Why This Anesthesiologist Has A Problem With Monitored Anesthesia Care (MAC)

I have a major issue with MAC.

To be more specific, I have a major issue with how we communicate the concept of MAC to our patients, anesthesia care team members, and proceduralist colleagues.

MAC stands for “monitored anesthesia care,” and we tend to throw it around and use it interchangeably with a lot of other terms:

• Sedation
• Procedural sedation
• Conscious sedation
• Twilight anesthesia
• Light anesthesia

The fact is, these entities are not the same, and I feel pretty strongly that we do a disservice to our patients and our colleagues by not being more specific with our language.

The American Society of Anesthesiologists makes the following important distinction: “Monitored Anesthesia Care (“MAC”) does not describe the continuum of depth of sedation, rather it describes ‘a specific anesthesia service performed by a qualified anesthesia provider, for a diagnostic or therapeutic procedure.’ Indications for monitored anesthesia care include “the need for deeper levels of analgesia and sedation than can be provided by moderate sedation (including potential conversion to a general or regional anesthetic).”

So I argue, in its most technical sense, determining a patient to be appropriate for a MAC anesthetic, tells very little about the depth of sedation they will be under, which frankly, is what most proceduralists and patient’s care about.

Now don’t get me wrong, I’m totally guilty of being busy running four rooms and will say in passing to one of my experienced CRNA colleagues, “sure MAC should be fine for this case.” But I am really pushing myself to be specific in language with my patients and colleagues. Because individual interpretations of MAC may vary substantially.

Luckily, I don’t need to invent these definitions, because they’ve already been clarified for us by the ASA:



This is the language I strive to use in my preoperative conversations, as well as my discussions with surgeons and colleagues.

As an example, one of the most common anesthetics performed in the country is for endoscopic procedures like colonoscopies. My preop conversation, for a healthy person undergoing screening colonoscopy, will often go something like this:

“The type of anesthesia you will be receiving for this procedure will be monitored anesthesia care with deep sedation. Sometimes folks refer to this as twilight anesthesia. We will put medicine through your IV so you will be asleep for the procedure. You will not be as deeply unconscious as if you were to be under general anesthesia, and therefore you will not need a breathing tube. However, the medicine can affect your blood pressure, heart rate, and breathing, and that’s why we will be there to monitor and support those functions as necessary.”

Most patients are satisfied with this description, and I don’t think it leaves too much ambiguity.

On the flip side, if I’m taking care of an elderly patient with multiple comorbidities (other chronic health problems) who needs a tunneled dialysis catheter, I might tell them, “the type of anesthesia care you will receive is called monitored anesthesia care with minimal sedation. You will receive some medication through your IV to help relax you, but you will likely be aware of what is going on during the procedure. The majority of your comfort will be ensured by the local anesthesia provided by the surgeon.”

I will then tell the surgeon, “Hey, this patient is going to be awake,” and I will inform any other members of the care team model the same.

As with many situations in life, appropriate expectation setting can do wonders.

The other big issue I have with MAC is the belief held by patients, largely propagated by non-anesthesia health care professionals, that MAC is safer than general anesthesia.

I’ll never forget, toward the end of my fellowship we were transitioning from performing most of our TAVRs (a minimally invasive approach to replacing the aortic valve, designed for patients “too sick” for open-heart surgery) under general anesthesia, to performing them under MAC, as was the growing national trend. We had an especially sick, morbidly obese patient with severe pulmonary hypertension who we chose to intubate and provide a general anesthetic. The very talented and senior surgeon was LIVID. He stormed into the operating room and shouted, “I don’t get it! If this guy is so sick, why would we do general anesthesia?!” I have no doubt he only wanted what was best for the patient, but I also have no doubt he doesn’t understand many of the nuances that go into an anesthesiologist’s decision making.

Similarly, I receive letters from cardiologists all the time saying, “Patient is cleared for MAC anesthesia.” Again, I know their intentions are good, but they don’t actually know.

So is MAC safer than general anesthesia?

The answer is: It depends.

It can be. But this depends on the depth of sedation required for the procedure, and the other health problems the patient already has. While general anesthesia undoubtedly has its own risks, establishing general anesthesia from the onset, with a secured airway (breathing tube), can often allow for a more controlled and safer situation than one that might need to be urgently or even emergently adjusted or rescued.

An attending I liked very much during residency must have known the way to my heart was through movie quotes, so he phrased it just like Pat Morita in the 1984 masterpiece The Karate Kid: “Walk right side, safe. Walk left side, safe. Walk middle … sooner or later you get squish like grape.”

That is to say, for very sick patients, you either allow them to be completely awake, or completely asleep (general anesthesia). Obviously, this is an overly simplistic generalization, but I think the concept is solid; sometimes the most trouble arises in that middle ground along the continuum of sedation.

So bottom line:

If you’re a patient: Trust us. We’re the experts. We want to do what is best for you.

If you’re the proceduralist: Trust us. We’re the experts. We want to do what is best for you.

Stephen Freiberg is an anesthesiologist who blogs at The DADesthesiologist.

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