Gradient of Anesthesia

Although we learn a lot from our textbooks, mentors, and lectures, we're at a stage in life where we develop our own theories, hypotheses, and concepts about things. Over the last four years, my understanding of anesthesia has changed simply from my experiences with it. I've not read this in a textbook or review article, I've never seen it in a lecture, but I've developed a concept of anesthesia where its a gradient of neurologic quiescence. That is, for me, anesthesia is not a black-and-white on-or-off state. It's not a switch we activate and deactivate. It's not a binary brain characteristic. 

This is not how most people think of anesthesia. Although simplification probably makes things easier, textbooks, insurance companies, surgeons, and patients often think of anesthesia as sedation ("monitored anesthesia care") versus general anesthetic. Patients expect "twilight" sedation for a colonoscopy. They expect to be "completely asleep" for brain surgery. When I talk to patients, I often use these distinctions.

But I'm not sure I buy it. Instead, I think of anesthesia as a gradation of varying consciousnesses. I can achieve a state of anesthesia where a patient will respond and talk during the surgery but remember very little of it. I can achieve a state of anesthesia where a patient's EEG is asleep and I don't expect the patient to remember anything, yet she is breathing on her own without ventilatory support. I can achieve a state of anesthesia where the brain is asleep and the patient doesn't breathe, but if they feel pain, their blood pressure and heart rate will rise. I can achieve a state of anesthesia where the body knows nothing; a surgeon can make an incision and the vitals don't budge. All those states are very different, have different risks, require different medications, and have varying level of difficulty in management. Some are required for particular procedures. Some are better for specific patients. All these variables play into the "art" of anesthesia.