MAC keeps you very drowsy during surgery. You may be awake, but you likely won't remember much. And you won't feel pain. With MAC, medicines are given through an I.V. (intravenous) line into a vein in your arm or hand. A local anesthetic will also be injected into the skin and muscle around the surgical site to numb it. The anesthesia provider monitors you during the procedure. They check your heart rate and rhythm, blood pressure, and blood oxygen level.