“Awareness” During Monitored Anesthesia Care (MAC)

Over the years, I’ve read and received accounts of patient experiences along the lines of: “I woke up during anesthesia!” This piqued my interest as awareness with recall during general anesthesia (GA) is a dreaded albeit rare complication occurring in ~0.1% of general anesthetics. Emergent cardiac, trauma, and obstetric surgeries are risk factors since a “full GA” can lead to hemodynamic decompensation. In these situations, I’m faced with a balancing act – recall vs cardiopulmonary collapse.

Delving further into the description of these experiences (medications/doses utilized, how these procedures are often done, etc.), it’s hard for me to believe that ALL of these stories are truly awareness under GA. Instead, I think patient expectations need to be addressed. Much of the general public equates “anesthesia” with “unconsciousness.” However, monitored anesthesia care (MAC) is a form of sedation-based anesthesia with varying depths (minimal, moderate, deep) often utilized for procedures. MAC cases tend to recover faster post-operatively and often times require less intravenous agents which can be associated with nausea, vomiting, constipation, and drowsiness. This is usually aided by intravenous sedation and regional anesthesia techniques like peripheral nerve blocks.

“Being aware” is perfectly normal under conscious sedation (hence the name). Patients drift in-and-out of a light plane of sleep. For this reason, I paint the picture of exactly what patients can expect pre, intra, and immediately post-operatively, so they understand what they may experience BEFORE it happens. To some degree, this also helps alleviate anxiety. Admittedly, as anesthesiologists, we need to do a better job of setting expectations with MAC pre-operatively. Post-op, it’s important to provide reassurance and tease out exactly what patients remembered. This can range from experiences when they were in fact conscious (ie, pre-operatively) or even dreams they had during surgery that are misconstrued as awareness.

So remember, with sedation/MAC, you likely WILL be intermittently conscious. You’re not “waking up during surgery” as you were never completely unconscious to begin with. Some of my patients are just too sick for a general anesthetic with its associated airway interventions, hemodynamic changes, and post-operative recovery course. Therefore, patient safety considerations in the context of the scheduled procedure dictate my anesthetic plan (GA vs MAC).

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  1. So, well said, and a great, great topic. I lecture my students on the types of anesthesia and never connected “locked in syndrome” (supposedly when one is paralyzed but not sedated during surgery) as a likely just a variation (and misunderstanding) of MAC.

    • Thanks so much, Bill! It’s important that we don’t dismiss the possibility of awareness with recall under GA, but also educate patients with what they can expect during the operative experience.


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