatricians only). Usually it’s at the end of their shift, so for example someone calling the Day Center where my sister in law works would get the doctor’s visit sometime around 2-3pm (end of the morning shift) or 6-7pm (end of the afternoon shift). If they need the doctor faster than that, the call gets transferred to the ambulance service (and there’s doctors on ambulance duty).
It’s considered part of the doc’s normal work hours, it’s already calculated into their yearly hours.