Well, you can either cut his earlier nap a bit shorter so that he will go down for his 1pm nap a bit early, so he can have a sleep before the Dr... or put him down at 1 and let him sleep 30 mins or however much he can before getting to the Dr, and then trying for an additional catnap (or longer catnap) after the Dr. If all else fails, an early bedtime should help you get back on track for tomorrow.