What Kind of Doctor?

After making love, the woman said the man, "So, you're a doctor?" "That's right," replied the doctor smugly. "Betcha don't know what kind of doctor." "Ummm...I'd say that you're an anesthesiologist." "Yep, that's right! Good guess! How did you know?" asked the guy. "Because throughout the entire procedure, I didn't feel a thing."