Monitored anesthesia care (MAC) means that an anesthesia specialist will care for you during your procedure. The specialist will make sure that you get the level of anesthesia you need to be comfortable. They'll also help keep you safe. They can change the type of anesthesia if needed. And they can help with any breathing trouble or other problems.
MAC is most often done when higher doses of sedative medicines are planned. So some people use the term "MAC" to describe sedation that makes you fall completely asleep.